•SOL MATT1'*"*1" • !•* EAKTH SCIENCES LIBRAK' I.89.Z- To... , I/ I have the pleasure of presenting, in the name of the board of regents of the University of Minnesota, this copy of volume III, part II, of the final report on the geolo/ und natural history survey of M ii»irx»t \ \IH\N ANIt NIK STl! \TI«, I! Al'II ir AND i»|STIilP,ITIi»N n| THE FOSSILS. MY N. H. WINCHEI.L AND E. O. ULRH'H. STHATHJRAPHK DIVISIONS OP THE LOWER SILURIAN IN MINNESOTA. The reader will see by reference to the table of stratigraphic designations in Part I of this volume (Intnxluctiun, pp. 1 and li) a list of the special names used in the greater part is volume. As, however, the use of the various designations is not entirely uniform in the several chapters, and in order that the future student may have some guide in the study of these format - in the field, it is necessary to present an exact definition of the stratigraphy. The published reports of the Minnesota survey have given stratigraphic sections at various places, but it has not been found possible heretofore to so adjust them as to show any close successioual order, aside from that already given. The following might be considered as expressing an average composition of the Trenton division of these strata in southeastern Minnesota, taken in Olmsted county. It is essentially the same as that published in the first annual report, and takes into account only the lithologic character of the strata. AVERAGE SECTION OF THE TRENTON PERIOD. 1 Loose fragment* . . 4 4 feet. 2 Magnesian limestone, buff. . .... 30 feet. 10 Inches. 3 Slaty and argillaceous... ; •. iuebe*. 4 Magneslan limestone, t>u(T. iif.-<-t, fl Inches. Shaly llmestoi ... 5 feet. 6 Magneslan limestone, buff 20 fret. 7 ArRillo-magnaRlao limestone with much interbedded shale (nr shaljr inn— ••!,.•>. Lowest seen RacepUculltes - 4 Inches 8 Shales, with thin argillaceous sheet* of llmetton. 18 feet. 9 Gray or earthy (bluish) limestone, with ohaly parting* 37 feet. -nating limestone and shale .-•. « Inches. II Gr>«-n -hal.'.. 42 feet. i -art limestone, buff on weathirink', I'luc within, with Interbedded sha 22 feet. :»7feet, 8 Inches. THE PALEONTOLOGY OF MINNESOTA. Of the above the first nine numbers and a portion of the tenth may be considered as representing the Galena, of Iowa, Illinois and Wisconsin, though that will do violence to the lithologic criterion oa which Profs. Hall and Whitney, as well as Moses Strong, determined the base of the Galena. But, as we will show further on, the shaly character of the lower part of the Galena in Minnesota is merely a local feature of the group similar to that which pertains more or less strongly also to the underlying divisions which we parallelize with the Black River and Birdseye limestones of New York. Nos. 1 to 6 represent the whole of the Maclurea bed, and 7, 8 and 9, the Pusispira bed, while the upper part of No. 10 is the Clitambonites bed. The lower part of No. 10 and the upper part of No. 11 represent the "Upper Blue" and "Upper Buff" limestones of the Wisconsin geologists and the Black River group of New York, while the lower part of No. 11, together with the whole of No. 12, corresponds with the "Lower Blue" and "Lower Buff" limestones of Chamberlin, the Birdseye limestone of New York geologists, and the Stones River group of Safford. While a dependence upon lithologic characters in classifying the Lower Silurian strata of Minnesota is very liable to lead one into serious errors, the chances for overcoming the difficulties are greatly increased when the faunal characteristics of the various beds are minutely investigated and fully appreciated. This statement, however, is not to be understood as intimating that the lithologic characters are either entirely unreliable or useless in separating the beds. Qn the contrary, when judiciously employed in connection with the evidence afforded by the fossils, they are of great assistance in determining the age of the beds and in correlating even widely separated exposures of any of them. Familiarity with the beds shows that the shales and limestones of each have certain recognizable peculiarities, and there is something about the preservation and appearance of the fossils of each sufficiently distinctive to enable an expert in such matters to recognize, in at least nine cases out of ten, the bed and often the exact locality from which they were collected. On the opposite page we present cuts of five actually measured continuous sections showing the character and thickness of Lower Silurian strata in Goodhue and Pillmore counties. None of the sections contain either the St. Peter sandstone or the lower part of the Stones River or Birdseye limestone, and only one (No. 5) contains strata above the Trenton. On another page, sections 6, 7 and 8 show the entire series of rocks, from the St. Peter sandstone up, seen in the three counties of Ramsey, Goodhue and Fillmore. These may be consulted to supplement sections 1 to 5, of which explanations follow. - I KATA. Ixxxv I — d I 1 , 1 TOM THE PALEONTOLOGY OF MINNESOTA. EXPLANATION OF SECTIONS 1 TO 5. Nos. 1 and 2, Sections of Black River group shales with the upper portion of the Stones River group and the lower bed of the Trenton group. 1 was taken at a locality between five and six miles south of Cannon Falls, Goodhue county; 2 at a point about one mile east of the same town. 1. Vanuxemia bed of Stones Kiver group. 2. Stictoporella bed, consisting of soft shales and several layers of limestone. The latter are thin and largely made up of fossils, among them Stictoporella frondifera, Pachydictya foliata, Homotrypa minnesotensis, Anolotichia impolita and Rhynchotrema minnesotensis. 3. Ehinidictya bed, consisting in the lower part almost entirely of soft, greenish shales, holding very few fossils. In the upper half or two-thirds there are numerous, more or less irregular, subcrystalline limestone plates, largely made up of fossil remains, chiefly Bryozoa, with Rhinidictya mutabilis very abundant. 4 and 4a. Ctenodonta bed. In section 1 the lower four feet is a bed of dark shale in which no fossils were observed. The upper part contains five or six irregular layers of limestone, weathering red, which are filled with fossil shells, among them several species of Ctenodonta, Crytodonta tenella, C. affinis, Plethocardia umbonata, Whitella scofieldi, Matheria rugosa, and numerous Gastropoda and Cephalopoda The first layer contained, besides some of the species named, some plates of a large species of Carabocrinus, and in considerable abundance a slowly tapering tubular fossil, between one and two inches in length, that greatly resembles the Salterella billingsi which Safford regards as one of the most characteristic fossils of his "Central limestone " in Tennessee. In section 5, the bed is thicker and the lower portion is less sharply distinguished from the upper. 5 and 5a. Phylloporina and Fucoid beds. These consist almost entirely of soft and highly fossillferous, greenish shales. The fossils occur mostly in bands, and where they are most abundant they are of ten consolidated into rough limestone layers, rarely exceeding three inches in thickness.' Bryozoa are exceedingly abundant in the Phylloporina bed, and as a rule in an excellent state of preservation. 7 Of the more striking and common forms we may mention Phylloporina corticosa, Trigonodictya conciliatrix, Prasopora conoidea, Homotrypa tuberculata and Batostoma montuosum. In the Fucoid bed the fossils occur more sparingly, and the Bryozoa are wanting almost entirely. At the top there is a rough layer of impure limestone, a foot or more in thickness, which may be recognized at once by its rusty hue. It is sometimes divided into two or three layers, and when it contains any fossils at all they are always imperfect. 6. This, the lowest or Clitambonites bed of the Trenton group, consists chiefly of yellowish shales. In the lower eight or ten feet there are numerous irregular or nodular layers of impure limestone. These are very fossiliferous, and it is in this portion that such characteristic species of the bed as Clitambonites diversus, Strophomena scofieldi, Orthis meedsi, Prasopora insularis, Callopora ampla and Eridotrypa mutabilis are nearly always to be found. Near the middle of the bed Callopora goodhuensis and a small variety of Plectambonites sericea are very abundant. The upper seven or eight feet consist entirely of shale, and in this portion fossils are exceedingly rare. 1. At the top of section 2, we recognized a small remnant of the Nematopora bed. Section 3, as exposed in an old road about two miles southeast from Cannon Falls. 4. Ctenodonta bed. 5. Phylloporina and Fucoid beds, both covered except at the base and top. 6. Clitambonites bed. 6a, horizon of Clitambonites diversus; 66, of Callopora goodhuensis 6c, unfossiliferous shales. 7. Nematopora bed. Drab to blue shales, including five or six layers of limestone, the latter very fossiliferous. Orthis meedsi var. germana, Homotrypa similis, Pachydictya pumila, Rhinidictya minima, Nematopora ovalis and N. granosa are both characteristic and common. At the point marked Cx some good specimens of Clitambonites diversus were obtained, while the shales immediately beneath it, when washed, afforded, beside the fossils above named, numerous minute Bryozoa of the genera Arthrodema and Helopora, and six species of Ostracoda. 8. Lower part of Fusispira bed, here consisting entirely of gray shales, quite unfossiliferous except between twelve and fourteen feet above the base where about a dozen good specimens of Cydospira bisulcata were found. • Section 4, showing the whole of the Fusispira bed and the upper part of the Nematopora bed; Prosser's ravine near Wykoff, Fillmore county. 1. Nematopora bed. A layer of limestone two feet thick at the top. Obtained here Orthis meedsi var. germana, a variety of O. borealis, Platystrophia biforata, Strophomena trentonensis, Rafinesguina alternata, Rhynchotrema increbescens, and several undetermined Ostracoda and Bryzoa, the latter not well preserved. CORRELATION OF STRATA. llXXvii 2. Twelve feet of shelly or thin-bedded argillaceous limestone, tbo surface of the layer*. In the I..W.T half especially, being rmitfh v .• I'M- middle several large Impressions of Btotptaeutite* owrni, <.„.• • Hilt.- ilf!.-.-n I iii-he.. in f th.- p-mis i>ipl-»ir,>i>tut. Above this layer fossils are comparatively rare, but beneath It they are al.'iii.l:iMt though r jt h«-r illrtlcutt to obtain perfect, since they must be broken out of the solid lime- \ . r . ,.TS we obtained here Rafnetquina deltoidea, PledamboniU* gibbon, Zyyotpira upVimi, Anbmyekia belK#riata, ByuongfMa inltrmtdia, CWonyeWa undnta, CUnodonta intermedia, Cjrrtodon/n abrupta, C. gtrmana, E*dode*m« tuneatwn, X. camprtMum, PiUoconrhaf minruvXennt, EcryliopUnu ouxmanu* JNuwptra inflala, F. nobilu. F. pl'inulata, Tmchonema roWnwi and I'latgmetoput robbinti. At-.ve No. S this ravine exposes about Ofty feet of massive dolomltlc limestones of the Maclurea bed and then about twenty feet of shaly layers belonging to the Utlca group. Sections, Moving ttrnta at MMI in ond near a tmaU quarry, about too and a half mUa north of Spring Valley, Minnetota. 1. About nine feet of thin and unevenly bedded or laminated, bluish-gray, crlnuldal limestone. The whole appears solid in a fresh exposure but breaks up under the weather. The crlnoldal fragments have evidently been much rolled. 2. Twenty feet of even bedded, compact, gray limestone. In layers fifteen Inches or leas thick, i.vers becoming too thin and argillaceous In the upper part for building purposes. Between the lime- stones there are bands of soft shale, the whole bed being composed of about one-third shale and two- thirds limestone. At the top several layer* will be noticed containing the separated parts of Amphut or Itatelut mnximu* In abundance. Six feet beneath the top a band of shale contains Leptobolta oondcn/K STKA IxXXJX HUDSON RIVER o* CINCINNATI PERIOD. \ ^ i" $ • o EA c" ^ P H D • I XC THE PALEONTOLOGY OF MINNESOTA. The St. Peter sandstone has a wide geographical distribution, being known by outcroppings in Canada, Michigan, Wisconsin, Minnesota, Iowa, Illinois and Missouri, and through deep borings in Indiana, Ohio and Kentucky. In the northwest it consists almost entirely of silica, but in the vicinity of Cincinnati, where it is the principal source of the " blue lick water " of the artesian wells, it contains a considerable amount of calcareous material. Stones River group. This name was proposed by Prof. J. M. Safford in 1851 (Amer. Jour. Sci. and Arts, 2d ser., vol. XII, p. 352) for the Lower Silurian strata of central Tennessee which in his "Geology of Tennessee," 1869, we find fully described under the names Central limestone, Pierce limestone, Ridley limestone, Glade limestone and Carter's Creek limestone. In the latter publication the group name is abandoned under the misapprehension that the limestones so designated are strictly equivalent to the Trenton group of New York. As we are confident that this was an error, we propose to resurrect the name. In our opinion the four lower members of the Stones River group as originally defined, are equivalent to the Birdseye limestone of New York and the " Lower Buff " and "Lower Blue " limestones of the Trenton, in Illinois, Wisconsin, Iowa and Minnesota. The group is strongly developed in Kentucky and from here it doubtless extends as an unbroken, though diminishing sheet, westward into Missouri and northward into Canada. According to the evidence now available it seems that in geographical distribution, thickness, and paleon- tological interest, the Stones River group is nearly or quite equal to the Trenton limestone itself. Being thin and, according to report, not readily distinguished paleontologically from the overlying Black River limestone in Canada and New York, the Birdseye limestone, a name that we think must give way to the geographic designation proposed by Prof. Safford, has not been generally recognized. In Tennessee and the western and north- western states the group has been almost universally regarded as representing part if not all of the Trenton limestone, while the Galena limestone, which is the exact equivalent of the Trenton limestone, was by most investigators believed to represent a local upper member of the Trenton, and by others the western equivalent of the Utica slate. A careful and extended investigation of the stratigraphy and paleontology of the Trenton and Cincinnati periods, however, proves most conclusively that the generally accepted views of the equivalents of the Galena and other limestones resting on the St. Peter sandstone are incorrect, and that Prof. James Hall's early surmise respecting the presence in the northwest of strata representing the Birdseye and Black River limestones of New York is essentially correct. As regards the Nashville group, which Prof. Safford, chiefly because of the presence of two fossils, Cyrtolites ornatus and Byssonychia (Ambonychia) radiata, in 1869, concluded CORRELATION OF STRATA XCI !<• be the same as the Hudson Kiv.-r group of New York and Canada, it is, with the exception of a portion of the upper member, indubitably Trenton, and occupies the same interval which in th«- northwest is taken up by ona. The two fossils mentioned hold pecisely the same position in Kentucky, but here there can be no doubt concerning the age of the strata in which they are found since they lie beneath the base of the Utica. Again, as neither is strictly identical with the well-known Cincinnati or Hudson River types of the species, the important use to which they were put by Prof. Safford is, to say the least, unwarranted. Even if the supposed identity of the two shells and the Hudson River types to which they were referred had been corroborated or established by more recent investigations, the weight of the evidence thereby afforded must have been deemed insignificant as opposed to the abundant data upon which we base our conclusion that both the Galena and Nashville groups are strictly equivalent to the Trenton limestone of New York. Neither of the two species in question has yet been found in Minnesota, but a variety of the OyrtolUes, to which we give the new name rctrorsu*, occurs in the Black River shales in Fillmore county. We describe also a small variety of C. ornatu* from the Clitambonites bed in Goodhue county, which corresponds very nearly in position with the Tennessee strata holding C. retrorntt Ulrlch (C. ornatus Safford, not Hall). We have not seen an entire exposure of the upper member of the Nashville group, and are therefore somewhat in doubt respecting its nature and position in the geological scale, but certain fossils in the collection of Prof. Safford cause us to suspect that it includes a few layers at the top representing portions of the Hudson River period. However this may turn out, we have no doubt whatever about the lower 70 feet of Safford's College Hill limestone (his section on p. 276. Geology of Tennessee, gives the whole a thickness of 120 feet) since that much at least is strictly equivalent to beds occurring near Frankfort, and other localities in Kentucky, at the top of the Trenton and always Mow the base of the Utica group. Division* of the Stone* River group recognized in the Upper MiMiuippi province. Buff limestone. This, the lowest portion of the group, rests apparently conformably upon the St Peter sandstone Its thickness in Minnesota, Wisconsin, Iowa and Illinois varies between twelve and twenty-two feet, the average thickness in Minnesota being about fifteen feet At the base there is often a bed of green shale or an iron-stained layer of sandstone. The latter was noticed at Janesville, Wisconsin, there eighteen inches thick, while a combination of the two. varying both as to thickness and composition, has been observed at several points in Dodge and Olmsted counties in Minnesota. The lime- stone proper is compact, buff on weathering and bluish within. In Wisconsin it usually occurs in heavier beds than in Minnesota, and its fossils are not as well preserved there as here. The latter fact is probably due to the greater prevalence of clayey seams and the purer character of the limestone layers in Minnesota. As to the fauna of this bed. it is not large in the way of species but individuals of some of them are often very abundant. This is true, especially of the region about XCll THE PALEONTOLOGY OF MINNESOTA. Minneapolis and St. Paul. Here we frequently meet with thin slabs, one s de of which may be filled with good specimens of a small variety of Rhynchotrema minnesotensis, Orthis deflecta, Strophomena filitexta, Rafinesquina minnesotensis and Leperditia fabulites. Perhaps ten or twelve othe^ species have been observed in this bed at St. Paul and Minne- apolis that may be considered as common, while all the others are rare. It is to be noticed also that very few, if any, of the common species are limited to the bed, but that nearly all of them are quite as abundant in the succeeding beds of limestone. For this reason no paleontological designation is proposed. Vanuxemia bed. This designation is proposed for the upper part (about twelve feet) of the limestone series at St. Paul and Minneapolis. It is in part equivalent to the ' ' Lower Blue limestone " of Wisconsin. The upper five feet are full of fossils, preserved, however, chiefly as empty molds and casts. Still, on the bed planes, Brachiopoda and other shells, as well as trilobites, are often very well preserved. Leperditia fabulites, Rajlnesquina min- nesotensis, Orthis tricenaria, Glathrospira subconica, Trochonema beloitense, Lophospira con- radana, L. serrulata, and Vanuxemia dixonensis are very abundant, and the last four highly characteristic of the bed. Vanuxemia obtusifrons, V. sardesoni, Maclurea depressa, Helicotoma umbilicata, Conradella triangularis, and Gyrtometopus scofieldi, also are characteristic but much less common. In giving "Formation and locality" of fossils described in this volume, these two limestone beds are, as a rule, not separately referred to. It is to be understood, therefore, that the designations "Trenton limestone" and "lower limestone of the Trenton forma- tion," may mean either one or both beds. Stictoporella bed. This term applies to the ten feet of shale and limestone ("lower third of the Trenton shales") resting on the Vanuxemia bed at St. Paul and Minneapolis. Here it is a well marked horizon, containing an abundant fauna of which Bryozoa are the principal element, no less than thirty-nine species of this class being represented. Stictoporella frondifera, S. anguaris, Pachydictya frondosa and Anolotichia impolita are always abundant and, as far as known, are to be found only in this bed. Among the interesting fossils is a fine new species of starfish, of which three specimens, the largest four inches across, were found at Minneapolis. The great abundance of Bryozoa, and the fact that nineteen of the thirty-nine species pass on into succeeding beds might be considered as good evidence for uniting the Sticto- porella bed with the next group rather than with the Stones River group. But this would be an error since it is clearly nothing more than the upper member of the Stones River group, which, in tracing it northwestward from Beloit and Janesville, Wisconsin, where it cannot be distinguished from the "Lower Blue limestone,'' gradually becomes more and more shaly. The conditions seem to have been eminently favorable for the development of bryozoan types, so it might be expected that many species would be ushered in, that, in this region, reached the night of their development first in the upper part of the next bed. The same intimate faunal connection with the succeeding beds is exhibited also by some of the other classes of fossils. As shown in the list nearly 44 per cent (42 of 96) of its OORKKI.ATION OF STRATA. fauna pass on into the next bed or reappear in one or the other of the succeeding beds. If. however, we examine these species we notice that of the 42 forms which it holds in common with lau-r divisions at least twelve species of Bryoeoa, Brachiopoda and Trilobita rnn^e through throe <>r inon- irmups. and therefore ought not to be taken into account in determining the question under consideration. Deducting these the percentage of species passing upward is considerably reduced, while the remaining fauna is more in accordance wall that of the preceding limestones. As it is. over half of the entire fauna is received from below. In comparing the Stones River group as developed in Minnesota with equivalent rocks at other localities embraced within the limits of the Upper Mississippi province, we find that the lithologic characters change towards the east and south. Thus at Beloit. Wisconsin, and at Kockton, Illinois, the Lower Buff and Lower Blue limestones are more nearly alike in texture and composition than is the case farther west in those states. In the quar ;ockton these beds as well as the Upper Buff limestone are enough alike to have been considered by Whitney and Worthen as the same as what the Wisconsin geologists have more recently distinguished as the Lower Buff. At Mineral Point, Wisconsin, and Dixon and Dunlieth. Illinois, the Lower Blue is a pure limestone and readily separated from the Lower Buff. In Minnesota, however, the strata equivalent to the Lower Buff are a purer limestone than usual in the northwest, while the strata which we parallelize with the Lower Blue are magnesian in the middle member (Vanuxemia bed), clayey in the lower, and an alternation of pure crystalline limestones and shales in the upper. The Trenton period of the northwestern states may be divided into three regions in • each of which the lithologic character of the various beds is approximately uniform, namely, the Minnesota area, the region included between the three towns of Dixon, Dunlieth and Mineral Point, and the third including the towns of Janesville, Beloit and Rockton. In the first, the period includes much shale, in the second, a good proportion is pure limestone, in the third, all the beds are more or less distinctly dolomitic. These lithologic areas, if we may so call them, of course merge gradually into each other, and probably are due to conditions depending upon the distance of each area from the Lower Silurian shore line. Of Wisconsin sections of the group of strata under consideration, the one which, so far as known to us, offers the greatest resemblance to the St. Paul section, occurs near Benton. Wisconsin. Here the "Lower Blue limestone" is terminated above by two beds corresponding in position and fossils, and fairly well also as regards composition, to the Vanuxemia and Stictoporella beds. In ceutral Kentucky the rocks which belong to this group form precipitous bluffs, often over two hundred feet in bight, along the Kentucky river from Frankfort to and beyond High Bridge. Nearly the whole of this section consists of massive dove colored limestones, exceedingly like and unquestionably equivalent to the Birdseye limestone of New York. The base of the group is not exposed in Kentucky so that we have only the XC1V THE PALEONTOLOGY OF MINNESOTA. evidence of deep borings to show that it is underlaid by the St. Peter sandstone. For the same reason we cannot give the entire thickness of the group in Kentucky. About 325 feet of it are exposed at High Bridge, but judging from certain fossils which occur at the base of the section at that point, we believe that no less than fifty feet more are covered. Indeed, there may be much more since the fossils in question are characteristic species of the Ridley limestone of Tennessee, and if the underlying limestones have as great a thick- ness in Kentucky as in that state, which, considering the fact that the beds equivalent to the Glade limestone are much thicker at High Bridge than in Tennessee, is highly probable, the covered portion of the group equals quite a hundred feet. The upper part sometimes contains much shale and is highly fossiliferous, many of the species being identical with those which occur in the upper beds of the group in the Minnesota region. Tetradium cellulosum Hall sp., perhaps the most characteristic fossil of the Birdseye in New York, is very abundant in this portion of the group at High Bridge and Frankfort. The typical Tennessee section consists of from 300 to 340 feet of alternating thin and heavy bedded, light blue and dove-colored compact limestones, the texture very much like that of the Upper Blue limestone ("Glass rock") at Dixon, 111., and Mineral Point, Wis., and not greatly different from occasional layers found in the Lower Buff at Minneapolis. The lowest member (Central limestone) is thick bedded and decidedly cherty, and some of the layers are full of silicified fossils in a good state of preservation. Salterella billingsi and Leperditia fabulites, the latter, perhaps, the most characteristic fossil of the group, occur in great abundance. Other fossils having an interest in this connection are Pterotheca alternata, Gonioceras occidentalis, Ctenodonta gibberula, Bucania emmonsi, Lophospira perangulata, Liospira abrupta, Solenospira prisca, and Ceraurus pleurexanthemus, The next bed (Pierce limestone) is chiefly remarkable for the wonderful profusion of its Bryozoan fauna, some of the thin layers being completely covered with bifoliate forms. The "Ridley limestone" is heavily bedded again, and contains a rather peculiar fauna, much of it, especially among the Bryozoa, new to science. Orthis sitbcequata, Rafinesquina minnesotensis and Phylloporina sublaaxt are not uncommon. The "Glade limestone," with a maximum thickness of 120 feet, consists of thin or flaggy layers and some shale. It is highly fossiliferous and contains many species that are characteristic of the group in Minnesota. Black River group. This group, though never very thick (usually from 20 to 100 feet) is still widely distributed, being recognizable in Canada, New York, Vermont, Pennsylvania, Tennessee, Kentucky and in the northwest. In Canada and the eastern states it is usually a heavy bedded limestone, and so it is also in Tennessee, Kentucky, Illinois and Wisconsin, but in Minnesota it consists almost entirely of greenish shales. The Tennessee and Kentucky strata which we place here have been called "Carter's Creek limestone " by Prof. Safford. In Kentucky the group is less than 50 feet thick, but in Tennessee it is as much as 100 OOKKI I TKATA. v. \ feet The rocks contain considerable chert and the fossils are nearly always silicifled. Characteristic fossils are Teiradiinn columnar*, <'«lti-ln*ma prof HIK I n in. h'ni'huifiHiiinn &i/>i'ri'(/i-i-riHin ruyosum, Triptocerat pUinodortalutu, Ai-tinocrnu bigibyi.Orthoceraiarciuiliriilniii. O.lfmn-uri, T. }>ltinoconvfrvm,Orthi» prclineUu, RfCfpfaculiles occidentala, and Cnmnriiclmliii rugosa (Ulrich).* In Wisconsin and Illinois the group is represented by the "Upper Buff" and "Upper Blue limestones." The average thickness of the two beds here is probably less than 40 feet They are well exposed in the quarries at Rockton. Illinois, where the upper member carries fossils clearly indicating the Phylloporina and Fucoid beds of the Minnesota section. We collected here, namely, Orthu pectinella, O. intfuilimiritt, Slrophomena trrnlonensis, Agelacrinus maryintilitt, Hythotrypa laxaia, Rqflnesquina inquassa, Arthropora f>i/nrrp of the Black Hirer llnmtone. The fomll weal to each *nnulatl..n-<-laaplnc the annulawd rod *o a* to leave about ooe-iblnl of It* circumference expoeed to view. Not Infrequently the rod , l.ancee suddenly from oor .Ide of the branch to the other. Inaa unbraached fra«mee>t before u* UU occur* twice In thecpaecof « mm. The beet *peel»e*j* were fovad Dty. XCV1 THE PALEONTOLOGY OF MINNESOTA. The Black River shales of Minnesota (Trenton shales of this volume — particularly those parts which are distinguished as middle and upper thirds) may conveniently be divided into four beds as follows : Rhinidictya bed. This bed is usually referred to in the following descriptions as the " middle third of the Trenton shales." It consists of dark green, soft shale, not over 5 feet thick in Fillmore county, and between 20 and 25 feet in Goodhue and Ramsey counties. (See sections 1, 2, 6, 7 and 8). It is very fossiliferous, particularly in the upper half, where the fossils, Bryozoa mainly, occur in thin calcareous layers in great quantity and variety. Rhinidictya mutabilis is exceedingly abundant, as is also Batostoma winchelli, while no less than 25 of the 57 species of Bryozoa may be said to be common. Excepting the Mollusca, which occur as casts of the interior, the fossils are in an excellent state of preservation. Ctenodonta bed. At St. Paul this bed is scarcely distinguishable from the Rhinidictya bed, several of the leading Bryozoa being quite abundant in it. However, in Goodhue county, where the bed is from 6 to 10 feet thick, Bryozoa are almost entirely absent while the Mollusca occur in great numbers. No less than 43 Lamellibranchiata have been found here and over half of the number are restricted to this bed. The Gastropoda are almost equally numerous while the Cephalopoda are, as far as number of species is concerned, nearly as well represented here as in any other division of the Lower Silurian in Minne- sota. The bed contains considerable iron and in Goodhue county can always be recognized by the red or brown color of the fossils and weathered slabs. The latter frequently become oolitic exteriorly, the grains being concretions of limonite of lenticular form. Ctenodonta socialis, C. scofieldi, C. compressa, C. planodorsata, Lyrodesma acuminatum, Matheria rugosa, Whitella scofieldi, Cyrtoceras comiculum, Archinacella deleta, Raphistoma peracuta, Lophospira oweni, and L. spironema, are some of the characteristic fossils. Under the descriptions of some of the Lamellibranchiata this bed is distinguished as the "upper part of the middle third of the Trenton shales." The name Ctenodonta bed is used only in the chapter on Gastropoda. Phylloporina bed. This bed has a thickness of from 10 to 15 feet in Ramsey and Goodhue counties, but it is much thinner in Fillmore county. It much resembles the Rhinidictya bed, and like it contains a great number of Bryozoa, but instead of the bifoliate forms it is the monticuliporoids that predominate here. Homotrypa subramosa is very abundant at most localities, as are also Prasopora simulatrix, P. conoidea and Batostoma montuosum, but the most distinctive and easily recognized fossil is the Phylloporina corticosa. Of four Echinodermata one, Agelacrinus rrtnrginatus, occurs in the "Upper Blue" in Wis- consin, and at the base of the Trenton in Kentucky. Lamellibranchiata, Gastropoda, Cephalopoda and Trilobita are rare, but the Ostracoda are well represented and some of the species are abundant. In the descriptions of the fossils this bed is not separated from the following, the designation "upper third of the Trenton shales " applying to either one or both. CORRELATION OF STRATA IOV11 or nrthi* pectinella bed. This bed is scarcely recognizable in Fillmoro county, but at St. Paul and in Goodbue county it is a well marked horizon. It is full of one of the so-called fucoids, the Oamarocladia rugosa. a fossil which we regard as the cast of a branch- ing sponge. (See foot note, p. xcv. ) It is very characteristic of the bed in Minnesota ami iM-curs in the same group in Kentucky. Other characteristic fossils of the bed are Orthi* •iflln and x>r»i>h»mena*eptata. In Minnesota the bed is generally terminated above by a roughly bedded, rusty, semi-crystalline layer, one to three feet in thickness. The rest of the bed. with the occasional exception of one or two thin limestone layers, consists en tin- 1 y of blue shales similar to those of the preceding beds, excepting that it is largely made up nf comminuted fragments of organic remains. The Furoid bed may in a measure be considered as a passage from the Black River group to the Trenton group. On both paleontological and lithological grounds, however, we are satisfied that it is really a part of the former. The rather limited fauna is more clearly related to the Black River than to the Trenton and it was not till its close that any marked lithological change took place. In Minnesota, it is true, the strata following are • at first still shaly. but instead of the preceding blue and green colors, we now have a yellowish or gray tinge, while the prevailing fossils, excepting several Branchiopoda. are nearly all distinct In Wisconsin and Illinois the two groups are just as easily separated, while in Tennessee and Kentucky, no one could fail in separating the Orthis bed from the Carter's Creek limestone. Paleontological ly there is always a decided break between the two groups. This is. perhaps, least in eastern Canada where the Black River group is also lithologically much like the Trenton limestone. In the eastern states and Canada the Black River group is remarkable for the abundance and great size of the Cephalopoda. In other regions, however, this class of fossils is not so strongly represented, although the group everywhere presents some of the leading species— less of them in Minnesota than anywhere else. But in Wisconsin and Illinois the "Upper Buff limestone" again contains more Cephalopoda than anything else, although most of the species occur also in the underlying " Lower Blue limestone". Still, this seems to be the case with the Cephalopoda not only in Wisconsin but in Canada, K. -mucky and Tennessee as well. The summary tables immediately following the list of fossils show that of the 296 species found in the Black River group of Minnesota. 189 are restricted to the group, 72 occur also in the Stones River group, and 58 pass into the following groups. Trenton group. (Oatena limestone, and tholes. NtuhviUe group.) When the Lower Silurian faunas of Canada, the eastern states and of Kentucky and Tennessee are compared with those which characterize the various divisions of the Lower Silurian in the northwest, it seems strange that it has not been recognized heretofore that the Galena limestone, instead of being a local upper member of the Trenton or the equivalent of the Utica slate, is really equal to the whole of the Trenton group in New XCV111 THE PALEONTOLOGY OF MINNESOTA. York and Canada. That this is a fact, is, we think, shown beyond any question whatever by the summary tables following the list of fossils. As given there no less than 107, or 87 per cent, of the 123 species common to the Galena of the northwest and one or more of the four other regions compared, occur elsewhere in the Trenton group. This percentage is increased to nearly 95 per cent., if we consider only the species that are restricted to the group in the northwest, since of 76 of such species 72 occur elsewhere in the Trenton group. That the Galena is a distinct group by itself is we think again shown conclusively by summary table No. 1. This gives a total of 305 species, of which 227, or about 74 percent., are restricted to the group. The Trenton group everywhere is a limestone, usually thin bedded and with more or less of shale in the lower part, and thick bedded and coarser textured in the upper. Sometimes, as at Frankfort and Covington, Ky., and Nashville, Tenn., there is some shale also near or at the extreme top. In the eastern states the lower part is black, the upper dark gray; south of the Ohio river both divisions are of lighter shades, the lower part being dark gray or blue, the upper a light gray or dove-color and when shaly a darker gray or blue; in the northwest the~whole may be of various shades of buff, or the lower half may be in parts yellowish, grayish or with faint blue or greenish tints. In the northwest, if the group is traced from southern Wisconsin into Illinois and then around the supposed upper Mississippi barrier into Iowa and Minnesota, a gradual change in the lithologic characters of the group will be noticed. In the first locality the Trenton or Galena is a dolomitic limestone throughout, in Illinois it sustains very little if any change, but in Iowa, as for instance at Decorah, the basal part is decidedly shaly and contains some layers of nearly pure limestone. In Pillmore county, Minnesota, the pure limestone has increased very materially in thickness, over 100 feet being of this character at Wykoff, leaving only about 50 feet at the top (the Maclurea bed) retaining the dolomitic feature that pertains to the whole of the group in southern Wisconsin. In following the group through Olmsted county into Goodhue we observe that now the lime also is gradually replaced (from the bottom upward) by more and more of argillaceous material, so that in the last county, between the post offices of Hader and Holden, only about 20 feet at the top of the Fusispira bed is still a pure limestone. Only a few feet of the Maclurea bed is left in Goodhue county and this seems to be essentially of the same character as in Fillmore county. North of Goodhue county all of the Trenton, save the lowest member (Clitambonites bed ) has been swept away, so we cannot say positively that the Maclurea bed, like the Fusispira bed, was eventually also replaced by shales. In Minnesota the group is divisible into three or four beds as follows: Clitambonites bed. This division (see sections 1, 2 and 3) consists of yellowish, light green or drab shales, with more or less of thin, indurated clay or impure limestone layers in the lower two-thirds, At the top there is a bed of light shale without hard layers, five to ten feet in thickness, in which fossils are very scarce. In the remainder, however, fossils are exceedingly plentiful, and, excepting the Mollusca, very well preserved. The whole bed is from 15 to 22 feet thick at St. Paul and in Goodhue county. Like the KKLATK'N o really r*»»rd. the bed u the upper member of hi. OHkMu bed (GMItambonltre h*4 of Ihta book). Afftln It I. poMlMc that thrl»y»r« In quMtloc mtn •otlr»lr or»rlook*rl by him. ( for »Utrmet. of SarriMmT* P*p«n Me pp. »m »od xlrllof U>« Inlr.«lur1l,,n t., p.rt I <>f thl> rnlum*.) ' PalBoaiolocjr of S«w York. vol. VIII. pi. 1 ft*-. I and II. UN. < Th« specie* of this KMIU are referred •rovliloaally to XwntropMa In thl. rolume. pp. M. ML C THE PALEONTOLOGY OF MINNESOTA. and is now called Cyclospira bisulcata. This leaves the genus Camarella without any known representative in the Silurian rocks of Minnesota. This lower division of the Pusispira bed is referred to occasionally in the description of the fossils as the "Nematopora bed" or as the "top" or "upper portion of the Galena shales," but in most cases the fossils are credited simply to the Galena shales.* Fossils are abundant, some of them extremely so. Common forms are plates of Glytocysiites sp. undet., Helopora mucronata, Arthrodema armatum, Nematopora ovalis, N. granosa, Pachydictya pumila, Rhinidictya minima, Homoirypa similis, Mesotrypa discoidea, Orihis meedsi var. germana, Clitambonites diversus, Schmidtella subcequalis, Halliella labiosa and Tetradella lunatifera. If a distinct name is desired for this horizon, that of Nematopora bed would be appropriate since this genus is represented here by four species and is unknown in all the other beds. Above the Nematopora horizon we have a series of strata for which the name Pusispira bed is proposed and to which the name should eventually be restricted. As has been stated already the lower portion of the bed has been separated by Dr. Sardeson as the " Camarella bed " while the upper portion he named " Lingulasma bed." The first of Dr Sardeson's names we have shown to be untenable, the second is objectionable because it is based upon a fossil that is very rare and in the opinion of the writers probably not distinct from the Lingulasma schucherti which is a rather widely distributed fossil of the Cincinnati period. We doubt also our right to extend the application of the name to strata which Dr. Sardeson holds to be distinct. Our name is based upon the occurrence here of at least nine species of Fusispira, four of which seem to be restricted to the bed, while two occur also in the Clitambonites bed and the others continue into the lower part of the Maclurea bed. In Fillmore county, as may be seen from section 4, (pi. xxxv), the Fusispira bed consists of a continuous series of thin bedded and more or less pure limestones little short of 100 feet in thickness. Nearly every foot of the bed as exposed in Prosser's ravine near Wykoff is fossiliferous, and some of the layers are crowded with shells. In tracing the bed through Olmsted and Dodge into Goodhue county the lower part becomes gradually more and more argillaceous (see sections 3 and 7), the fossils at the same time becoming less abundant and finally exceedingly rare or wanting entirely. The Mantorville quarry layers, which we place in the lower part of the bed, are peculiar in reassuming the magnesian character which had been lost before the bed entered Minnesota. The rock here is a firm and durable limestone in courses varying from three to thirty-six inches in thickness. All the fossils except the inarticulate brachiopods and graptolites occur as casts. We collected here the following species: Lingnla iowensis, I* hurlbuii, L. n. sp., Schizotreta pelopea, Strophomena trilobata, ' It la unfortunate that the subdivision of the Lower Silurian strata Minnesota could not be carried out before this volume went to press. It would have prevented some nacouracles, tnough we would doubtless have fallen Into others and In the end perhaps have prod uced more confusion than prevails now with the provisional nomenclature whloli was adopted by agreement among the several authors who have contributed to the work. Although we had a working conception of the various subdivisions, It was not till the close of the field season of 1802 that they were fully understood and characterized so as to be recognized at once by their fossils and llthological peculiarities. By this time, however, nearly 400 pages of the volume had been printed, and it Is In this portion that most of the errors and ambiguities occur. CORRELATION OF STRATA. . i gibbota, Cyclotpirn biaulcalii, RrrrplacuIHe» otceni and Mnrrhi.«,ni» Trrnloo period bjr Prof, Hafford. Tb* Richmond expoaar** braid** ar* larger and nor* caaneMrtoUe of ib* croup ibaa Urn** near Lebaoo*. Ohio. CIV THE PALEONTOLOGY OF MINNESOTA. upper Trenton species, while C. halli Nicholson, of which the typical form occurs in the Stones River and Black River groups, recurs here as well as at the top of the Trenton in slightly modified forms. Then we have varieties of Teiradium minus Safford and Proiurea vetusta Hall, two Trenton species; while the following Trenton types, Sirophomena filitexta, S. trenionensis, S. trilobata and Rhynchotrema increbescens are represented respectively by S. neglccta, S. rugosu. S. nutans and R. capax. And all these species, moreover belong to the predominant fossils of the group. Still, of the total number of species known from the group (over 300) nearly three-fourths are restricted to it. Only two of the groups of the Cincinnati period are represented in Minnesota, viz: the lower and the upper, an I both by but a small thickness. The Lorraine group thins rapidly in a northwestward direction from Cincinnati, and probably runs out altogether before reaching Kankakee, Illinois, where the volume of the whole period is less than 250 feet; and much the greater part of this seems to belong to the Richmond group. The Utica group also is probably wanting entii-ely in the northeastern corner of Illinois, but in the northwestern corner at Savannah, where the whole period is little less than 100 feet thick, the lower 50 feet belong to this group, while the upper represents the Richmond group. Prom a paper by Prof. J. P. James* it appears that the Cincinnati period occasionally exceeds 100 feet in thickness in Iowa, but on the whole it diminishes slowly northward from the latitude of Savannah. The Utica group in the Northwest seems to be a relatively deep sea deposit, and, in Iowa in particular, probably represents, so far as time is concerned, not only the Utica but the Lorraine of the Cincinnati region as well, without however at any time receiving any of the characteristic fauna of the latter. The Lorraine deposits and fauna of the Cincinnati province were derived from the easUnortbeast and for some reason (perhaps deep water) did not extend into the northern Mississippi province. At the beginning of the Richmond group the Cincinnati province received an incursion of northwestern species like Hyolithcs parviusculus and Colcolus iowensis James. In Minnesota the Utica group (see section 8) rests on the unevenly laminated, bluish- gray, crinoidal limestone, which forms the top of the Trenton, and consists of 20 feet or more of layers of impure, evenly bedded, compact gray limestone, varying from 2 to 12 inches in thickness, separated by thin seams of shale. In the upper part of this bed the limestone layers are prevailingly thinner than in the lower part, and contain an abundance of small specimens of Asaphus megistos. The interbedded shales contain I'lectambonites sericea, Orthis testudinaria, varieties multisecta and emacerata, Triplecia ulrichi and a number of undetermined Bryozoa, while about 14 feet above the crinoidal limestone one of the layers furnished numerous specimens of several species of Lingula, Leptobolns occidentalis and Diplograptus puiillus. The above describes the beds and fauna of the group as it is exposed in the vicinity of Spring Valley. Farther south, between Granger, Minn., and Graf, Iowa, the fossiliferous * American Geologist, vol. 5. no. 8; I860, CORRELATION f>l -Ti:ATA <-\ bed becomes thicker and more argillaceous, taking it as a whole, and contains molluscan species of the genera < 7»-»i.;'/.i»i/.i, < 7,./,.;i/,,.r/is and Orlhooertu in increasing abundance. u' upon the Utica we find in Fillmore county from 10 to perhaps 25 feet of more or less thin bedded argillaceous and siliceous limestones belonging to the Richmond ;rroup. Some of the layers are full of tin« fossils, chiefly Brachiopoda. and these are often silicifled, in which condition they have been collected by hundreds near Spring Valley. With very few exceptions, all the fossils that have been found in these layers occur also in tin- 'imond group <>f Illinois. Indiana and Ohio The strata of this group in Fillmore county are quickly decomposed and covered with soil, so that satisfactory natural exposures are rare. The fossils may sometimes be picked • f the worn soil of old fields but a more abundant supply was obtained in the cuttings along the railroad between Wykoff and Spring Valley. A few of the characteristic species ii-tliin snl> 'futmliiutrin (large variety). O. tchitfu-lili, l\nfinf»quinn Whitfield sp., Rhynclmnrlln m/xtr. Xlrophomena neglt'ctn, /.'/o;/iu rarinhili; Ctcm> • lunln ximilin. ('. n-i-nrrn and .SYrv/jMaamn nixticiim. lying the fossiliferous layers of the Richmond group, may be Keen in two places near Spring Valley, one about two and one-half miles north, the other one mile east of the town, about six feet of sandy layers weathering into irregular lumps and thin shells. Some of these contained fragments of large crinoidsor cystids, and from the loose material we obtained several fine examples of Hm-lin sphceroidulit, a common Upper Silurian foisil; also spiculesof Ifyalonit-Hn suliwytt which occurs nearly everywhere in connection with tin- IHntliti. Though these six feet are probably to be regarded as Upper Silurian the passage lithologically from the Richmond group is exceedingly gradual. Succeeding the foregoing bed and followed with not very strong evidences of uncon- formity by Devonian strata, is a sandstone four feet thick which here and there contains large numbers of small quartz pebbles, varying between one and ten mm. in diameter This sandstone we assume to belong to the Oriskany of New York. TABULATION OK THE LOWER SILURIAN SPECIES OF MINNESOTA AND GENERAL REMARKS INTRODUCTORY TO SAME. In the following tables the student will find the names of all the species known to occur in the Minnesota strata of the Trenton and Hudson River periods, excepting the St Peter sandstone. To these are added a number that are likely to be found within tin- limits of the state but are as yet known to occur only in the neighboring states of Wis- consin, Illinois and Iowa. With these the total number of forms catalogued is 809. Species described in the volume from other regions are not included in the list since they have no bearing at present upon the points which the tables are intended to bring out These tables show also the stratigraphic and geographic distribution of the species, while the summary tables which follow the list show how the faunas of the various stratigraphic divisions compare with each other and with those recognized in the Cincinnati, Tennessee, N.-w York and Canadian Lower Silurian regions. CV1 THE PALEONTOLOGY OF MINNESOTA. The total number of species and varieties in the Lower Silurian, belonging to the classes studied, which have been discussed in the volume, is eight hundred and eighty-one, and of these six hundred and ninety- three have been identified in the state, and ninety have been obtained from other states, and are likely to be found in Minnesota. They are distributed as follows: Sponges. 11 species, of which one only has been found in Canada. Graptolites. 3 species, all of which have been found in New York and Canada. Corals. 10 species, of which 4 have been found in New York and Canada. Bryozoans. 162 species, of which 15 are in New York and Canada, and 17 have not been found in Minnesota. The 19 large genera, i. e., those containing four or more species are the following: Stomatopora 4 species. Monticulipora 5 species. Bhinidictya 9 species. Atactoporella 4 species. Pachydictya 7 species. Homotrypella 6 species. Escharopora 4 species. Homotrypa 8 species. Stictoporella 6 species. Prasopora 8 species. Helopora 7 species. Mesotrypa 5 species. Artbroclema 5 species. Callopora 9 species. Nematopora 4 species. Batostoma 8 species. Phylloporina 4 species. Monotrypa 4 species. Leptotrypa 4 species. Of this total 9 species have not yet been found in Minnesota, leaving 102 species in 19 genera, which are known to occur within the state. The other 30 genera, of which one (Heterotrypa) does not occur in the state so far as known, contain 51 species. Brachiopods. 81 species, of which 20 species (and 2 varieties) occur in New York, and 33 species (and 4 varieties) occur in Canada. There is a total of 40 species common to Minnesota, New York and Canada. Of the 81 species considered, 8 are not found in the state, making a total of 73 species of known Lower Silurian brachiopods. The large genera, having each four or more species, are: . Lingula 12 species. Strophomena 12 species. Orthis 17 species. Of these 3 are not found in Minnesota, leaving 38 species in 3 genera. The other 24 genera contain 40 species. Two of these (Schizambon and Rhynchonella) have not been found in the state. Lamellibranchs. 131 species, of which 18 are not found in Minnesota, 7 are in New York (and Penn. ), and 5 in Canada. Nine species are common to Minnesota, New York and Canada. The large genera, i. e., those containing 4 or more species, are the following: Ambonychia 4 species. Cyrtodonta 16 species. Clionychia 5 species. Vanuxemia 15 species. Modiolopsis 11 species. Whitella 12 species. Orthodesma 4 species. Ctenodonta 26 species. Endodesma 5 species. Technophorus 4 species. Of these 15 are not found in Minnesota, leaving 87 species of Minnesota lamellibranchs in 10 genera. The total number of genera is 27. The other 17 genera contain 29 species. CORRELATION OF STKATA. CV11 Oialropodt. 287 specie*, contained in 4fl genera, of which 149 species and 41 genera have been found in Minnesota. 80 of the Minnesota species occur in New York or Canada. The large genera, containing 4 or more species, are as follows: Archinacella 13 species. Llo*plra 13 specie*. . 7 species. Eoloniarla. 8 species. Cyrtolltes.. 7 species. Ilnnuotoma. 10 species. Protowarthla.... 8 species. IMIcotoma. lOspecles. TetraooU « species. Maclurea 7 species. Bacanla 18 species. Trocbonema 13 species. SalplDgoMtoma. 4 species. Euoema 6 species. Uooradella 10 species. Gyronema. 4 species. Bellerophoo 11 species. Cyclonema. 11 species. Carinarupsls 6 species. Holupea. llspecles. Raphlstonilna .. 4 specie*. Subulltes 8 specie*. Lophosplra. 38 species. Kuslsplra 10 species. Of the 242 species contained in the above 24 large genera, 125 species and all the genera are represented in Minnesota. 45 species are contained in 22 smaller genera; of these 24 species and 17 genera are represented in Minnesota. Cephalojxxti. 49 species, all occurring in Minnesota. 15 of these have been found in New York or Canada. 38 species are contained in 5 large genera, and 11 in 8 smaller genera, making 13 genera in all. The large genera, containing 4 or more species, are: Cameroceras 4 species. Cjrrtoceras llspecles. Trlptoceras 5 species. Ortboceras 12 species. Oococeras. 0 species. Ostracodt. 67 species, of which 5 have not been found in Minnesota. Only one of these has been reported from New York and Canada. The 8 large genera, having 4 or more species, are the following: Leperditella 6 species. Prlmltla 8 species. Schmldtella. 6 species. Eurycbllloa 6 specie*. Aparchites 7 species. Dlcranella. 4 species. Prlmltlella 5 species. Uythocyprls 4 species. Of these genera two have not their full complement in Minnesota (Leperdifella, and Hylhocypris, each 3 in Minn.), leaving 42 species in the state contained in 8 genera, and 36 species contained in 6 large genera. The total genera of ostracods are 22. The other 14 genera contain 22 species. Trilobite*. 40 species, of which 8 have not yet been found in Minnesota. Of the 32 species, 17 have been found in New York and 7 have been reported from Canada. There are 20 species of trilobites which are common to Minnesota, New York and Canada. Only two genera contain as many as 4 species, viz.: Isotelus, 4, and Pterygometoput, 4; but one species of the latter is absent from Minnesota. The total number of genera is 24, but three of these have not been found in Minnesota. In the descriptive portions of the volume, excepting the last chapter (Gastropoda), temporary strati graphic designations are generally employed in assigning the fossils to their respective geologic horizons. Thus the limestones of the Stones River group are in THE PALEONTOLOGY OF MINNESOTA. most cases not distinguished, the .species of the Bluff limestone and of the Vanuxemia bed being as a rule referred to the Trenton limestone or, more exactly, to the "lower limestone of the Trenton formation." As we have said in discussing these beds on page xcii, their faunas are not greatly different. Still as the fossils from each are readily recognized in Minnesota by their modes of preservation,— those of the lower bed retain their shells while those of the Vanuxemia bed as a rule are casts merely — we have care- fully separated the species which, so far, appear to be characteristic of each. The greenish shales lying between the Vanuxemia bed and the yellowish or grayish shales of the Clitambonites bed were divided into three unequal parts or thirds, "lower, middle and upper thirds of the Trenton shales," corresponding in a general way with the Stictoporella, Rhinidictya and Phylloporina beds. The Ctenodonta bed is occasionally referred to as the "upper part of the middle third of the Trenton shales," while thePucoid bed is sometimes called the "Orthis pectinella horizon." The " Prasopora insularis horizon " is the same as the Clitambonites bed, and it is this bed that is usually meant when the text refers a fossil to the "Galena shales," though that term frequently also includes more or less of the Fusispira bed. As a rule, however, the shales of the latter bed are distinguished as the " upper part of the Galena shales. " On the other hand, limestone deposits of the Fusispira bed in Fillmore county, the equiva- lents, of which in Goodhue county are referred to as Galena shales, are included with the rest of the Fusispira bed in the term "middle Galena.". In accordance with the sense of the last term, the Galena or Trenton group was divided into three lithologic divisions, the Galena shales, the middle Galena, a portion consisting principally of pure limestone, and the upper Galena or Maclurea bed, a magnesian limestone. The Maclurea bed alone maintains the typical dolomitic character of the Galena, but it diminishes in thickness from south to north, and may not have extended beyond Goodhue county. The lithologic changes in the strata have caused a slight overlapping in the designations of the special horizons. Thus the "Middle Galena," in speaking of localities in Goodhue county, refers to the solid upper part of the Fusispira bed, while it refers to the whole of the bed when Fillmore county localities are mentioned. It is to be remembered that the Galena shale is merely a lithologic phase moving northward from county to county, and that it does not represent accurately any time interval in the Trenton at large. If studied only in the region between Cannon Falls and Berne the upper part of the shales would probably be separated as a distinct bed, as indeed was done by Sardeson who called it " Camarella bed." But as this merges gradually into the rest of the Fusispira bed, both lithologically and faunally, there is very little reason, if any, for the sub-division. Occasionally reference is made in the volume to the Anastrophia bed, and the Upper Clitambonites horizon. These refer to shales in Goodhue county immediately over the Nematopora bed. It is the same horizon as the Platystrophia beds in Fillmore county, as that term is used in the 19th annual report. ;l.l..\ II..N <.K STIIATA. CIX In general, taking the whole area in which th.-se Tronton formations are found in Minnesota, there may be said to be three grand Uthologic features alternating, from below upward, us follows: Limestone, shale, limestone. Hitherto it has been customary to place in the Galena the upper limestone and in the Trenton the lower limestone, leaving the intervening shales in an unascertained relation. It is, however, now clear that the Galena alone is strictly equivalent to the Trenton limestone of New York, while the green shales beneath the Clitambonites bed and the limestone beneath these are to be correlated respectively with tin- Black River and Stones River or Birdseye limestones. The lower limestone, therefore, should no longer be spoken of as the Trenton limestone except in a broad sense, while the name Galena, if retained at all in this connection, should henceforth be used only as expressing a Uthologic phase of the Trenton group and not as a distinct geologic horizon. That the Galena is simply a lithologic phase, the prevalence of which was known to become reduced in passing from Iowa northward into Minnesota, was recognized in some <>f the t-;irli«T reporU of the survey. It fades out gradually, and shales and shaly lime- stone take its place. There seems to be no other horizontal lithologic change than that which can be attributed to varying conditions of the same oceanic expanse dependent on nearness or remoteness from the ancient shore line. The present surface strike of these formations in southern Minnesota is northerly, and in Lower Silurian time, as well as now, that must have been toward the ancient land area of the region. Nothing, therefore, could have been more natural than that the limestone phase should be replaced, at the same horizon, passing northward, by a lithologic phase embracing more and more of shale. The Black River formation is affected in the same way. Shale beds occupy the strati- graphic position of limestones in Iowa and Wisconsin. So far, then, as the nature of the sediments may affect the distribution of the oceanic life of the Lower Silurian in the upper Mississippi valley, deep sea species would be crowded out more and more on approaching the latitude of the falls of St. Anthony. Such vertical oscillations as may have taken place in the bed of the ocean apparently were felt uniformity over the whole region, and they may be supposed to have been the prime cause of the grand vertical changes in the nature of the rock. These two components in the cause of faunal variation in the Lower Silurian rocks must both be admitted to have had their legitimate effects, but they operated differently. While a natural vertical succession of forms would be brought about by the action of one, in any certain locality, by the action of the other a lateral* variation was caused. This lateral variation introduces such irregularity that it is plainly impossible to construct a stratigraphtcal scheme for the whole area, and consequently, it is difficult to assign all of the species uniformly to definite stratigraphic limits. This is true of those species that are easily affected by changed environment, and to a certain extent it is necessarily true of all th<> s|>ecies concerned. Two formations of the Hudson River period are recognized in southern Minnesota, namely, the Utica and Richmond groups. As a rule the two divisions are not distinguished CX THE PALEONTOLOGY OF MINNESOTA. in giving the "formation and locality " of the species found in them, but the fossils are mostly referred simply to the Hudson River formation. Now, whatever stratigraphical terms are employed in our provisional efforts to fix the horizons of the fossils here described, it is to be understood that the position and range assigned to each in the following list is in accordance with our latest and best information. Continued investigations in the field and laboratory have enabled us to correct some errors and given us more definite knowledge concerning the geologic and geographic distribution of the species. We do not, of course, wish to intimate that the list is in any wise permanent or reliable in all parts, yet we are confident that the changes which may be necessitated by future discoveries will not materially affect the conclusions which we have drawn from the facts brought out by the tables. Now and then the vertical range of a species may be extended, but such defections will be more than equalized by the new discoveries that are continually rewarding the efforts of the collector. The geologic position and range of each species found in Minnesota is indicated by the letter x in one or more columns. Species occurring in the upper Mississippi province, but not yet discovered within the limits of the state of Minnesota, are distinguished in the columns by a dagger (f) instead of by the letter x. The number of these might have been largely increased but it was thought sufficient for our purpose to include only those which we may reasonably expect to find in the state. In the column devoted to the Pusispira and Nematopora beds, those species which are restricted to the latter division are indicated by the letter n instead of by the letter x. The letter f in the Phylloporina and Fucoid beds' column distinguishes the few forms that are particularly characteristic of the Fucoid bed. Finally, in the columns showing occurrence of species in other regions, the following abbreviations are used: Cincinnati region, R for Richmond group, L for Lorraine group, U for Utica group, T for Trenton group, B for Black River group, and S for Stones River group; Central Tennessee, T for Trenton group (Nashville group of Safford), B for Black River group (Carter's Creek limestone), S for Stones River group (Glade, Ridley, Pierce and Central limestones of Safford) ; New York and Canada, H for Hudson River group, U for Utica group, T for Trenton group, B and S for Black River and Stones River or Birdseye limestone, and C for Chazy group. In Canada the Black River and Birdseye are not separated, hence, in this column the letter B stands for either one or both. ( iiiWfnsts Owen la fllotui Ulrlch .. . KaufTella palmlpea I V . .. •apongla fubranxMa Ulr 1 1 iii' II* liKC'iiKiM* I'lrlrli iloneftoU'nsls Dlr Hrach *) robblnsl I'lrlch Ca la thin in i''j clavalum Ulrlch Calatliiuin ('• i h<*xatC"nallfi Ulrlch Camarocladia dlchototna U. & K Caiuarorladia frutlcoaa tllrlch Camarucladla ruguu Ulrlch cotupacla Billing* •'Hf rapt us tvpicalis Hall Llcbenarla lypa n. up. . .. Ucbenarla inl'nor, n "HP Sin-pi«lasma prufundum Conrad Streptelasma parasltlcutn, n. sp X X X X X t X ? X z X MrepU'laania breve, n. up St rvpielasma corolculum Hall Siri'[it4>lasQia rustlcutu Hillings Protarea vetusta Hall I'ri.t.ir«M \>'t>i-t:i \;ir ... Tetrad lu 111 nilous var Aulopora (?) trentooeosia, n. sp. BRYOEOA. Vlnella repeas Ulrlch BUNBAlapon proutana Miller Stomatopora fnflata Hall X X X X ? n n n n a X n X Stomatopora turglda Ulrlcb. Iterenlcfa nilnne»olen»l» Ulrlch Dlaatoporlna flabellata I'lrlch Mltoclema I T) mundulum' Ulrlch Khlnldlctya mutabllU 1 Irlch Khlntdtctya muUblll* Tar. major Ulr. . . . Khlnldlctya luutabllls var. seollls, n. Tar. Khlnldlctya paupera Ulrlch X X X t V X X X X X X X X X X T X X X ? 1 r X X Khlnldlctva neffitcta. n. sp Hhm. Klilnkllrtya minima Ulrirh Khlnldlrtva minima Tar. modesta, n. Tar. Ithlniillctva dddts Ulrlch Khlnldlclya tremoDenstfi Ulrlch Khinidlciya nlcholsonl Ulrlch Rhlnidlctya graodls, n. sp Khlnldlctya pedlculat*. n. sp Kurydlctra'niulllpora (? Han sp.). Phrllodlctya f rondo* i Ulrlch Phyllodlctya varla. n. sp. .. . Pachydlctya follata Ulrlch Pachydlctya accidentally Ulrlch. . Pachydlctya flmbrlata I'lrlch Pachydlclya elegans, n. sp. ... .... Pachydlctya punilla Ulrlch Pachydlctjra magolpora Ulrlch cxn THE PALEONTOLOGY OF MINNESOTA. BRYOZOA. - tc - Trenton Period. lll.lM'tl ul •indni.nli Piriixl. Cincinnati region. Tennessee. X h 0 t- k B Z Canada. Stones Elver Group. Black River Group. Trenton Group. 1 Utlca group. Richmond group. te a « h B I Vanuxemiabed. j« "3 o o. 2 _0 £ X y X X X X X X X X X X X X 'd S a K « _o 5 "3 » X X X X ff X X X X X X X X X X X X X X X i a a - a o 1 a - 5 X Cfl 13 V & « If - c S>. 3C A a. X X X X X X X I X X X X « i I "a | 5 X X X X X X X X I X X \ X yi V S •O^ s a ag ga Is Is 7. ~ a o feZ D 11 n n n n n 11 n n X y ? n 1 Maclurea bed. Trigonodictya conciliatrix Ulrlch 160 168 168 171 172 174 175 177 178 178 180 181 182 183 183 184 188 188 191 192 1QO X X X X t t t X X S ?T K i: s * s T L R B s S S S T T T T- T T T \ T Escharopora iinmi hu'is. n. sp Escharopora subrecta Ulrich Escharopora recta ^ Hall ... Escharopora n mil HIM is, n. sp Escharopora (9) limitaris n. sp Phaenopora incipiens, n. sp PbaeDopora wilmingtonensis, n. sp Arthrupora simplex Ulrich Arthropora bi f urcata, n. sp Arthropora reversa, n. sp Stictoporella rigida Ulrich Stictoporella dumosa, n. sp Stictoporella angularls Ulrich Stictoporella " var. intermedia, n. var. Stictoporella frondifera Ulrich Stictoporella cribrosa Ulrich . .... Arthrosty lus conjuoctus Ulrich Arthrostylus obliquus Ulrich Helopora di varicata Ulrich Helopora al ternata Ulrich Helopora mucronata Ulrich Helopora quadrata, n. sp 193 194 195 196 198 200 201 203 204 205 206 206 209 210 211 212 218 219 219 220 221 223 224 225 22' 229 230 230 231 232 234 235 236 23' 23f 239 240 240 242 Helopora elegans, n. sp Helopora harrisi James Helopora sp. uodet Arthrocletna striatum, n sp Arthroclema cornutum Ulrich Arthroclema armatum Ulrich Arthroclema pulchellum Billings Artbroclema sp. undet (1) Nematopora ovalis Ulrich Nematopora granosa Ulrich . . Nematopora delicatula Ulrich Nematopora conferta Ulrich Phylloporina sub'.axa Ulrich Phylloporina reticulata Half Phylloporina halli Ulrich Phy llopori na corticosa Ulrich Monticulipora wetherbyi Ulrich Monticulipora incompta, n. sp Monticulipora grandis Ulrich Monticulipora arborea, n. sp Monticulipora cannonensis, n. sp Atactoporella typicalis var.pra-cipta.n.var Atactoporella insueta, n. sp Atactoporella crassa, n. sp Atactoporella ramosa, n. sp Homotrypella instabllis Ulrich Homotrypella multiporata, n. sp Homotrypella subgracilis, n. sp Homotrypella ovata, D. »p Homotrypella mundula, n. sp Homotrypella gracllia Nicholson Homotrypella rustica, n. sp Homotrypa minnesotensis Ulrich Homotrypa exilis Ulrich Homotrypa separata, n. sp Homotrypa intercalarip, D. sp Homotrypa subramosa Ulrich Homotrypa " var. insignis Ulrich. Homotrypa tuberculata, n. sp Homotrypa similis Foord OOIU:l.I.Ml"N <>K VI'KATA. rxni BBTOKU : Tn-nlon Prrlad. i a 3 a t t t t | , i i 1 y • M II... k up. ii ion Uruup L L. J J 4 1 3 s I A 1 X X X X X X X X X t 1 • i ! 5 - i 1 • s 17 i : I o ;; 1 I I ; rv jia callott, n. up. -•i M M Ml Kl • n • Bl 266 J.-> 259 286 380 III va 284 HI j- M IK :•- 270 271 271 ^71 •J7^ l.T-1 277 J> n n •:-; --- n • M J-. m HI • M :•• m M -•: M w n 301 ". M a a .' : 0 : X X X \ X X X X X X X X X X t X X X X X X X X X X X X X X X X X X X X X T X X y X X X X X X X X X X X II X X II II X X X X n y X X II II V I T T T 1C 1C T T n T 1 T • T T T T T T T T T T T Pnuopora Kiiinilairix Ulrlch Pnuopora c'lntlffua Ulrich. ... Prwoptira rotmidfii I'lrirh. .. Prunpore *»-lw\ m Xirholvni. Pratopora aAlni* l'i>'.ri| Pnuopora oculata Foord : . i r i - i) - 1 > A«pi'l.ipora parasitic* Ulrlch A»i>ii|ii[»ir:i < < k'antula, n. »p • vpa intl.la Ulrirh M. -..•: . pi UMi : !••!. ii -; Meaoln pa Rrldotrypa .ibtlls var. minor, n. vmr. Krid.itrrpa <>xit;ua. n. up. .1 Hlnffularls t'lrlch... Dekayella pri'iiuntia. n *p... I vkayella var. simplex, o. var. . . Dekayfclla var. ti.rv ikr--ra, n. var.. Dekayella var. echlnata, n. var. . Oekayella var. mulllpora, n. var Dekayla treotoneoslH Ulrlcb Callopora angularls n. up Galloper* n rsa Ulrlch. Callopora undulata Ulrlch Callopora inultlubulata I'lrirh Callopora ampla, n. sp Callopora goodl; «p Callopora dumali->. n. -p CalloDora pulchella, n. sp Callopnra pulcbella var. perHlmllls, n. rai Callopora crvnulala. n. sp t Mplnlrypa lltnitaris, n. sp IHplotrypa ncjsloria. n. op Ratostoma fcriili- I'lrirh batoatoma niaitnnpore, n. sp RaUwloma var in in, i Ratosioma huui BatoM'.ma winrh-ni Kir BaUmtoiii.i iiniinMoteose, D. op Ifi-nuiihragina Irnuum I'lrirh hratcua ottaweoM FOOM • hrairnia lenulniun . hM^ma imp.Tfr.-tum I'lrirh Stromat'itrvpa ovatn • rypa maitaa. n. up M»ru>tr>pa iotabulata, n. -|> M«np:i n«-lnntrv|ia ruiiiiiljt^. n -| i.i I'lri.-h irlcb Trcmaiopora (?) var u.var CX1V THE PALEONTOLOGY OF MINNESOTA. BRYOZOA AND BEACHIOPODA. 0> CO • JL, 311 315 316 317 317 319 318 320 321 322 323 325 327 328 329 330 330 331 339 341 342 343 344 344 345 346 349 351 352 348 347 353 354 356 358 360 358 365 366 368 369 370 372 373 374 375 376 379 381 381 382 383 383 385 388 :SKM 389 390 390 393 393 Trenton Period. H\nls.>ii ,i Cine limit Period. d 8 -r o c. g 1 ja "3 c 5 T TULR T U L T U L T T UL 8 HT B T K B l Tennessee. 4J (H O > to • Canada. Stones River Group. Black River Group. Trenton Group. Utica group. Richmond group. 3 CO h Q> | •a S — 'g IB « 3 S > X X X X X X ? £1 S: £ a o t3 *J CO Rhinldlctya bed. Ctenodonta bed. Fucold and Phylloporina beds. Clitambonites bed. Fusispira and Nematopora beds. Maclurea bed. Cunstellaria varia, n. sp. X ?x X X X X X X X i X X X X X X X X X 9 X X X X X X X X X X X X X X X X X X X X X X f X X X X X X ? X ? X X X X X ? X n X n X X X X X X X X X X X X X X X X X X X ? X X X X X t X X X X S s B T T T T T T U T T T T T H T B T T T U T T B T T T U r n Ant T BT T H Stellipora antheloidea Hall Nicholsonella laminata, n sp Nlcholsonella ponderosa (?) Ulrich Leptotrypa hexagonalis Ulrich Leptotrypa claviformls, n. sp Leptotrypa acervulosa, n. sp Spatiopora labeculosa, n. sp Spatiopora iowensis, n . sp Crepipora perampla. n. sp By thotry pa laxata Ulrich Anolotichia impolita Ulrich Ceranaoporella distincta Ulrich Ceramoporella inclusa, n. sp Ceramoporella interporosa Ulrich Diamesopora trentonensis, n. sp Ceramophylla frondosa, n. sp BRACHIOPODA. Li ngula elder! Whitfleld Lingula philomela Billings Lingula rici nlformis Hall Lingula var. galenensis W. & S Lingula modesta Ulrich Lingula clathrata, n. sp Lingula coburgensis ? Billings Lingula iowensis Owen Lingula beltrami, n. sp Lingula n. sp. (? canadensis Billings)... L (Olossina) deflecta W. & S L. (Glossina) hurlbuti N. H. Winchell. . . Lingulasma schucherti Ulrich Li ngulasma galenensis W. & S Dlnobolus (?) parvus Whitfleld Siphonotreta (?) minnesotensls Hall. Leptobolus occidentalis Hall Orbiculoidea lamellosa ? Hall Schizotreta pelopia Billings Schizotreta mlnutula, n. sp Trematis huronensis? Billings Trematis ottawensis Billings Schizocrania fllosa Hall Cran la setigera Hall Crania granulosa N. H. Winchell Crania trentonensis Hall Craniella (?) ulrichi Hall Pholidops trentonensis var. minor, n. var. Clitambonites diversus Shaler Clitambonites " var. altissiruus, n. var. Scenidlum anthonensis Sardeson Parastrophia hemiplicata Hall Parastrophia " var. rotunda, n. var. Parastrophia scofleldi, n. sp Strophomena incurvata Shepard Strophomena neglecta James Strophomena " var. acuta, n. var Strophomena trentonensis, n. sp Strophomena septata, n. sp Strophomena rugosa Blainville Strophomena " var. subtenta Hall. . Strophomena planodorsata W. & S CORRELATION OF STRATA. CXV \- II1"I'"I>.\ \M' i..\MKi.i.ini; AM ii i ATA. i Trvntoa Period. i 1 I ! 1 i 1 i i | tata*. -,.-.- up. III . O rou p. Trenton Group. i i p 1 «i 1 b ^ I * > 1 i • 2 J : i! i 1 ! i , § NMnttopOf* (Md*. I .- 1 Mri>|.liiiii)i-na « 3»4 3M 3» .-: .:.- m 401 403 403 406 407 406 410 411 414 4 Id ii- ia 424 m u: W m 4:11 433 434 ; • 437 440 441 446 M 161 451 r. 161 M m i t-. »<, i-. H »• i«; ;• i- 1 4!'I i •- «•'. !• «•• »••• 1- f- i'- f I X t X t X X X X T X X X X X X X X ? X f X t X X 1 BTULR LR • Til 8 ton 8 B 8 T 8 B T B - 1 TH T 8T n - - T TH TUB T T T T BU>H TH T T T 1 II T T T T BrY T II T B T ch to n B ton BT BT BT T H C'hT BT BT B to n BT B BT ch tu n BT II H BT u n T T T T T •iiKMia trllobala Owen Stropbomena tluctuuM Hill Inn-. inmena billing*!, n. ip St n i 'hotuena Mofleldl W. & S. >T ri'phomena cmaclata W. & S Raflneoqulna mtnnesotensls N. II. Winch. lUtitu««|ulna " var. InquuM Sardeaon. Raflnesquina deltoldea Conrad Kattnneyi N. II \\ O. (Dlnorthls) meedsl W. AS O. (DlnorthU) - Tar. germana W. A S . northlfl) »ub nchotretna alnsl N 11 Wlnchell.. KhTnchntrema Inaequlralvls Castelnau. Khynch..trema " Tar. latlcostata W. & S Rhynchotreina capax Conrad BlvoetaMlta - kattooattoosta i. 1 lop Kbyncbooella (?) neenah Whltflel Cycl<»plra blsulcata Kmnion* LAMBLLIBKANCIIIATA. \ Atiil-.nvch.a t»-;.iMrlata Hall • Ambonjrcbla amjRdallna Hall.. . laniefloM Hall.. . - i | SloajChla •• ..• ;• .1 r rich Ollooychla uodata Kmmons BjMooychla Intermedia M. A W. CXV1 THE PALEONTOLOGY OF MINNESOTA. LAMELLIBRANCHIATA. si I Trenton Period. Hii'ls-.ii «> Cincinnat Period . c 'Si • q j: "5 js 5 Tennessee. M S t* V Canada. Stones River Group. Black River Group. Trenton Group. Utiea f?roup. Richmond group. fc a a tt V s Vanuxemla bed. Stlctoporellu bed. Rhinldlctya bed. Ctenodonta bed. Fucold and Pllvlloporlna beds. Olltarnbonltes bed. Fusispira and Nematopora beds. Maclurea bed. 500 504 506 506 507 508 508 509 609 510 51) 512 515 516 517 518 518 520 521 622 524 524 526 527 527 529 52!) 531 532 536 537 538 538 540 540 540 541 541 542 542 543 544 544 545 546 547 547 547 550 551 552 553 553 553 554 555 556 556 557 559 t X X X X t X X X t t X t t X X t X X X t X X t X X X X 9 9 X X ? X X X X X X X X t X X X 9 X X X t X X X X X X X X X X X X X o X X X X X X t X X X X X t 9 X •> X X X K 11 K T 8 B T S II 11 T T n T T T 1! T H T Modiolopsis chatfleldensis, n. sp Modiolopsis concentrica H. & W Orthodestna subnasuturo M. & W OrthodGsma canal iculatutn, n. sp Modiolodon patulus, van undescribed — Modiolodon (9) gibbus, n. sp Prolobella striatula, n. sp • (=C. subovata Ulrich.) Cyrtodonta afflnis var. fillmorensis, n. var. Cvrtodonta tenells Ulrich . Cyrtodonta grandis Ulrich Cyrtodonta grandis var. germana Ulrich. Cyrtodonta grandis var. luculenta Sard. . Vanuxemia dixonensis var. iosueta, n. var Vanuxemiaumbonata, n. sp Vanuxemia **ut>rotunda, n sp COUi: I.: i\ LAMELl.ll.KANt IIIA 1 \ 1 >- 1 t 9 \ *t.utpiiii>bed. I-pm «|(uodoiefig nmuw Pwiod. [*lte«.»fc«l. 1 H i 1 1 1 • 1 * K ' ! • III Trenton >P d B 1 _ X t X t t i I X X V 9 X X X X X X 1 • d [ i j - 5 ll ll I 1 - >- Vanuxemla ahrupia, o. »p. . . . M I n ••••. H H •-.- •.,,: :.,.- ,.-. m m m '•: :• '.-.-, H .- sn in H ••«' ••• - '• '•'- -•' '" •i •••'.• HI -.,- "••• aoo go ....; Ml ,.,. aoi BM aos .., am aoo .,]., 611 '•.14 liU i.i:. • i. -.17 '.!' '-'- •: •;. •j) •"•' 62j t X 9 t « t X ? t X t X X X X \ t X \ X X X X X X \ t X X X X X X X X X X X X X X X ? y X X t X t X X ? X X X X X X X I ? t K R ?R II 8T R U II K R r i. it 1. K 8 B 8 B T T T n 1 n T B B Yaiiuxi'iii Vaou> •: ln-iil, n. ->|i . . •*, ii. «i> i|fi*a Dlrlch Whit.'ll.i i>l Whit. insular!* Whittli'i'l \ u Whit, k conciM :b Wlilt. !i;l, Ii >(i • x. mi!-. MI Whlltleld .•Il.-!i|i I'inrh • •D . ••ntrlaw II a 11. i n.i-iita II Ui^ta, n var... I HIlboMUtA, D. Sp. CteDodonla run.'ifiiriuls n. up i, Salt.-r Cteaodoota planodursata Ulrlch. . . Ion la 1 im^'a D . Irtch ..tit a medial Is, n. sp I'.nta M'ntidili, n. sp v socialls, n sp.... mda Hall t ralvlni. n. sp. i all»-rtlna, n ~ .... Innta tlli-triala, D. sp ... . i slmulatrlx, n. sp lonta a-: . •••!•. lunla alta II . ( 't'-innl'iiiia rt-«'urTa Ulrlrli ; h >rus cuD«uvlus ririrh - 1! -. I Trnitumi actiniinitiim. n CD . •It-Mina raononeose, n. sn... . . - riri.-h • sma •ubelli|iti<'utn I'lrii'h Khy t Imya Klnuata. n. 8p Cuoeamya truncalula, n. up.. CllllcatllVU 'il.lnll^M 1) -|. Sphennlium parallfluni, n. sp Sph«'nnlium strutum. n. »p SafTurdla ventr.i Saffor : loruUUlrlrh S.i!T..r.|? i in -1. --.i f rii !i CXV111 THE PALEONTOLOGY OF MINNESOTA. GASTROPODA. X X X X ? X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X y X X X X X X ? X X X X X X •> ? X X X 'J X • X X X X X T U B T B T U L R 1! T 11 U B 1! T T T s n (var B T T S B T S BT S s T 8 T S B U L, T 1! T U L B T Blelcionopsis subcarinata, n. sp Archinaceila powers!, D. sp A n'ti i ii;uvll;i depressa, D. sp Archinaceila perovalis Whitfleld Archinaceila deleta Sardeson Archinaceila valida Sardeson Archinaceila semicarinata, n. sp . Archinaceila simulatrix, n. sp Archinacella subrotunda, n. sp... Archinaceila instabilis var. incurva, n.var Archinaceila rotunda, n. sp Pala'aciuu'a humilis, n. sp Scenella superba Billings Scenella magniflca, n. sp Scenella belottensis, n . sp Scenella coropressa, n. sp Scenella affinis, n. sp Scenella obtusa Sardeson Scenella radialis. n sp Stenotheca exserta Sardeson Cyrtolites ornatus var. minor, n. var Cyrtolites retrorsus var. flllmorensis, n. var Cyrtolites carinatus S. A. Miller Cyrtolites disjunctus. n. sp Cyrtolites dilatatus, n. sp Protowarthia rectangularis, n. sp Protowarthia pervoluta, n sp. . . . Protowarthia cancellata Hall Protowarthia concinna, n. sp Tetranota bidorsata Hall Tetranota bidorsata var. minor, n. var. . TetTanota sexcarinata, n. sp Tetranota macra, n. sp Tetranota obsoleta, n. sp Tetranota wisconsinensis Whitfleld Kokenia costalis, n. sp Bucania halli, n. sp Bucania minnesotensis, n. sp Bucania emnionsi, n sp . . ... Bucania elliptica, n. sp Bucania sublata, n. sp Bucania lindsleyi Safford Bucania, sp. undescribed . Salpingostoma buelli Whitfleld Salpingostoma sculptilis, n sp Salpingostoma imbricata, n. sp Conradella flmbriata, n, sp Conradella obliqua, n. sp Conradella dyeri Hall Conradella dyeri, var. cellulosa, n. var. . Oxydiscus subacutut*, n. sp Bellerophon troosti Safford . . . Bellerophon platystoma M. & W Bellerophon similis, n sp Carinaropsls acuta. u. sp Carinaropsis minima, n. sp Carinaropsis phalera Sardeson Pterotheca attenuata Hall I'M \-i niNt-rt tin- lulliiwiii: ions mi pages cxix and cxx of |.;ut !_'<.! viiliiiiu- :t til' tin- I:INM. K I- PI ik I ..I tin- I .'CM/- >xic;il inn! \:it unit Hi Minnc*»t:t \ix. ..himpim parangulatn var. acuminata n. var. mul l.opliimpira acumiinilii, 11 »ji . p. 998. >plio»l>irii (?) major read Hormotoma (?) mnjor Hall. p. 1O1N. -.1 alii ii). 1. 1 iiiM-n I.i,i»|'ira modota. n. »p. Ctenodonta bed. i Iliirniiitoma grm ; II. .mi,. i. .MM xrm-ilm vnr. noodhuciiUK. n. var |i. - >. i, u. .<|..i, 1. 1 IK-.I ,rlocauln* irhlcrti inarrt Cu-locnulu» nex'ectun n. »p., p. lojo. Clitamlmnito •'•'After Ophilrtinn inblaxa incert var. Kcijurn*. n. var.. p. 1O31. Puuipira lied. CXX. \dd M.iiliiiui.i •.iihrntiinda \Vliitticld. p. 1O4.1. Maclurcn bed. Trochonema variani read Trocbonema vagrnmt. n. tp. p. 10-19. Inwrt (Bunema) l>etwern jjrncric and »pecinc name* of Trochonema nalteri and Tro- chonema robl.i . « For Trochonrmn sp. read Tn>chonema (Ennctna) limile n. up., p. 1053. Truchonema liratnm read (iyrnnemn liratum n. sp Trochonema pnlchellum read Gyronema pulchelliim, n. >p. Trochonema nemicarinatum read Oyronema irmicarinatum Sailer. hnema percarinatum Hull read Ovronema duplicatum, n. up., p. 10S5. li.neinn tcxtili> read Striiphostylus textili* n. «p.. p. IO64. llnlnpea prrene i* from the Fniiapira bed. For Holopea lubnndata read Holopen pnludiniformii Hall, p. 1O67. Clitambonitnt bed and in the Trenton of New York. Suliulite* conradi occur* also in the Ill.-uk Kiver group in Canada. \I>A - ! .- • i , . 1 3 5 i 1 1 i a BlMk i: .. • Group. Tr» •up. : D Richmond croup. H 3 S : i * . X X X 1 X X X X X X X X X X X X X X X X i - • 1 - :• i 5 ! i ; I : ii . -f 1 \ s •i >i i.) ... 986 ... .„; .,- X X Tx X X X X X X X t X X X X X X X o X X X X X X X T X X X X X X X X X X X X X X X X X X X X X X X X 'X X X X X X X X X X X X \ X X X - T 1 1 ~ I: H II T 8 T s 1C 1 1 B U T I. T I' 1. U 8T BT B T T L K B T L T BU T T - 8 II 1 T - T T 8 8 BT 8 8T B S B T 1 T a s T TU T T T T T II B T T C II T II T II II Ifltkw 11 T B T B T B lt?T I»TH T II II 1 T Cal. B •> baoonl Whit!! : 1|\ [' ;. - .;. || . . TlUll 11 . ' tii-s sp. utlilcstTL' • 1 CoDularla sp uncl'-scr bed Kaphlst'niia pcrarutum ti - Raphlsimuina rugala, n. ftp Omosplra alexandra Billings phosplra tilrlni'ta Hall •'ira ntilii|iia n sp nradana, n. sp . I'ira h«'llcU>r<~i var. wlsi-^i \ ar 97 M ... i>hosplra (juadrlBulcala, n. sp LophoApira spiruni-ma n sp phueplra s«>rrulala Sailer •-. n 977 m M M '•-: m M 994 Iu i'bosplra perangulala Hall n. w*f< . . / fa . 7.7^ LophoMpIra 'li'vata, n. sp LiiphiKtpIra peracula, n. sp 'splra medlalls, n. sp ; hosplra perforala, n. -| splra owenl, n. sp phosplra pulchella, n. sp . Lophosplra sumnercosis Safford Lophoeplra augusllna Billings ; h<.sp|ra augusllna var. nilnncsolensls, n. var ... Llosplra mlrula (fall (., ittispir i Llosplra vitruvia Billings 99S Liospira progne Billings w 00 003 004 006 008 001 010 on 015 OK 016 017 • •J- •- 030 031 (IT? X Kotomarla dryopc Billings •ia. n. sp .. . BoUituarlrt supraclngulala Billings. ClalhniMpira suhcooTca Ball Clathrnxpira ri.mra. D. sp Clathrosplra convexa, n. sp Plethrwplra semele Hall Us Hall t'ima gracllls var. anguslata Hall. Horinolouagracllls var.iiiultlvnlvls.u.vat !"iua suhangulala, n. op Bormotoma i-nnfi-rta, n. sp. •molotua belllcincta Hall -Owlflcauluii ii-hiiTii. n obleDospIra prlwca ('?) Billings Solenospira pagoda Sailer ^Qpbllellna siitilaxa, n. sp. OpETIetlna angularly n. sp Bcrvllnp'. anus M 3t W ., n. sp toma planulata var. robust*, n. var :. I **J H*T+*t*. / ^J-.i^^'CtL?t tlli^KS - «WAu^,. A.^ ( f ^.. , f-HJt*. C?!?!'^ h*,tt 1+cl ?t cxx THE PALEONTOLOGY OF MINNESOTA. GASTROPODA. 1 Oi Trenton Period. udson or ncinnit Period. Cincinnati region. Tennessee. 1 New York. d •a a a a u B T U H B T T Stones River Group. Black Elver Group. Trenton Group. Utlca group. Richmond group. q t o ; Vanuxemla bed. Stictoporellabed. j 2 1 a 3 X X Ctenodontabed. KucoiO ana I'nyllnporlna beds. Clltambonltes bed. Fusispira ana Nematopora beds. Maolurea bed. Helicotonia umbilicata, D. sp 034 036 037 040 040 041 041 047 048 048 050 051 051 052 053 X X X X X X X X X X 9 X X X X X X X X X X t X X X X t X X X X X t X X X X 0 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X ?8 ? S 8 T? I, « T B T T L T ? T L S S T T s s S B T T S B T H T T T T Eccylioniphalus undulatus Hall Eccvliomphalus subrotundus, n. sp...... Maclurea nitida n sp _.Maclurina cuneata Whitfield /••''^'Maclurina manitobensib Whiteaves J Trochonema umbilicatum Hall Trochonema beachi Whitfleld Trochonema beloitense Whitfleld Of.H 052 056 054 053 1060 1065 1066 1065 1066 1067 1066 1065 lOfifi Trochonema niota Hall Trochonema pulchellum, n. sp •f fPmeironemfil percarinatuiu Hall. / Holopea pyrene Billings. /jUi.'^ lA^jA Holopea similis n sp . ,.../ 1068 1068 106 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 108 Platyc%V^. Fusispira inllata var. veritricosa Hall... F^usispj ra i n termed ia, n sp FiiMspira subfusifdnnis Hall Fu>ispira planulata, n. sp Fusispira vittata Hall . t, Fusispira vittata var. vatidnaKti. var... Pustepira elongata (?) Hall. . . -V Meekospira subconica. n.sp. . . .\. . fi. -• k>' 1 && *-* \ / \r F* / •i/>vu^ /fa&-'.f*,/ft) /• /t, Y> J I *.*.*. ^*^t ;:KI.ATI"\ or 8TBA i \ CKl'HALolttPA AM. OSTHACODA. . • 1 Mrt. Cincinnati ration. B|OM> up 1. . . Group. up. a it I A 5 t 3 ' ] 1 « M 3 1 - •1 i t i ' - i 1 ; | _; ciem M "i-"i>A. Naniio aulctua, D. sp 770 774 777 >• rac 7-; rai 784 m 7- 7-- 7" TM TM ret M ra TM 7 a :• 703 TM 7V 7- 797 7" TM N'H 101 HI -,, m 807 .,,- ^, 810 -: -II ill 834 837 837 840 841 841 • i. • iJ 1 X X X X X ht X X X X X X ?t T X X X X X X X X X t X X X X X X X X X X t t X X X t t X t t t t X X X X X X X X X X X t X X I f V \ • X X X X X X X X X X X X X X n n X X X X t SBTUL 8B II - i: II - U?L 8 8B II 1 - l I 8 - 1 - 11 1 T T 8 - 1 1 T T T T T 1 T T II T II s II T T II T 11 T T 11 T II T T T II B»T -; Canirroccra-H nr:ii» j'.iii • Art moc«ra» Dlf A<'t in -•• \\lnt Ili'M A''t :inK*era* reni"i !»>-pi urn Hall < >rtli<>ceras nlcollctl, n. >| ( )rth«»vra» • uri, n. sp <>rth<>ceras bllini-.iiuiu Hail Orthixvra- --Hi .... Orthocoraa teouUtrlatmn Hall < >rth'x-rr;is t»-liranil. n. ->p Ortlincvra* Junceum D • Orthocerancf. aiiiplicauiiTatum Hall .... ••«ra> planoconvexum Hall Trlptooeru planodonatom Whltfleld. . ••erasowenl, n. sp. '•eras, up. oeras Iambi Wblteares vras ancem Hall . . ••ras occldeotale Hall •ceras apcrimii Whit/eaves. . . • ra-> inuiiici-furiiii- Wliilflelgi • ras HXlKUUtii Kill:: '•sotense, n. sp Oncoceras lycu- Hi. ••ras carver!, n. sp Oncoceraa douRlaMl, n. sp . .. ras pandloD Hall t.'vrt<«-'-ra» t,. |< .- Hall C\ rt.M-.'r.i. '• M.| •« ,-• ,.\ ••ras halllanum il'( irlil^i. Cyrtocenu bllllngsl - :."inrbt| • r.i-. iiilnni>ai» '•ilium Hall CyrtoceraM norwixKll, n. sp. Cyrtowras shumardi Gyruceras dupllcodtatuni Whitt1>-l £ o K Canada. Stones Kiver Group. Black River Group. Trenton Group. O, i be a o •s p Richmond group. "Lower Buff." Vanuxemia bed. •o 1 41 "o E O a o o & Ehinidictya bed. Ctenodontabed. Fucoid and Phylloporinn beds. Clitanlbonites bed. Fusispira and Nematopora beds. Maclurea bed. Scbmidtella subrotucda, D. sp 643 644 644 045 645 645 646 646 646 647 648 648 649 649 651 651 652 652 653 653 654 655 655 606 658 660 661 661 662 663 663 665 665 666 666 668 669 669 671 670 672 673 674 X X X X X 9 X X t t t t X X X X X X X X X t X t t X X •) X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 9 X X X X X X X X n n n n n n n X X X ? X X X X X X X t X X X 8 T U S K T U U S K U S T U S TtO R T tO It TtO H S * S s Til TH T II S T U H T un T r ii C'h to T 15 H It U T U II ch to H T U H cal ch T Aparchites ellipticus, n. sp Aparchites ^rani labiatns Ulrich Aparchites neglectus, n sp Aparchites millepunctatus Ulrich Aparchites flmbriatus Ulrich Aparchites arrectus, n. sp Aparchites chatfieldensis, n. sp Aparchites mimit issimus var. trentonen- sls, D. var Primitiella constricta, n. sp Primitiella limbata, n. sp Primitiella simulans, n. sp Primitiella flllmorensis, n. sp Primitiella unicornis Ulrich Primitia upbami, n sp Primitia mammata, n. sp Primitia santi-pauli, n. sp Primitia micula, n. sp Primitia celata, n. sp Primitia duplicata, n. sp Primitia tumidula, n sp Primitia gibbera, n. sp Halliella Tabiosa, n. sp Beyrichia initialis, n. sp Eurychilina reticulata Ulrich Eurychilina " var. incurva, n. var. Eurychilina subradiata Ulrich Eurychilina ventrosa, n. sp Eurychflina (?) subdBquata, n sp Eurychilina (?) symmetrica, n. sp Dicranella bicornis, n. sp Dicranella spinosa, n. sp Dicranella Cl) simplex, D. sp Jonesella obscura, n. sp Bollia su li:ri | uat a, n sp Bollia unguloldea, n. sp Drepanella bilateralis, n. sp Drepanella macra Ulrich Drepanella bigeneris, n sp Dilobella typa, n. sp Ctenobolbina fulcrata n sp Ctenobolbina crassa Ulrich 675 673 676 677 679 680 682 682 683 684 Ctenobolbina ciliata var. emaciata Ulrich Ceratopsis chambers! Miller Ceratopsis " var. robusta, n. var Tetradella quadrilirata H. & W Tetradella lunatifera Ulrich Moorea angularis, n. sp Moorea pu nctata, n . sp Moorea (?) perplexa, n. sp Macronotclia scofleldi n sp Cytherella (?) subrotunda, n. sp 685 686 686 687 689 689 690 692 692 699 70 70 70 Cy therella (?) rugosa Jones Uytherella •' var. arcta, n. var... Bythocypris cylindrica Hall By thocypris (?) curta, n. sp Bythocypris grant), n. sp Bythocypris (?) robusta, n. sp Krausella ina'qualis, n. sp Krausella arcuata, n. sp TKILOBITA. Calymmene callicephala Green Isotelus gigas Dekay Isotelus maximus Locke Isotelus canal is Conrad ' oltKKl.ATlON OF !» rxxui Ti:ll...|.| i A IIV'I'I.KMATA. ETC. . . a TIMMM p.rk«i. rtmsr , 5 j i I { VcV.".1; Of TrrnloB up. j .- M .n." 1 1 K i 5 I • • • | 1 : e 1 2 . i* susa* Whltfleld m MM m 714 Til Til m m m ::i It M : I in 742 744 744 741 T47 T4t 754 755 1SI 759 \ X X X X X X X X V v t X t t X X X X X X X X X X X X X X X X X X t X X 1 B 1 a • T 8T T VBT 1 T 1 1. i - T BT I T T T T T II 1. ! -II B B T T T 11 to 11 T T T T T T BT - Billion tiatus Walcof Thalcops ovala ' Hilling* • l.i-rti n -| •u» lunalus lit ... -• achatea Billings. . ... •'. . )>i.Tvk"'Mi.-i..|'ii- oaHlMftahM H.I:: '„ . • 11 X y X X X t t t t X t X t t t X X X X X X X X X X X X X X ?x X X X X X •f x X X X X X X n '' KntTliiurii" rartcoatatus Walcott .. . Eocrlnur ;«• n. so. .. Argee wesenbergensU var. paullanus, n. rar Platymetopus cucullus M. Jt W Platymetopus robblnsl I" I rich Platymetopus bicornlw Ulrlch .li:s Hall Harplna nilnnesotensls, n. sp Harplna cf. H. ottawensls Billings. Harplna rutrellum, n. -i » HiKuDKiUfATA and other fossils not deacrlbed In this rolume. l>vn •itius laxus Ulrirh . . . Pala'ocrinus artlculosus Vlrlch . . . Glyptocrlnus. Caralxx-rinu* magnlflcutt ' Carabocrlnua. Carabocrlnus... . Cremacrlou* pundttiiN 1 Irir): . Pleur Pleuf' '•rstltea grano- Olyptocaytllea grandi* Ulrirh (tlyptocystltes, sp. und<>t New starfish New startlnh . . . I'lgsbyl Billings Agelacrlnus Agelacrlnus Llchenocrlnus craterlformls Hall and varieties Llcheoorrinus afflnls Mi t X X X X X X X Cyclocystoldea. Paaceolun globoaus Billings ;>hycus ottawaensl- 1 ites (lldsoluti. Corotilltea, n. sp Oirnulit4->i -p. unil'-t ' >rt<.nla. »j> unili-sH-r of aprcirs found in each >*dt, group* mxi />#rwxb of Hi,- --.Ini-Kin 111 Miinnniild, number of »<\me rewiw/ from brlow and patting up. nn-l riiimrVr n -tlinuet. Trrnloc period. 1 . : i 1. . . r ... , D»l| ,M 8ton«* River croup. Black River iroup TrvatoB (Toup. UUca 1.: 1 | . ft group. V»nu« H.r.-ll. .- 1. 'hyllo «irlii» Iwd. .11 m ••: ES M»,. lurvn bed. / t- o Nu tuber of specie*. . 0 ?|« 0 31 0| 10 10 2 21 I 0 1 Hi 0 10 6|4 3 4 3|2 4 ||l 1 13 • 11 0 1 0|0 1 "•low and pa»n- 1 Ilk' lip Niitnu-r of specie* restr to beds h I • c Niiintit-r of species 31 ?|9 • 12 0|3 0 10 0|1 1 1 1 1 1 0 2 no 1 !«elow and paSS- iMK' up NumlxT <>f specie* restricted to groups f i a e • •r nf s|»vi«". 0 ?ie 0 11 4| 10 0 10 10| 4 3 -' 4|6 18 4 3(3 1 15 3|0 1^ 8 III 5 9 210 7 0 0|0 0 • Received from below and pass- ing ti|> Nu in tier of species rest; to bed* gj c . 19 ?|4 15 39 4)3 32 16 2)0 13 4 1 |0 3 4 0|0 4 Received from below and pass- ing up Number of species restricted to KfOUDB. . 1 3^ Nu in tier of species. 12 1 | 10 2 13 9|9 1 7 7|3 0 1 6|4 0 2 2|2 0 2 2|2 0 10 • |t 4 17 7|3 8 0 0|0 0 Received from below and pass Mltf up Number of species restrict** to beds. . ... ^ E • Number of species 1« ?|0 10 1 5|4 0 21 6|3 13 :t 3|2 0 '. 2|0 3 Rec«lvl* 11 12 210 10 0 0|0 0 0 0|0 0 K- • • : '•• :i; '- ••» i'. ! j .1 — iiilf up Number of species rest t<> groups IPi lnl» for • . ,:.. "iit^r^f tyinlii H MM 15 177 •11 | H 70 90 :-> ^- • 64 40 111 ;:• : 66 133 1 222 1 20 tomiHiajc 48 1 128 1 8 K«c'd from below and pvwtnf up • spwrlw racuiotad to bed* .. Number ^f ipnln 240 ?,04ffi J- 72158 !- • 306 *2»714 101 13 j, g 07 Rm'd from below and puMtnc op. No. of cpeclw raxrlcMd to group*. " Number of tglnlll OM ?! 18 fH 113 H Itoc'd from belov and panliu up. No. uf *ped«* mlihilXl to period*. CXXV1 THE PALEONTOLOGY OF MINNESOTA. Comparison of Lower Silurian faunas in Minnesota with those of equivalent formations in Canada, New York, Cincinnati region and central Tennessee, showing the number and position of the species that are common to Minnesota and one or more of the foreign regions named. Toial number ofl species. Occurring else- I where. Cincinnati region. Central Tennessee. New York. Canada. Percent of occur- rences in foreign rofks regarded as equivalent. 8t Bl. Tr. D.R. St. Bl. O.I. O. B. Bl. Tr. I.H B.B. Tr. I.H Co?lenterata. I. Stones River group 8 11 9 8 2 6 5 6 2 1 2 4 1 2 2 1 2 1 6 2 2 2 2 2 1 1 1 2 2 2 1 2 4 2 Q 1 100 84 100 100 II. Black River group III. Trenton group IV. Hudson River period Echlnoder- inatll. I. Stones River group 6 13 12 6 2 2 6 1 2 2 4 2 1 1 4 100 II. Black River group Ill Trenton group IV. Hudson River period Bryozoa. I Stones River group 44 91 65 12 11 16 25 4 6 1 3 12 14 2 2 4 3 3 1 1 5 5 1 5 9 1 5 14 73 100 100 11. Black River group Ill Trenton group IV. Hudson River period Brachlopoda. 22 28 43 34 14 19 24 18 6 4 3 5 8 5 2 4 10 13 5 1 5 6 12 8 6 2 1 2 1 2 8 7 3 1 4 6 4 2 1 1 1 5 12 17 5 1 3 5 5 7 15 9 3 5 14 20 8 1 4 5 11 S3 75 95 83 II. Black River group III. Trenton group IV. Hudson River period Lamulll- branchlata. 32 47 46 20 7 7 8 13 1 1 1 6 1 1 4 13 4 1 1 2 1 1 1 4 4 2 1 1 4 100 100 100 100 II. Black River group IV. Hudson River period Cephalopoda. 31 12 16 2 16 7 10 2 10 3 6 8 4 4 2 1 2 1 2 2 5 1 2 1 1 1 2 2 2 1 0 1 2 0 5 4 4 0 0 4 2 2 4 5 6 0 0 0 76 57 70 100 II. Black River group III. Trenton group IV. Hudson Kl ver period Gastropoda. I. Stones River group 67 50 77 17 32 24 34 9 16 6 3 1 6 9 7 2 6 12 25 4 4 7 5 6 16 6 7 6 2 4 2 2 10 1 •3 1 1 1 7 4 10 2 1 2 1 3 11 6 7 6 6 8 3 2 3 2 3 75 58 82 ti7 II. Black River group III. Trenton group . IV. Hudson Ri ver period Ostracoda. I. Stones River group 19 39 15 8 5 2 3 3 4 1 1 2 2 3 3 1 1 1 1 1 100 100 II. Black River group III. Trenton group IV. Hudson River period Trlloblta. I. Stones River group 16 5 21 6 4 13 4 5 3 1 1 1 2 5 4 1 1 3 4 6 2 4 1 1 1 1 1 1 4 3 3 3 2 2 1 4 4 7 4 3 4 5 2 2 2 3 2 10 4 1 1 5 4 100 75 85 100 II. Black River group. III. Trenton group IV, Hudson River period Total. I. Stones River group 246 290 305 113 96 86 123 59 Found elsewhere in 83 55 87 88 80 47 107 53 II. Black River group III. Trenton group IV. Hudson River period KKI.ATK'N OF STRATA. OXXVII Tn),l,- nli» inn./ number of gpecirt restricted to each of the Lower Silurian groups in the •T Mia*i*aii>i'i region, number of tame occurring in one or more of the four <>Vu-r x, and Ihf formniinna in irhn-h Ihry are foitml. Kou t.Jr her • in fnu mle I--, rl,,-r r In H i! : i 1 ; i .- 1 i \ j! 1 I M -. z j 1 D Richmond. 1 k'roup... Hlirk Ki\i-r gmup... Xrrtit<*n group •• 4 1 g 0 3 •» .; •' I Stone* River group... Black River group — TreDloD group 4V • t,n 18 • -, IB 1 2 e i 1 J 10 ;i gmup . . •> | -• .- 1 ' tic* group 4 ? n I ii)i>nd group «... i] 4 4 1 A | 4 Stones Rlvt»r group Black River group Trenton ^r -. 11 10 0 0 4 4 I Stone* River group Black River group — Trenton group 22 « 9 9 1 a 0 2 1 1 ;, I'tlca group n n - I 'tlca group o 0 •-- e : Richmond group 1 n - , Stone* Blver group. Black River group — 24 6ft 45 11 e n 2 1 .'{ is 1 Stones River group — Black Itivrr group — 16 12 11 7 1 n 7 1 1 | ' 1 I 1 o ^ | i 1 'ituood group 10 I A - Uii'hinund group 4 ? 2 * - Stoom Rivergroup... . V»T tproup.... Trent on group 10 11 "4 e 5 1(1 5 4 1 1 10 1 1 Stones River group. . . Black Rl ver group — Trenton group 10 0 13 6 0 7 6 1 A 1 7 | 1 2 0 '(I s 15 9 1 g Richmond group 0 rmirln»t» Stooes River group.. . . Black Hiv. r ^rr«up.... 25 38 II a 6 U 3 6 11 - i *. MM River group . . Black River grouj iilon group IM III m 00 31 76 • 4 6 21 2 3 8 72 1 1 2 \ *tic* group | •; fl i •a group. .... 11 1 10 j Richmond group 14 10 10 - Richmond group — 87 33 1 .J CXXV111 THE PALEONTOLOGY OF MINNESOTA. Dates of publication. Some of the chapters in Part II were published in advance, at the following dates, in a small edition of 100 copies, viz. : The Lower Silurian Lamellibranchiata, June 16, 1894. The Lower Silurian Ostracoda, July 24, 1894. The Lower Silurian Trilobites, September 27, 1894. The other chapters in Part II have the date of publication of the volume, though still circulated separately in the same manner, February 15, 1897. ACKNOWLEDGMENTS. The authors of the chapters in Part II desire to thank the following persons for assist- ance: Dr. C. E. Beecher, for the use of specimens belonging to the Peabody Museum, Yale University; Dr. C. H. Bobbins, of Wykoff, and Mr. R. H. Hasse, of Granger, Minn.; Prof. Alpheus Hyatt, Boston, Mass.; Mr. J. P. Whiteaves, Ottawa, Canada, for the oppor tunity to examine type specimens belonging to the Geological Survey of Canada; Prof. J. M. Safford, Nashville, Tenn., for the use of many specimens from Tennessee, and Prof. R. P. Whitfield, of the American Museum of Natural History, New York, for similar favors. ERRATA. FOR PART II, PAGES 475 TO 1081. r P. 490. Fourteenth line from top, after which insert I. P. 504. Fifteenth line from bottom, add M. modioliformis M. and W. P. 536. Eighth line from bottom, for "8UBOVATA, n. sp." read HURONENSIS Billings. (A V recent comparison of our specimens with the original types of Billings' species has shown that they belong to the same species.) P. 637. Omit the paragraph which occupies the eighteenth to the twenty-second lines from the top. P. 681. Eighth line from bottom, add recurva Ulrich, similis Ulrich and ? hamburgensis Walcott. P. 632. Ninth line from top, before Tetradella insert Cerahipsis Ulrich. P. 657. Ninth line from bottom, for " Ceratella" read Cemtopsis. r P. 659. Fifth line from top, for " Ceratella chambersi " read Ceratopsis chambersi. Explanation of plate XXXIX, thirteenth line from the top, for " CTENODONTA GiBBERA"read CYRTODONTA GIBBKRA Explanation of plate XXXIX, thirtieth line from the bottom, for "CYRTODONTA SUBOVATA, n. sp.," read CYKTODONTA HURONENSIS Killings. ADDITIONAL ERRATA are to be found as follows: for the chapter on Lamellibranchiata on page (p $28; or the chapter on Cephalopoda on page 812; for the chapter on Gastropoda on page 1081. WILBUR H. SCOFIKLD. Thoro remains one further duty to discharge. It is a duty which is fraught with sadness, but which is performed with cheerfulness. Wilbur H. Scofleld, one of our collaborators, has died during the preparation of this volume. II- residence at Cannon Falls made it a point of rendezvous for parties in the service of the survey going to and coming from the southern portion of the state. Added to this convenience his interest in geology and his collection of fossils from the Lower Silurian brought him into constant intercourse with the members of the survey corps, and they all formed for him a >imn»f personal attachment. His cooperation, which was always gener- ously granted, has added much to the scientific value of this volume. Some feeble testimony to that service is seen in the dedication of several species to his name. He was a native of Livingstone county. New York, born October 15. 1840, and removed to Minnesota in 1855, settling at Cannon Falls, a frontier hamlet As the village and the country developed, he came to be recognised as one of the best and one of the foremost ••ns. He served as teacher, postmaster, and president of the village council, and at the time of his death he was president of the Board of Education. He was tendered a nomination to the State Legislature but declined in favor of his brother, Hon. James L. Scofield. He began the collection of fossils and their classification under the sole instigation and guidance of an inquisitive and enterprising mind, and, without association with scientists, necessitated by physical disability, he acquired great proficiency and manifested unwonted skill in the determination of species. His life and his service to geology illus- trate the opportunities which lie in the pathway of the citizen who thoughtfully observes nature and who enters upon a systematic inquiry into the phenomena that surround him. i,Knl. NATURAL HISTORY SURVKV (>K MINNK.snl \. PALEONTOLOGY. • II AITKK \ I. ^ __^__ ^^___^^«A Till-: LOWER SILURIAN i.AMKi.u r.u.\\M IIATA « >l- MI\M->« >TA \ number <>f name- fur this class of molln-k-. commonly known us niu- have. fniiii time to time. been proposed. Init none of them, save Hlainville's Lrnn' hintti. which, on the whole, is an appropriate designation, has enjoyed more than merely temporary popularity. Of the other names, that, proposed by (ioldfn— in 1" done presents fair claims to recognition. -ince it> adoption would produce that most desirable element uniformity, in the terminology of the varion- Ml compri-ed in the suhkinplom Mnllnsra. Hlainville's name, however, has six year and is so well established in literature that it is doubtful if the con- fusion which would result fr a change of names would be -utliciently compensated for by the superior advantages of Goldfuss* term. The Limellibranchiata agree with the Brachioixxla in having Itivalved shell-. Init .litter in having them, as a rule, e«|iial and inequilateral instead of ine<|iii\alved and equilateral: they are, furthermore, placed on the sides of the animal (for which reason we distinguish them as right and />v/). instead of above (dorsal) and below tral). From t he Gastropoda and Cephalopoda they are distinguished by wanting a distinct head, in having bivahed -hells, a bilohed mantle and lamelliform gills developed in pair-. icnilly the animal illy developed, of oval, rounded or ti versely elongate form, laterally compressed and enclosed in the two fleshy, often more or less united. lol>es of the mantle. Within the latter, which are attached to and secrete the calcareou- or perlaceous valves, we have first the lamelliform gills. and between these the wmou- internal : a> the heart, intestines and organs Of generation, and the month and anal opening, and usually also a protru-ible muscular foot Numerous moditicat ions of the mantle lobe- , - uesthey are separate, at other times their mai . Aether so as to enclose the animal as in a sack. In th> COM an opening is toft in front for the 476 THE PALEONTOLOGY OF MINNESOTA. ILaiuellibranohiatu. of the foot, and another in the back serving for both the inhalation of water and the expulsion of the excrements. The posterior opening may be further modified so as to form two more or less distinct tubes or siphons, and these may be retractible or of such size and consistency that they project permanently through the gaping posterior margin of the shell. In most instances the siphons afe capable of being completely or partially retracted, and the line of attachment of the muscles of the mantle producing this retraction is bent inward more or less decidedly. When such an inbending of the pallial line (as the attachment of the mantle to the inner surface of the shell is called) is found in fossil shells the inference is regarded as conclusive that the animal possessed retractile siphons. When, on the other hand, the pallial line is simple (i. e., without a sinus) we are obliged to conclude that the siphons were either very small or wanting entirely. The foot — a perfectly retractile organ, presumably of locomotion — lies in the anterior part of the shell between the gills and mantle lobes. Its form is various, but commonly compressed, hatchet or club-shaped, and the muscles which produce and regulate its action are attached usually above or behind the anterior adductor. Not infrequently chitinous threads spring from the lower side of the foot. When these are developed in sufficient number to form a bundle or byssus, the shells may thereby attach themselves to foreign bodies, and in such cases the anterior margins of the valves do not close tightly, but leave what is known as the byssal opening. Among paleozoic representatives of this class the Ambonychiida? afford the best instances of shells with a byssal opening. Of all the organs of the animal none are of greater importance to the paleon- tologist than the strong muscles (adductors) which serve to close the valves. There may be only one, the posterior, as in the recent oyster, or of the two the anterior one may be disproportionately small. In the majority of cases, however, the two muscles are approximately of equal size. Other and much smaller muscular scars may be noticed, especially in the umbonal cavity, which were produced by muscles which partially supported the movements of the gills and palpi and, as, already stated, of the foot. The shell in which the interest of the paleontologist is chiefly centered consists largely of two layers, the outer, secreted by the thickened margin of the mantle, being composed of vertically arranged prismatic cells filled with calcite, the inner of structureless thin parallel leaves. Generally a delicate chitinous epidermis is spread over the cellulose layer. Growth of the valves begins at the apex or beak, a more or less prominent point situated almost invariably somewhere along the anterior half of the hinge margin. Further increase takes place principally at the periphery, producing, when the edges of the mantle are entire, a simple, more or less regularly T>ml»okj«y I ItUAi H10I-ODA 177 conoontrio, xtn.itmii (growth lines) of the -urface. Mat when the mantle edges are undulating or dentate the concontric L'niwtli lines are crossed by radiating strisc or plication*. Tin- various parts of the sliell are conveniently brought out and illustrated in tlio following section on tonninology. TKRMINOLOOY. The designation of the various parts of the outline depends upon the position in which the shell is placed. I shall adopt, because it is certainly the mo-t convenient if not always the most natural position, the one in which the beaks are placed uppermost and the hinge line nearly or quite horizontal. The part in front of the beaks, toward which they are usually inclined, is therefore considered as the anterior end, while that behind them, often much the largest and widest, is the posterior. The upper edge is known as the lin-il or w <,f liyttonyrhi.i radiata ( Aml|.-nitu'. This specimen is from Ciin-inn.it I, Ohio, and I* pi«ullar In having thr right valv. side of tlKiir.-) prcserTed as a cart of th.- .-xt.Ti.ir and th.- l.-ft vaUe as a cast «.f n,. Is shown the pallial line (at p) running along the an: ,t iirnl. r th.- I- t's THE PALEONTOLOGY OF MINNESOTA. LTennkflogy. margins. This line may be parallel with the hinge, but more commonly diverges more or less strongly posteriorly. The hight is given in one or two measurements; the former, when the shell is approximately equilateral (as in many species of Tellinomya) or elliptical in form (Clidophorus) with the greatest hight subcentral or beneath the beaks; the latter, when the shell is elongate or has one end much wider than the other (Orthodesma and Modiolopsis). In such cases two lines are drawn at right angles with the hinge line, one from the beaks to the ventral margin, the interval between the two points being the anterior hight, the other across the posterior end, from the posterior extremity of the hinge, giving the posterior hight. By thickness is understood the shortest distance between the points of greatest convexity of the valves. Area or Escutcheon: A variously shaped, usually elongate, inflection of the dorsal edge, generally longitudinally lineate, and serving as a receptacle for the ligament. When the area is restricted to posterior to the beaks, as in Cuneamya, it is, strictly speaking, to be called an escutcheon. Lunule: A similar, but shorter and commonly heart-shaped inflection or distin- guishable area in front of or beneath the beaks. Cuneamya offers good examples. Gaping and closed shells: The valves fit either closely all around or they may f;iil to do so and gape at one or both ends, and sometimes ventrally. Byssal opening: A small, distinctly modified portion of the anterior margin, through which the byssus protruded. Among the paleozoic types the Ambonychiidd' furnish the best examples. lienk: A more or less prominent point on each valve, usually bending forward and overhanging, in a variable degree, the dorsal edge. It marks the point at which growth began, and generally is situated anterior to the center of the valves. Many species of Tellinomya, Nucula and Clinopistha afford exceptions to the last rule. Umbones: The use of this term, which is generally applied in a sense synonymous with beaks, is here restricted to the gibbous rostral portion of valves in which the beaks are incurved over the hinge line and invisible in a side view. Umbonal ridge: A more or less strongly rounded or angular ridge-like prominence, extending from the beaks or umbones toward the posterior extremity of the shell. Example, WhitMa. Cardinal or dorsal slope: Generally applies to the flattened or concave declivity from the umbonal ridge to the dorsal edge posterior to the beaks. When the declivity on the anterior side is sufficient to be noted it is designated as the anterior cardinal slope. !>\ .inff mil rrntrul slopt* are 8elf-eX|'lanatoi \ tenuv nuil liijumrnt: An elastic, horm band, of variable length, serving to hold the valves in (• i. .HI. -II. .iifi -ihuiN'd ir \ .m.tUy over the dorsal edges close behind "i under tlu> beaks. Hut rarely preserved in fossil she I ii/iimm- This is generally of cartilaginou- c.inM^tency. ami ..ft. -n I. ut a modification or extension of the external ligament. In the latter • ease it lies along the i inner bonier of the hinge, where its presence ma\ be indicated by linear thickened supports which, in casts of the interior. ma\ MMBflttlDM be OOnfbVIKlad with mi|>re»ion> of lateral teeth. (H'AifWA/). \ true nit. TIKI! cartilage. n>-ii;illy occupying a small pit beneath the benk- '•>'•. Ill .iii.l \ III. i- found in .Yn/-i//.. .mil many other types of the secondary ami more recent rocks, but is rather rare among paleozoic species. fig. in. Wtatrati*a Hingt Tgpet, Miuclet and Pallia! Imprtniont. 1 an.l II. iiitr of a nk'hi vml\v of Lyrvdeima major I'lnch. of thr natural nlze, and th«- ]»rtiiiii "f the valve x 2: upper beds of tho Cincinnati ({"'"P "f Ohio. HI. hinge of a upecle* of A'uriiiaiwi, nhowinK Internal canilatte pit at r. I \ . t, . rlorof a left valve of Vatmxemia kay*ia*a Safford, sp.. fr»in th<- upp<-r Trenton liiii.~.!nn.- ,,• inllnal t.i-ili: /. r. p>Mterif>r lateral teeth: a. a.. anUrlcir adductor, and /• -vs|nn-. ;,., palllal lln> j+ a left vahv of an unnamed variety M Bfmonfckia radiata Rail, »p. hN^p«MBtaMWrfatelfOkrudotJ Ull. 1847.) f nun th.- lower bed* of the CloeionaU grot th.- |«.«t«Tii>r ;i(|.|ii.-t-.r impreMlon^p. a.) and the pallia! line an- nMwMr a., posterior addii. li m.. two palm of pedal mu- VII. ini.Ti'.r of a shell with a »trongly sinuate palliaJ line (*), and an internal ligament pit Ltitrnria eUiptica Botay. Pliocene, Bhodus (one-half nat ta outline of i ! —I In with Fig. 34. land II VIII. iHi.l.-t.-nnlned spooler •'' I fnpipn This term .ii'|.iie- to the teeth in general, but more especially w ben these are nmner. -n- U |iial. a; in ^v&f i y -ili.-a. S;ich specimens are rare in the Northwest, but common in the ><>lii| limestones of the Trenton in Tennessee and Kentucky, and in the Hlack Kiver limestone of Canada. Beautiful specimens of this kind are to be found weathered out. or I. lock- of the limestone may be treated with dilute acid with the same result. The first essential in the study of fossil Lamellibranchiata is to determine \\hether or not the material, as it lies before us, has retained its original form. • rtion through pressure in the rock matrix is a most fruitful source of error a ii. I one that even the greatest experience cannot entirely negative. It is evident that the -ofter and, consequently, the more yielding the character of the matrix, the greater the degree of the distortion. It is least in limestones and dolomites ami greatest in shales and slates. The direction of the distortion depends upon the position occupied by the shell with respect to the bed planes of the enclosing rock. Fig. 37. Ilt,utr.,ti»a distortion of *h«lU through premurr • side of a ftpeclrnen of ModMoptta modiolari* Conrad, th«- hutht of which has been reduced, ai shown In mitliti-. to lew than half what It wan originally. 6. a «bell of the aame gpecics greatly comprmatd teogthwls. -h<-ll <>f an undeacribed •pecle* of OKMcmya. from <>lii<>. lilustratlng the effect of prcj*urc on HhelU .m-upjrfnK an otll'iue po- in thenhaleu. The line *-b indicates the plane of the (traUaod tea l»<>tt"iii. (See OK. 38.) The exceedingly .liverse results of the pressure, especially in specimens from shale, are most puzzling to the beginner. If a shell happened to stan-l ui«on eml. its lei -a i 482 THE PALEONTOLOGY OF MINNESOTA. [Preservation and methods of study. will be greatly reduced; if upon its base, the bight; if upon its side, the thickness. When these positions were in no wise oblique, the beginner may fail entirely to notice the distortion, which, when their position in the strata is oblique to the plane of deposit, will be more or less clearly obvious to him because of the unsymmetrical forms of the two valves. A careful examination, however, will reveal, at any rate oil specimens that have not been much weathered, certain fine parallel lines on the sides of the crushed shell. These lines are coincident with and probably produced by the deposit laminye of the matrix, and an experienced student may, with their aid, at once determine the direction and perhaps the amount of the reduction of the par- ticular dimension affected. It is to be remembered that the pressure under which the fossils suffer acts, except in comparatively rare instances, in a vertical direction only. Complete shells are generally compressed more or less obliquely, for the simple reason that after the death of the animal the natural position of the shell, with respect to the plane of the sea bottom, must be" approximately as shown in fig. 37, c. For the same natural cause, the disunited valves are better calculated to preserve the original outline, because they are most likely to lie upon their inner edges, the latter being, therefore, at right angles to the direction of the pressure; in which case, under ordinary circumstances, the only dimension that can be altered is the thickness, this being reduced according to the amount of compression sustained by the surrounding rock. Fig. .'«. Illustrating how to obtain a restoration of an obliquely compressed shell. The inner mil line represents the specimen as it is now {see Ug. 3C-c), the miter one a restoration of its original form. S I!. plane of sea bottom; d.-p., direction of compressing force. In making the restoration shown in fig. 38, only the two regions or points a and b can be assumed as having retained their positions on the original boundary, because there alone the outline of the shell coincides with the direction of the com- pressing force. The only effect the latter could have had upon them was to increase their convexity and to press them down slightly beneath their original positions. On all other points, however, the effect was a reduction in the convexity of the "-r-r- -, •n.lmlfcnfrufguilj I IAM"' Ilinv !-, outline and .«,!,-, Mti,-ntl\ of the size of the specimen. The rostral region of the right valve was greatly reduced and flatten* -I. tint of the left not so much reduced ami nia.lt> more strongly convex at .». In the lower half of the shell the result of distortion was reversed in the two valves. In the restoration, assuming the two vahes to have been equal, we draw a curve through the point a that is intermedi.it. in convexity between tin- flattened curve of the rostral half of the right valve and tli.- -.happened one of the left. An equivalent curve is then drawn for the right valve ami then continued to and beyond the point k We now have the original outline of one of the valves as it would appear in an end view. The outline of the other \.tl\o being equally curved, only in an opposite direction, is then easily finished. Has MIL' s.,tisiied ourselves as to the original shape of the shell, it is first desirable to determine whether the valves are equal, as in Modiolopsi* and Wlntrlln, or unequal, ;i> in rttrinni ami Arislerclla. Next we note the relation of the various part* of the outline to each other, the relative width of the two ends and other features bearing upon the determination of the contour. Now the position, altitude and degree of fulness of the l-eaks and umbones is taken into account. The former may be terminal -ituated at the anterior extremity of the hinge line and projecting as far forward as the margin beneath them), as in Ambonychia; or they may be nearly central in position, as in some species of Ctenodonta. Then the umbones may be strongly gibbous and the beaks curve over the hinge line (Cuneamya, \Vhittlla), or they may be U>s> full ami comparatively erect (Clionychia), or depressed, or scarcely distinguish- al.le (< >/• !•»,,,!' It't and Clidophorus). Decided deviations in the position ami altitude of the beaks are generally of generic value, but lesser modi Heat ions are likely to prove of merely specific importance. The character of the surface markings will prol .ably have been taken into account at once. In the next order, and here we usually credit them with generic and greater value, the student should observe the presence or alwence of a .byssal opening, of the lii'uile ami escutcheon, and the character of the area. He should note also whether the edges of the valves fit tightly or gape at one or both ends or ventrally. His next step is to observe the position, distinctness and relative size of the various muscular impressions, the adductors particularly. Nor is he to forget to trace out the pallial line. Next he may find internal sockets, plates or ridges, that supported internal ligaments, or to which muscles were attached. Finally, he will observe the method of Inurement. The hinge may be edentulous, in which case an external ligament (perhaps internal also) may usually be assumed if not found (see fig. 85, IV). In Modiolopsis there may be a slight thickening or rmlimentary cardinal tooth in each 484 THE PALEONTOLOGY OF MINNESOTA. [.Classification valve beneath the beaks, in Matheria there are two in the left and one in the right, in Cypric,ardites three or more, and these are added to by the development of lateral teeth (fig. 36, IV); some types may have radiating teeth (fig. 36, 1 and II); in others the whole hinge margin will be divided transversely into numerous small teeth, while still others may present a combination of short transverse and long lateral teeth. On the whole, after giving due consideration to other pecularities, modifications in the structure of the hinge are to be ranked as of the highest importance. CLASSIFICATION. The class Lamellibrachiata, or Pelecypoda, is variously divided by authorities. It is neither necessary nor desirable that the numerous systems should be considered here, since it is my impression, and here I merely follow the opinions of some of our latest and highest authorities, that they are all more or less misleading and inade- quate. The fact is, we have not yet arrived at that stage in knowledge where a really natural classification is possible. Too little of the paleozoic representatives of the class is known well, and until more is learned of the evolution of the recent types from their fossil ancestors no attempt is likely to prove more than provisional. What we want now are facts and when sufficient of them have accumulated I doubt not the desired natural scheme of classification will evolve itself. Still, since we have systems, they may as well be used till something better is furnished. Of course, only paleozoic types are here considered, and in viewing these alone, I cannot say that I am satisfied with the following arrangement. In drawing it up I have paid due attention to the arrangements proposed by Tryon, Stoliczka, Zittel, S. A. Miller and others, and sought to avoid what has seemed objectionable in each. At best the result is premature, and in submitting it in the hope that it may prove a little nearer the truth than their schemes, I beg that it may be considered with lenity. Mtehlau-l ,-,", CLASSIFICATION OF PALEOZOIC I. \\li:u. 11:1; \v HIM \ Snbklngdom M< >LI .1 SCA. o-LAMKI.UBRAM-lMATA. ,,„„*,„,, . W«-lw.rt. Mantle lobe* separaU-, siphon* wanting Palllal Ho.- without »lnu- Suborder MONOMYAHIA. A tingle adductor UIUM-I.-, tra- iim.-ri.ir one wanting'. Family PECTENID^K. Lamarck. KIIA : Avieulopteten, McCoy; Cnmipecte*, Hall; Kuchondria, Meek; Lfriopfettn, Hall; Wlnchell; PteHnopeeten, Hall; Strtblopttria, McCoy. Suborder HKTKHOM YARIA. AnU-rior adductor muscle »ery small, the posterior one large. Family AVICULIDvK OKNKUA: Aetinoi>teri,i, Hall; BakevtlHa, Kin*; Krte*ode**a, Hall; Olfptad«tma, Hall; Ltopforia, Hall: Leptode»ma, Hall; Limoj,trra, Hall; JToMptero, Meek and Wortht-D: Jfonofb, Hr»,on: ? Palatopinna, Hall; PofUonomya, Bronn; PMndotnoiioNf, lU-yrlch; I'trHnea. Ooldfumir , Hall); Ptrronitella, Hlllinifs; /'fcrroTufcj, McOoy; f PlfeMopUria, Hall. Family PINNID/K. Gray. GKNKKA: Aviculopinna, Meek; Pinna, Llnne. Family AMBONYCHIID*:, Miller. GRNKRA: AUonyehiu, Hri.-h: Ambongchia, Hall ( rtttrirtrd ) : Amphito-lia, Hall; Anomalodonta. Mll!i-r: Anopirra, Ulrlch ; liguonyrhia. Ulrlch: Bymopttria, Hall; Clionjffkia, Drlch: H*tuapltim, — ^L, : Ui*f ' V WruJonycAw, Ulrlch; JTyfi/arca. Hall: /'nteocordia. Hall: I-lttkomftilta. Hall. -"»<«, Ulrlch. Family CH.«NOCAKDHD.K. Mlll.-r. KIIA: CktPMoeordM, Meek and Worthcn; Mryamlxmia, Hall. Family MYTILIDjE, Lamarck. OKNKKA : '- Anthrneomga, Salt.-r: V .-liifAracoptera, Sailer; Go*tirttia, BarroU; , Bolton) ; Modittla, Hall ; JfeKoto, Lamarck ; JTya/iM, Koalock ; JTyMfap*, llall : Hall. /^ .. Family MODIOLOP8ID h. GKNKBA : Jrf»MMMy«, Ulrlrh: ' MrttereUa, Ulrlch: CWpomya, Ulrlch; f Cymatonrta, Ulrlch; I . Hall: f JKMMaMM, Ulrlch; JBwymy Oonte*V»«. UlHeb; ModWo^M, Hall; M<»liamorphn, Hall; CMAotlMmn, Hall and WhliOeld; T PnUtUa, Ulrlch; f Ptilom*rha. Ulrlch; ^ Pymiomya, Miller. 486 THE PALEONTOLOGY OF MINNESOTA. H'Uissitu'iil ion of palrozok1 Lui Family CYPRICARDINIID^E, (Provisional.) GENUS: Uypncardinia, Hall. Family CYRTODONTID^E, Ulrich. GENERA : ? Cypricanlites, Conrad; Cgrtodonta, Billings; liuiii/i-oiliinln, Ulrich; Mntlicrin, Hillings; Ortonclla, Ulrich. ? Ptycliodesnut, Hall; \'annxcmM, Hillings; Whitella, Ulrich. Suborder HOMOMYARIA. Mantle lobes either separate or united posteriorly. The two adductor muscles of nearly equal strength. Family ARCID^E, Lamarck. GENERA- Carbonarca, Meek and Worthen; Macrodon, Lycett; Nyassa, Hall; ? Spenotus, Hall. Family PARARCID^E, (Provisional). GENEUA : Cardiola, Broderip; Cardiopsis, Meek and Worthen; Dexiobia, Winchell; Olyptocardia, Hall; Lunulicardium, Mi'mstcr; Oroecardium, Herrick; Panenka, Barrande; Paracardium, Hall; Pararca, Hall. Family NUCULUXE, Gray. GENERA : ? Clidophonis, Hall; Ctenodonta, Salter (Tellinornya, Hall ); Goniodon, Herrick; Nucula, Lam- arck; Nuculanu, Link; Nuculites, Conrad; Palceoneilo, Hall; ? Pyrenommis, Hall; Yoldia, Moller. Family LYRODESMID^E, Ulrich. }£ GENERA: Allodesma, Ulrich; Ischyrina, Billings; Lyrodesma, Conrad; Technoptyorus, Miller. Family TRIGONID^E, Lamarck. GENERA : 'i Cytherodon, Hall; ? Schizodus, King. Family UNIONID^E GENERA : ? Amnigenia, Hall; ? Anthracosia, King; Prisconaia, Conrad. Family ELYMELLIDyE, (Provisional). GENERA : Elymella, Hall; Glostites, Hall. Order SIFIIONIDA, Woodward. Mantle lobes more or less united; siphons of varying lengths, either separate or united, arc developed; both adductor muscles well developed. * Family SOLENOMYID^C, Gray. GENKHA : Soltnomna, Lamarck; Clinopistha, Meek and Worthen; Phtlmnia, Hall. Family SANGUINOLITID^, Miller. GENERA: Promacrns, Meek: Sanymnoliles, McCoy. , , ^.. _t- CU^, ..ulcL^mfc,^,., •tour.* IMlMl.M.Kl lOtHiM. Klir, CMMMpi, Ifaafe MM tomy.t. I -Iri.-h: I U.K. Hall. ,«-,imj,,,. Hall ami Whltfl.-M: <;mMmy.i.i. I . '.-/..win McCoy » fi SphMwtlM, Mlll.-r; S»r>, ti.-li. \irriD.i-: AslarMla, Hall. i Mi:<..\l.'MM,.vril> GKNKKA: ilegalodo*. Mfyalom,*, Flail: - /'/^/,, --„,./,, Fwulljr LUCIMD.K. K«hmyo*. IMMTHYIJID.K. Hall. ••us: Prothfrif. M----k. The litcratun- p.-rtaining to Iy>wer Silurian Lamellilmincliiuta is not only meager luit. in great part, unrelialde. The principal cause for the latter is to be found in the want of experience of the authors, who, failing to understand the effect* of pressure to which a large proportion .if the shells have been subjected, have thrown together as identical widely different forms, and oft. -nor. perhaps, distinguished the nens from those which have more nearly retained the normal form. The illustrations also are too often, if not entirely worthless, misleading. Here, more than in any other part of the study, the greatest care and exp.Ti.-nce are required. Kntire and undistorted »pecinn-ns are not by any mean- the rule, so that -li. 488 TEE PALEONTOLOGY OF MINNESOTA. [Classification of paleozoic Larnellibranchiata. restorations of the outline, if the figures are to be of real assistance in the identifi- cation of the species, are generally not only desirable but necessary. An absolutely correct reproduction of an imperfect specimen might be quite sufficient for the trained specialist, but not for the beginner. He requires all we can give him, and' I know from experience that an approximation even to an " absolutely correct repro- duction " is anything but common among illustrations of early Lamellibranchiata. In the accompanying plates nearly all the specimens are represented as entire, but in each instance the fact of the restoration is mentioned or indicated by a fracture-like line. Respecting the drawings, I shall say only that they were in every case made by myself and with as great care and fidelity to nature as I could command. The synonomy of the species is scarcely as complete as I could wish, but as the volume must be kept within certain limits, and because it is in many instances at least doubtful that current identifications of the old species are really the same as the originals, I have restricted the synonomy to the citation of the first work con- taining a description and such of subsequent memoirs as added materially to our knowledge of the objects under consideration. Desiring also to save as much space as possible for general remarks, I have generally avoided what seemed unnecessary repetition by giving full descriptions of the principal species only. In characterizing the others I have depended chiefly upon comparisons, which, if they are complete, I hold to be more useful than bare descriptions. While the greater part of the northwestern material used was collected by myself, and is riow part of my private cabinet, about one-fourth of the whole belongs to the survey museum, for which, as is shown by the museum register, the specimens were collected chiefly by Prof. N. II. Winchell, Prof. C. L. Hoi-rick, and Messrs. W. H. Scofleld and Charles Schuchert. For much of the remainder I am personally indebted to Mr. Scofleld, who, with unusual generosity, allowed me to select anything I desired from his extensive- private collection of Minnesota fossils. I am under obligations also to Dr. C. H. Bobbins, of Wykoff, Min- nesota, for several choice specimens from the Galena limestone of Fillmore county; likewise to Prof. C. W. Hall, Mr. A. D. Meeds and Mr. A. H. Elftman for good specimens collected by them in the vicinity of Minneapolis. '1:1.1.11 KAN. Ill V |8I UiiiivlllbranrhUla.l Class LAMKUJl;i;\N< III \T.\. i l.K< \ II H)A.) K.unily AMBONYl llim.K, Miller. Valves i-qnal. very inequilateral: l>eaks prominent, terminal or nearly so; posterior cat-.linal region more or less alate; anterior side abruptly convex, with or without a byssal opening. Small cunlinal and elongate jM^t.-rior lateral teeth may be present MI wanting. Posterior adductor impression large, bilobed (the upper part probably fi.nin-1 liy a pedal muscle), situated above and behind the center of the valves. Anterior adductor wanting or very small, situated in the umbonal region. Pallia! line simple, strongly impressed in the anterior region, becoming obsolete near tin- anterior extremity of the hinge. This family is unquestionably a valid one, and readily distinguished from the iiliiln with which its old genera are usually associated. In that family of shells the valves are always unequal and drawn out in front of the beaks into a distinct wing or lobe. The Ambonychiidtr, on the contrary, are always equivalved and with- out an anterior wing, the situation of the beaks being approximately terminal. As may be seen from the scheme of classification on page 485, 1 have extended the limits of the family so as to include several genera that are very differently arranged by other authors. Thus Amphica-lia, Hall, is regarded as the type of a new family by Miller, while Whitfield has said that the genus is probably identical with Lcptodomus, McCoy, and Meek and Worthen placed it near Pteritua. But, as I shall show in another work, .1 /»/,/ Ha possesses every essential character of the present family. Palteocur I, p. 1«3. Not AmbongcHia, Hal!. IV,y. Pal. M. Y., vol. Ill, pp. 200 and 5t3: nor of American aod European author* generally. K.imvalvt»l and profoundly inequilateral shells; valves ventricose, very thin, dosing tightly all around; beaks full, strongly incurved. Surface with tine radia' -tri ;e, crossed by concentric growth lines and obscure undulation-. Internally a thin plate passes vertically down from the anterior end of tin- hin^e plate separating a THE PALEONTOLOGY OF MINNESOTA. t LLanu'llihriim-hiat :t small lobe, immediately beneath and sometimes a little in front of the beaks, from the umbonal cavity. Hinge plate narrow, with a few ligament striations and two small oblique cardinal teeth; no lateral teeth. Muscular impressions and pallial line very faint. Type: A. bellistriata Hall. It will be seen that the foregoing description of this genus is, in many respects, widely different from that adopted by all preceding authors. Hall's original diag- nosis is, of course, too broad and on the whole indefinite, since it included species which subsequent study proved to be quite different from the typical species.^ Again, the commonly accepted characterization of Ambonychia, since the publication of Hall's notes on the genus in 1859, is based upon his A. radiaia and not upon A. belli- striata, which, of all the species placed under Ambonychia by him in 1847, alone is entitled to the distinction of being the type. Ambonychia, therefore, as generally understood, is synonymous with the group of shells which J. now propose to name Byssonychia, and quite distinct from Ambonychia as based upon A. bellistriata and A. orbicularis (Emmons), the two species first following the original description of the genus. This new interpretation of the genus may produce some confusion, but it -is necessitated by the rule of priority, which demands that when no type is mentioned the first species to follow the original description must be regarded as the type of the genus. Having then no alternative but to accept A. bellistriata as the type, I have redefined the genus in accordance with the characters presented by that species and four others, A. orbicularis Emmons, A. planistriata Hall, A. affinis, n. sp., and A. amygdalina Hall, all of which, with the possible exception of the last, are unques- tionably congeneric. Compared with other members of the family, Ambonychia, as here understood, differs from Clionychia, Ulrich, in having a small lobe-like cavity beneath the beaks where, in that genus, there is a mere thickening of the margin of the valves. In casts of the interior the whole upper part of the anterior side of Clionychia is impressed to the edge of the valves, while in Ambonychia the same part presents a small protruding, vertically elongate lobe, separated from the anterior side of the rostral cavity by a sharply-impressed thin line. This lobe reminds one greatly of the anterior adductor impression of Vanuxemia, but I could not satisfy myself that it really lodged such a muscle. Other differences are that in Ambonychia the valves are more ventricose and the umbones and .beaks more strongly incurved, while the surface is marked not only concentrically but also radially. In Byssonychia there is a byssal openiqg in the anterior side and the hinge is strengthened by two or three slender posterior lateral teeth. The Upper Silurian genus, Amjrtiicoelia, Hall, may I \MKI.I. Ill; \\. MIA I \ I'M ' ' 1 1 il ] l>e iin.ri' nearly related to . I ml". »n/.-/i/.i than eitherof the genera nient miied Certain it i- that I tin.l it mi, I-.- .lilli.-ult to point out the di-tiii^mshin^ features than I e c:i>es. Tin- genera I appearance of the shells of the two genera (A mboHif ami .\Htfilii,;ili,i) i~ MTV -unilai.l.otli in thomatterof form and in their Hurface mark- ing. Tin- hiii- MTV much the same in the two genera, the Vine! diilerence I'fin- that the area i- wider in . I »/«/./,/,•„ //«. The greatest difference, however, soemH to li.- in the anteni-cardmal region, where the margin of the hitter is thickened, ''•*" •' ' I"' interior to appear as broadly impressed in this region. AMKONYCIIIA r IATA Hull. l-I.ATi: XXXV. KIUH. 1 nncl I Amlio*tchia pliinittriul,, MA 1. 1., I". I I: ] • 9g\ I. Sur. Win., p. 32. Shell obliquely aeii minute-ovate or subrhomKoidal. ventricose, with the i*>int of • convexity near the center of the antero-cardinal half. I | .| .er half of anterior -id«> xiuiievvliat llattene.l. nearly straight, sloping liaek ward slightly, and more rapidly below, into the basal margin, which, with the greater part of the interior edge, forms a semicircle; postero -cardinal margin subangular, hinge line straight, one- third or a little less shorter than the greatest length of the shell beneath. I teaks prominent, strongly incurved; umbones full and rounded; posterior cardinal slope concave. Surface marked by distinct, broad and shallow concentric undulations ami tine radiating strue, of which about twelve occur in "> mm. at the margin of an average example. These stri.i , which are flattened and separated by very narrow interspaces, are cancellated by another set of even finer concentric lines. Test very thin, hinge plate narrow, apparently with two cardinal teeth in each valve and no lateral teeth. In good casts of the interior the antero-cardinal lol>e is sharply defined. This rare and beautiful species is readily distinguished from /(. Mlixtriuta Hall, and .1. o;7//>M/i Kmmons, sp., but that form, aside from the fact that it has the characters of Clionychin, is less ventricose, of somewhat different shape and without radiating lines. For comparisons with /(. tiffinis t'lrich, see that 'nation and iorafffy.-Knmi tho I ue llm^ton*" »t Mineral Point and Delolt, WiMoa- -m .-i «t Canm.n Falls. MlnnemU, and Lee cuunljr. Illinois. *** Rfff. No. 8327. 492 THE PALEONTOLOGY OF MINNESOTA.. lAmboiiychla bellistrlata. AMBONYCHIA BELLISTRIATA Hall. PLATE XXXV. FIGS. 1 and 2. Ambonychia bellistriata HALL, 1847. Pal. N. Y., vol. i, p. 163. Not Ambonychia bellistriata S. A. Miller, 1874, Cin. Quart. Jour. Sci., vol. i, p. 14. » The Minnesota specimen illustrated on the accompanying plates differs slightly in its outline from the original figures of the species given by Hall is the work cited.* The hinge line is a trifle longer and the anterior side less uniformly curved. Still, I cannot for a moment doubt its specific identity with the types of the species, since it possesses all the more essential characters. The beaks and umbones are very prominent and strongly incurved, and the radiating striae fine (about twelve or thirteen in 5 mm.) and apparently of the same character as in A. planistriata, except- ing that they show no traces of the fine concentric lines noticed in that species. Compared with A. planistriata the present species is found to differ in the relative narrowness and greater prominence of its uinbones, and in wanting the shallow con- centric undulations, which are always a striking feature of that species. A. orbicu- laris is a more erect and rounded form, and not so ventricose. The name Ambonychia bellistriata occurs in all the published catalogues of the fossils of the Cincinnati group, but the species referred to in the lists is really a very different one. Indeed, it is a true member of the proposed genus Byssonychia, and closely related to the type of that genus, B. radiata Hall, sp. Formation and locality.— In the central part of the Trenton limestone at Middleville and Treuton Falls, New York; and in the middle Galena near Wykoff, Minnesota. AMBONYCHIA AFFINIS, n. sp. PLATE XXXV, PIGS. 5-7. This species or variety is most probably a later phase of A. planistriata Hall, and as it resembles that species very greatly it will be sufficiently characterized by pointing out the differences. Thus, the beaks and umbones are a little less tumid and the convexity of the shell correspondingly less. The shell is also a trifle more erect and rounder, the hinge line slightly shorter and the postero-cardinal margin more rounded. Finally, the concentric undulations are much more obscure, while the radiating striae are coarser, there being only eight in 5 mm. to twelve in the same space for that species. At first I thought the species might prove the same as A. orbicularis Emmons, sp., but a comparison with Hall's figures in vol. i of the Palae- ontology of New York, will show that the anterior side of the New York species is •An examination of the types of the species, which are now preserved In the American Museum of New York City, proves that flu*- *<• ''nil 4'i (unyc/ii will be found on perfect specimens, in which case the species would stand very near A. Mlistriala, differing from it, so far as we can now see, chiefly in its greater size, less incurved beaks, flatter anterior side and less angular postero-canlinal margin. The anterior lobe is longer, more sunken and less sharply defined in this species than in the others here referred to Ambonychia. Formation and locality.— Middle Galena of Good hue county, Mlnn.-sota. The Now York typ,- <,f the species Is credited to the Trenton limestone at Adams, Jefferson county. Hilling* al*o catalogue* the species from the same horizon In Canada. Genus CLIONYCHIA. I'lrirh. Ambonitehia (part.) HALL, 1847. Pal. N. Y.. vol. I, p. 163. ClioHgehui, ULICICII, 1892. American GeoloKlst, vol. x. p. 97; CKcmyeMo, MII.I.KU, 1802. First Ap- pendix, N. A. Geol. and Pal., p. 899. Shells equi valve, moderately convex, subalate posteriorly; beaks terminal, com- IM i atively small, not very prominent and but little incurved. Cardinal line straight, rather long, forming an angle of less than 90° with the anterior side. Surface marked concentrically only. No byssal opening, the margins closing tightly all around. Mus-'tilar impressions situated in the postero-cardinal third, large, bilobed, the lower lobe much larger than the upper. Pallia! line simple, extending from the posterior adductor to the rostral cavity. Hinge plate of moderate strength, without cardinal or lateral teeth, excavated longitudinally for a linear ligament. Upper part of anterior edge thickened, producing a more or less well-marked impression in this part of casts of the interior. Anterior pedal muscle attached a short distance behind the beaks. Type: Ambonychia lamtlloxa Hall. 494 THE PALEONTOLOGY OF MINNESOTA. LAinbunyc-liia aiiivj-'dalina . This well marked genus embraces probably the simplest and earliest types of the family, from which all the other genera descended. Yet, while a direct line to Mytilarca and Plethomytilus seems obvious enough, I must confess my inability to bridge over the gap between the radially ribbed genera on the one hand — and these form a very natural and closely interrelated group — and those in which the surface is marked with concentric lines only, on the other. At present, therefore, the evi- dence favors the conclusion that in times preceding the Chazy -there existed a more primitive type still that combined the characters of the two groups. Compared with Ambonychia, as here restricted, the present genus differs in its smaller umbones and less incurved beaks, in wanting radiating striae and in the structure of the anterior side, there being, instead of a clavicle-like plate or ridge beneath the beaks, a mere thickening of the margin, leaving a cavity or impression in the cast where that genus presents a small lobe. Mytilarca, Hall; which probably was not evolved till after the close of the Lower Silurian, is distinguished by its cardinal and posterior lateral teeth, and more oblique form. In the remarks following the original description of the genus I mentioned Ambonychia umygdalina Hall, as belonging here. This I now believe to have been an error. Respecting A. nitida and superba, described by Billings from Anticosti, and other concentrically marked species that have been referred to Ambonychia, it may suffice to say that they are not congeneric with the types of that genus. Their true relations cannot be established until we know something definite about their hinges. Some of the species in question are much like A. acutirostra and apJtiea, two species described by Hall from the Niagara rocks of Wisconsin and Illinois that should go with Mytilarca and not with Clionychia. CLIONYCHIA LAMELLOSA Hall. I'LATE XXXV, KIUS. 10-14. Ambonychia lamellosa HALL, 1861. Kept. Sup't. Qeol. Sur. Wis., p. 31; WHITFIKLD, 1882, Eep. Wis., vol. iv, p. 205. Ambonychia attenuate HALL, 1861. Rep. Sup't. Qcol. Sur. Wis., p. 33; WHITFIKLU, 1882, Rep, Wis., vol. iv, p. 206. Shell obliquely subquadrangular or subovate in outline; hinge line straight, generally but little shorter than the length of the shell beneath; anterior margin nearly straight, sloping backward five to fifteen degrees from a vertical line, below curving rather rapidly into the strongly convex basal line; posterior margin more gently curved, joining the hinge line sometimes sharply at other times gradually. Valves rather strongly convex, most ventricose in the umbonal region and near the anterior side where the slope to the edge is abrupt; cardinal slope gentle, in some cases nearly flat, in others distinctly concave. Beaks terminal, small, acutely i attenuate in casts, generally riming slightly forward, projecting l.ut little above the hinge and incurved, Iteueath them the anterior side of caste present* a broad and often sharply-detined depression which, in extending downward, gradu- ally .he. out at or a little beneath a point midway between the base and the hinge. Surface, specially near the free margin-, marked with numerous, unequally tnlmted concentric lines of growth, having the appearance, even on the caste, of being the edges of overlapping lamellae. Hinge plate rather strong, without teeth, the ligamontal area wide and faintly striated. Mu-cular scar bilobed, situated almost entirely within the postero-cardinal third of the valve, Pallial line simple, extend- in- up the anterior side apparently to the cavity of the beak. The form of this species seems to be quite variable, but after a careful study of numeioi^ specimens I have concluded that much of this supposed instability is due to distortion through pressure. On the other hand, for the same reason, 1 found it utterly inpo>sil.le to detect really normal specific differences between the specimens which Hall in his original work and Whitfield in the later volume cited above have separated as two species under the names Ambonychia lamtllosa and A. ittrmmta, (»p. tit. plate V, fig. 6) represents, instead of the left, most surely the right side of an obviously distorted specimen. It is a little surprising that a paleontologist of such wide experience as Prof. Whitfield should have failed to observe the evidences of distortion, and more so still, that he should mistake one valve for the other, especially of a specimen that preserves the posterior adductor scars. These we know are situated in the postero-cardinal third of the valves. Imt his error leads him so far astray that he asserts without qualification "they are situated near the anterior border of the valve." This species cannot be confounded with the associated Ambonychia />/ -.. much like the preceding c . lamdlosa) that it scarcely deserves specific recognition. Critically .•iiinpare found to tlilter in tint folio, 496 THE PALEONTOLOGY OF MINNESOTA. LCllonyclita crecta— rhomboldea. respects: The umbonal slope is less defined, the whole surface being more uni- formly convex, the beaks not so attenuate and more incurved, and the concentric growth lines not nearly so sharp, much more numerous and more equal. Casts of the interior are almost smooth, and the shell substance must have been very thin. The anterior side also is less concave, the shell smaller and the valves proportionally a little more convex. Formation and locality.— Central part of the Trenton limestone at Minneapolis, Minnesota. Mus. Reg. No. 5099. CLIONYCHIA EEEOTA Hall. PLATE XXXV, FIGS. 17 and 18. Ambonychia erecta HALL, 1861. Rep. Sup't. Geol. Sur. Wis., p 32. This species also is exceedingly like C. lamellosa, and for a time I was inclined to question the "propriety of maintaining it. A more careful comparison, however, has revealed slight peculiarities that cause me now to view the separation with some favor. The valves of C. erecta are not so convex and more nearly square, the outer side being almost vertical and more produced below, the posterior side is straighter above and the postero-cardinal angle sharper. In all other respects the two forms are, so far as we can learn, identical, C. nitida is more oblique, its valves more convex and their surface markings finer. Formation and locality.— Trenton limestone Beloit, Wisconsin, and Minneapolis, Minnesota. CLIONYCHIA RHOMBOIDEA Ulrich. PLATE XXXV, FIGS. 19 und 20. Clianychia rhomboidea ULRICH, 1892. Amer. Q-eol., vol. x, p. 97. Shell, as seen in casts of the interior, of medium size, very oblique, rhomboulal in outline, the anterior and posterior and the dorsal and ventral margins subparallel. Dorsal edge nearly straight, likewise the posterior, the two lines meeting at an angle of about 120°. Postero-ventral margin sharply curved, the ventral side gently convex and rounding almost uniformly up to the base of the anterior side, from which point the outline continues to the beaks in very nearly a straight line. Beaks terminal, small, pointed, projecting slightly above the hinge line, scarcely incurved. Umbonal ridge strongly convex, extending toward the postero-ventral extremity in a slightly curved direction, so that the slopes on the anterior and ventral sides are more abrupt than on the opposite sides. Point of greatest convexity a little in front of and above the middle. Interior with hinge plate rather wide and strong, and the anterior edges of the valves, for a short distance beneath the beaks, much thickened inwardly, the decay !.\MU.|.IM;\N. 111 \ i ,, oftheshHl leaving a d.-tmrtdepressi,,,, „, thecaste. Muscular ncaw large. Ml.. .il-ut mi.lway in tin- po>ten, car Imal half ,,f the valve, the t v, k. the upper .,ii.. ,,val in -hape ami about ,,n,. -third ;w large M the i- nearly circular lower one. Tin- p,M.-i-i..r extremity i> more |.m.li. i more narrowly oim-d than ii, "'' to tins genus. i loralii,,. l^,w, r limestone of the Trenton formation at Minneapolis Minn. Mia. Keg. No. 5530. UNHATA l-'.mmon*. > a. in-..;. ll.-iK.rt K, p. aw. JtabMfeMa Mutate HAU., 1847. i , .,ric, vol. i, p. 165. Shell snbijnadrate. canlinal margin long, straight, anterior side strai^lit, ni-aily \.-rti.:al. curving sharply Itackward below into the gently convex base, which in it- turn < iirves rapidly upward into the broadly rounded posterior margin; ant cardinal angle about 85 , postero-cardinal angle about 115". BeaU prominent, attenuate. >li^htly incurved, with the umbones strongly convex, the anterior -lope alirupt. the rapidity of the descent becoming gradually less in following the margin around to the posterior extremity of the hinge, where it in very gei • -animal -lope conca\e. becoming strongly so and very abrupt in noaring the lx- Surface marked with broad concentric folds, which are strongest on the cardinal and miilional slopes and fade away gradually in curving around to the anterior >idc. Immediately beneath the beaks the anterior side of a good cast of the interior I a -harply defined lunule-like impression, which, having been occupied by an internal thickening of the margin of the valves, wag scarcely indicated on the exterior of the shell. Hinge plate narrow, muscular impressions undetormii The above description is based upon the specimen illustrated on plate x.x It presents no evidence of distortion and seems to be in every respect in a good .ition. Compering thfe eXMUple with Mall's description and figures of the New York type- of the species we observe that it differs in several lar« that mi-lit be regarded as important. The outline is more nearly quad rate, and the convexity of the valves less, giving a form that deviates from the figures of the New York -pet-mien precisely a> ' . rrectn does from ' '. InmeUosa. Hall also mentions the absence of a "definite lunette." while such an impression i- ly present in the casts of the Minnesota specimens. Despite these difleren • I am almost contident of the spe<-itic identity of the latter and the tyjHjs of the species, because I am inclined to doubt the actual existence of the discrepancies noticed. 498 THE PALEONTOLOGY OF MINNESOTA. [Bjraaonyohia. The broad undulations of the surface distinguish the species from the other shells referred to Clionychia. Formation and locality. — Middle Galena, Fillinorc and Goodhue counties, Minnesota: associated with Zygospira uphami W. and S., Vanuxemia abrupta Ulrich and Lichas (Hoplolichas) robbinsi Ulrich. The original specimen is from the Trenton limestone at Watertown, New York. Genus BYSSONYCHIA, n. gen. Ambonychia (part.), HALL, 1847. Pal. New York, vol. i, p. 163. Ambonychia, HALL, 1859. Pal. New York, vol. iij, pp. 209 and 523; also of all American and European authors who have described that genus subsequent to this date. General aspect as in Ambonychia, Hall, excepting that the beaks and umbones are not so full. A well-defined byssal opening in the upper half of the anterior side. Hinge with a striated ligamental area, several small cardinal teeth and generally two or three slender lateral teeth near the posterior extremity. Posterior adductor impressions large, situated a little behind the center of the valves. Pallial line simple, terminating in the rostral cavity. Type: Ambonyckia radiata Hall. (See fig. 35, vi, p. 477.) The erection of this genus became a necessity when a critical study of Ambony- chia bellistriata Hall, and several other species undoubtedly congeneric with that peculiar type of the genus Ambonychia, proved them to be without not only lateral teeth but a byssal opening as well. On the other hand Byssonychia has nothing like the anterior subrostral clavicle, while the external radiating costae are nearly always stronger than in Ambonychia. We have, therefore, at least three ordinarily valid generic differences to separate the two genera. Indeed, there is room for one or more intermediate genera. Two very nearly such groups actually exist in the Cin- cinnati rocks and I hope to publish descriptions of them in the next (7th) report of the state geologist of Ohio. One(Allonychi«) will contain, besides the type, Ambony- fltin (Megambonia) jamesi Meek, two new species. They are all more erect shells, possessing a protruding byssal opening, a short hinge with wide ligamental area, but neither cardinal nor lateral teeth. The other group (Kridonychia) is based upon several elongate new species, having but little incurved beaks, scarcely ventricose umbones, a long and narrow byssal opening, thin hinge plate and no teeth. liystionychia is closely related to Anomalodonta, Miller, but is distinguished by its hinge, that genus having neither true lateral nor cardinal teeth. It is to be admitted, however, that in certain species, otherwise precisely like Byssonychia, the posterior lateral teeth are nearly or quite obsolete. Descriptions of these and other new species of this genus have been written for the Ohio work above mentioned. ' Tin- AmtottycUa /«.',, /H,-,/iVi Meek an.i \V, ,.-»[„•... ,,f the Galena, teems to be the earliest species of now know ... IVrhaps contemporaneous « form. occu- Tin* in the Trenton ,,f K,nt,, i Tennessee, that i< marcel, guMuble. from the llud-on Uuor /• which two only an- d,-cnbed (I rdrona and robuta, of MHIer) occur in th, Km-r uii.l fine, .mat. n>ck-. So far as known the genus became e ,.th th,. close of tin- l.o\\i-r Silurian. INTKKMKDIA Meek >llit.> are somwhat excavated in the upper part of the front in tl surrounding the small byssal openinj:. and between the latter and the points of the l»eaks tin-re i> a -mall protuberance representing the filling of a little cavity at the • •mity of the hinge plate. Surface marked by rather fine radiating plication-. the total number, as near as can be determined from casts, being between forty-five and tifty. They are coarser on the ventral slope than on the posterior wing, always -implr and increase in strength with the growth of the shell. On large casts the i- are not defined except at the free margins, the rest of the surface being smooth. Mu-cular -mi and pallial line unusually obscure, their positions and form not certainly determined. This little ^I.ell i< a tru«- /• !'i" and i|uit<> ditl"rent from Ambon Hi- '•i Hall, with which Meek and \Vorthen compare it. It is related to the follow- luit a nearer ally is found in the / Irich, of the lower part of the • 'incinnati expo>ur»>s. That species, of which anexcellent internal cast is figured on page 479 (Kg. :!•'•. pi. \ <. less gibbous, more oblique and has smaller beaks, wi the inux-iilar scars and pallial line are n-u.illy nn> •i m I l.r:ility (ial-na lltnesUinc, MountCarn.il. 1 '-hk«*h. Wykoff. Mint)' - 31 ut. Itrg. No 500 THE PALEONTOLOGY OF MINNESOTA. tByssonycbui teuuisiriaUi . BYSSONYCHIA TENUISTRIATA, n. sp. Fig. 39. Byssonychia tenuistriuta, n. sp. Hudson Biver group, Granger, Minnesota. The. right side and a front view of an imperfect cast of the the interior. Mus. Keg. No. 8371. Shell rather small, subovate, moderately ventricose in the urabonal region and anterior half, compressed in the postero-cardinal region where the surface is dis- tinctly concave; anterior slope strongly convex, but scarcely abrupt; beaks small, projecting but little, moderately incurved. Hinge line comparatively short, the outline passing rather gently into the broadly-rounded posterior margin; basal line strongly convex, curving uniformly into the ends; anterior side slightly concave above, neatly convex below. Byssal opening small, its position high, it and the surface around it appearing in casts as a distinct impression immediately beneath the beaks. Surface marked with very fine radiating striae and obscure concentric varices of growth, both showing through the marginal parts of the shell, so as to be visible on good casts of the interior. The total number of the radiating stria- is probably more than seventy. Near the base of the specimen figured eleven were counted in the space of 5 mm. This species is closely related to B. vera Ulrich, (see ante p. 471), fig. 36, V) from the Utica horizon of the Cincinnati group of Ohio, differing from it chiefly in its finer radiating stria; and more impressed byssal opening. B. intermedia M. and W., of the Galena, has coarser striae and is a more ventricose shell. Formation and locality.— Ilare in the upper part of the Hudson Kiver rocks at Granger and Spring Valley, Minnesota, and in an equivalent position at Richmond, Indiana. Mus. Reg. Nos. 8370, 8371. Family MODIOLOPSID^], n. fam. Shell equivalved, usually elongate ovate, but varying to oblong subquadrate, generally thin; valves fitting closely or gaping slightly at one or both ends. Beaks near the anterior end, but never terminal. Hinge long, of variable strength, edentu- lous or with one or two cardinal teeth in one or both valves. Ligament long, linear, external and internal. Anterior adductor impressions rather large and distinct, situated between the beaks and the anterior extremity; above them a very small •ad I |..-.lal niiiM-le KW, IWenor adductors large. MTV famf!\ impressed, s lew than their diameter from the posterior extremity of tin- h.iu lm"'r * f rmlw> »*»"Hv with on,, or two obtuse ridge-like tin- 1,,,^ from tin- U'.ik> ..l.li,,n,.ly l.ackward toward tln< . f the ventral n Of the WHOM genen included „. this family in the srh, , ,„, pa Hi' K\ I am -ati-lied t hat some of those preceded I._V aquation maik will lie MI. or later placed cU.'where. No more -at i -factory arrangement having suggested it the\ W,MV i-efenv.1 here, because thoir known characters agree with one or anotl.rr • •f the more typical genera. Tim-. AH**tU*, a>idr from it- unequal vai l- l'an^ faviiraMy with Kurym ndella seems to be related to Mml,»- • /"/- al" ' V'xliolopgu and Cymatonota, while Psiloconcha, in a gen way. resemliles Aifimnmfn. Hut of I'l/iinontyn too little is known to venture an o|iinion as to its ultimsite placement, the only excuse for recognizing the genus in thi- ronneetion being that it would be even more out of place in any of the other familie-. The po-ition of I'rolobella also is quite uncertain. ie of the species of Modiolopsis remind us so strongly of Modioln ami Mij,H-vnd,,i that we can scarcely escape the conviction that the latter genera, which are placed in the families Myiili,l,i ami I'msinMr by Stoliczka and Xittel, have really descended from Modiolopsis. Still, I am of the opinion that the paleozoic M constitute a more natural grouping by themselves than can be attained !•>• any of the courses adopted heretofore. The position usually assigned to .l/<«/;W«/wia i- near Modiohi in the family Mi/filiJir, l.ut Stoliczka and Zittel see greater reseui- I'lanees with Myoconcha ami therefore regard the genus as an early type of the I'xtsinidi?. But both of these families, the first in partiulur, seem to me to include heterogeneous material, and if they were revised according to the genesis of I.imelliliram-hiata. I have no doubt their limits would be greatly modified. The first reason to influence me for the separation of Modioloptu from tin- MytUida occurred during; a comparison with Mynlimi. K on i nek, a genus that, whih- it seems to be very ju>tly as- «ith Mi/tilii*. has no relation to Modtoloptit. lnil«>ed, according to my xicu. the progenitors of M:i,ilinn are to be Bought for aiming the . lwi/«»/N/c////W'/. Next, a comparison with recent -pecit - of Mixlinln proved that while a general inlilance obtaineil there were >tii :i features in which the genera here -ed as the Moiliulujixidof agreed thoroughly among themselves and differed from ••f'l. Thus, in the latter, ami : true of all the MytUi>l>r. the ante' aililm-tor impre>-inn i- ai\\a\- -mailer ami the posti t lie canlinal margin as well a> of a >hapr. ini-luding the prolongation fonne "n tlu'wi 502 THE PALEONTOLOGY OF MINNESOTA. the configuration of these parts in the latter is much more like what we see in the ( 'ri/todontidic. Another feature in which the Modiolopsid<(> resemble the Cyrtodontidce, and one that, so far as 1 am aware, has never been noticed in Modiola nor Mi/tilus, is the presence on the inner surface, at any rate of all the thick shells, of one or two obtuse ridges extending from the beaks obliquely backward and toward the ventral margin, producing corresponding more or less well-marked furrows on casts of the interior. Finally, there is to be urged that it is only a few shells, like Modiolopsis modio- laris and M. concentrica, in which the anterior end is narrow and unusually short, and a byssal sinus present, that exhibit any striking resemblances to either Modiola or Myoconcha. No one would, I believe, say this of elongate shells like M. arguta and M. angustata, and when it comes to Orthodesma, which can be shown to have origin- ated in the same stock that pixxjuced Modiolopsis, all agree in removing that genus far from the Mytilidii'. The many points of agreement that may be noticed between the Modiolopsidce and the Cyrtodontidce probably indicate a close union of the two groups in times preceding the Chazy; but, as far back as our knowledge now extends, there prevailed at least one important distinguishing feature. Namely, there existed a difference in the shell structure which, though its exact nature is unknown, is nevertheless clearly evidenced by the appearance of the two groups of fossils when they are preserved in soft shales, the shells of the former always being covered by a black or dark film never seen on the latter. Genus MODIOLOPSIS, Hall. Modiolopsis (part.), HALL, 1847. Pal. New York, vol. i, p. 157. Shell more or less elongate, usually subovate, widest posteriorly; valves moder- ately ventricose, closing tightly all around. Beaks small, near the anterior extremity; urnbones depressed by a flatbening or depression which crosses the valves obliquely and widening causes a straightening or sinuation of the basal outline. Hinge of moderate strength, rarely straight, generally somewhat arcuate, without well-marked teeth; an obscure oblique thickening beneath the beak of one valve and a corres- ponding depression in the other occasionally distinguishable. Ligaments linear, external and internal, chiefly the former. Anterior adductor impression subovate, large, deep, sharply defined on the inner side, occupying the greater part of the small anterior end. Posterior scar very faintly impressed, large, subcircular, situated near the center of the posterior third of the cardinal slope. Pallial line simple. Anterior pedal muscle forming a minute pit in the under side of the hinge plate beneath the beak. Posterior pedal muscles large, attached just above and in front of the adductor. M..I I. \MKI.I. II li\N, III \ M. HI.,.//,,/,;, ,t,| x| fe ben iMtriotod a...i defined, thii ,».» .,,1,tl,llte8a we,,.mirko(, , „, low,-,- ,!,. -hell, Th- old, .„.„.. klp ^ I'lack Kner dirttom Of kUTVeoto. fnrmati,,,, Some of these an- ,v.| th.t. i,v iradnaJ m Mi.ii.MtjnnHof the base, evolved specie* of the tf. «, Utt, '.mo there existed elon^u- forms like i/ m.-ommon v.tho,,/;,,,/,,,,,,, t hat we cannot do,,l,t that they indicate th, primil -t,,ck from whirl, .i/.../,../..r;. ;lll,| orthodetma were evolved. The .»/. .,„„,/„ lllie ••••ntim,,.d and formed a reasonably complete chain through M M. »>,,,„>/„/.,. aii.l one or two undescribed tpecies of the middle lwd« of the 'mnnnati Kf(11I|, illtll .,/. ,„„„ „,,,• .„ „ ;U1(| w & common ^^.^ ^ ^ ^^ ^ ..f that seru-s ,,f r«M-k, in Ohio and Indiana, and in- Aliens from equivalent «trata in Minnesota. I., this case the form was shortened, the anterior end particu- larly. In tlu> .17. m,,,liniliri* line, however, the changes were different Here we may o with M. >/Hi,7,Xanoval form with the posterior end broadly round.-.] an.) widest Tin- MM-ins to have Rone over into an uppi>r Trenton species (M.subreda Ulricb, Ms.) having a murh narrower posterior end-indeed, the back and base are nearly pamllt-l. M.-xt follow the type hy easy stages through varieties occnrrinK in the I horizon to the normal form of M. modiolaris. Much indeed might be siid upon these not only interesting hut important questions of evolution, and nothing would please me more than to be allowed to demonstrate the positions here outlined. Hut tim,- and space are lacking, and the few points made are offered chiefly in the ho|* that the suggestions may stimulate students to researches in similar lines. The Held i« inviting and the results to be obtained all important. The relations of the genus to the other genera of the family treated of in tin- chapter will be discussed in the remarks following their descriptions. No compari-ion of .J/.,,//o/o//.--ix and Modiomorpha, Hall, has, so far as I can learn. ever been publi>hed. This is strange, since the 8|>ecies of the two genera are strik- ingly similar. As a rule it seems they are regarded as differing widely, but in what n-pecte we are not informed. Mr. S. A. Miller, for instance, places them into two di-tinct families, but fails to state his groun.N for the separation.* A mistaken idea seems to prevail— where it originated I cannot say— that the hinge of Modioloptu has lateral teeth, and this i a- the principal difference I >et ween the two genera by Nettleroth.; Now. let ii- tee what differences really exist between tln-m Taking Modiomorpka ''•""• i ' -eut.ttive of the Devonian genus, we find that, to Car as external characters are concerned, it would pass very well for a species of ;en .•» .-iii-l rala«H>lolu«r. |l IS*; M*. 504 THE PALEONTOLOGY OF MINNESOTA. [Modiolopsis simtlis. its interior, in a casual glance, would pass, there being the same large and deeply- impressed anterior adductor scar, and nearly every feature with which those conver- sant with species of Modiolopsis are familiar. The exception is in the hinge, which is found to have a slightly oblique fold or tooth over the muscular scar in the left valve and a corresponding groove in the right. In true Modiolopsis this tooth is wanting, or rather, it is but little developed, since an obscure thickening of the hinge plate between the muscular impression and the beak is noticeable in many species of Modiolopsis. Another feature is observed in Modiomorpha concentrica that may be • of importance. Namely, the hinge plates posterior to the beaks are wider than in any Modiolopsis known. They extend inwardly and at the same time diverge, probably for the reception of a strong internal ligament, the removal of the thin plate leaving a sharp slit a little within the cardinal edge of casts of the interior. The value of the character is to be tested only by its persistence in other species referred to Modiomorpha. It is a matter worthy of being looked into, for it must be admitted that another difference between Modiolopsis and Modiomorpha, besides the only one now recognizable, is, to say the least, desirable. Of the numerous species which have been placed in this genus many proved distinct when subjected to critical study. Others look doubtful, but must remain here for want of material to determine their relations. Of those to be removed some fall under the new genera about to be proposed. Thus, M. plana Hall, M. alata Ulrich and perhaps M. truncata Hall, belong to KuryHtifa; M. nn'/'onnis Ulrich, to Modiolodon; fllfr*>*4te-tf+ M. sulelliptica Ulrich, to Allodesma; M. cincinnatiensis Hall and Whitfield, M. pulchella^ Ulrich, M. cancellata Walcott, M. oblonga Ulricb, M. pholadiformis Hall, and M. superba Hall to Avtinomytt; M. gesneri Billings and M. trentonensis Hall, to Endodesma. M. Iji&yH •€•!'<' iiusula Conrad, sp., and M. subnasuta Meek and Worthen, belong to Orthodesma, Hall and Whitfield, and M. carinata Hall, possesses all the essential characters of (loni- ofjliora, Phillips. Of Upper Silurian species M. recta Hall, from the Niagara of Wis- consin, is a Matheria, while the M. dicteus of the same author and locality, and M. jirim itjenia Conrad, sp., of the Medina, have slender cardinal and posterior lateral teeth of the Cyrtodonta type. MODIOLOPSIS SIMILIS Ulrich. PLATE XXXVI. FIGS. 1 and !>; PLATE XLII. Vic,. W. 1892. Modiolopsis rimilis KLUICII. Nineteenth Ann. Report, tleol. N;it. Hist. Sur. Minn., p. 225. Shell of medium size, obliquely elongate ovate, highest in the posterior half, contracted at the beaks to between one-half and three-fifths of the greatest bight. Hinge line nearly straight, about half as long as the shell posterior to the beaks. Anterior end small, neatly rounded; ventral margin gently convex, nearly straight LAWi • HI vi \ in the mi.l.||i>: po.termr end l-roadly rounded, -dighth pn,d<, i more Ktrongly convex in the lower half, tin- upper more yi-ntly curvd an. I -oni-times fon obtt^yugnlarjttDctioii with the hinge I. !.e-»eventh of the en lengtli nf -hell Mund the anterior extremi' ,-r small. incurved. proje, • ...... leniti-ly al.ove tln> hinge; umliones compressed in the cast, a little less *.• -hell. Sin-fact- moderately .-.•uv.-x. mo,t prominent 'lie unil>ODal ridge, thp latter n little stronger than UMUI! for species of this gemw. Cardinal -lope concave. A l.roa.l ami .-..nipanitively well-«hMin«».l in.'-ial .Irpression extends obliquely acron th.--li.-ll from the Leak and, expanding, caoaeH the tttraigbteninR of the ventral mar- Kin. Kxivi-tii.;: in this part the shell is very thin, and the anterior muscular • which i> c(ini[»aratively <.f small n .-arcely distinjrui.shahle in casts. Surface r.ithrr Mi,.,-iirely marke«l with nninen.u- tine concentric lines and a few stronger varices of growth. A- might lie e\pecte put the -pecie* into the new genus, but later comparisons have shown that Arlitto MMprwas at that time already well established and that M. similia belongs to the line which finally produced M. liolarii. Then the comparatively strong mesial de| -ion indicates .lA"//oA,vi's and not Artin«m«, - Compared with Minnesota Trenton species, all the others referred to Modiolopgu narrower postericrrly. The At4in«mya niperba Hall, sp., has a larger anterior It'* / end. the postero-basal margin more produced, and the umbones larger. The nmle-cril-ed Kentucky -prcie- referred to in the i proves to be ly related to C. ntbovatn I'lrich. , .i»./ /.HI/I/». -MiiMI- tlnr.l of the 'I ,alc« ml MlomvpnlU, MlnonoU. Ml MS, f». *p. ri.ATE XI-H. Klii!' I? and ML This ,11,'H i- -o much likr ' 'u7i.v that at tir-t I believed it might bel- to the same species. C'arefully compare«l. however, it proved to differ in several characters that are more important than striking. The umlxmee are larger and very little compressed, and the mesial snlcna, which is a well marked featur- in that tpede* i- MU -liable.. The outline also is a li? ditlerent. the posterior bight, being i y somewhat less than in the preced- ing >pr. 506 THE PALEONTOLOGY OF MINNESOTA. [MndloIopMis owcni //,. ; It .-^i . , f. This species ought, perhaps, to go with Actinomyn rather than Modiolopsis, but as I have so far seen only the exterior of the shell, and therefore know nothing of the internal characters, it seemed best to refer it to Modiolopsis provisionally, because of a general resemblance to M. similis. I wish to say further, that I would not be surprised if the shell proved to have the hinge of a Cyrtodonta, several species of which it resembles quite as much as it does Modiolopsis. Formation and locality.— Near the base of the Trenton formation, Murfreesboro, Tennessee. MODIOLOPSIS OWENI, n. sp. PLATE XLII. PIGS. 15 and 16. This species is founded upon a single and not very well preserved cast of the interior. It seems to belong to Modiolopsis and very near M. similis, with which species it should be compared. As far as can be seen its valves were a little more convex, the mesial sulcus narrower, the anterior part of the shell somewhat inflated and the posterior part comparatively narrower. Formation and locality.— Galena shales, about five miles south of Cannon Falls, Minnesota. MODIOLOPSIS AEOUTA, n. sp. PLATE XXXVI, FIGS. 3-6. Shell small, ventricose, elongate, highest posteriorly, the length twice the greatest hight, and three times the hight at the beaks. Cardinal margin straight; anterior end unusually long, sharply rounded at the extremity of the hinge beneath which it slopes backward gradually curving into the straight ventral margin; poster- ior end strongly convex and most prominent in the lower half, above curving more gently and very gradually into the dorsal edge. Beaks a little more than one-sixth of the length from the anterior extremity, moderately prominent and incurved, com- pressed; mesial impression scarcely more than a mere flattening of the sides of the shell; umbonal ridge rather sharply rounded. Point of greatest convexity of valves very near the center. Surface with concentric lines, sharp, subequal and thread- like on the cardinal slopes, here with about ten in 5 mm. at their strongest parts, becoming faint before they pass over the umbonal ridge in their course to the anterior end where they are again somewhat thread-like. In good casts of the interior the anterior adductor scars are large, prominent, and marked on their inner halves with transverse lines. The surface markings do not show through the shell so as to mark the casts. Hinge thin, apparently edentulous. An average specimen is 24 mm. long, the largest seen about 31 mm. This is one of a number of closely related species ranging from the lower Trenton to the middle beds of the Cincinnati group. They are all elongate, especially so for MKU.II.l; \N< IIIA 1 A mim.l i to the Leaks. Tlu-ir L'eneral expression, therefore, i- decidedly like n,-tli»,l,sniii. of which some niemi.er of this lin<> is believed to have Keen the ancestor, in »,//„„/,.,,„„, the \ahes gape slightly at the ends, wliirli is ,,,,t the case in these -hells. In that gemis again the |..,mt of greatest thickness i- more or less behind the center, while in all the referred by me to .l/-.,//W.»//.x/x this point i> central or anterior to t h.> r,.i)t.-r. Kurt h.-rinon', iis stated under the generic .!••-. rip tion. tin- \l ••,-.i,,la line tract's • -nidual .It'Kivcs into M mncrntrini II. ami \V.. \\hii-li is a M"ilii>l<>i>sis in every respec-t . M it'iixi. of the (ialena shale*, has stronger concent n.- -trui', and these extend further forward an. I are vi.-ilile on the internal cast, is scarcely so convex, with a deeper ine-ial depression and more obtuse umbonal ridge, and more rounded and -horter anterior end; M. »ii/iil»i,l^ Mall, is without the even thread-like lines on the cardinal >lope; and M. jn*l,it Cincinnati rocks, has a more truncate posterior margin, more uniformly rounded anterior end, and more nearly parallel dorsal and ventral margins. tation and locality.— Middle thlnl ..( ih. Tr.-ni..ii shale*, Minneapolis St. Paul, Chatflcld and .tain. Mlnnt-soU. Hit*. Rty. No. 8360. MODIOLOPSIS NANA, H. ftp. I'LATF. XXXVI. KIQ. 7. This small species is closely related to M. argtita. The differences are as follows: The valves are not quite as convex, the umbonal ridge is less sharply rounded, the mesial depression a trifle deei>er, and the anterior end a little shorter and more uniformly rounded. The most -triking peculiarity, however, is found in the con- ric lines which show very distinctly on casts of the interior, are coarser (eight in •") mm.), more regular and continue of the same strength over the cardinal slope, umbonal ridge and forward into the mesial depression, near the center of which they are lost In M. tnyti/i,:./,. Hail, as identified in Minnesota, the surface of the casts is very iirely marked with concentric lines, and the posterior extremity of the hinge line suliangiilar. Only two -penmen- have been seen. Of one the length is I'.i mm.. the posterior higlit '.!.:{ mm., the anterior bight 7/J mm., the thickness 6 mm. Of the other these dimension* are ,ely If,. S, 6 and •". mm. Formation and loealilf.—Gnlrn* "hales, nnar Cannon Falls, Minnesota. 508 THE PALEONTOLOGY OF MINNESOTA. [Modiolopsis mytiloides. MODIOLOPSIS MYTILOIDES Hill/. PLATE XXXVI, FIG. 8. Modwlopsis mytiloides HALL, 1847. Pal. Now York, vol. i, p. 157. Three incomplete casts of the interior are referred to this species. They agree very well with Hall's description and figures, except in being proportionately higher. But the general appearance of his figure 4«, particularly in the abruptness of the postero-basal curve, causes me to believe that the original of the figure has been compressed vertically and is therefore narrower than normal. Compared with M. arguta and M. nana, which are closely simulated, it is found to differ in its surface markings, which are fine, with stronger wrinkles of growth, the latter showing only on casts; the concentric lines are, therefore, not equal nor thread-like. The outline differs in the subangular junction of the posterior and cardinal margins. The mesial depression also is more pronounced and the end of the casts in front of the depression more swollen, causing a slight concavity in the ventral margin. Formation and locality.— Trenton limestone, Middlevillc, New York; middle Galena, Goodhue ami Fillmorc counties, Minnesota, and Oshkosh, Wisconsin. According to Killings, in the Trenton and lihick River groups of Canada. Mus. Reg. No. 8361. MODIOLOPSIS CHATFIELDENSIS, n. sp. PLATE XXXVI, FIGS. 0 and 10. Shell small, subelongate, the length a little less than twice the bight. Dorsal and ventral margins nearly straight, subparallel, diverging slightly posteriorly; anterior end rather long, rounded; posterior margin broadly rounded, scarcely oblique, curving gradually into the hinge line. Beaks compressed, projecting little, situated about one-fourth of the entire length from the anterior extremity. Valves moderately convex, thickest at the middle, the umbonal ridge sharply rounded in the upper half; mesial flattening distinct, very gently concave. Surface of cast exhibiting rather broad and unequal concentric furrows which, on the shell itself, seem to have separated sharply-elevated lines. The latter were probably restricted to the cardinal and posterior slopes. Anterior adductor scar large, its inner edgo sharply defined and curving forward. Hinge apparently thin and edentulous. Length 10 mm., postei'ior hight 5.2 mm., anterior bight 4.5 mm., thickness 3.3 mm. This species is not elongate, like the M. anr/ustata Ulrich, of the Cincinnati rocks, its anterior end is shorter and the sides of the valves flatter; with a better defined umbonal ridge than in M. subparallela Ulricb, also occurring in that higher series of strata at Covington, Kentucky. Compared with Minnesota species, it is perhaps MKl.l.ir.KAM Ill \ I \ "•"'.' \t. • >-./ ,' .,. \\ Mil \\in.-ii it i- abo .1 ..... naiad it 1^ bowwor; rmdttj ugi-hed l.y it- Mirface markings, which an- lint visible on tin- ca-ts of that -per an oblique anterior ami po-terior end- and more nearly parallel ventral ami dorsal margin-. In M lall. which i- probably not a true .l/...//.-. the me-ial depression is much more di-tim t. t/ .,./ 1,-r ami more oblique | t.-iiorly. ami lia- more regular surface markings. formation ility.— Miil- (liinl iiiall. eloiiL-.iti- ovate, the. length twice the greatest or posterior hight. V.tho thickest a little above the center, ratln-r uniformly convex, the umhonal ri.lge ami me.sial ilepre«sion Leing l.oth nearly obsolete. B -mall, between one- fourth ami one-tifth of the entire length from the anterior extremity. Dorsal margin gently arcuate.' anterior eml narrowly Imt almost uniformly roumle mm., thickness (left valve only) about 2."i mm. I'onsiderably like, ami probably a near relative of M. nn/ufa. but ditler- in the more uniform convexity of its surface, obsolete unibonal ridge and less oblique anterior margin. The posterior end also i- comparatively narrower and the shell -mailer. Ai-itlm-lf-i nitiilnln is a>Soci;ltt>d but cannot be confounded, -ince it is a -uiooth shell, with unequal valves, and much wider posteriorly. i/i/lf.-A- v ith PUthoeardia umbonati, Uatheria rnyota and otli marking il,. U|>IHT (art of 1 1,.. nu M . thinl <>( th.- Tr^nt..!! -hale* near Cannon Fall*, Mlnn.iw.ta. MODIOLOPSIS Co I'l. All \X\VI KIO8. 14. M. Ifa. Mixtiolopnteoneai'i I I.I;K il, 1802. N " 37. Shell very small, elongate, the greatest hight a little les- than the length. .ircu.it,-. the posterior end much the wide-t and broadly mumled. the anterior exceedingly short, narrow and contracted beneath the beak-: the latter are small. compressed, and project but little above the hinge. Might of posterior third about two and one-half times as great as at the beaks. I>>r-um gently arcuate : thirds of ventral margin -tr«>: >•. a fact due in a great measure t<> 510 THE PALEONTOLOGY OF MINNESOTA. [Modiolopsis ennrriii rica width of the mesial sulcus and the rapid descent of the surface included in it. Umbonal ridge slight, cardinal slope, convex. In a dorsal view the anterior half of the shell appears compressed, yet the point of greatest thickness is very near the middle of the length. Surface marked with simple concentric lines of growth. Hinge plate very thin, without teeth or appreciable thickening under the beak. Muscular scars not observed. This peculiar species, which is decidedly mytiloid in appearance and probably not a true Modiolopsis, is distinguished at once from all known Lower Silurian Lamellibranchiata, except M. arcuata Hall, by its strongly arcuate form. Hall's species is represented as larger and with a straight instead of convex back. Formation and locality. — Same as the preceding. MODIOLOPSIS CONCENTRICA Hall and Whitfield. PLATE XXXVII, FIGS. 15 and 10. Modiolopsis concentrim HALL and WHITFIELD, J875. Pal. Ohio, vol. ii, p. 86. . Shell rather exceeding medium size, elongate ovate, highest in the posterior half. Hinge line arcuate, gently declining toward the extrejnity and rounding gradu- ally into the oblique posterior margin, the same curve continuing to the lower third when it is sharpened in turning forward into the basal margin. The latter is gently convex in the posterior half and anterior third, the part between being very slightly concave. Anterior end very short, narrowly rounded. Beaks small, compressed, projecting very little above the hinge. Surface of valves moderately convex, most prominent a little in front of and above the middle; this point is on the umbonal ridge, which is low, broadly rounded, and not a conspicuous feature. Mesial sulcus shallow, forming an undefined depression across the valves from the beak to the middle third of the basal margin. Surface marked on the cardinal slope and poste- I rior end by regular, even, concentric furrows, four to six of them in 5 mm. in their strongest parts. These furrows are most distinct along a line following the middle of the cardinal slope; in crossing the umbonal ridge they become suddenly obsolete, existing on the sides, basal portion, and anterior end only as fine irregular striae of growth. In casts of the interior the concentric furrows are distinctly visible on the posterior half of the cardinal slope. The mesial sulcus is much deeper and rather sharply defined on the posterior side by a strongly convex ridge extending obliquely across the cast from a point a short distance behind the beaks toward the basal margin, which, if the ridge did not become obsolete before reaching it, would be intersected at a point about three-fifths of the length of the shell behind the anterior extremity. In front of this ridge the surface is impressed and flattened to the 1. \MKU.1I.K\M Ml \ .Ml lM»l -frongly elevated tilling of tin- anterior adductor scar. Tin- l.ittor is large. <>f oval shape. hori/.ontally marked in it- upper half, sharply .lelined all around ami. became of tin- brevity of the anterior end. is -it nated partly I.eneath the point ot' tlje l*ak. > faintly impressed that its exact shape cannot U> deter- mined with tin- material at hand. 1'allial line distinct only in the anterior half. where it con>i-ts of an obscurely pii-tulose raised line. 'I'o this species I refer provisionally a badly distorted mould of the exterior of a right valve, collected by me at Spring Valley in 1887. Its surface is marked precisely as described above, but the reference is still rendered doubtful by the fact that its anterior eii'l i- a little longer than is normal for the species. There is, how- MO reason to don I >t flu* M. >nr>-nlri<-j».r I»M|- ,,f it,.- Cincinnati k'r"iip at •;•- in Ohio, Indiana and Ki-nturky. I'mliably also In tin- Ilinl-m Ki\.-r shall", rn-ar Spring Valli-y, Mlnncsot*. MoDIOLOPSIS KXCELLKMS, M. 8f. PLATE XXXVI ^ li. »• l»-|4. This specie^, of which we have tive specimens, is closely related to M. concentric,! Mall ami \\ hitfield. and was at first confounded with it. A careful comparison howevi-r proved its ili>t inertness in the following respects: It attains a larger size, the casts are more uniformly convex, with the mesial snlcus, on both the shell and the cast, much shallower, for which reason the ventral margin is very slightly convex where it is sinuate in that species. The outline differs also in the postero- cardinal region being less uniformly curved and more prominent at the extremity of the hinge. The anterior end is longer so that a line drawn from the point of the 1'cak across the shell at right angles to the hinge line passes within the inner border of the anterior adductor scar, whereas it cuts a third of the scar away in M. mncen- Finally, the concentric surface markings are liner ami the difference between tin-in a« developed on the cardinal slopes and on the sides of the shell is a much -triking feature. The number of the concentric lines at a point about midway -seen the beaks and the posterior extremity varies in different specimens from to nine in •< mm. What I regard as a nearer ally occurs at the top of the Cincinnati hills. Tin- outline of this species i> intermediate between figures ti and ]:\ of plate .\.\.\\i. In its characters also it approaches one almost as nearly as the other. nation and /.- Pt>cr part of the Hudson Kiv.-r K"-up. Sprint; Valley ami Granger, Iflooeaota. W M /.. ; N - .:; THE PALEONTOLOGY OF MINNESOTA. [Emrymya. Genus EURYMYA, n. gen. Modiolopsis (part.) HALL and DLRICH. Shell thin, short, compressed, high and subalate posteriorly, greatly narrowed anteriorly, transversely truncate-ovate or subtriangular in outline. Cardinal margin straight, base oblique, gently convex. Beaks small, near the anterior extremity. Umbonal ridge moderate, rounded or subangular. No mesial sulcus, the surface of the valves forward and downward from the umbonal ridge being slightly convex or Hat rather than concave. Hinge strong, with a broad longitudinally striated liga- mental area posterior to the beaks, and beneath them an obscure cardinal fold or tooth in the left valve and a corresponding depression in the right. Muscular impressions and pallial line apparently as in Modiolopsis. Type: Modiolopsis plana Hall. The alate appearance of the postero-cardinal region, rounded base, absence of a mesial depression, and the presence of a striated ligamental area are the principal distinguishing features when compared with Modiolopsis. The anterior part of the hinge is precisely as in Modiomorpha, Hall, but the Devonian shells, upon which that genus is founded, have no posterior striated ligamental area, while in nearly every other respect they agree with Modiolopsis. The new genus Modiolodon has one or more strong cardinal teeth in both valves, no ligamental area, and a mesial thicken- ing of the inner sides of the valves that produces mesial sulci on the casts. Besides the type only one other species has been described that I would place in this genus without question. This is the Modiolopsis alula Ulrich, from the hill quar- ries at Cincinnati, Ohio. A third form, if it is really distinct from E. plana, occurs in the middle beds of the Trenton in Kentucky and Tennessee. A possible fourth species is the Modiolopsis truncata Hall, a rare shell of the Cincittmrfi rocks. This species is known only from indifferently preserved caets'oTthe interior. So far as these admit of judgment, the species might well be classed with Eun/mi/ti. Of the hinge nothing is kuown beyond this, that it was stronger than usual for Modio- lopta. EURYMYA PLANA Hull. I'LATK XXXVI. FKJS. 27 und 28. Modiolopsis plana HALL, istil . I!. •],•(,. Sup't. Geol. Sur. Wis., p. 30; Geol. Wis., vol. i, pp. 38 and 438, lltf. 6; ULIUCH, 1892, Nineteenth Ann. Kc[>. Geol. Nat. Hist. Sur. Minn., p. 224. Shell rather small, compressed, subtriangnlar in outline, alate and highest posteriorly, the greatest hight and length (the latter measured parallel with the hinge line) respectively as six is to seven. Cardinal margin straight, nearly as long I.AMKI.I.ll.i: Uf< HI \ M .llolop.1. n.n. I as the shell: anterior end very small, sharply rounded ,i!«»ve, curving backward into the slightly convex, medially almost straight. li;i>al margin; posterior edge gently curved, truncate, nearly vertical. strongly convex below; above turning abruptly into the hinp> line. Beaks small. Imt little incurved. not prominent, about one- sixth of the length of the shell behind the anterior extremity. I'mbonal ridge mod- erate. cardinal slope flat or slightly concave, ventral and anterior sin]*'- depressed convex. Surface marked with distant strong concentric lines of growth, and between these with a liner set. In casts of the interior the anterior muscular impression i- well marked, not very largo, vertical, situated in front of the beaks and close to the cardinal margin. A little more than one-third of the scar is divided on" above I distinctly impressed transverse lino. Posterior scar indistinct, much larger than the anterior. -it uated behind the center of the posterior cardinal slope. Pallial line simple, rath'T'li-tmct, not following the outline of the shell, being farther removed from the margin in the postero-basal region than elsewhere. Hinge as shown in figure 28 on plate xxx vi. Free casts of the interior of both valves, being without the hinge plate, are longer in proportion to the hightthan are the impressions of single valves. The shape of the shell will distinguish this species at once from all Minnesota Lamellibranchiata except Mnthrria rugosa and Cyrtodonln n finis, both of which occupy a higher horizon and have a different shell structure. I have before me ten more or less complete silicified shells from the middle Tren- ton or "Orthis beds" of Tennessee and Kentucky. These belong to a species that is closely allied to K. plnnn and which may be called Kunjmya subplana, n. sp. The n«-u species does not attain the size of the Minnesota form, and is not so high and more oblique posteriorly, while the margin is le-- narrowly rounded in the postero-basal region. The Cincinnati species, E. alutu (Modiolopsit alata Ulrich) is a slightly shorter and more compressed shell, with a more convex ki-al margin and ditlerent anterior muscular scar. formation and locality.— Lower limestone of the Tn-nt4.ii formation In Minnesota at Minneapolis, ml and Cannon Falls. In Wlsc<>n-iri the special seems to be restricted to the "Lower limestone at Janesvllle, Beloit and >I int. -Uu ... 749, 757, SOU. V)12. 5013, M82, 6368, 5869. 5834, 8312. ,1> AUTIHOMVA, II. grn. Modiolopdt (part), of various authors. Sh.-H ovate, more or less elongate, narrowing anteriorly. Valves moderately ventricose, fitting each other tightly. Anterior end short, l.nt not excessively go. Base gently convex, occasionally straight, never sinuate. Mesial sulcus want; -33 514 THE PALEONTOLOGY OF MINNESOTA. [Actinomya. Beaks comparatively large, full and rather prominent. Umbonal ridge generally strongly rounded, sometimes subangulai'. Surface with concentric lines of growth and often with radii or divaricating folds; the radii sometimes restricted to the inner side of the shell, showing on casts of the interior and not on the exterior of the shell itself. Muscular scars and pallial line as in Modiolopsis, excepting that in the majority of the species they are very faintly impressed. Hinge plate edentulous, very narrow, especially so under the beaks, a little wider and grooved on each side for the reception of a linear internal ligament. A similar external ligament prob- ably also present. Type: Modiolopsis cindnnatiensis Hall and Whitfield. Fig. 39. a, a large right valve of Actinomya cincinnatiensis, mostly devoid of shell, showing the muscular scars and delicate internal radii on the cast; 6, the hinge of another right valve of the same species; c and d, hinges of a left and a right valve of -Actinomya pholadiformis Hall, sp. The student will do well to compare these hinges with those of Modiolopsis and related genera, figured on a suc- ceeding page. This genus brings into very natural association a number of Lower Silurian species, the described forms of which have heretofore been placed chiefly with Modiolopsis. These are Modiolopsis dndnnatiensis H. and W., M. cancellata Walcott, M. pulchella Ulrich, and two undescribed species from the lower or Utica horizon of the Cincinnati group, JF. subcarinata, n. sp., from the Galena, and Modiolopsis superba Hall, M. modioliformis Meek and Worthen, and Orthodesma saffordi Ulrich, from the lower limestone of the Trenton formation. Besides these, I propose to place here another group of species, so far known only from rocks above the Trenton, that approaches Modiolopsis in the strength and definition of the anterior adductor impression, while differing from that genus, and therein giving us a clue to their origin, in the convexity of the basal outline and absence of a mesial depression or so-called "byssal sulcus," and in the character of the hinge, which is thinner, and thus more like that of an Orthodesma than of species of Modiolopsis of the same size. Four species of this kind, all from the Cincinnati rocks, are known to me, only two of them, however, being described, i. e., Modiolopsis pholadiformis Hall, and M. oblonga Ulrich.* •Mr. 8. A. Miller has described three forms having surface markings like A*tl niiitr i>1u>ltuUformts. These wn/ be distinct from Hall's species, but I cannot now admit that they are. The one called M.mlcnta Is almost ci-rtainly fomnlc-ii upon vertically compressed specimens of the phoiodi/ormte, while the If. eorrugata Is. so far us I can make It out, In no wise different from the same species. I. \MKM.I l;i:\M H1\TA .'. I .'. modtollformJ. 1 The systematic posit i<>n of Artinomyn seems to be nearly intermediate between Orthodesmn ami .l/f»//. from the latter in the thinner hinge plate aii'L-h.-il. ami from l.otli in tin- <-oii\.-x basal outline and absence of a mesial A«TI!fOMYH MoI'lol.lKoKMI-. M.. .,,ii II .,-'/,„ II \TE XXXVI. HOB. 10 .od » modioliformu MKBK and WOHTIIKX, 1888. Oeol. Sur. III., vol. Ill, p. 204. Compare Jfoftoioprfi tujvrba HALL, 1881. Bep't,, Sup't. Oeol. Sur. WIs., p. 31. Shell of im-liiim size, elongate, obliquely ovate, much the widest in the posterior half; strongly convex. Hinge nearly straight, rather short, extending anterior to tin- l.i-.ik- almost half as far us posterior to them, and posteriorly less than half the rol>al>ly <>f >|>ecific importance. Figure 20 is taken from the type used by Meek and Worthen. The specimen, though a good one, is slightly distorted by vertical pressure, and imperfect in front and along the base. To facilitate com- parison with ti^r. I'.i. the missing parts have been restored in the figure. This fine species I regard as in every sense an Aifinmnya. It is, \tcr\ ffordi Ulrich. than any other known. Imt there is little likelihood of confusion between them, that species being a higher shell, with a larger anterior eml ami somewhat smaller umboncs. It has also several ra£ modioliformis M. and W. sp., only smaller, not so oblique, subalate and higher posteriorly and consequently not so elongate. The hinge also is longer, the posterior margin more erect and the junction between them subangular. The postero-basal margin, furthermore, is not so sharply rounded, while the beaks are less incurved and farther apart. Surface of cast entirely smooth except between the umbonal ridge and the postero-cardinal border, where a number of very fine radiating striae are obscurely visible. This species reminds somewhat of the New York Trenton Modiolopsis avicu- loides of Hall (Pal. N. Y., vol. i, p. 161; 1847), but I cannot believe they are identical. Indeed, it is more likely that they will prove widely distinct. I know of no Minne- sota species with which it might be confounded. • Formation and locality.— Rare in the shaly part of the middle Galena of Goodhue county, Minnesota. Genus ORTHODESMA, Hall and Whitfield. Orthodesma, HALL and WHITFIELD, 1875. Pal. Ohio, vol. ii. p. 93. Shell elongate, usually increasing slightly in bight posteriorly. Anterior end comparatively long, contracted in front of the beaks. Valves moderately convex, usually with a strong umbonal ridge and a broad mesial depression in front of it, their edges fitting tightly along the straight or sinuate ventral margin, but leaving a narrow gape at each end. Umbones prominent, wide, compressed, often extending posteriorly as low cardinal ridges between which the hinge is sunken. Hinge plate edentulous, very thin, long, extending in almost a straight line from the posterior cardinal angle, past the beaks, nearly to the anterior extremity of the shell. Liga- ment linear, internal and external, the latter chiefly. Posterior muscular scar large, very faint, elongate ovate; anterior scar large, though scarcely half the size of the posterior, well defined, ovate or approaching semicircular in shape, the vertical diameter the longest. Pallial line simple. Shells thin, marked externally with more or less distinct concentric striae and wrinkles. Type: Orthodesma rectum Hall and Wliitiield. The above diagnosis does not agree exactly with Hall and Whitfield's original description of the genus, but as it corresponds with the fossils no apology is neces- ,,„ . . I. \MK1.I .'.IT OrtlMMlrMitft. ] sary. They make, for instance, the erroneous statement that the hinge plate in bent down in front of the Leak-; ami the lictition- feature has become so well established in literature that it -tan. Is as the most important peculiarity of the genus, indeed, M the only one separating it from Urthanntn. Conrad. Now, despite the fact that the limp- plate is nearly or unite as straight in <>,-th'.*/••» than M'nli>ilnjn«u. have been placed under Orthodesmn that are very different from tin- types, some of them belonging, I believe, to other families. Thus, 0. byrnesi S. A. Miller, ami u. ntift;l,l,.»;,n//,«v»M,-/i,/. whil,- o. snjfordi Ulrich, should be referred to Aetinomya. )/ ORTHODKSMA MINNESOTKNSE I 'I rich. PLAT! XXXVII. KIOS. 1 1 and 14. Orthodetma minnrtotrn* I 1.1:11 n, 18B2. Nineteenth Ann. Rep.Oeo. Nat. Ulnt-Sur. Minnesota, p.2J8. Shell small, elongate, subrhomboidal, with the dorsal and ventral margins nearly straight and parallel; the length two and one-half times the width. Beaks small, inrurvoil. compressed, projecting moderately above the hinge and situated about one- fourth of the entire length from the anterior extremity; posterior urabonal ridge sntiangular, cardinal slope abrupt, in casts of the interior with a linear impression close to and on each side of the hinge line. Anterior end small, contracted a little in front of the beaks, almost uniformly rounded; posterior end obliqin-. -lopin^ upward ami forward from the produced ami narrowly rounded lower part Interior with the anterior pair of mii-cnlar - 'her distinctly marked ami large; above and between them and the beaks, two other very small pair- of scars are to be seen on the .-peri men figured above, but the posterior muscles left no appreciable impressions Surface of caste with few obscure folds of growth. This shell is related to 0. mrrninni Hall and \Vhitlit>l»!.,• hinge line. Beaks not promim-nt. com- pressed, >itu;it<-i between ooe-fifth and ooe-dxth of the length of the ihefl behind tiu> anterior extremity. Surface of cast showing moderately di.stim-t irregular concen- tnr undiilatmn*. u Inch are most strongly defined on the umhonal ridges and on the il:itf«>iu..i oreonemTfl Hank-. These are crossed on the cardinal slopes by two obscure Miln. Anterior iniiM-tilar scar moderate in size and definition, ovate; small pedal musriilar scats ili>tinct above them. The val\.>> of this shell gape very slightly posteriorly and pn.l.altly also in front. l)iit upon tliis point the material at hand presents no conclusive evidence. They have also the point of greatest convexity a little behind the center. Both of these features are characteristic of Orthodesma. On the other hand the species presents conM.lt>ral.le resemblance to the early elongate forms of Mn,li,,lopsis like M. arguta, 1'iit this indicates, I believe, merely, what I have already stated, a common origin for the two genera and not that 0. subnasulum was evolved from the Modiolopsis. I come to this conclusion because the present species is even nearer the 0. ntinnesottiue which occurs in the same beds holding M. anjiiln. Further, as regards the develop- mental history of Orthodcsma, I view 0. minnesotense and 0. subnasulum as the earliest known stages in the line of development that produced 0. curvutum II. and W., and one or two undescribed species occurring at Cincinnati, Ohio, while 0. rectum H. and \V., appears to have been derived through intermediate species from 0. sdiuchfrti. Specifically 0. subnasutum is distinguished from O. minneaotense by its more elongate and posteriorly diverging form, better defined mesial depression, the longi- tu.linal sulci on the cardinal slope, and more distinct concentric folds. As regards the name of the species, it will be seen from the synonomy that Meek and Worthen first called it Modiolopsis subnasuta, being evidently unaware that the same name had been used previously by Prof. James Hall (Can. Nat and Geol.. vol. v, p. 148; 1860) for an Upper Silurian species from Canada. This fact '"•ing brought to the notice of Prof. Worthen he, in 1882, proposed to change the name to Mmlwhpxis carrollensis, and this specific designation will have to be used -lioulcl the Canadian species also prove to be an Orthotleanm. Hut until that has been established, the original name will have a clear field. Cation and loeality.— Thf tvp.-s i,r the specie* are from the Galonm of Carroll county, IlllnoU. -prclniun here figured and deocribed Is from the same horizon near Dlion, IlllnoU. lo Minnesota the specie* to to be looked for In the "Madura beds" < -na. 520 THE PALEONTOLOGY OF MINNESOTA. [Orthodesma canaliculatum. ORTHODESMA CANALICULATUM. PLATE XXXVII, FIGS. 7-11. Shell elongate, the length three times the hight; cardinal and basal margins straight, nearly parallel; posterior margin oblique, rounding into the hinge line, below which it slopes backward with a gentle curve to the postero-basal extremity where it turns abruptly into the basal line; anterior end contracted in front of the beaks, of moderate length, rounded, most prominent a little above the middle. In a side view the beaks project very little, are compressed by a broad shallow sulcus which crosses the valves and occupies a large part of the anterior three-fifths of the shell; umbonal ridge rather distinct, extending from the beaks to the postero-basal extremity. In a cardinal view of casts of the interior, the only condition in which the species has been noticed, the hinge line is strongly depressed, lying at the bottom of a wide and deep channel, deepest between the rather widely separated beaks and gradually shallowing posteriorly. Casts usually almost smooth, exhibiting only a small num- ber of obscure concentric furrows. One specimen preserves a small part of the shell and this shows that near the dorsal edge the outer surface is marked with somewhat regular raised lines, about six of them in 5 mm. The best preserved casts exhibit in the posterior half of the mesial sulcus a number of obscure radii. Anterior muscular scar sharply defined at the inner side, rather small, broad-oval or circular, occupying the middle two-fourths of the upper half of the anterior end. Posterior impression somewhat larger than the anterior, subcircular, with a narrow prolongation extend- ing forward nearly parallel with the posterior cardinal margin. Pallial line distinct in the anterior half, consisting (on the casts) of a straight row of obscure pustules extending in a slightly oblique direction from the base of the anterior adductor impression toward a point much wearer the ventral border. There are several peculiar features about this specie's. (1) I have never seen its valves separate, a fact indicating, if it is not fully accounted for by the next circum- stance, a strong ligament. (2) Its natural position seems to have been with the anterior end down, and so it is commonly found in the shales, and in consequence it is often greatly shortened by pressure. (3) The channel-like depression of the hinge; and (4) the unusual course of the anterior half of the pallial line. These peculiarities distinguish the species readily from all others of the genus known. Formation and locality.— Hudson River group, Spring Valley, Minnesota. Fragments have been found at many localities in Ohio and Indiana where the upper beds of the Cincinnati formation are exposed. Good specimens, however, are very rare. UoUlulodo. I.VMKU.IKKAM IIIATA. 521 • im, Mi»|iin|.n|i.i\. „. gen. ^emi- i> much like that of Ischyrodonta. Ulrich, and I might have placed the species under that genus were it not for the fact that their shells are of the same composition as those of .l/-/»W«/i.s/v. while the shells of that genus are gen- erally heavier ami of the more calcareous nature characterizing the Cyrtodontidl«<»iii/. Kitf. II. <'i'l/iomfa eoH'trictu I'lrich, top nf Tn-nton urmip, Frankfort, Ki'ntii<-k> . a, rljfht val»e, .nk' i h>- iiMiul characters of the speclw: b. Interior of a left valve: r. interior «f an nn|» rf.. t v.i < "Ipomya evidently belongs to the .l/»mi.^,i are associ- ate! with it, I, ut they can all be distinguished without the slightest trouble. formation and tooaW/jr.-Mlddk- third of the Trenton shal.-s, Chttfleld. Minnesota. M*». Beg. No. 8450. Genus ENDODESMA, n. gen. Shi'll elongate, the dorsal and ventral margins subparallel, equivalved, generally vciitricose. Mesial depression deep, often producing a decided oblique contraction of the shell and a sinus in the basal outline. Urabones compressed, elevated consid- erably above the hinge line on the anterior side, but not on the posterior side. Hinge thin, apparently edentulous. A strong linear internal ligament was attached on each side to a rib or ridge. Back of shell flattened or with the edges of the valves bent inward without, however, forming a true escutcheon. More or less well defined Innule in front of the beaks. An obscure sulcns in the middle of the cardinal slope. Shell very thin; surface marked with concentric growth lines. Muscular scars and pallial line so faintly impressed that they have not been determined satisfactorily. Type: Endodesnta ciineatunt, n. sp. This well marked genus is placed in the family Modiolopsidir chiefly in deference to the views of Mall, Hilling*, and Meek and Worthen, who have each described a species as belonging to Modiolopsis. According to my own conviction there i- little indeed to suggest that genus, the shape of the shell l>eing often quite different (in this respect some of the >; remind of Orthodesma) and the mesial depression deeper, while the faintness — so far as can be seen the total absence — of muscular scars on casts of the interior is not only a striking but an important difference. In the faintness of the muscular impressions the new genus agrees with the mn-t ical forms of Arfini. but they an> distinguished at once by their want of a mesial contraction, in consequence of which their basal outlines are gently convex instead 526 THE PALEONTOLOGY OF MINNESOTA. [Endodesrua cuneatum. of sinuate. Endodesma finally is separated from all true Modiolopsidce by the lunule in front of the beaks and the sulcus and ridge on each side of the hinge line; A more natural placement of the genus seems to me to be near Rhytinn/n, Ulrich, which is regarded as an early type of the Pholadellidce. But as Endodesma evidently is a complex primitive type with characters suggesting widely different Lamellibranchiata it is probably good policy to defer coming to a final conclusion as to its position until we know more of the origin of the group of species and its development in times succeeding the Trenton to which all the species now known are restricted. Six species of Endodesma are illustrated in this work. Besides these, Modiolop- sis? trentonensis (Conrad) Hall, is almost certainly also referable to the genus. ENDODESMA CUNEATDM, n. sp. PLATE XXXVI, FIGS. 33, 34. Shell elongate, the length and greatest hight, which is subcentral, respectively as nine is to four. Valves strongly convex, the point of greatest thickness on the umbonai ridge above and in front of the center; cuneate posteriorly. Dorsal mar- gin gently arcuate, passing rather gradually into the posterior outline; the latter is prominent and sharply rounded near the middle, nearly straight in the upper half and slightly convex below; ventral margin gently convex in the posterior half, straight or barely sinuate near the center of the anterior half, and rather strongly convex in front; anterior end short, most prominent and narrowly rounded in the middle, very slightly concave in the upper half. Beaks of moderate size, strongly incurved, with a rather distinct lunette beneath them; mesial sulcus clearly defined; umbonai ridge unusually prominent, subangular near the beaks. Cardinal slope abrupt, concave, in casts of the interior showing a well marked curving depression and ridge on each side of the hinge line. Surface of cast with a few obscure con- centric folds. Anterior muscular scar very faint, situated just within the anterior extremity of the shell, of semielliptical shape, the inner side straight. This species must be closely related to E. trentonense Hall sp., from the Trenton of New York, but in the figure of that species the anterior end is quite different, being shorter and obliquely truncate. The anterior end of the Minnesota form is more like that of the Canadian E. gesneri Billings, sp., but in other respects these two species are quite distinct. Formation and locality.— The specimen figured, which is the only one seen, was discovered by Dr. C. H. Robbins in the middle Galena near his home at Wykoff, Minnesota, and kindly given to the author for description. I.AMKI.I.llii: \N« IIIATA. '..'7 Kado4«B» orU>«M>ti OODK8MA P<> I'l.ATK XXXVII. KlOS.t lad*. Of this species I have seen only a single imperfect -pf-mien— which under ordinary circum-tance-* \\oiild scarcely merit description. Being however the most recent existence of the genus now known it i- of interest as it may give us a clue to tin- later development of the genus. As may be seen from the figures the species is closely related to / •'»/»/ but, as the name implies, the posterior width (bight) is greater in /.. fH>st/ntii»i. In a cardinal view both ends also are more obtuse, giving ter convexity to the sides; the umbonal ridge, though prominent, is not so -harply rounded. the umbones fuller, the anterior end shorter, and the posterior margin more !>r<>aul>u<|ti». Iowa, where It was collected by Mr. Charle* Srhuchrrt. Mut. Reg. No. 8345. DODR8MA ORTHONOTUM Meek and \\'urllien. PI./VTK \\.\VII. FIGS. I ami* Modioloptu orthonota MBKK and WOKTIIKN. I-<6«<, Cny.l Sur. III., vol. Ill, p. 206. ModioloptU reetiformu WUKTIIKN. ISO; Hull. N... 1, II! .«. Shell elongate, the length being nearly three tinn-i the hight; valves quite convex, the greatest convexity being a short distance above the middle, in front of which they have an undefined concavity commencing in the umbonal region and widening and deepening to the base in front of the'middle. Cardinal margin long, very nearly ->traight or but slightly arrhcd; posterior margin oMiquely substrunca- ted, sometimes very faintly sinuous above, and rather narrowly rounded below the middle; basal margin i> far behind the center that I am constrained to believe the figure overdrawn or the specimen abnormal In this respect. I AMi:i.l.ll.K\N( II! ' * uml—u.,, i < .11 1 1 met tone, I re U raMon to b> > occur* In Miiiinv-.:.i .in. I a will )*• w.-ll t<. MM ,|- .li« ami ml. If t: . ijrfntri <*-<-\i: • .f tin- slat.' It will in.«i-t|ir.. :h. (iulcna. MWDESMA CNDOv >/>. B \\xvi i lu. a. Shell hallow. Lunule narrnw Imt shaply defined. Kidge and sulcus rather \vhat in-regular <-<>ncentric lines of growth; on the dorsal slope and umhonal ri'lp' a number of large and very irregular undulations or depressions. Thi- -pecies is distinguished from K. gesneri Billings, sp,., and E. orthonnhtm M. A \V. -p., by its stronger lines of growth,, the irregular surface undulations, and mure uniformly rounded posterior margin. formation and^locaiitt.— "Upper Buff Beds" of the Tr>>rii<>M fnrinatlon, <>nc and a half miles west »f ll.'li>it, WtaootWteTwbWl It wan collf.-i.-ut more especially upon a difference in the composition of the sheik That -ome difference, whatever it* nature, really existed a comparison of the fossils will render ohvious at once. Thus, I have collected from the same bed of shale species of I/ . / .lopsis, Aetin»my+, Orthodetmn and /'M'/.X-KW/I./ The -li.-ll- ..f tin- tiiM three genera were coated with either a black or dark In-own film, while those of the last matched the color of the shales or were a few shades lighter. A Millie ;md not very typi.-al species occurs in the Galena of Minnesota. At least seven and probably eight species are found at various horizons in the Cin- cinnati jrroup. Two of these are figured on the preceding page and one was •rihed by me in 1^79 as Orthodesma subovale (Jour. Cin. Soc, Nat Hist., vol. _'. \>. The other- I hope to describe in the next report of the Geological Survey of Ohio. P-II.OCONCHA MIHNK8OTKN8I8, n. Sp. PLATB XXXVI. FI08. 31 and & 11 rather small, moderately elongate, highest posteriorly, the length about twice the greatest bight. Hinge line straight, nearly as long as the entire shell;, anterior end rounded, much narrower than the posterior; basal margin gently and uniformly convex; posterior end suhtruneate above, slightly produced and strongly rounded in the lower half. Valves rather strongly convex for the genus, the great- onvexit y in front of and above the middle. Beaks small, situated between one fifth and one sixth of the length of the shell behind the anterior extremity. Um- !"inal rid^e subangular in the rnstal region and unusually prominent for the genus. Anterior to the ridge the surface of the shell is gently convex. <'anlinal slope slightly concave, abrupt near the beaks. Surface marked with fine concentric lines which are thrown into obscure folds in crossing the umhonal ridjre. Internal char - unknown. This species is doubtfully referred to Psiloconcka. It differs from all the other species of the genus in its greater convexity, proportionally narrow interior end. and comparatively prominent umhonal ridge. I mi^'ht have placed it with tiphenolium, Miller, but the shell is not -uliicienf ly \vntricose. the unbones are too «mall. and there is no luiinle iti front of the beaks, while a -iiu'ht pi|> separates the edges of the valves at the ends. and locality.— Middle Galena, Pleuant Orore, MlnneaoU. 532 THE PALEONTOLOGY OF MINNESOTA. [Prolobella. Genus PROLOBELLA, n. gen. Shell equivalved, moderately convex, very inequilateral, obliquely acuminate- ovate. Anterior end very small, auriculate or subnasute, sharply distinguished from the body of the shell. Basal and posterior margins rounded. Hinge thin, apparently edentulous, rather short and not produced at the posterior extremity; just in front of the beaks a short clavicle-like process produces a sharp linear depression in casts of the interior. Surface marked with concentric lines of growth and radial striae or plications. Anterior adductor scar small, situated in the anterior lo.be. Posterior impression and pallial line not observed. Type: Prolobella striatula, n. sp. It is almost certain that Conrad's Avicula trentonensis and aviformis, which Hall in 1847 united as one species, are congeneric with the Minnesota species which is made the type of this new genus. These shells are not true Aviculldce, their valves being equal and without the prolonged posterior wing. Nor do they fit much better into any of the other families. They seem to be remnants of one of those complex primitive types that give the systematist so much trouble to classify. In this case there is almost as much reason for placing the genus with the AmbonycMidce as •with the Aviculidce or the Modiolopsidce. With such types it is good policy to defer conclusions until the collector has furnished us with the missing links. And they will be found sooner or later, for the lower paleozoic rocks are teeming with undis- covered fossils. PROLOBELLA STRIATULA, n. sp. PLATE XXXV. FIG. 27. Shell rather small, obliquely subovate, moderately convex. Anterior end very small, somewhat auriculate, narrowly rounded, and rather sharply distinguished from the rest of the shell. Cardinal margin straight, about half as long as the shell posterior to the beaks, passing with a gentle curve into the posterior margin, which is oblique and moderately convex to the lower third where the outline bends rapidly forward; basal margin almost uniformly convex; anterior outline strongly sinuate beneath the ear. Beaks full, slightly prominent, not much incurved, just in front of them the cast shows a vertical linear depression extending from the hinge half across the narrow sinuate part of the'shell. Umbonal ridge inconspicu- ous. Surface with a small number of obscure concentric lines, and in the antero- basal third with numerous very fine thread-like radiating striae. This species cannot be confounded with any other Minnesota bivalve known. From P. trentonensis Conrad, sp. of the Trenton of New York, it is readily distin- .,.,, -1:1.1.11. KAN, IIIATA -,.;.; j:ui*lied l,y its greater hight, dillerent outline, an, I liner radiatm- The latter are also most distinct in that species centrally win-re they are V • entirely in trfctofe formation and tooaMjf.-Mltldle Galena. Plevna t Grove, Minnesota. .ally Cl'RTODONTIDyE, n. fam. Shells commonly ovate or rounded, rurely elongate, valves generally ventricose or strongly convex. Shell substance calcareous, without epidermis, usually thick. Hinge plate often massive, strong, with from one to five cardinal teeth; elongate posterior lateral teeth usually present, but may be wanting. Ligament chielly. external. Anterior adductor scar strongly impressed, rather large though always Miialler than the much more faintly impressed posterior adductor. Pallial line simple. The generu included in this family seem to form a very natural group. With one exception. /V»/rWrv///./. Hall, a Devonian genus, they are all restricted to the Lower and Upper Silurian rocks and many of the species rank among the most important fo--iU of the various beds in which they occur. The individuals also are often very abundant, while their pn->c-r\ation is on an average better than that of any other group of paleozoic l.ivai The principal genera are variously placed by systematists, but the An-l,l,t have been most favored. The conclusions of the authors seem to have been biased by a supposed resemblance between the hinges of Cyrtodonta and Macrodon and to Stolic/ka the relation is so obvious that he is led to say "the former may be consid- ered as the predecessor of the latter in geological history." Now, after careful ; in. it K.D, I am obliged to dissent in so for at least as to claim that the case is tar from proved. So far as we can now tell the last species of Cyfalonla (Upper Silurian) are as far removed from Mm radon as are the earliest, while the first species of Mm-rodon (Devonian) is no nearer Cyrtoinntelieve, indicate something more than a merely accidental agre* I should hold that Macrodon was not a member of the I- ice that ^ei in- most certainly did not arise in ' 'f>-nodonta. 534 THE PALEONTOLOGY OF MINNESOTA. [Oyrtodonta. The Cyrtodontidce seem to me to be a family of shells that is essentially Lower Silurian, the Upper Silurian species being both few in number and of small size and thin-shelled. Indeed the evidence at hand goes to show that the family became practically Bxtinct with the close of the Upper Silurian. If this is true then we cannot very well ally them with recent families of shells, and as they con- stitute an easily recognized group of genera it has been deemed necessary to estab- lish a new family for their reception. The Cyrtodontida>, despite the well developed dentition prevailing among the typical members, seem to represent a very early type of structure, and one that probably antedated both the Ambonychiidae and Modiolopsidce, to which also they appear to be more closely related than to any other of the contemporaneous families. Thus certain of the earliest species of Vanuxemia (e. g. V. terminalis) greatly resemble true Ambonychia, while the majority of the Modiolopsidce present, aside from the hinge, an internal conformation of parts that is decidedly like the prevailing appearance in the present family. Perhaps the only constant difference between the shells of these three families is that while those of the Ambonychiidce and Modiolopidce were provided with a well developed epidermis those of the Cyrtodontidce preserve no trace of such a covering. Genus CYRTODONTA, Billings. Cyrtodonta, BILLINGS, 1858, Can. Nat. and Qeol., vol. 3* p. 431. Palcearca, HALL, 1859, Pal. N. Y. vol. ill, p. 27: also 12th Rep. Reg. N. Y. Mus. Nat. Hist., p. 10. Angellum, S. A. MILLER, 1878, Jour. Cin. Soc. Nat. Hist., vol. i, p. 105. Cypricardites, HALL, and most American authors, (not of CONRAD). Shell varying from transversely or obliquely ovate to subcircular, moderately ventricose. Beaks prominent, rather tumid, incurved, situated in the anterior third, fourth or fifth of the shell. Surface marked with concentric lines of growth. No lunule nor escutcheon. Hinge plate strong, nearly straight, often with a narrow and not sharply defined ligamental area. Cardinal teeth well developed, subequal, generally obliquely curved, sometimes nearly horizontal, two to four in each valye, situated mostly in front of the beaks. Posterior lateral teeth usually two or three in each valve, strong, elongate, more or less curved and slightly oblique, situated near the extremity of the hinge. Adductor muscular scars placed immediately beneath the two sets of teeth, both subovate, the posterior very faint, the anterior only moderately impressed. Pallial line simple. Types: C. rugosus and C. canadensis of Billings. This is an excellently defined genus and one of the largest of the paleozoic genera of Lamellibranchiata. It is also pre-eminently a Lower Silurian genus, the MliK \\< Ml VTA -I'tnlft | I pper Silurian form- now referred t«. it l.ring luit impoverished remnants of the powerful .-tuck tliat preceeded them. ••x liave l>een placed under Cyrtodonta or Cypi \\ i* n-ually conM-iere.l a> identical, that have no right there. Thus of forty-nine species '•i.i I at CypriomKta K\ B. A. Miller in the 1889 •dttkmol hkNortfi \mei- QeoL ami 1'al.. only eleven can with reasonable certainty be said to belong to Cyrtodonta. These > /en*!*. Inironetuis, rugosa, spinifera and xubcarinata, all •iKe.l l'\ Milling V/y//,i Meek and Worthen, and C. obtusa, $affordi, suban-in- ami snlisiHifulntn of Hall. The remainder belong to \Vhitflla. Ortonella, Vanux- in and .\ftxlinlodon, or are too little known for positive generic placement.* EM mentioned we must add seven that have been described since the pnMieation of Mr. Miller's list: also fifteen new species, of which ten are published in thi* work This makes a total of twenty-six valid Lower Silurian • species positively known to have the characters of the genus as above defined. Two I pper Siluriai , us Hall ami .17. jirtmigenia Conrad, ap., fall under Cyrtodonta. These have unusually thin shells but their binges are essentially as rir>ir">•>! Hillings proposed and fully illustrated his genus Cyrtodonta. In the following year Hall published (in Pal. N. Y., vol. iii. p. 27, and 12th Rep. Reg. N. Y. p. 10) his genus PaUearca in which he proposed to include precisely the same group of shells. In the museum report mentioned (p. 13) Hall reproduces Conrad's sketch of the hinge of irditts with the remark that both the descrip- tion ami figure of that genus as given by Conrad correspond in many respects with /'"•' -hdiil.l an examination of the typical species prove the two identical atvr name will give place to that of Cyfiri Finally in a supplemen- tary note to vol. iii ip. .Yjl) he again uses this cut ami now adopts CypricardUes in place of hi-/ .1 ml Hilling*' two genera Cyrtodonfa and Vanuxemia. I have not noticed that the Canadian geologists have given up the use of Cyrtodonta. In the United States however, with a few exceptions all use Cy]»-ir,ir:* instead, while of European authors Uigsby adopted Pa/awmi and the majority of the otl < 't/r/oH(a. •Tbr following belonc lo HTWtaBn: klitdivtd plrfwirtof BUlinti.; DMpOMtomii vat qtutmftlarl* of Whllflvld: •Ur^ln^Hiti§ Meek ud Worxbeo: ud WMHMM of BalL Tb« n»w g~*r» OrU~tU l» to*»Ar4 mfam C. ***-! t. A. Mlllrr C.MB^MMM Afford, ud Hlata. imMnmhH mad rrtuii*ilii Hall, bclonc to rowmmte. white C. va*n and »lu*mt at tefford twfcwc to UM 536 THE PALEONTOLOGY OF MINNESOTA. [Cyrtodonta subovata. The above is a fair statement of the case as I found it when I began the present work. Had my studies shown what both Billings and Hall conceded to be the case, that Conrad's sketch of the hinge of Cypricardites was identical with that of Cyrtodonta and Pala'arca,. I would most surely have sided with Hall and adopted the oldest name. But here was the rub. Comparisons with the hinges of numerous species of this family of shells have demonstrated beyond question that Conrad's figure and description of the hinge of Cypricardites does not correspond exactly with that of any true Cyrtodonta or Vanuxemia known. He represents the cardinal teeth as diverging from the beak much as in a Lyrodesma and says that the anterior one is the "largest and most prominent". Neither of these conditions is ever present in Crytodonta. On the contrary the teeth are subparallel, and to be called horizontal rather than radial, while the anterior one, if any can be so called, is the smaller. Nor have I seen any Cyrtodonta with five cardinal teeth, the usual number being three; two is not uncommon, but four is very rare. We are now confronted with the question, did Conrad correctly describe and illustrate the hinge of his genus? This question can be determined only by a study of the type of the genus. But here again we meet with trouble for of the sixteen species originally referred to the genus only one, his C. curtus remains, the others having proved generically distinct, being now referred to other genera. The genus must then, if it stands at all, be based upon C. curtus. I do not know whether the hinge drawn by Conrad represents that of this species or not. For the present we must assume that it does, and further, until we know the contrary, it must be accepted as correct. From this standpoint then it is evident that Cyrtodonta and Cypricardites are not synomymous, and that both may stand for the present. I would suggest that, however the question may be eventually terminated, Cypricar- dites may for a long time to come serve as a convenient temporary receptacle for those species which because they are insufficiently known cannot be definitely placed into other genera. CYRTODONTA PLATE XXXIX. FIGS. 28, 20, 31-33, ? 30 ami '- V,. .Shell somewhat obliquely ovate, narrowest anteriorly. Dorsal margin short, less than half the length of the shell posterior to the beaks merging gradually into the uniformly rounded posterior margin, base gently convex, anterior end short and rather narrowly rounded; outline distinctly concave between the anterior extremity and the projecting umbones. Beaks incurved, umbones prominently rounded, inconspicuous. A slight flattening of the surface between the umbonal ridge and •I I.I II;K\M IIIATA. •lit. the anterior basal margin. Surface i •umitli in tlit> youn^ and middle stage* but with age one or more very s fro i -inal imbrications are developed. In aged examples the anterior end i- proportionally narrower than in younger ones. Hinge plate of moderate length with a narrow ligamentul area. Cardinal teeth three in eurh valve, sub-liori/ontal, their inner ends thickene. which i- from the Trenton limestone at Cannon Falls, also di tiers a little, "but in this case oblique pressure has produced distortion that may account for the differences. Thisrspeeic* ieetesely related to both f '. Awromr/mrand rnnadensis which Hillings dwuibcd from the lower Trenton or Hlack Hirer limestone of Lmke Huron. Com- pared with iwthontio specimens the first proves to he narrower posteriorly and the s»eond wider in front, rn the latter the -nmbone» are also more inflated. The hinges of the two apacioo ao figured by HiHinps «re atoo somewhat formation and locality \*n (if the «pccle« were found In tb.- Ittnlwye »nd low.-r Tn-iit.ni llmestooe near Hlj;h Hn utky. The uritdnal of Fi*tirv :«> i- fn.tu Hi-- tui.ld!.- thirtl of tin- Tfiiton •balwatSt. Anthony I'ark, Si. I'aul. That of Figure 45 from th. Tr.-nton llmedtooe at Cannon Fall*. . TODONTA JANESVILLKNSI8, H. Sp. PLATE XXXIX. riOS. » »nd ». Coinp. Cgrtodonta AUKMMNJU BtllingB, 1858, Can. Nat. and Goo!., vol. til. p. 432. Shell of medium si/.e, strongly convex, somewhat obliquely ovate, wide-t posteriorly, the hight ami length about as two is to three. Outline almost uniformly rounded for an oval, with a -liu'lit prominence at the beaks and occasion- ally at the posterior end of the hinge line. Anterior end very short. Beaks a little compressed, rather small, incurved, projecting hut little above the hinge. In casts of the interior the umbonal ridge is strongly and the surface in front of it slightly depressed. Anterior adductor scar, well defined, ovate, small, not more than half the size of the posterior scar. The latter as usual is scarcely -liable. I'.illial line well in. irk- I. particularly in the basal and anterior parts, llm^e plate 538 THE PALEONTOLOGY OF MINNESOTA. [Cyrtodonta ;unpl;i of moderate strength; cardinal teeth -three in each valve, sub-equal, curved and rather oblique; posterior teeth slender, two or three in each valve. Surface of shell with somewhat irregular concentric lines of growth. No trace of these are to be seen in casts of the interior. It is possible that the casts above described really belong to C. htironensis. Although I have compared them with an authentic example of that species, labelled by Billings himself as from the original locality for the species, I could not satisfy myself. The Wisconsin casts are certainly distinct from this specimen, having smaller umbones and shorter anterior end, but the latter also does not agree with Billings' figures. Very likely the illustrations are not entirely trustworthy. Compared with C. subovata, the species is distinguished by its shorter, narrower, and less distinct anterior end, comparatively greater length, less produced and more oblique cardinal teeth, and more distinct muscular and pallial impressions. That species also attains greater size. Formation and locality.—" Lower Blue beds" of the Trenton at Janesville and Beloit, Wisconsin. Mu». Reg. No. 8323. CYRTODONTA AMPLA, n. sp. PLATE XXXIX, FIG. 34. In the outline this species resembles C. subovata and C. janesvillensis very closely. It is known only from casts, but these are distinguished at once by the oblique ridge running from the beak toward the posterior third of the base. On the anterior side the surface descends sharply from the ridge into an unusually wide flattened space. C. janesvillensis is also narrower anteriorly and relatively more convex. Another species with which it is to be compared is the Galena form described by Meek and Worthen as C. obliqua. The outline of that species is different being narrower in front and more produced in the pqstero-basal region, giving the shell a more erect appearance. Its valves are also a little more convex. C. glabella is shorter. In the associated forms of Vanuxemia the anterior adductor scar is much more sharply defined. Formation and locality. — Trenton limestone, Cannon Falls, Minnesota. CYKTODONTA BILLINGSI, n. sp. PLATE XL, FIGS. 2-6. Cypricardites ventricosus Whitfield, 1882 Geol. VVis., vol. i v, p. 209, pi. 5, fig. !i. Shell of medium size or less, transverse, obliquely ovate, highest in the posterior half; valves strongly ventricose in the umbonal and central regions. Hinge line at least two-thirds the length of the shell, slightly arcuate, posteriorly declining I.AMKI.I.lHKANi I11AI \ 589 '.«•!. I and passing gradually into the broadly and uniformly curved posterior r basal line most proinii t an. I >tn>n^: \ liehind the center, in frontof which point it ascends rather npidly with a much more gentle curve into the short, small ami sharply rounded anterior end. Umbones full, large and prominent, beaks -null ami «.trontfly incurved: umliomil ridge siihangular near the beaks only, iucon- -picmui- in a lateral view. Surface marked with concentric lines of growth. These, with the exception of a few near the margin, are obscure in the material at hand. •Mental area very narrow. Hinge plate of moderate strength, with three slightly curved and nearly horizontal cardinal teeth and two or three slender posterior lateral teeth in each \al\ «• Pallial line and anterior adductor muscle distinct, the •!• rather small and of obovate or subrirrular shape; posterior adductor faintly impressed, -ituated immediately beneath the lateral teeth. Internal umbonal sulcns and ridge slightly developed but always distinguishable on good casts of the interior. Although closely simulating several others this is still to be regarded as a well marked species. It may be compared with C. huronensis Billings but will be found to be higher, more erect and more ventricose. The umbones also are larger and the cardinal teeth longer and more nearly horizontal. C. obliqua Meek and Worthen has a straighter basal line and is more produced in the postero-ventral region. C. ylaMlus and C. persimilis have a more rounded outline and smaller umbones. C. subovata is longer, wider in front, not so ventricose, and has smaller umbones. A shell that is likely to prove more troublesome to separate than any of these is the •'.//<- iixfinla decipiens. They are associated in the same strata at Minneapolis but when good casts are available they may be distinguished at once by the higher position and much greater sharpness of definition of the anterior muscular scar in the I ' i>M—iMe that the \Visconsinspeciesreferred by Whitfield to Cypricm ventricosus Hall, sp., in 1882 (loc. cit) is not identical with C. f illustration, if correctly drawn, would indicate a distinct form. However that may lie it is quite certain that he had this species before him when he drew up his description, since it is not uncommon at the localities mentioned by him. It is en-tain also that neither the specimen figured by him nor the form now narm-d after Mr. K. Hillings, the founder of the genus, are the same as the types of Hall's /•;.///«,Wm rentrii',,*,! (Pal. N. V.. vol. i. p. I'M: 1M7|. Indeed they are widely di- tim-t nor 'odonta at all. On page 271. Pal. N V . vol. iii. Hall figures another species of t'Hlnntti which he refers to his vtntricoaa as a ral;i. Th • i- w same as C. billingsi being longer and having a well developed legamental area and 540 THE PALEONTOLOGY OF MINNESOTA. ICyrtodonta affinls. different cardinal teeth. In all these respects the shell agrees much better with an authentic example of C. carinata Billings, now before me, and as both the Palwarca ventricosa of Hall and the Cyrtodonta subcarinala of Billings are from the Trenton limestone in the northern part of Lake Huron, they are probably indentical. Formation and locality.— Lower Trenton limestone Dunleith, Illinois; Beloit, Janesville and Mineral Point, Wisconsin; Cannon Falls and Minneapolis, Minnesota. CYRTODONTA OBLIQUA Meek and Worthen. PLATE XXXIX, FIG3. 35 and 36. Cypricardites obliquus MEEK and WOKTHEN, 1868, Geol. Sur. 111., vol. lii, p. 311. Of this species I have seen only the original type figured and described by the authors. Their figures being unsatisfactory, it seemed worth the while to prepare others, especially as the species may at any time be found within the limits of the State. It is to be looked for in the middle and lower beds of the Galena in Fillmore county. The type specimen is from the Galena at Scales Mound, Illinois, and is now preserved in the Illinois State Museum. CYRTODONTA AFFINIS, n. sp. PLATE XXXIX, FIGS. 20-23. Shell small, rather compressed convex, obliquely subovate, alated and much the highest posteriorly. Dorsal margin straight or very gently arcuate, rather long, not passing gradually into the broadly and uniformly rounded posterior margin, the junction being obtusely angular; ventral margin but little convex, ascending rapidly to the small and narrowly rounded anterior end. Beaks small, projecting very little; umbones compressed, due to a flattening of the antero- ventral slope; umbonal ridge moderately distinct in the upper half; cardinal slope gently concave; greatest thickness on the umbonal ridge above and a trifle in front of the center of the valves. Surface with fine indistinct concentric strh« and distinct sublamellose lines of growth. Hinge of moderate thickness; cardinal teeth small, short, four in each valve; posterior lateral teeth very slender, four in the right valve. Muscular im- pressions rather faint, not well determined. Length 20 mm.; posterior (greatest) hight 15 mm.; anterior highest 10 mm.; entire thickness 6.5 mm. A variety reappears in the middle Galena. This is relatively more convex and not quite as high posteriorly. Length 15 mm.; hight 10 mm.; thickness 7 mm. It may be distinguished as var. fillmorensis. The typical form of this species is associated and was at first confounded with Mutltcrlii ruyosa. Aside from the hinge, which is of course very different in the two forms, the Mather in is distinguished by its much shorter, subtruncate anterior end. •KI.I.IHKAV IIIATA "•»! • I. >nt a p»r»».l Citrtnlnntu hulli Nettleroth. -p.. fntin t lie upper ln-.U of tin- llud-on river ^roup of Kentucky. is shorter and thicker. an. I ha< more prominent Leaks and uinl>onal rid Formation and locality.— Thf typical fnrm upper part nf tin- mnl.i;.' third i.f tin- I i. .11 v Mi i.f Can iiMMOta. The Calroa variety was collected n«mr Wykoff, III I1 liilll»r.- r CTRTODONTA. PARVA, n I'l.Al I \\\l\. 1 li.- ?4»nd ». This small species seems to be closely related to C. ajjinis 1'lrich and ('. lialli Nettlenith. sp. In some respects it is intermediate between those species, ditlering from the tii st iii its greater convexity, stronger umbonal ridge and larger anterior end, these beiiiK point- m which the shell agrees rather closely with the latter. From both it di tiers in the more abruptly rounded postero-basal margin and straighter ventral outline. Adductor scars very faint, undetermined. The specimen being a cast of the interior, the detail of the hingement could not be made out with certainty. ^atest length, 9.5 mm.; greatest hight, 6.5 mm.: thickness, 4.5 mm. Formation and locality.— Middle Galena, near Fountain, Minnesota. CYRTODONTA ROITLATA, n. sp. PLA ; • IIUB. »-». Shell small, moderately ventricose, nearly erect, the outline uniformly rounded iMilirirculur) except at the dorsal margin, which is straight behind the beaks and somewhat insinuated in front of them; hight and length about as five is to six; posterior extremity of hinge angular. Beaks small, incurved, scarcely prominent, Mttiated about one-fourth of the length of the shell behind the most prominent point on the anterior margin. Umbonal region full, but not excessively so; point of greatest convexity a little above and in front of the center of the valves; postero cardinal -lope gently concave, cau^injz this part of the shell to appear as slightly alate. Surface marked with tim> concentric lines, with a few (those shown in the illustrations) stronger th.m the rest. Shell and hinge plate thin; dentition undeter- mined beyond this that it is essentially as called for by the genus. Muscular scars unknown. I am not acquainted with any species of Cyrlndnnt'i. d»>>cril»ed heretofore, with which this one mi^'ht l»e .-unfounded. ' y.fr>»»»///>- 1'lrich. a much larger speciee, is in outline somewhat like it. hut on comparison proves to have the beaks situated farther forward and to be proportionally less ventricose. S« i-ecies belonging 542 THE PALEONTOLOGY OF MINNESOTA. [Cyrtodonta obesa. to the genus Vanuxemia agree even more closely in their outlines, but in all of them the shell is much thicker and the hinge generically different. Of all known species the two next described are to be considered as the nearest. Formation and locality.— The real types of the species were obtained from Mercer county, Ken- tucky, where they were found in a cherty bed equivalent to the Black River limestone of New York. Two specimens, both a little larger than the Kentucky types, were collected in Minnesota. Both are from the middle third of the Trenton shales, one at Minneapolis, the other near Fountain. Mus. Reg. No. 8336. CYRTODONTA OBESA, n. sp. PLATE XXXIX, FIGS. 10, 11 and 12. This species is, so far as our knowledge extends, very closely allied to C. rotulata. It is also associated with it in both Kentucky and Minnesota, but I cannot say that I experienced much trouble in separating them. C. obesa is more gibbous and oblique, the anterior end is shorter and much more obtuse in a cardinal view, the posterior cardinal slope narrower and scarcely to be described as alate, while the outline at this extremity of the hinge is more rounded; the entire outline is to be called broadly ovate rather than subcircular. The umbones also are more prominent and inflated. Length, 14 mm.; from beak to posterior extremity, 14 mm.; hight at center of shell, 11.; thickness, 10.5 mm. In another specimen these dimensions are respectively 14.2, 14, 11 and 10 mm. The above measurements are furnished by two silicified examples from Kentucky, which are to be regarded as the types of the species. Besides these two evidently young shells from Minnesota localities are referred here provisionally. They are too oblique for C. rotulata and have not the proper shape for C. cingulata. The out- line is very nearly as in C. obesa, but they differ from the Kentucky specimens in being less gibbous, especially in the umbonal region. Formation and locality.— In cherty beds equivalent to the Black River limestone of New York, in Mercer county, Kentucky. Specimens doubtfully referred to the spocios were found in the middle! third of the Trenton shales at St. Paul and Preston. Minnesota. CYRTODONTA GIBBERA, n. sp. PLATE XXXIX. FIGS. 13-15. In this specimen the umbones are more inflated even than in C. obesa. They are also situated farther forward, the anterior end being very short and exceedingly obtuse. Although the posterior extremity is subangular, the form on the whole is more rotund, the hight of the shell being greater. C. rotulata is much less gibbous in the umbonal and central regions, less oblique and a little longer, particularly in LAMKl.UHi: AM MIA •loot* (UbrlU. flu- part that i- in front of the beaks. Several spent'- <>f l'./m dillerent intern- ally, >•) that casts of the interior could not possibly l>e confounded. l-.-n-tli. ll.-J iniii.: from umbone to postero-basal margin. U.s mm.: bight at middle of -hell. 1:1 mm. thickne—. 11 mm. 'i/ify.— Due of Hi- mlddl.- Catena, about thirteen mile* M>utb of Cannon KalU, CTRTODOMTA OLA BELLA LYnV/,. 1'I.ATK \\\l\ I IOS. J7»od «.. ~\cardit*» gla> 1888, NIoeUM-ntli Ann. R«p. Ocol. and Nat. Hlat. Sur. Minn., rM. Ctprifantitet minnr*>frn«j SAKDK8ON, April, 1892. Bull. Minn. Acad. Nat Scl., vol. III. p. 338. Shell of medium -i/e. moderately convex; broad ovate or subquadrangular in outline, with the back straight ann full, with the line of greatest convexity — not sufficiently defined to be called a ridge — extending obliquely across the valve from the beak linal -lope Hat, rather al>rupt; between this and the undefined umbonal ridge, the surface is again tlatteiifl: anterior and basal slopes gently convex. Surface marked with somewhat irregular concentric lines of growth. Good moulds of the interior show that the hinge plate was strong, the liga- mental area very narrow, the cardinal teeth at least two and strong, and the poster- ior teeth two or three in each valve. The beaks are prominent, incurved, and com- -ed because of a sulcus that crosses the valves a little obliquely, but is lost before reaching one-half the distance to the ventral border. On each side of the sulcu- i- a faint ridge. Anterior adductor distinct, rather small, ovate, acuminate below. 1'allialline distinct, especially the anterior part where it appears as a sharply • letint-.l pu-tulo-e ri'lge in the cast. Posterior adductor ovate, the long diameter • :<-al. nearly three time- the size of the anterior, situated ahout one-third of it.- length beneath the posterior end of the hinge plate. Thi> tine shell is an early form of the group of species of which C. germ 'lillinysi are more typical representatives. It is di.-tiiij/uished from them all l>\ the more anterior position of the beaks, and great- r promin. of the antero-basal margin. The next species, though very similar in most respects, belongs to another group of species, in which the internal r id stilru- i- indistinguishable. 544 THE PALEONTOLOGY OF MINNESOTA. [Cyrtodonta pesrslrallis . Formation and locality.— The original type is from the middle third of the Trenton shales at Minne- apolis. A small cast of the interior, belonging to the survey collection, was found in the building lime- stone at the same place. Casts occur also in the lower Trenton limestone at Beloit, Wisconsin and Dun- leith, Illinois. Mus. Reg. No. 5100. CYRTODONTA PERSIMILIS, n. sp. PLATE XXXIX, FIGS. 41 and 44. This form, which is known only from casts of the interior, was confused with C. glabella until a critical comparison proved it to be not only distinct but to belong to another group of species. The outline is very much alike in the two species, but here even some constant differences are to be observed, especially in the shape of the margin at the posterior extremity of the hinge, where the present species is more angular. But the main difference lies in the fullness of the umbones, there being no appreciable sign of the sulcus and ridge which cross this portion of casts of that species. This difference is very obvious after it has once been pointed out. The beaks are also more strongly incurved and the hinge bent downward anteriorly in a greater degree, while the plate is probably also of less width. Finally, the posterior muscular scar is closer to the hinge and the longer diameter of the impressions more oblique. The systematic position of the species is near C. rotulata, C. cingulata, and C. tenella. The first is more rotund in outline, less oblique and has fuller umbones, the others are higher and have the beaks situated farther behind the anterior extremity. At Minneapolis C. persimilis is associated with a small Vanuxemia that is not easily distinguished unless the casts are clean and in good condition. The latter (V. decipiens,)differB somewhat in its outline being proportionally narrower anteriorly, but the principal difference lies in the character of the anterior adductor scar, which is much more distinct from the umbonal cavity. In short, the species is not a Crytodonta but a Vanuxemia as now defined. Formation and Locality.— Trenton limestones, Minneapolis, Minnesota, "Lower Blue Hods" of the Trenton formation at lir.loit, Wisconsin. CYRTODONTA OVIFORMIS, Ulrich. PI, ATI: \\\i.\. Kit;. i.;; IM.ATFO XL. FIG. i. Cypricarditex oviformis I'LKK n. 1802. Amer. Geol., vol. x, j>. !)!i. Shell rather above the medium in size, moderately convex, but little oblique, the outline almost regularly oval, with the posterior end a little the widest and a slight straightening along the cardinal margin. Beaks small, situated between one-fourth and one-fifth of the length behind the anterior extremity; erect, compressed and not LAMKLLIBBANi ill \ I \. .•iiUln ] incurved in ca-K ..f the intci mr; in the sln-M projecting \.-ry little al.ove the hinge line. . 1'iiil.onal ridge very indistinct. with tin- [mint of greatest c,,i,\exity a little above ami in fmnt of the middle. in t lie ca^ts there is a more or less sharply defined ami unusually wiile depressed or llatteneil strip running from the Leaks downward. Hinge plate wide ani-iuii nf the Geological and Natural nesota. Mut. Reg. No. ." €•» CLATA Ulrich. II • I 108. 7 »ud I. CypricariKtrifinijul'it.i i ,. • 11 -UH-nth Ann. Rep^Gool. and NaU HUt Sur. Minn., p.tt6. • MMu- the medium size, ventricose in the central and umbonal region, ol>li«|ue. narrow anteriorly and broadly rounded posteriorly; the outline on the whole, excepting a slight prominence at the postero-cardinal edge, almost regu- larly ovate; hinge line rather short posterior to the beaks, slightly convex. Beaks of good • rongly incurved, projecting well above the hinge, situated a little more than one-fourth of the entire length behind the anterior extremity; umbonee prominent, full, with an obtusa ridge or line of greatest altitude running from the beak rds the postero-basal side: anterior and cardinal slopes both .-lightly ooacave. the latter descending more rapidly. Point of greatest convexity near the middle of a line drawn parallel with and one third of the bight of the shell beneath the hinge. Surface marked with v.-ry tine concentric line-. <•. 'faded, and distant irregular lines or wrinkles of growth. Shell sub-tance thin. Internal c: acter- unknown. -35 546 THE PALEONTOLOGY OF MINNESOTA. LOyrtodontu tcnella. This species seems to be rather closely related to Cijrtodonta canadensis Billings, but is more erect, comparatively higher posteriorly and has its outline more pro- duced and more sharply rounded in the postero-cardinal region. C.tenella has a longer hinge line and is more uniformly convex. C. grandis Ulrich, is a larger and almost circular shell. Although the hinge and internal characters are unknown, I cannot doubt that the species is a true Cyrtodonta. I judge further that it belongs to the group of species of which C. persimilis and C. rotjilata are typical members* Formation and locality. — Middle third of the Trenton shales, Minneapolis, Minnesota. CYKTODONTA TENELLA Ulrich. PLATE XL. FIGS. 15-19. Cypricardites tenellusULRicn, 1892. Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 237. Shell of medium size or less, moderately ventricose, not very oblique, subovate, widest posteriorly, slightly alate and subangular or sharply rounded in the postero- cardinal region. Hinge line long, slightly arcuate, posterior margin straightened in the upper half, broadly rounded and produced a little in the lower half; ventral margin rather strongly convex, most prominent a little behind the middle; anterior end more or less narrowly rounded. Beaks small, incurved, projecting moderately beyond the hinge line; situated about one-fourth of the entire length behind the anterior extremity; umbones full, prominently rounded. Cardinal slope slightly concave. Surface marked with rather tine concentric striae, and sometimes with strong distant lines of growth as well. • Shell substance very thin. Hinge plate narrow, a good part of it forming a finely striated ligamental area; two very slender posterior lateral teeth in the right valve, and the same number probably in the left; anterior teeth obscure in the specimen, consisting apparently of two slight horizontal folds in the margin of the shell, muscular impressions very faint. The hinge plate and teeth are thinner in this species than in any other known from Lower Silurian deposits. In two Upper Silurian species, however, C. primigenia Conrad, sp. (Medina), and C. dictica Hall, sp. (Niagara), the hinge is quite as slender if not more so. C. cingulata is a more ventricose shell, especially in the central and umbonal regions; the outline is a little different, being longer from the beaks to the postero- ventral margin, and the hinge line shorter. C. grandis and its varieties germana and luculenta, the first and second from the Galena, the last from the Hudson River group, are very similar shells, differing chiefly in the greater strength of their hinges. IKLLIbUANCHlATA of wliiit may !>•« a -mall variety of < .!• nc/ln occur in the Trenton liniostonr at Minneapolis. The largest seen (Muv K.^'- N" ^"">. i- »nly 1- nun. l.»n^. Aside from the matter <>f -\/>\ they agree very well indeed with the types of the species. and loeiilit]/. f|i|>. -r j.arl "1 inidd!.- t hinl nf ' ilcn, about «lx rollM •OUth of OUBM Kails, Mtu. Reg. No. 8339. OKA^•|)I- I'lrn-li; uml I I \TE XI.. FI08. rirardifM yram/u ri.un ii. lv«i. An. Q ytrmaHU* I'l .1:1. n. I-'. iittiAnn : N i' II " mi., p. 836. liirulrntui SAKUKKON. 1892. Hull. Minn. Acad • Cyrtodonla grandit, and v;i - :in«l la! "f a |»T' upper Tn-num. twr, miles south »f Hiiruin. K. of a small left va: ••. with -itninciT surfari- m;irkir . • and local irly.'ntir.- ra- small frm«iii.-nt «.f a cast -if th-- int«>rl:>r 'if a , pn-«-rvi: ' «n'l cardinal t.-.-!h. g. Irawn wi- so as to show th«- ''nti: .imwn In flifun- <• and !>»• a large ri^-lit valve of gtrv Tin' specimen i- preserved as a partial mould of the exterior. Another -perimen fnun t!i»> lialena near Wykoll may l>e -aid to he identical in it- characters with the original types of gerwtinn. The >p(>riiiu>ii represented l.y tig. 10 is one of a number in which the Balance of agreements i> with the variety rather than with typical ynimlis. while tin- original of fig. 11 was made \ther \ariety wa> found in the Trenton of -ee by Prof. Jas. M. Saflord, ami sent to m<> for examination. The illustrations -how that in its outline and general appearance this new \. riety gernutna and ('Jfiiflla. It differs, however, in the teeth which are stronger and more curve-1 than in those forms, being on the whole more like those of ( '. ,/r.indis and C. *«//»/e called < 'i/rtmlnnfu i/rnntlix, var. ind-riHnlin. Mr. Sardeson has Driven the name Inmli-nt'i doc. cit.) to a Hudson River form of which the hin^e and exterior of two fair examples are represented on Plate XL, by figs. 1:5 and 1 J. This form I cannot now regard as specifically distinct from C. yrandis, -ince it is almost identical with var. :/» -inana, the only dillerence being small ones in the hinge and that the umbones are somewhat larger in the luculeiiln. Two other stages in the development of this series of shells, in these cases per- haps of specific importance, occur in the upper beds of the Cincinnati group at Nirh- mond, Indiana. These I hope to describe in another publication. P,>rmntiiin an>t lnrtilil>j.-'l: f C. grandit and the var. germana, are fnun tin- u|i|HTTi . Ii.uivill,'. K.-ntii.'kv. Ca-i- "f 1 he species and variety have Ix-vn found in th«' middle and ; Wyktiff, Linn- Ciiy, and otln-r liK-.ilitl«i ID Mlm 'media !• «o far km.wi. fn.in th-- 'I - null, in T.Tin.-sscc, when- it i.'-i-ur- in a — «-i;il mil with I ily llm«iUtni-i..f tip II -r group at Granger and ntlu-r - in Fllliiion* count " - >ta. Mu». K*g. Nt*. > S380, 8333. Var. luculenta "332. DUfl \ AM XKMIA. Hillings. r.mujrmui, lln.i P l««. ico-e. olili«|iie. acuminate ovate to -nil.circular; anterior end very short and small, the posterior l.roadly rounded. I'mLone- full, prominent, \yosiks strongly incurved. Surface with concentric growth lines only. Hin^e -tron^. with teeth as in Ci/H'xl-mf'i. two to four, rarely more, cardinal, and two to four posterior lat> teeth in each valve. T. iuently striated tra- B elongated ligUMBta] area generally | Iductors. the anterior depn—ion very -harply delined and deep, and -ituatod in a prolongation from the anterior end of the hinp- \ 550 THE PALEONTOLOGY OF MINNESOTA. [Vaiui.xeintii dixoiiensis. in casts of the interior forming a distinct lobe-like prominence, often of reniform shape, immediately in front and sometimes partly between the filling of the beaks. Posterior scar indistinct, larger than the anterior. Pallial line simple. Internal umbonal ridge well developed. Type: Vanuxemia inconstans Billings. As a rule this genus can be distinguished from Cyrtodonta by the more nearly terminal position and greater prominence of the beaks, but the final and only reliable test lies in the position and character of the anterior adductor scar. -This, in being excavated out of the hinge plate instead of being placed on the floor of the valve, makes so obvious a difference that I cannot see, now that it is pointed out, how any one can fail to discriminate between the two genera. Between twenty and twenty-five valid species of Vanuxemia are known to me. They are all Lower Silurian and, although Billings has placed a Devonian shell here, I am almost satisfied that the genus became extinct with the close of the Hudson River deposits. VANUXEMIA DIXONENS-IS Meek and Worthen. PLATE XXXVIII, FIGS. 1-5. Vanuxemia dixonensis MEEK AND WORTHEN. Pro. Chicago Acad. Sci., vol. i, p. 16; also 1868, Geol. Sur. 111., vol. ill, p. 297, pi. 1, flg. 5a, b. Shell beneath medium size, very gibbous, obliquely acuminate-ovate, the nar- rowly rounded rostrum forming the small end of the oval. Outline gently arcuate dorsally, and usually rather sharply rounded at the posterior extremity of the hinge; from this point around the lower half of the shell, the outline sometimes forms a regular semicircle, but it is more common to find that the center of the base is more or less produced. (See fig. 4.) Anterior end rounded, projecting very little, if at all, beyond the nearly terminal beaks. Beneath the latter the outline is insinuated often strongly, but in most cases more gently than in fig. 5; in a front view an unde- fined heart-shaped lunule-like depression. Umbones tumid and prominent, with the beaks curving strongly inward and forward. An obtuse curving ridge extends from each beak backward along the depressed hinge line. These dorsal ridges form a broad flattened or rather concave" back to the closed valves. Just within them an impressed line, defining a lanceolate escutcheon-like area, is sometimes distinguish- able. Surface marked with strong, but unequal concentric lines of growth. In casts of the interior the beaks stand far apart (much more so than in the shell), are very prominent, broad, much compressed, concave on the inner side, sharp- edged in front and very little incurved, while a more or less strong and nearly vertical sulcus and ridge marks the anterior half. The dorsal ridges are shaiper than < r. th \ »mnrn.:» .ll>. .111-11. 1. rmr. llu< -hell it-elf, iiii-1 a flattening of tin- -urface boneatli thoni i- u-ually di-tinpii-l, Anterior niu-ciilar impivs-ion di-tinrt, rciiifdnii, the pair funning ;i strongly i>-lined lobe at the ha-e ;> ami well rounded in I", ili.i-inrnxis.. .pared with other species, I'. i-»tnmine at Miaoen; '. Paul; less abundant a i . utti.-r loralttlfs In .uebedi" •t Jancsvilk-. Illinolt. Xtu. Reg. Nos. 202, 320, 070, 3030, 5006, S62S, 5527, 6ff7«, 8322, 8930, 8331. V \NI-.\K.MI\ m\ ii. PL* This name is propo-e-l pn>vi>ionally for one or two casts differing from the ordinary form of I". <-onsin. A few specimens from the upper part of the limestone at Minneapolis, are doubtfully referred here. Mil*. Reg. Nos. ?5101, 8319, 8321. , i.. \MKI.I.IHK.\N. iii.\T\ ;,;,:{ -ul- rr. t« ! >. ;i. itp. I'l • .-. »-**. Q0>ri.->ir./ifrjn>rur: . 1. 1 Wmi KIKI.I.. 1-71. ! ,.. vol. Iv, p. 808. pi. V. 11*. II. Casts of the interior tabouroabur, -trnn-iy convex, suberect. with strong erect scarcely incurved I -uated nearly one-fourth of the length of the shell behind the anterior extremity. Hack (without liinge) nearly straight; flattened sulcu- wide. •li^im". ' 'i''«'p. vertical, causing a marked ..... npre.-sion of the anterior part of the umbones; usually includes one or two obscure vertical ridges. Hinge plate strong, with sr Ton^ly oblique cardinal and three posterior lateral teeth in each valve. • There i- no doiiht in my mind re-pectin- the -pecitic .li-tinctnos of this shell and the smaller and much more al>un< hint I '. r»fnn,ireaks. Umbones of moderate si/e and promineiK-e, Imt litth- compressed, beaks incurved. Hinge plate of mi..]. -.-iigth. the detail- of it- structure not well determined. Anterior mu-cu!ar MM rath,-, -mall, and not so strongly defined as usual for the genus. 1'al- lial line indistinct except for a short distance beneath the anterior muscle. Thi- -pecie-, though -mailer, seems to be intermediate in its character between . .VM/«T*V/./ Ch-ich and I'. 1,.,,/i,,,,,, Saflord, -p. It is of more rounded form and has larger and more prominent umbones fhan th.- latter, while in these same features it fail- to ,.,,ual the former. The anterior muscular -ca,- ,s .smaller and unus.. shallow, other ditterences may be noticed but those mentioned will, it i- b,.|i. sutlice for the recognition of the q station and Joca/i/y^-Tn-nU.n liinwU.m'. MiniK-aimlls an.1 C.inm.n Fallg, Minnw-.U. n. This sp.-cies, ,-eem-. on the wi -en much like I. readily distinguished by the remarkable strength of its hinge and the great itiU-i 554 THE PALEONTOLOGY OF MINNESOTA. [Vanuxemia obtusifrons. thickening of its shell in the umbonal and anterior parts. The beak is compressed in the cast, very prominent and not at all incurved; the anterior muscular scar strongly defined, large, of subcircular form with the inner side truncated; the pallial line is distinguishable all around and, for some distance beneath the anterior muscle, strongly defined by a deep and unusually wide furrow, out of which the anterior side of the body of the cast rises very abruptly. Ligamental area high and strongly striated longitudinally; cardinal teeth strong, comparatively long and slightly curved, three in number; posterior lateral teeth three, strong and a trifle more oblique than the cardinal teeth. Dorsum of cast broad and flat. The external characters of the shell ^are unknown, but as the species doubtless belongs to the most typical section of the genus, they will probably prove much as in V. inconstans, V. dixonensis and V. rotundata. Formation and locality. — Middle third of the Trenton shales, St. Paul. Minnesota. VANUXEMIA OBTUSIFRONS Ulrich. PLATE XXXVIII, PIGS. 15-19. Cypricardites obtusifrons ULKICH, March 3, 1892. Nineteenth Ann. Rep., Geol. and Nat. Hist. Sur. Minn., p. 233. Cypricardites vicinus SARDESON, April 9,_1892. Bull. Minn. Acad. Nat. Sci., vol. iii, p. 339. Shell rather large, moderately ventricose, very oblique, subovate, much the highest and broadly rounded posteriorly, with the beaks subterminal, incurved, not very prominent nor large, and the umbones strongly rounded. Anterior end obtuse, the upper part forming nearly a right angle with the hinge line, the slightly project- ing junction between the two lines rather sharply rounded; postero-basal half of shell broadly semielliptical; dorsal outline very gently concave. Surface markings con- sisting of irregular, fine and coarse, sublamellose lines of growth. Casts of the interior with the beaks large, very prominent, compressed and strongly incurved at their apices; umbonal ridge and sulcus of moderate definition, nearly parallel with the anterior margin. Anterior muscular scar large and strongly defined, excavated out of the-hinge plate, in the cast having the appearance of a strong process projecting from the under side of the base of the beak forward and upward to the anterior extremity of the hinge; posterior scar illy defined, large, ovate, situ- ated close to the posterior end of the hinge. Pallial line distinct. Hinge with three cardinal and three posterior lateral teeth in each valve, both sets strong. The cardinal teeth are situated under the beaks, finely toothed on their sides, slightly curved and usually oblique, ranging at an angle of 45° or more with the hinge line.* •The original (Inure of the Interior of this species It faulty In its representation of the cardinal teeth. The type specimen has been Injured at tills point and In euch a manner that T quite overlooked the actual remains of the I \MKI.I. ii. i:\\. Ill \ ui. » ••nlfM»iil 1 The .-prcie- ma\ !'e compared with I Millin- M.ill. -p. I inn'i Saltord. -p.. I ml \ . uinlxmntn. V.i ..... f tli ..... f..mis, howc seem to me sutliciently similar • .-r the separation of the i troublesome. ' M:- \ \M.\tMlA I-I.XTI \\\\ II I I XXXVIII. I IU. tt. •i..iu. I 'i i;i. M, 1892. Nln.-t..-nth Ann. !:.•[ Minn, | Shi'll a little above tin1 ii)ftraightened and slopes forward rapidly, meeting with the cardinal line to form an angle of ahout \'.\'» : the iminediate junction liowever is not perceptibly angular. In the oa.sts the beaks project strongly, are nearly terminal, pointed, slightly incurved, greatly compressed, and somewhat twisted. A strong sulcus extends from the beaks to the postero-basal part of the casts; this sulcus occupies the larger part of the anterior slope, and from its inner side the umbonal ridge, constituting the highest portion of the surface, rises abruptly. For the reasons mentioned the anterior slope appears flattened and in p.irt concave, while the posterior is air uniformly convex to the margin. Cardinal slope abrupt, especially near the hinge. (iiitta-perdia impressions bring out the internal characters in a very satisfactory manner. They show a wi.lt? and faintly .-triated ligamental area, two lateral and two cardinal teeth, both pairs large and distinctly crenulated on the sides. The cardinal pair are considerably curved and the lower one forms the upper boundary of the very ,-harply impressed anterior miiM-ula (in the whole the hinge impre.»e> one as being unusually strong. The posterior muscular scar is large, ovate, slightly prolonged below and but faintly impressed. Comparing casts with the associated I', nhfusin-nna. which is nearer than any. other now known, the presei: M its greater obli«juit\ anterior end, much stronger umbonal sulcus. and be1 ned ligamental area, and stronger as well a- more coarsely crenulated binge teeth. mntion and totality . — Blue Uimwtoni- < u hole surface neatly rounded. < >utlim< obliquely acuminate- uvnid with the anterior IMP! narn>ul\ rounded ami projecting scarcely, if at all, beyond the beak-. from which tin- margin -lope- backward with a gentle curve into U)6 bftB6; posterior end broad. uniformly rounded; cardinal ma: unit three-tifths as long as the diagonal length of the -hell. rounding into the interior margin. Surface with faint wrinkle- of growth and probably with finer concentric lines. Shell su! thin. Hinge plate rather narrow, with two long posterior and two or three short cardinal teeth in each valve. The latter are difficult to 866 becan-e uf tin- clo-.dy iii. -lined Leaks. Anterior ninsciilar impression, as seen in casts of the int. n., |\ visible in a side view, being overhung by the side of the Umbo. In an end view they appear like two narrow vertical lobes tapering upward and placed ju-t beneath the free portion of the beaks. Posterior scar very faint, large, ovate, situated a short distance beneath the extremity of the hinge. 1'allial line distinct considering the thinness of the shell. In the thin shell, its general form, and particularly in the character of the anterior mu.-cnlar impres-ion-. I /,//// innl!x reminds strongly of Ambonychin. It i- Me that this resemblance i- merely coincidental, but 1 must say that I do not l>elieve it, even if I can not now present plausible arguments to show that it expre»e> natural relationship A> a rule, it is not good policy to speculate in ontological .[iie-tions, but in the present instance I may be pardoned when I state my conviction that the Ambonychndu are an off-shoot from the same line of development that produced \'ni>i described in this report are found at Minne- apoli- in the same beds that have furnished V. terminalis. All of them occur as casts of the interior, yet not one of the others is at all likely to be confounded with the present species. The principal peculiarities of the latter are the terminal beaks, alrno-t hidden anterior muscle scar.-, the thin shell and the absence of the internal ridge-like thickening which in nearly all species of the genus produces a more or leas well marked sulcu- the umbonal and anterior pa rts of casts. Formation .in./ l,,c,ilit,j lini.-st. 1 Cann»n Falls, Mlmn*oU. Al«o ID M**. Rt : :i>0, 8320. MIA BATRIA1 I'l.ATf. XXVVIll IK. -L- .••'"\ I' fft. Cgrtodonta biyniu,. .IIP. I*.'.' /..lyni.miM I 1.1:1. n, !-'•- r Minn., p. 340. - trian.jui -'- I '•'•>•'• M 3«- Shell of mediu! Mioderately convex, obli-pie. broadly Milwvate • quadrate, narmwing anteriorly, the hi, i length 'ivoly a- nine is to ten; .558 THE PALEONTOLOGY OF MINNESOTA. IVami.xoiiiia haynlana. hinge line nearly straight, rather long, terminating subangularly behind; posterior margin broadly rounded, slightly oblique, generally forming, with the basal margin a semicircle drawn to a diameter but little shorter than the length of the shell, and equalling the greatest hight; anterior end projecting very little beyond the beaks, nicely rounded from the end of the hinge, sloping backward in the lower half and passing very gradually into the basal line. Beaks only moderately prominent, strongly incurved, approximate; umbones full, uniformly convex to the beginning of the faintly concave dorsal and posterior slopes. Surface marked with more or less obscure and unequal concentric lines, some of them often, especially near the margin of old shells, being of a strongly lamellose character. Hinge of moderate strength, the plate varying between 2 and 3 mm. in width at the middle in adult specimens; about half of the width taken up by a long and very finely lined ligamental area. Posterior lateral teeth constantly three in each valve, nearly straight, ranging at an angle of about 40° with the hinge line. Cardinal teeth varying in number and size. As a rule they are at least 10° more oblique than the posterior ones and normally of nearly equal size, finely toothed or striated and three in each valve. The variations are evidently due to irregularity of development, Rarely there are two large ones with a small one on each side; more commonly one. two, or even all three will be divided, so that the total number may reach six. Anterior muscular scar sharply defined, semicircular; posterior scar ovate, as usual very faintly impressed; pallial line quite distinct, except in the posterior part. Umbonal cavity small, compressed; anterior internal thickening of the valves gen- erally rather sharply defined on the inner side. Casts of the interior, the only condition in which the species has been found in Minnesota, have small compressed pointed and scarcely incurved beaks, projecting slightly beyond the hinge line and situated farther behind the anterior extremity of the shell than is the case on the exterior. The ridge immediately behind the anterior flattening or sulcus is well marked, as is also the pallial line and the ante- rior muscular scar. Indeed the natural casts correspond exactly with artificial ones prepared from typical Tennessee and Kentucky specimens of the species. This is a widely distributed and well marked form, about which a number of closely related species or varieties are grouped. One of these, V. subrotunda, occurs in Minnesota, but in lower beds than the typical form. It is distinguished by its more circular outline. Another, V. abrupta, from the Galena of Fillmore county, is more easily separated by its more nearly terminal beaks, very obtuse anterior side, thinner shell, and in wanting the ridge which marks the casts of V. hayniana. A third form is found in the upper Trenton of Kentucky. Being a smaller shell I called it nnna (Cypricardites nan UK I'lrich, 1892. Nineteenth Ann. Rep. Geol. and Nat, VkBuiMaU »ut •< Hist. Stir. Minn., p. i.1:1,1.!. i "n compari-on it pro\ed to have a thinner shel! 'iiore erect ami more rounded in outline. al-o more ventricose ami with a -trouper umbonal ridge, while there are only two cardinal teeth instead of three or more. A fourth form I prop.»e scum to de-cribe. in one of tl: Ja, under the name of tibbosa. It i- fn.ni the lower Trenton of central Kentucky, and ditler- from the present Bp< .• more gibbniis. in having larger unibones, almost terminal beaks and more obtu-e anterior - \ tifth is associated with the preceding in Kentucky. and also occurs in Tennessee. It is a very thick shell and attain- to larger size than I'. Inujnimn, from which it dill'ers further in its form which is higher and -traiyrhter and more obtuse in front. Hut the principal differ- ence lies in the ligamental area which i- at lea-t twice as high as in adult examples of Satlord's species. The area i- -liown in four specimen- and in all of them its bight urn. or more at the middle and in one it is quite 5 mm. For this form I propose the name Vnim inlin•.;. since they agree much better with that specie* than with true \ . /«/y/j/V/MO. .u/; ff-t «( -tr;it;i. Tin- tlr^ Is at the bMe of the Traoton UnMtOOt in M decomposed llmcatone has li-ft nunii tfcnnd hori/.»n. whii-h i- n.-:ir Hi- t«.ji of tin- Tn-iit«in, ;«*ed at - i|cm»; th. utht-rn niilrMiid N-IWI-PII Itiiivln and DanvilU-. In MIIHH--..I . t t« t"- iv-trii-N'd to Hi. (iali'iM «hul«-s. In which It occurs as casts of the iur at s«'\ - in liiHxihin' county and at St. Paul. \ XM'XEMIA SUBl:oTI'NH\ ». ri.\ This species ditler from I . lun/ni'tna SatVorcl .>p.. to which it is doubtless \ closely allied, in its more uniformly rounded outline, broader anterior end and shorter hinge line, and in having the beaks smaller and situated farther behind the anterior extremity. The convexity of the va -o is less, and the >hell is thin- ner, particularly in the umboiial and anterior part- where the internal thickening is so little that no perceptible .-ulcus nor rid^e is left in casts of the interior. the same reason the beak- •- mu-t be more rounded and larger, so that how- ever much the exterior of the two -hells may resemble each other, casts of interior would be distinguished very readih. V. n.ina I'lriiMi. from the upper Trenton in Kentucky, i- a smaller shell: with more ventrico-e val . mbonal 560 THE PALEONTOLOGY OF MINNESOTA. [Vanuxemla abrupta. ridge, and longer hinge line. Of associated species, Crytodonta glabella Ulrich, has a similar outline, but there is no relationship between them since that species is as true a Crytodonta as this is a Vanuxemia. Formation and Locality.— In the upper part of the middle third of the Trenton shales, Goodhue county and Chatfleld, Minnesota. VANUXEMIA ABRUPTA n. sp. PLATE XXXVIII. FIG. 39-44. Shell a little beneath the medium size for the genus averaging 20 mm. high and 24 mm. long; rounded or subquadrate in outline, with subterminal beaks, tumid in the umbonal region and in front of the center, the anterior end very obtuse, the surface in the upper part rounding abruptly inward to the edges of the valves so that in a side view of casts of the interior the sharply defined anterior muscular scar is quite hidden beneath the filling of the umbones. Hinge line straight, long, terminating more or less abruptly posteriorly; posterior margin broadly rounded, occasionally nearly erect, usually a little oblique; anterior side truncated above, rounding below; base rounded. Casts have full and rounded and well incurved beaks, and the con- vexity of the surface continues without a sign of the sulcus and ridge exhibited by the casts of so many species of this genus. As near as can be determined from the impressions, the hinge plate was narrow and bore two, in one case apparently three slender posterior lateral teeth and two cardinal teeth in each valve. Pallial line and posterior muscular impression very obscure. Surface almost smooth, the best specimens only showing remains of fine concentric lines. This well marked species is believed to be related to V. nana and V. hayniana, but the subterminal beaks and obtuse anterior end will distinguish it at once. From V. terminalis of the lower Trenton, which certainly is also very much like it and perhaps a more natural ally, it is separated by the more erect form. Formation and locality. — Middle Galena, Filloiore and Goodhue counties, Minnesota. VANUXEMIA NIOTA Whitfield (?Hall). I'i.ATE XXXVIII. FIG. 35. fCyprieardites niota HALL, 1861, Rep. Supt. Geol. Sur., Wis., p. 20; also 1862, Geol. Rep., Wis., vol. i, p. 38, Fig. 8, p. 438. Cypricardites niota WHITFIELD, 1882, Geol. Rep., Wis., vol. iv, p. 208. I am very much inclined to doubt that this species, a specimen of which was submitted to Prof. Whitfield, is the same as the one described by Prof. Hall. If it is, then the original description is anything but accurate.* • Hull's <" •'•riptlim nf ' <• i reads as follows: ••Shell broadly siiboviite. lirnaili'-i at I lie post, i-ii.r ,.,,,1; in,,! es very i.">bbous. beaks inemved. little elevated, situated about one-four! li nf the !enj:lli of the shell nun the anterior end. ( ardlnal line st r;ilsht )• »oni it reads I should say that he refer- to a ./«;i/.ilii i or •rsimilix and not to a \fmia which the shell here inuli" ieration Undoubted!} tl The latter dillers iii :it lei Cbaneten brought out in Hall ption. and cither one would in my opinio suHicient to defeat specific identity. Thus. he says the Leak- arc "situated al.out fourth tlie length of the -hell from the anterior end." whereas in Whitlield'- ; they are much nearer the anterior extremity: then he gives the impression that the anterior, [inferior and hasal margins are almost uniformly rounded, while in the present -pene-. the outline is alway- more or less quadrangular. I'nder the circum-tatices 1 might have Keen ju.-titied in proposing a new name, but as the questions involved would .still lie open (a study of the original of Hull's description alone can an.-wer them), if -eemed best to refer to the species provisionally as abo "in nioln \\'hitfield ('llalh .-losely related to I'. liina Satlord I Iricli. l-'rom tlietir-t it is di-t in^iii-hed I >y its greater convexity and length, more anterior and larger Leak-, and almost rectangular instead of rounded anterior side. The ca-t figured on plate xxxvin preserves the impressions of the hin^re teeth. The cardinal teeth were rather -mall, nlili.jue. and numbered four in each valve. The posterior teeth were slender, nearly horizontal, and three in nu in her. In V. gibbosa the anterior margin forms a wider angle with the hinge line, the shell was a little thicker, the hinge stronger, and the cardinal teeth larger, not exceeding three ii. number and less oblique. In artificial casts of that species the anterior muscular -MI proved to be comparatively larger, and to project farther anterior to the filling of the beaks, which again are of larger size than in ninfn. I . !"iii of the iJalena belongs to the same group of -pecies but is a much larger and rounder shell, and in casts has more compressed and less incurved beak-. .i/i-.ii me/ In-nitty.— Tup <.f ihi- ue Beds," mid \>**- I.'IIJMT Huff !(«•<]•." nf tin- •.t«n formation at I Min.-r;i; . -in. ami Uork' Mu*. Keg. No. 8321, 8325. \ \M \KMIA WOKTIU M I'lrirli. I-I.MI \\\ Cfprirarditrt s, 1888. I <->;» wortheni 1'i.itifn. l«». Ain.-r. '. Shell large, moderately ventrico-e. -ul.erect. snlicircular. the length a little • han the hight. the beaks nearly terminal, the dorsal margin aim «ht, rather long and with the extremities rounding abruptly, th- or one projecting beyon u-ual fur the genus, very di-tinct. 1, . and parth ..pped above liy the tilling of the beaks. I'allial lint- .-harp in tln> antt-rior two-lift \\-. nl.scnrc Ix'hiii.l. I '• interior miiM-ular inipn^mn tecie> i- u>-«. \ith several of l'>/i-f»il,nifn that, under ordinary condi- tinn-, ai -ily di-tingni-hed. The feature to be chiefly relied upon in separating them (/. r of the anterior niu-mlar scarl i- ii-nally oli-ciired l.y • talli/ed remnants of the shell. When these are iviii"\ed ami a clean .-a-t of the inteior i't'on produci'd the ditiiculties will have been overcome. -ince the I iu.r, ////./ ma\ then lie di-tingni-lied at mice from th- / hy the much greater di-tinci and ch;i .f the anterior mu-ciilar -car. (I'omp. ligs. :{ and 4'J on plate xxxix.l Form-itinn and foou/rty.— Tr.-nt<.n lln >, Minn. Mut. Reg. No ^H»T ? 6 1. £> us MATH KIM A. Billings. ltatlirri.1, liM <*. Can. Nat. and Oeol., vol. Ill, p. 440. il eijuiv .-ry iiieipiilateral, oblong (juadrate or suboval; I mil anterior. Surface marked with concentric growth lines only. Hinge of moderate, strength or rati. ,. with external linear ligamental area posterior to the beaks, two small, divaricating cardinal teeth beneath the beak of the left valve and only one in the right: no lateral teeth. Adductor impre--ion-.two; the anterior one -mailer and better defined than the po-terior. I'.illial line simple, obscurely defined. Type: Miitlii-riu h-neru Billings. Only four or five species known to me have the characters of this genus. They are all small shells and with one exception belong to the Trenton. .!/. tenera is from that hori/.on in Canada, one or two mi.le-cril- r in Kentucky, and M. M Minnesota, while ti. Hall, which i- a true Mntli. belongs to the Niagara of \Vi-con-in and lllinoi-. M \i in - <'<•//. -v UK! ao. heria ntyota TI.KK n, l-«nl II large for the gen lal. wide-t pn-teriorly. with ti terminal, small, incurved, projecting -lightly al- a stroi . 564 THE PALEONTOLOGY OF MINNESOTA. [Whiti'lU. umboual ridge. Anterior end descending abruptly from the beaks, below rounding sharply into the nearly straight ventral border; posterior margin produced and strongly rounded in the lower half, obliquely subtruncate above, forming an obtuse angle at the junction with the hinge line; the latter very gently arched. Surface marked with strong concentric wrinkles and finer lines of growth. Shell substance of moderate thickness. Hinge plate strong, flat, slightly arcuate, the upper half of the width posterior to the beaks, finely striated lengthwise. Cardinal teeth small, situated just beneath the beaks, directed toward the postero-basal margin, with one in the right valve and on each side of it a deep socket for the reception of the two teeth of the left valve. Anterior muscular scar rather distinct, subcircular, situated immediately beneath the teeth. Several additional specimens of this well marked species were collected during the summer of 1892, among them an entire left valve showing the hinge. This has two cardinal teeth and no posterior laterals, so that there can be no longer any question as to the generic position of the shell. Only two other species belonging to this genus are known to have been described. These are M. ienera Billings and M. recta (Modiolopsis recta Hall), from both of which M. rugosa differs in the much greater hight of the posterior end. The shape of the shell reminds one greatly of Ischijrodonta and certain species of Cyrtodonta, but in the former the cardinal teeth are much stronger and the ligament internal instead of external. The hinge of Cyrtodonta, with its posterior lateral teeth and curved, more numerous, and longer cardinal teeth, is quite different, but when the interior is hidden the collector may experience some trouble in distinguishing the species from the associated Cyrtodonta affinis. Still, there is one difference that will serve his purpose very well, namely, the anterior end of the latter is rounded and somewhat produced beyond the beaks, whereas it descends abruptly from the beaks in the Matheria. Formation and locality.— Upper part of tho middle third of the Trenton shales, about six miles south of Cannon Falls. M inin-sota. Genus WHITELLA, Ulrich. H'liitcllu, I'uucn, 1890, Amer Geol., vol. vi, p. 176. Shell thin, obliquely quadrangular or suboval, equivalve, inequilateral, more or less ventricose. Umbones very prominent, the beaks strongly incurved; umbonal ridge prominent, subangular or sharply rounded. Cardinal margin straight or slightly convex, the edges inflected to form a sharply defined escutcheon extending beyond the beaks sometimes quite to the anterior extremity of the shell; area finely striated longitudinally. Hinge line straight, from one-half to two-thirds the length M KM.! I.KAN. II1ATA. WI.I1.1U oli|l.|U«U.) of the shell, with two t<> li\f rather olnl.|iie folds ur teeth in front of the beaks. l'o*terior portion of hinge apparently ed.'iitulou*. Ligament proli.ilily l-oth e\t> :iii-l internal, tin- latter only along the posterior t hird of t lie hinge line, win-re it WM supported liy an internal ridge in each valve. Two -implr adductor impre**ion*. t lie posterior 01 r'.iint; pallial lint- simple, marginal; interior of shell lined \\itli a nacrous film. Surface nf *|iell wit li tine c<> ncen trie line*, and *oine times with stronger concentric undulation*. Ty I './I./M.»/« I' I rich. Ni- more ea>ily re- : -*MIII- of Lamelliliranchiata than tlii- i- known from the I.owi'r Silurian rock*, and of those restricted to that system, none i* more important in the way <>f ~pecu-> and 'li>tril>ution. Twelve -pfcic-. nine of them ton. the rest from the Hudson Ifivi-r ^roiiji. are de>crit>ed and figured in this work. Two other* wen- dr*crilied hy mo in IS'.KI, from the ( 'incinnati group of Ohio a* II'. itnif»nr.if,i. while another pair. Itimii and plrlteiti, from the h'iver roek* of Ant icosta, were douhtfnlly referred by Hilling* to hi* j.'fnn* 'i. With the latter - Hillings describes two others as Cyrtmlm and f. acutninlihio. ;il*o lielonj:* here, while a very large species from tlie upper beds of the *ame formation remain* to l>e descril>ed. Species of this genus have been referred to Ihlnhi-'i M. ' frifinlites Conrad, and Cyrtodonta Hillings. McCoy describes hi* ;.".'n-. tainin^ inei|uivalve shell* in which the binge is edentulous. <' and Ciirtuiliintn hoth have well developed posterior lateral teeth and quite different cardinal teeth. In the latter also the shell is thicker and the ligamental area never nor is the umbonal ridge ever so prominent as is commonly the case in Whitelln. \\ II1TKI.I.A IMU.IVl! ATA I'll PLATE XL. FIOS. 11 and a. \\'hit«lla oblin .'< a, IS»t. Ani.-r. Gwil., vol. vi. |, 177 Shell large, oblique, suhrhomhoidal in outline, produced in the postero-basal region, \entrii-ose. with point of greatest convexity above the middle; beaks rather small, prominent. *li^htly incurved. *itnated nearly one-thin I of the length of the hinge line from its anterior extremity: unibonal ridge well marked, the cardinal slope concave Ant nail, narrowly rounded merging gradually the evenly and only moderately convex ventral margin. Posterior end sharply curved and produced below, gently convex and slopit;. id in the upper ha meet the slightly convex, cardinal margin. K*cutcheon well marked, wide, shallowest 566 THE PALEONTOLOGY OF MINNESOTA. LWhttella quad rangu] arts, in front of the beaks. Anterior muscular scar elongate. Hinge thin, simple posterior to the beaks, in front of them, with one long and slender horizontal tooth and several slightly oblique short teeth above it. The dimensions of a cast of the inte- rior, of the average size, are as follows: greatest length, 50 mm.; greatest hight, 38 mm.; greatest convexity, 24 mm. A large specimen is 59 mm. long and 42 mm. high. In W. sterlingensis M. and W. sp., the umbonal ridge is much stronger, the cardinal area much wider, the anterior end short, the posterior margin different, especially below where it is narrower, and the length from the beak to the postero-basal extremity comparatively greater. W. quadrangularis Whitfield, sp., is a more convex shell, not so oblique, and has a wider cardinal area, and larger beaks. For compari- son with Trenton species see their descriptions. Formation and locality. — Hudson River group, near Spring Valley, Minnesota. In Ohio and Indiana tin' species is not uncommon in the upper beds of the Cincinnati group. WHITELLA QUADEANGULARIS Whitfield. PLATE XL, FIGS. 28—30. Cypricardites quadrungularis WHITFIELD, 1878. Jour. Cin. Soc.'Nat. Hist., vol. i, p. 138. Shell of medium size, gibbous, rather erect and nearly rounded or quadrangular in outline, with very large incurved, though widely separated, subcentral beaks, over- hanging the proportionally short but unusually wide ligamental areas. Length and hight subequal, the latter probably a little the greater; thickness more than two- thirds of the hight. Umbonal region very prominent, rounded anterior to the obtusely angular and rather inconspicuous umbonal ridge; behind the ridge the surface is a little concave and slopes abruptly toward the magin; anterior slope similarly abrupt and concave. Anterior end sharply rounded and most prominent at the extremity of the hinge; ventral and posterior margins sometimes forming a regular semicircle, but usually a slight prominence is perceptible in the postero- basal regions, causing a straightening of the posterior margin. Surface marked with somewhat irregular concentric lines and wrinkles of growth. In casts of the interior the anterior muscular scar is uncommonly well defined for the genus, and immediately above them, a pair of depressions forming the ante- rior end of the cardinal area, is also an unusual feature. Furthermore, a slight vertical furrow on the umbones reminds of Cy>1<> ( 'iiicinn.it i Hi-tory. This specimen is ;i mold of the exterior ami ha- I ..... n compre—ed in -uch a manner that tin- outline i- now niniat ur.illy quadrangular. tin- iiinl.oiial ridge too prominent ami tin- Leak- too narrow. I have eomp :. -fully with the northwestern -pecimen-. \\ Inch ar. -ft In- interior, ami wliilc I admit freely the the possibility of error, my coiiclu-ion for the |. resent is that they are specifically identical. Compared with other "f H'liiti-lln it will he finind that the shell 18 more erect and -horter. and the cardinal area wider than in any other known. \n osso- d form. CyrtotUmfa ///•'»«•//>•. var lnculrnl-1 S.irde-on. ha* much smaller Keak-. while they are al>o nearly in contact, the li^amental area being very much narrower. .UKl nMi. r iiii-ii> wi-ri- M|,I.H[|.M| from ai. n at Savannah, IlllnnN. irnl Spring ' -OENSIS Mttk illl'l \\''if/ln-n. X and 9. :>>ro~tein.r view, and ol>li«|iiely rhoml>oidal, as seen from either - •••rior m.tix'in olili.|iiely truncated, \\ith a long slope, which i- -lightly convex al>ove and faintly >inuou- near the middle; posterior liasal extremity jirod oldinuely liackward- and downward-, with a more narrowly rounded or -ulian^iilar outline; l>a^al in.irL'in a-cendin^r forward, with a moderately convex curve, and rounding up more or l< iually into the OT aim" liinge line si irdiual area moderately developed. Iteaks promiu.Mif. placed nearly o\er the anterior marL'in. .-trongly incurved and compre-^pd an: •••riorly. 1'mlnnial ridge> very prominent, -ulian.- 'idin^ from the 1 icaks oliliquely to ' r l.a-al extremity at an angle of al>oi. low the hori/.ou ot tin- hinge, thn- dividing each valve int .lieipial an-as of which the l-ehind i- flattened or -lighth -• l)etween the ridge and the moderately prominent ; lor-al i-L'e. and that in front and In i Hinge and interi«»r unknown.) "(i en^th. ine.i.-uring olilii|iiely from the !••• 'he pn-teiior basal extremity. 'J. I'M iiH-lsc-; di:c ,t right ang .e >ame. 1 .",() n, of the two valves when l.'i" inches." 568 THE PALEONTOLOGY OF MINNESOTA. [Whitolla eoinprcssii. The great prominence and sharpness of the umbonal ridge, the decided flattening of the postero-dorsal region and the narrowness of the posterior extremity are the features that distinguish the species from all the others referred to the genus, except W. hindi Billings sp., W. carinata Meek sp., and W. truncata Ulrich. The first of these exceptions is not so high, less gibbous, less oblique, has a more prominent and less broadly rounded anterior side, straighter posterior margin, narrower beaks and a cardinal area or escutcheon that is a little longer but not nearly so wide. The other two are sufficiently distinguished by their much smaller size. The specimen described by Meek in the Ohio Paleontology (loc. cit.) an'd doubt- fully referred to this species is certainly distinct. It my belong to W. hindi Billings, or to W. umbonata Ulrich, both of which it resembles more closely than W. sferlingensis, especially in the prominence of the anterior end, which of itself precludes all possi- bility of its identity with the present species. That it really belongs to one or the other of the two species mentioned it would not now be safe to say, since I have no means of learning to what extent the specimen may have suffered from compression. Formation, and locality,— The type specimen was found in the upper beds of the Cincinnati group at Sterling, Illinois. A small distorted shell from the Hudson River group near Spring Valley, Min- nesota, may belong here, but I cannot say as much for any specimen seen from the equivalent strata of Ohio and Indiana, despite the fact that the species is commonly believed to occur there. WHITELLA COMPRESSA Ulrich. PLATE XLI, FIGS. 6-9. Whitella comprensa ULKICH, 1890. Amer. Geol., vol. vl, p. 180. This shell has an outline very similar to that of W. obliquata, yet differs con- spicuously from that species in having much less gibbous valves, the thickness in that species equalling about one-half of its greatest length, while in W. compressa the length is more than two'and one-half times the convexity. And yet the length of the latter is comparatively a little less than in the Hudson River group species. Comparing the two species critically we find further that in W. compressa the umbonal ridge is much less developed and the outline at the extremities of the hinge some- what different, the posterior part being a little more sharply rounded, while anteri- orly the hinge projects farther beyond the beaks and in a straighter line, so as to form an angular junction with the anterior margin. An undescribed form found associated with W. obliquata in Ohio, and which I shall call W. ohioensis, attains a greater size, but agrees in all its specific characters much more closely with the present species. Indeed the agreement is so close that we may be justified in regarding it as a reapparition of W. compressa, the only difference so far detected with certainty being a slight one in the outline. The Ohio form, namely, is a little narrower across the posterior half of the shell. I expect, however, that when more LAMKU.IIiKAN- III . perfect material ran be o>mpaivd nt her dilferences will become apparent, especially in their hinges and imi>ciilar impression-. the-e part- .ipp.Mrm- to be someu h.it tiger in the Trenton shales species. fofm-itiim .m./ /<«-. 247. Shell rat her beneath tin- nie«liiiin si/e. obli-pie, ventricose. widest posteriorly, • •/iiiilal: Keaks lar^>, ]»n)iiiiiit>nt. iiu-iirv»>«l; uniliones full, with .1 -harply rounded ri-l^e or lint- of tfilil.oMty oxt«'inlin^ lia«'kwanl from the beaks to the posterior extn-mity of the >ln>ll. I'anlinal ami posterior »\o\yes slightly concave. Anterior short, narrowly roumh'il; ventral e'l^e very gently convex; posterior end pro- and >bari»ly ronii.le«l in the lower half, more gently convex and sloping rapidly forwanl above, nu'r^inu' gradually into the cm ve of tho dorsal side. Hinge line about half as lon^ as the shell, with the edge inflected so as to form a narrow escutcheon, extending luit little, if at all, in front of the beaks. Internal ligameutul supports leave a distinct inipre^ion on each side of the postero-cardinal margin in casts of interior. Anterior nm-cnlar scars di-tinct though faintly impressed, situated in the antero-dorsal angle. Surface of caste, especially in the lower and posterior parts, marked with fairly distinct, rounded, concentric folds. The concentric undulations are stronger in this species than in any other known to me. It is shorter than II'. /»;•f thi- Tr.-n(..n shales at MlDDeopolU, Minnesota. WHITEI.I.A IM-UAT -p. in. i. Shell subovate or oliscurely trapezoidal, moderately gibbous, with well shaped and prominent umliones and strongly incurved beaks situated one-fourth of the length of the shell behind the anterior extremity. I nilmnal ridge moderate, roui except immediately behind tlir beak-. K-cutcheon nan> extending in front of the beaks. Surface of casts marked with numerou>. rather small, concei furrows, which in parts may be (puite regular, but in otheis are thrown into bundles so as to produce obscure undulations. Hinge unknown, muscular and pallia! impressions^very faint. 570 THE PALEONTOLOGY OF MINNESOTA. [Wliitelhi. niegainbona. The specimen figured has the following dimensions: From the postero-basal margin to the antero- cardinal angle, 33 mm.; from the same point to the umbones, 31 mm.; from the postero-cardinal margin to the antero-basal margin, 26.5 mm.; greatest or posterior hight, 24.7 mm.; greatest convexity, 16.5 or 17 mm. Though comparable in a general way with a number of species referred to the genus, the relations are not very close in any case. In the matter of outline it agrees best with W. compressa and W. ohioensis, but the umbones are larger, the valves more convex, and the surface markings much better defined, especially on casts of the interior. The umbonal ridge is not strong enough for W. scqfieldi, and the umbones too small for W. concentrica, while in the outline it differs in a similar manner from both of those species. Finally, in W. subcarinata and W. ventricosa Hall, sp., the anterior end is shorter. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. WHITELLA MEGAMBONA Whitfield. PLATE XLI, FIGS. 4 and 5. Cypricardites megambonus WHITFIELD, 1877. Ann. Rep. Geol. Sur. Wis., p. 73. Also 1882, Geol., Wis., vol. iv, p. 210. WJiitella megambona ULRICH, 1890. Amer. Geol., vol. vi, p. 384. Shell of medium size or less, oblique, subelliptical in outline, very gibbous, the con- vexity of the closed valves equalling very nearly the shorter of the oblique diameters, and about two-thirds of the distance from the beaks to the postero-basal extremity. Umbones very large, tumid, with the beaks strongly and obliquely incurved, their points being brought into close proximity; umbonal ridge prominent^ subangular near the beaks but becoming obtuse in receding from them; point of greatest con- vexity somewhat behind the middle of the shell. Hinge line very short, posteriorly passing rather gradually into the posterior margin; the latter is somewhat oblique and broadly rounded to the base where the outline turns rather sharply forward into the basal line, which continues with a uniform curve to the narrowly rounded— almost angular — anterior extremity; the latter projects about one-ninth of the longer diameter of the shell beyond the anterior side of the umbones. Surface marked by irregular concentric lines of growth, and distant obscure undulations. Anterior to the umbonal ridge the surface is rather strongly convex, while the posterior and cardinal slopes are flattened and exhibit along the center a more or less distinct sulcus. Escutcheon very short and narrow. Internal ligament supports, unusu- ally long, in casts leaving a well defined furrow on each side of the hinge line, extending from the upper part of the posterior margin almost to the beaks. Car- dinal teeth apparently as in W.scofieldi. Anterior muscular scar shallow, rather -mall. rounded. -ituated in tlio antero-dorsal angle. I1" and |..illi.il line undetermii: In ino-t -pecimen- there. -hree. thin. parallel and dl>lit|ue ridges on each side at the extremity of tin* hinge. The-e opposed sets of ridges are separated by an interval in adult examples, but it i* sea: !>e qiie.-t ioned t liat in an earlier Stage in the development of th.- -hell they represented posterior lateral teeth similar t<» tho-e of < 'i/i't'iilnntn. Thi> fact mti-t have an important hearing upon the qiie • •nealogy, Imt. in the absence of any knowledge of similar types in earlier strata, it i- not nou po-Mhle to .1; with anything like certainty of arriving at a true solution of the question. Tin- i- .1 well marked species and one that i- not likely to he confounded with any of the associated shells. Its nearest congeners seem to be If. scofieldi and 1C. uterlimjen.ti* M. and \\ . -p.. the latter particularly, but in both of these species the umbonal ri.l^e is more <-on>pieuous and the outline different. The former again has a longer escutcheon and hinge, much larger anterior end and more prominent postero-cardinal angle, while in the latter the -hell i- more oblique, the posterior angle narrower, the cardinal area murh wider and the Leak-- farther apart. Formation and locality. -L '<>n llrin>- \ isconsin and Minaoapollm Minn. \\nni .1.1 \ -ri.KiKi.iH I'lrirh. I-I.ATI M'hitrlla fcofleldi UI.UH n. !•"«• 1M| and 382. Shell of medium - y eonvex, moderately ol>lii|iie. -ul.t rape/oidal in outline, with the hinge line longer, -traighter and better defined than ii-ual. Ante- rior end unusually long and wide, the outline gently rounded from tin- .-ular junction with the hinge line; basal margin slightly con \ ex. oblique, descending to the .nded po-tero-ba-al angle; posterior mar-in .-ubtriincate. -lightly oblii,iit» and but litt' x in the upper half. I' inborn-- prominent, -ub.-arinate behind, with the beaks approximate, obliquely enrolled and -ituated a little more than one-third of the length of the hinge line behind it- 1 ridge is a conspiciou- feature, although becoming obsolete before reaching the postero-baml margin. Posterior to the ridge the -in ave; in front and •ath it convex. Surface marked by rather orts appearing as a double ridge in each valve beneath th : ior h.ilf of the e- erior liinge 572 THE PALEONTOLOGY OF MINNESOTA. [Wliitella truncata. teeth two in each valve, elongate, slightly curved, nearly horizontal. Muscular scars and pallial line faint, not well determined. This species is more convex and has a more distinct umbonal ridge than W. compressa, and a longer hinge line and larger anterior end than W. megambona, while the basal margin is more oblique and the anterior end much larger than in W. sul- ciirinata. Formation and locality,— Upper part of middle third of the Trenton shales, St. Paul, and near Cannon Falls, Minnesota. Also in the Trenton limestones ("Upper Buff beds") near Beloit, Wisconsin. WHITE LLA TRUNCATA Ulrich. PLATE XLI. FIGS. 10-14. Whitella truncata ULUICH. 1890. Amer. Geol., vol. vi, p. 385. Shell small, very oblique, ventricose, subrhoinboidal in a side view. Beaks nearly terminal, prominent, of moderate size, obliquely enrolled; umbones and umbonal ridge full, the latter angular and traceable to the postero-basal angle. Cardinal slope sharply defined and distinctly concave; anterior and basal slopes slightly convex and very rapid. Anterior end very short, scarcely projecting beyond the beaks, narrowly rounded, then sloping rapidly backward and uniting very gradu- ally with the gently curved basal margin. Posterior end truncated, straightened, forming nearly a right angle with the hinge line, and one of from 75° to 80° with the ventral edge. Escutcheon narrow, not extending anterior to the beaks. In casts of the interior, the internal cartilage support leaves two narrow impressions, one on each side of the posterior half of the hinge line. Dentition of hinge not observed. Muscular scars very faint. Dimensions of a large cast of the interior: Greatest bight, 13 mm.; greatest convexity (near center of shell), 15 mm.; length from beaks to postero-basal angle, 19 mm.; length from anterior extremity to upper portion of posterior margin, 15 mm. In a small specimen only 6 mm. high, the other dimensions are in proportion, except that the convexity is comparatively less. This species is closely related to W. scqfieldi, but may be distinguished by its smaller size, greater convexity, truncated posterior end, shorter anterior end and more pronounced postero-ventral angle. Formation and locality,— Galena, shales., Goodhue county, Minnesota. WHITELLA SUBCARINATA, n. sp. I'LATE XLI, FIGS. 22 and ?2S. This species is in many respects like W. truncata, but is readily distinguished by its lesser gibbosity, smaller beaks and more rounded shape. The umbonal ridge is HI ATA. WbllrlU ..-ntrl.-.*. 1 angular or *harply rounded and distinct .|iiite to the po-tcio-liasa! margin. An obscure furrow in the middle of the ll.it cardinal slope. From II il.ill. -p. which -coins to be its nearest convener. it differs principally m the greater *harpnett ami prominence of tlic ninl.onal rid^e. The anterior end i* much too small and short for II'. rnunty, Illinois. ow.th; MMI rcpr«'>fiit- an ancestral form or variety of the present - ''rom which al>o II'. >;-ntrirus(i, II'. tnttiniln and perhap- nthei >peciesas well have been evolved. More and better material, however, i- n»'ce*-ary In-fore -\\c\\ a \ iew of it- relations can be consdered either as proved or ili>pro\ • mitinii unit ln,-,iiiti/. '1 . tin- nil '. Minnesota. \Viim.u. \ .-,I>A IK XI. I. i nilia rrntrieo*! HALU 1847. P:t !. p. 16&. l:il-rarra tWK/HcoM, HALL, \K> III, p. 271, and TwHfth U<-p SUtc Cab., Ii|>. 10, 68 ai -<^rtod«' - n«i> Itn : •riruttu HAI.L, !•«•-' . - n..r WIIITMKLD, 188*. 3W. (-' Helievin^ that this species i> repre-ente.l amon^ the undetermined fragmeir l- from Minnesota, I thought it well to give illustrations of authentic specimens from the Trenton of New York. These were received in an exchange some time ago. l^uite recently I sent two of them to I'rof. K. I'. \Vhitlield. of the American MuMMim of Natural II A ho com | tared them with the original types of the species and verilied the identification. An examination of the New York examples established what I had already . namely, that the species is a true Whilelln and inmonly ltelie\ ' 'i/H<«Ii,n/,i. Its place in the ft« will' be seen at on« compared with other species of the genus figured on plate* xi. and u.i. The shell was thin, the beak- \\ere full and prominent iimlional riil^e. though not as -harply pecies of the gonu>. ,11 a more conspicuous fi-.itun- than in an , - of ('i/i-t»'l'>ntn. the hinge baa a narrow external lijMinental area or e-cutcheon, and rid^e-like supports fora posterior internal ligament. Imt no posterior lateral teeth. In short, the species presents 574 THE PALEONTOLOGY OF MINNESOTA. IWliitolla prteoipta. every essential characteristic of the genus Whitella. We cannot, however, say this of the specimens which were referred to the species by Hall in 1859 and 1862, and Whithfield in 1882. since in these cases we are dealing with inequivocal types of Cyrtodonta. The interior figured by Hall in vol. iii, Pal. N. Y., as Palccnrca ventricosa, is very different from the original Edmondia (now Whitella) ventricosa. That shell seems to belong to the species previously described by Billings as Cyrtodonta sub- carinata. The cast figured by Whitfield, if correctly represented, belongs to a species of Cyrtodonta as yet unknown to me. In his description, however, he included the species which I have named and described on page 537 as Cyrtodonta janesv Miens is, Comparing W. ventricosa with other species of the genus, W. subcarinata will be found to have a sharper and more prominent umbonal ridge. In W. rugatina and W. concentrica the anterior end is much larger; W. prtecipta is much narrower poste- riorly and a more elongate shell. Formation and locality.— ID New York the species occurs in the Trenton limestone at Watertown, Middleville and other localities. If it really occurs in Minnesota, it will be, I think, in the middle Galena of Goodhue and Fillniore counties. WHITELLA PR.ECIPTA Ulrich. PLATE XU, FIGS. 15 and 16. \V Intella prcecipta I'LKICII, 1890. Amcr. Geol., vol. vi, p. 388; more fully described and figured in 1892, Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 246. Shell of medium size, ventricose, very oblique, elongate-ovate or subrhomboidal in a side view, produced and sharply rounded in the postero-basal region. Beaks of moderate size, prominent, strongly incurved; umbones full; umbonal ridge well marked, traceable almost to the posterior extremity. Anterior end small, short, narrowly rounded; ventral margin gently convex; posterior end produced and narrowly rounded in the lower part; from the point of greatest extension to the posterior side of the projecting umbones the outline is gently and almost uniformly convex. Hinge line comparatively short, its length less than half the length of the shell, the edge inflected to form a distinct escutcheon, extending somewhat in front of the beaks. In casts of the interior the internal ligament supports have left distinct impressions of unusual width on each side and behind the impression pro- duced by the escutcheon. An obscurely defined ridge and sulcus is also to be seen running through the middle of the cardinal slope. Anterior muscular scar T'aint, subovate, acuminate below, situated very near the anterior extremity. Pallia! line represented by a thin raised line running parallel with the margin of the cast. Tins species is very similar to W. obliquata Ulrich, from the upper beds of the Cincinnati group, yet I do not doubt that they are really quite distinct species. That species grows to a larger size, is less elongate, wider posteriorly and with the I. \Ml.l. I. II i: \\< MIATA M. . . .-: , • umhones loss tuiiiiil ami not -n prominent. Tin- inr meiit s,,j, |l(Mt, alsn are very much less distinct. II MI oblique. shorter ami lias a longer hinge ami narrower escutcl ..... n. •i.( ;. r.j.'i.';/ t; Mlnne«<)U. .r.. X.ttd. 101 I'l.rril'H \|;|i|.\. llnch. I'lethocanlia, I Mm i l.iin., p. 243. il thiii. inequilateral, oblique. tumid. with margins dosed; I teaks large, :iiniMit. spirally enrolled ami eurviii'' forward. l'.i-:i-nor cardinal margin \\itli a narrow escutcheon or lunette. A strong and larjre process projects forward and downward from the underside of the liin-r ju-t l.eneath the ln-ak in each valve; one strong linear lateral tooth, or thickened internal cartilage -npport. l.eneath the posterior extremity of the hin^e line and rinse to the margin. Anterior muscular scar strongly impressed, situated in the antero-lor«al an^le, margined on the inner side l-y a cnrvrd ridge extending from the under side of the cardinal process. In casts of the interior the tilling of the anterior impn'-ion- form- a small but sharply defined l..l>e. I'o-terior inu-ciilar -car- indistinct, much larger than the anterior. situated just l>ehind the 01 f the postero-cardinul slope. I'allial line -implc. sulinuirginal, faintly itnpre>sed. Type: /'. nmb»natn I'lrich. In the original description of this genu- and of the typical species, I called the suhrostral [irocess a cardinal tooth. This view I now believe to be at variance with the facts, fur the reason that the supposed tooth does not project beyond the plane of the margin- of the valve and therefore could not have interlocked with a corres- ponding tooth or teeth in the opposite vahr. In the left valve, upon which the genus am! /'. unilmn'ilii rocess was somewhat injured in c in- away the adhering matrix. It is, however, sutliciently preserved to show that it had one large tr.i •• depression in the lower part (for which reason it was described as hitid) ami probably one or two in the upper part. In an imperfect ri^'ht valve, recently obtained from Kentucky, the process is similarly marked with a large depression in the lower part and two (perhap- tln.-e) smaller prominences al" In neither specimen are the upper prominences in a sutiiciently good state of pres- enation to admit of po-it .mit ions respecting their character and purpose. Still it i> reasonable to suppose that they represent hinge te those of \Vhitrlln. especially -h: \vithinthelineofthe hinge. A-tothe lower part of the process, why should it i. -upported a" internal cartilage? 576 THE PALEONTOLOGY OF MINNESOTA. [Plethocardla umbonatu. The shells of this genus present considerable external resemblance to those of Whitella, Ulrich. As a rule they will probably prove shorter, more erect and comparatively more ventricose. I believe also that Whitella offers closer affinities than any other genus yet known, and I can see that it may prove difficult in some cases to distinguish species of the two genera when the internal characters are not available. Of course such difficulties cannot obtain when the diagnostic characters of the hinge are preserved, since the strong subrostral process of Plethocardia is too marked a feature to be overlooked in comparing the two genera. Good casts of the interior even are easily distinguished by the presence of the small lobe beneath and in front of the beaks of Plethocardia, the muscular impressions being very much less distinct in the casts of Whitella. In the posterior part of the hinge, however, as well as in other respects, the two genera are practically the same. It seems to me more than doubtful that Plethocardia belongs to the family Megalpdontidce. A general resemblance to those heavy and strongly-hinged Devonian and Triassic shells, which are included in the family by Zittel, may at first strike one, but a critical comparison brings out too many important differences. I adopted the above provisional arrangement chiefly that attention may be directed to the genus as a possible progenitor of a remarkable family of shells. PLETHOCAKDIA UMBONATA Ulrich. PLATE XL, FIGS. 22-24. Plethocardia umbonata ULRICH, 1892. Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 244. Shell about 25 mm. in length, strongly ventricose, obliquely subovate in a side view, widest posteriorly; beaks large, very prominent, inrolled; umbonal ridge angu- lar, traceable to the postero-basal margin; cardinal slope narrow, rather sharply defined, concave. Anterior end very short, nearly ventrical, sharply rounded above; dorsal margin arcuate, graduating into the posterior curve; the latter is produced slightly in the lower part and accelerated as it turns into the broadly convex ventral margin. Surface marked with concentric lines of growth, some of them strong. Escutcheon narrow, extending backward from the beaks nearly to the posterior extremity of the hinge. Subrostral cardinal process large, projecting obliquely for- ward from the lower side of the hinge, with one large depression (? internal cartilage pit) in the lower half and several smaller ones (? teeth sockets) above. A strong, ridge-like thickening of the shell, probably representing either a postero-lateral tooth or the support of an internal ligament, occurs just within the postero-cardinal margin. Anterior adductor muscular scar situated in a cup-like depression formed by a curved ridge which proceeds from the under side of the cardinal process and 'KI.I.IIlKAN' IMA I \ the aiitero-caidmal margin of tin- >hi-ll: po-tc-rior -car indistinct, larger tlian the anterior, situated a short -li-tancr beneath the post-cardinal margin. I'allial line faint, -imple. -nlniiaiyinal. It is p<>— il>le that this specie- is not distinct from the ' 'tirt»,t»nt.i • <»;l!t«t»iiii of Hilling. Mix ti^'iire- of that -pe.-ies looks so much like the shell above described that I am nearly -ati>tie-d that they must be congeneric at least. It might l>e a U'hiffll'i. tint it i- not a true < om pared with / <>i situated farther back from the anterior extremity, the uinhonal ridge is rounded instead of angular and the outline different, especially that of the posterior end. which i- also wider. / locality J tli.- niKldl.- third »f tin- Tr.-nton shul. - ^x. tnlli* .-nutli of Cann-.n Falls. Mnin.-MHa uue«tone»i -.f • York. In '•' unt\. Ivntu-'kv. I'r.h'lll... \i;l>i\ SDBBBBOTA I'lrirli. 1-I.ATE X! a-17. 1'lethowrdia tulx,. n. 1^2 MtioUwnlh Ann. Krp. Oeol. and I Sur. Mftin., p. 846. 1 small. Imt little oblique, exceedingly ventricose, short, sul>elliptical in a si.lo view, with the dorso-ventral diameter much the longest. Beaks very prominent, large, strongly incurved, nearly terminal; nmbonal ridge strong, sharply rounded, with the cardinal and posterior slopes very abrupt and nearly flat. Anterior end very short, the part in front of the beaks of casts consisting chiefly of the sharply defined lobe-like filling of the anterior muscular impressions. Anterior and poste- rior margins gently convex, subparallel; ventral edge sharply rounded. Hinge line -hort, scarcely extending posterior to the urabonal ridge, as seen in a side view. In the casts there is a depression beneath each beak that is prolonged on each side around the mu.-cnlar -car. The escutcheon seems to have been narrow, but the internal ligament supports at the posterior end of the hinge line have left two strong grooves, one on each side. This species, though clearly congeneric with /'. umbonaia, is so readily di-tin- that comparisons are unnecessary. formation an./ Ineality. -Galena shales near Cannon Palls, Minnesota. -37 THE PALEONTOLOGY OF MINNESOTA. LNucullda-. Family NUCULID^E. Genus CTENODONTA, Salter. Nucula. HALL, 1843. Geol. Rep. 'Fourth Dist. K Y., p. 76; Amer. Jour. Sci., vol. XLVIII, p. 292; 1847, Pal. N. Y., vol. 1, pp. 150 and 316. Lyrodesma (part.), HALL, 1847. Pal. N. Y., vol. 1, p. 302. Tellinomya, HALL, 1847. Pal. N. Y., vol. 1, p. 151; 1857, Tenth Ann. Rep. Reg. Univ. N. Y., p. 181: also of the majority of American paleontologists since that date. (Not Tellinomya, the correct form of Tellimya, BROWN, 1827, as given by AGASSIZ in 1846 in his "Nomenclator Zoologicus.") Ctenodonta, SALTER, 1851. Rep. Brit. Assoc., p. 36; 1859, Can. Org. Rem., Decade i, p. 34. Paloeoconcha, S. A. MILLEII, 1889. North Amer. Geol. and Pal., p. 498. Shell equivalve, closed, usually largest anteriorly,* occasionally subequilateral, with the beaks situated sometimes behind the middle, but usually more or less in front of that point; surface marked by concentric lines of growth; beaks approxi- mate, generally small and never very prominent. Ligament external, rather small, situated immediately behind the beaks; no striated area nor internal cartilage pit. Hinge more or less arcuate, sometimes very gently, at other times bent almost at a right angle; with series of small curved or geniculated transverse teeth, which diminish in size more or less gradually from the extremities to the beaks; the series are continuous and gradually pass into each other in the typical section of the genus, but in other sections they are often interrupted beneath the beaks. Adductor muscular impressions two in each valve, subequal, nearly always readily distinguishable, and sometimes very deeply impressed, situated just beneath the anterior and posterior extremities of the hinge; scars of small foot-muscles have been observed in a number of species, one immediately above or in front of each of the adductor scars; pallial line indistinct, simple, submarginal. Type: C. (Tellinomya) nasuta Hall. Several reasons have operated in the rejection of Hall's earlier name Tellinomya in favor of Salter's Ctenodonta. First among these is the fact that Tellinomya was used for a totally different group of shells at least one year previous to the date of publication of the first volume of Hall's Paleontology of the state of New York, namely, in 1846 by Agassiz, in his "Nomenclator Zoologicus>" when he catalogued the correct form of the incorrectly constructed generic name Tellimya, which had been proposed by Brown in 1827. Believing that such corrections are allowable, 1 am obliged to hold that Tellinomya, Hall, cannot stand under the rule relating to •II i- unite difficult to establish which Is the anterior end in these shells. For the sake of uniformity 1 have, In each case, assumed thut the higher end (It Is usually also the rounder) Is the anterior. It may Me well t"> state, moreover. that I am not at nil satlsfled^that this rule should apply In the C. recurva section of the genus, nor t hat Salter. Meek ami Worthen, Hall and others who have described species of that section, are right in assuming that lite side toward which the beaks are tnrned Is the posterior. Though I have followed these authorities. I have done so chiefly Mi-eau-.e it seemed desirably, at any rate until the genus was worked up monographlcally, to have our descriptions as uniform as possinle. Had I followed rny own inclination it would ha\c Meen to reverse, in this case, the present application of anterior and posterior, upon the ground that tin- external ligament was situated upon the covex half of the hinge Instead of the con- .•ave. That this Is really a fact is, I bellere, C -In-ively shown in C. recurva. iSer plate xi.n. fig. 101.1 IW preoccupied ii. tines. Suitor objected t.. flu- adoption of Hall's name, !>• inappropriate aii"'". that being the arrangement adopted by him in all cases where he did see the ctenodontoid hinge. Nor can we doubt that Ctenodontn was acceptably -ibed at least five years before Tellinomya, Hall, was redefined in accordance with the true character of the shells upon which the genus .was founded originally. finally, the original description of Tellinomi/u was so totally at variance with the that Salter could not for a moment be blamed for failing to recognize the identity of /'. mi.tnfn and the >hell which he proposed to call Clenodontu. Taking all these defects of 7V/// Homy/ into consideration. I do not see how we can do otherwise than adopt CtenodonUt in preference to Hall's name. Had Tellin- ' not been preoccupied I would have suggested another solution of the difficulty, namely, to subdivide the genus so that both names might be used, at least provision- ally. Tellinomi/ii for the typical group of species and Ctene turned either forward or backward. Internally the struct me i- equally diverse. The hinge plate may be narrow or broad, nearly straight or bent rectangularly, and with out- wardly or inwardly bent denticles. The latter, though always smallest near the beaks, may form a continuous series from one end of the hinge to the other, or the continuity of the series may be interrupted beneath the beak. This interrupt 580 THE PALEONTOLOGY OF MINNESOTA. [Nuculldio may be produced, without materially affecting the arrangement of the teeth, by the development of a small pit immediately beneath the beak (see plate XLII, fig. 80), or the teeth may be so arranged that the two series of teeth are directed at almost right angles to each other (see plate XLII, figs. 39, 90, 101 and 102). Finally, the shell is often very thin and the muscular scars barely distinguishable, while in other forms the shell may be thick and the muscular imprints exceedingly strong. In the present work I have allowed all these divergent types to remain under the single genus Ctenodonta. This does not, however, say that 1 could not have sub- divided the genus into several, nor that I do not believe that such a course will eventually be considered not only possible but desirable. Meek and Worthen long ago* expressed themselves as favoring a separation of the subtriangular forms like C. alta Hall, from the more typical ovate or elongate species. And Dr. S. A. Millerf quite recently proposed the new genus Palceoconcha for one of the species of that group. He did so, however, under the misapprehension that the hinge of the species described by him is edentulous; so his evidence on the point is much weakened, for he would, most likely, not have proposed his genus had he understood the hinge fully. For the reason about to be mentioned, I am probably in a better position than any one else to speak of the possible subdivisions of this genus, namely, my efforts to collect a large mass of material have been successful, not only in the way of individuals, but in adding very greatly to the number of known species. Indeed, the Lower Silurian species in my cabinet outnumber the forms described previous to 1890 more than two to one. I believe, therefore, that with the careful study that has been given to this abundance of material, I am able to discriminate in a fairly trustworthy manner between the important and unimportant characters, to approx- imate truth in my views of the inter-relations of the species and to understand some of the genetic questions involved in the development of the family. The Lower Silurian .species may be arranged in six more or less well marked groups, as follows: 1. C. nasuia group. Elongate shells, narrow posteriorly, beaks subcentral; muscular scars moder- ately or distinctly impressed, hinge but slightly arcuate, teeth in a continuous series, straight or bent outwards. Species: nasuta Hall, nasuta, var. robusta \]\rich..subnasut(i Ulrich, ovifornm Ulrich, cunei/ormis Ulrich, regia, n. sp., tyennesseensis, n. sp., appressa, n. sp., crandalli, n. sp., iphigenia Billings. *Oeol. 8ur. 111., vol. Ill, p. 309: 1868. t North American Geology and Paleontology, p. 498; 1891. tThe new species, which are not described hi this work nor In vol. vil of tin- Ohio Geological Survey reports, are marked simply a- n. sp. Descriptions of these forms will, it 1- hoped, lie pulilMied at an enrly dute, Die phiiii on which they :m> illu-tr:ited being ready for pul>lir:it inn. I.AMKI.I.II.K \N> II1A I \ .UP.) II. C. hort, thick. with vcr\ *tronj.'ly defined nniM-iilar impressions; hinge strongly Kent, with the series of detiticlps interrupted beneath the beaks; teeth -traiu'ht or curving outward. Spi-cie*: 1/ililifrnln Salt«-r. ,;,nt>--i<-t-i Salter. attyelti Hillings, i-arinnta Ulrich. /»//imw/«r- i I Iricli. /.IH»/./ 1'lrich. III. ' '. l-Tnta group. Shells tonally of ovate form, rather thin, with muscular scars moderately dis- tinct; .Ifhtn-Ir- converging inward, forming a continuous series in the Trenton species. In the Hudson Kiver forms, however, the series is more or less interrupted l>y the development of a small and undefined pit just beneath the beak. Species: levata Hall. •l»nt>i Billings, nitidn Ulrich, medialis Ulrich. scqfiif'H I ° 1 rich, socialis Ulrich, harixvillensis Safford, danvillensis, n. sp., retrosa I'lrich. fiHstri'itn Ulrich, albertina Ulrich, simulntrix Ulrich, fuvtida, n. sp., madisonensis Ulrich. tecunda Hall, mlrin I'lrich. tnnn,f-.^,i I'lrich. urtt.irtil'ormix Salt. .|.-./i'.i I Irich. ,ilf,i Hall, "bli Hall. '^,y/^jL, /+*** •? . J VI. C. logani group. Thin giltbous shells, with subcentral large beaks; muscular -MI- f.iint: hinge hut little arcuate, tin- ilmticles in continuous series, bent inward. ies: logani Salter. l»>s ran^e. l>ein^ unknown 582 THE PALEONTOLOGY OF MINNESOTA. LNueulidae. above the top of the Trenton. Group III is by far the largest section of the genus both in its specific and individual development. It may justly be called the nuculoid section, since not only the general expression of the shell is decidedly like Nucula, but its internal characters likewise approach those of that remarkably persistent type more closely than is the case with any of the other groups here defined. I think that the evidence indicates very strongly that Nucula was developed from this stock. As is well known, that genus is distinguished from Ctenodonta chiefly in having a small but well defined internal cartilage pit immediately beneath the beaks. Now, although in the Trenton forms of Group III the hinge denticles form a perfectly continuous series, this cannot be said of the Hudson River species. In many, if not all, of these, namely, the series of teeth are more or less distinctly interrupted beneath the beaks by the incipient development of an at least similar pit. So far as it is possible to say, true species of Nucula occur in the Devonian, so it is but natural to assume that the missing links between them and the Ctenodonta levata group of species are to be found in the intervening Upper Silurian deposits. But here we meet with an obstacle in the fact that none of the Upper Silurian shells that have been referred to Ctenodonta (Tellinomya) and Nucula*, with the possible exception of Tellinomya curia Hall, of the Clinton group, belong to the C. levata section. It does not, however, follow that such species did not exist, though we must admit that it is a strange, if not a significant fact that they have not yet been found. Still, the significance of their absence is lessened when we consider that the Upper Silurian deposits throughout are relatively poor in remains of Lamellibran- chiata. It is also to be remarked that the forms which have occurred belong chiefly to families widely different from the Nuculidce. It is possible that the Devonian genera Palaioneilo and Nuculites also came from this stock, such a development being faintly indicated by C. fecunda and C. nuculiformis; but taking all the characters into consideration, and the direction of the variation that may be followed into the lower divisions of the Upper Silurian, Clidophorus seems to me a more Jikely ancestor for those genera. Group IV may be a departure from the C. recurva group, but, as it seems to me to be a more primitive type, I would rather consider the relation as reversed. The only objection to the latter arrangement may be removed at any time, since it is nothing more than that C. compressa, a typical species of the recurva group, has been found somewhat lower in the Trenton formation than the earliest known member of the pectunculoides group. •Very little is kt,own (if ihe. hlnne of the Up. Sll. species that have been referred to TcUinomya by Hall and others. •-<. that we :ire instilled lii (lnnlitliiK th;it they really belong to the KCIIUS. Those known to possess a dent ienlatcd hlntfe are inneh more like I'tilimnfihi than I I.AMKU.IU: \\rlll.\T\ >t di.stim-t of all the-. -••••• 'tns. It is certainly tin- least variable and tht> »>a>iest to recogni/e. the A-tarte-like form of the shells alone l>eiiig sufficiently diagnostic. The s»lin»tral interruption of the hinge denticles is very distinct and th»- point is often marked by a sort of pit. <|iiite undefined, however, that may have lodged an internal cartilage. .\U'-K/H may really have been evolved from thU type, since it would have required but a slight modification of the hinge, a depression or lengthening of the form, and a filling of the umbones. Ay it i-. ( '. n-rnn-,1 is nearer \nruln than it is to C. nasuta, but several species of the levata section approximate that p-nns even more closely, so that we are obliged to regard the balance of the evidence to be in favor of the levata group, unless both the groups have contributed to make \ucula as now understood. Of Group VI only C. logani is well known, so we cannot say much about affin- ities. The species are all Trenton, and their general aspect is quite different from the other groups. It is an interesting fact that all of these sections are represented already in the lowest geological division (considering the Hirdseye and Black River limestones as one) in which the genus makes its first known appearance; the nasuta group with the species tf*nes»tens\s and nasuta, the gibberula group by all of its species except C. caritwta, the levata group by at least five species, the petunculoides group by the specie? "nl'i-otunda, the recurva group by C. compressa, and the sixth gronp by C. lognni. Kadi group again is as sharply marked in these first species as it is at any subse- quent time: nor have we any evidence to aid us in deciding which of the six groups i- the most like the primitive stock. It is evident, therefore, that a long line of forms of this type must have existed in the ages preceding the Hirdseye of which we now have no knowledge whatever. The same remarks apply almost equally well to the other families of Lamellibranchiata, and one of the most remarkable facts in paleontology is the almost total absence of the class in the Calciferous, especially when we consider that that formation abounds in Gastropoda and Ceptuflopoda. I have carried on a number of very interesting comparisons between the species of ( 'tenodonta and certain forms of recent genera like Neil». Malletia and Sareptn, three nuculoid genera, and Asin-ra and other Arriii-i . If this work was not already growing beyond the limits alloted to it, I would gladly give the results of these comp;in-nh- here fully, but under the circumstances I am obliged to re-tri.-t myself to a few general remarks. The three nucnloid genera mentioned are very similar indeed to the r. nasuiii group of species, the first and second differing chiefly in having a sinu- ated pallial line, while the third has an internal cartilage pit beneath the beaks like .\ncula. Certain Cretaceous species of Asimm (f. >/. A. sulplanntn Stnli. . /..n .ire strik- similar to the C. pectunculoides section, the only difference of real consequence 584 THE PALEONTOLOGY OF MINNESOTA. [Otenodonta uasuta. being the presence of a low triangular striated area between the beaks and the hinge in the Axincea. Other Arcidce present almost equally close resemblances to C. loganL Aside from the ligamental area the principal characters of Area and Isoarca are practically the same as in one or another species of Ctenodonta. We have then three families of recent shells (as defined by Stoliczka) any one or all of which, and I believe it is the latter, may have been derived from this early type. C. nasuta section. CTENODONTA NASUTA Hall. PLATE XLII, FIG. 30. Tellinomya nasuta HALL, 1847. Pal. N. Y., vol. 1, p, 152; 1857, Tenth Eep't. Reg. Univ. N. Y., p. 183, ?flg. 2. (Figures 1 and 3 not strictly nasuta,) Ctenodonta logani SALTEB, 1851. British Asso. Rep., p. 63. (Not C. logani Salter, 1859.) Isoarca logani WOODWARD. Manuel Shells, p. 269. Ctenodonta nasuta SALTER, 1859. Can. Organic Remains, Dec. I, p. 35. Shells transversely elongate subovate', the length one-twentieth or more greater than twice the greatest bight; beaks rather small, not very prominent, incurved, situated about one-twelfth of the entire length in front of the middle; anterior end large, broadly and regularly rounded; posterior end produced, tapering, rather nar- rowly rounded at the extremity; cardinal margin nearly straight, basal line broadly convex except for some distance behind the middle where it is straight or more often gently sinuate. Greatest thickness near. the middle of the anterior half, equalling about one-third of the length of the shell. Umbones moderately inflated, the posterior cardinal slope defined by an obscure umbonal ridge, very abrupt for a short distance behind the beaks, more so than on the anterior side; a broad and very shallow sulcus crosses the valves obliquely from the umbones to the contraction in the base. Ligament attached in a sharply defined groove on each side of the hinge line, extending from the beaks about one-third of the distance to the posterior extremity. Surface marked with obscure concentric lines. The test being thin, casts of the anterior look much like the exterior of the shell itself. The muscular scars are faintly impressed and usually determined with difficulty on all except the largest casts. The denticulated part of the hinge is comparatively short, being but 21 mm. in length in a specimen 56 mm. long. Its upper margin is nearly straight, but the lower side is rather distinctly biconvex, the plate being con- stricted beneath the beaks to little more than half of its width on each side. The denticles form a continuous series, are small and vertical beneath the beaks, slightly oblique in front of them, and strongly curved outwards behind them. The entire series, so far as observed, contains twenty-seven to twenty-nine teeth, divided almost equally with respect to the beak. I. \MKI.1. II. I! \N< III .VI \ MM «t'ii*-'. None of the northwestern .-penmen- (if this species soon l»y me quite reach .• length of 4d nun., the average beiiiK about •_'"» mm. In Canada they grew to much ;ter -i/e, some of the specimens from I 'a i lunette's Rapid- mi tli«> nttaua ' having ii length of more than GO ram. A— ociated with thi- t>pMMI in \\I---OIIMII ami at 1'auquett's Rapid- there form which, though it ha- Loon identified unreservedly with C. tuisuta by Hall and •r-. I find to be not strictly identical with that species. The anterior end is higher .in.) larger, and the posterior end shorter, so that the beaks, instead of being in front of the midlength. an- a t rifle behind that point, the muscular impressions are deeper, ami the hinge plate i- on the whole narrower and much less constricted in the mid- 'lie. This form, for which I propose the varietal designation robust a, was figured by I'rof. Mall in the Tenth Annual Report of the Regents of the University of New York on page 183 as T>IHn<>may nasuta. He figures two specimens of which the smaller may belong to nasuta. The larger example, however (figures 1 and 8), I refer to the variety robusta, and I do so with the utmost confidence, the specimen being in my possession at thi- moment At Pauquette's Rapids the variety attains about the same size as the typical form of species, but in Wisconsin it is much the larger. Near the top of the Trenton in Kent ncky there is a form, that I shall call C. regia, which seems to represent the culmination of the differentiation begun in the variety robusta. In thi- Kentucky species the bight is even a trifle greater, the base is not Minute, the muscular scars are very deep, and the hinge plate stronger than in both the variety and the typical form of nasuta. Formation and locality. C. natuta occurs >|iarlnt{ly lo the lowei Trenton limestone at Minneapolis and in the n>Ul- Tr.-ui-n -hales In Guodhue county, Minnesota. In Wisconsin the specie* '•• abundant in th>- "Lower Blue" and the •' I'ppcr Buff" limestone* at Belolt, Janenvllle and Mln- • •r;ii Point, it has also been found in th<> -a mi- beds at IMxmi :iiul oth>-r localities in Illinois. In Canada It occurs in the Black River and Trenton llni.vttone* at Ottawa and numi-nni* oth.-r |*>lnU. The ordinal types of the species came fmtn thf Trcnfm limestone at Mlddlevllie and Tn-tit<.n K.iil-. N.'w York, and it.iN«u.-d by Prof. J. M. Safford among the fo&slN .,; in- "C, •ntra r>>ek ~ lonex In Tennessee. Variety rolnuta o i':i.i.(u.-t t.-'n l!.ipi:u < ittawa, Canada, nnd Ii i-r Ruff limestone at Belolt, Wisconsin. M*t Reg. N<. -.ii:. var. robiu-i XODONTA SI'BNASITV. I, i-i.ATr. xi. 1 1 nun. M-X Tlii- -hell is no doul>t closely related to C. nasiita. Imt. aside from its much smaller dimensions, it ditters in sevenil particular^ that have seemed of -ntlicient importance to merit -pecitic recognition. Thu- the posterior end is somewhat longer, the beaks being placed farther in front of the middle, the anterior en more obtuse in a dorsal view, the beaks are turned anteriorly rather than backw the lower margin of the hinge plate is almo '"ad of biconvex, while 586 THE PALEONTOLOGY OF MINNESOTA. LCtenodontn oviformis. the denticles are relatively more numerous on the posterior part, there being about sixteen or seventeen on this side of the beaks to about ten in front of them. Casts of C. nasuta again exhibit a rather well marked lanceolate depressed area extending posteriorly from the beaks about half way to the extremity of the cast. In C. sub- nasuta the corresponding area is not lanceolate, but consists of a furrow on each side of the raised hinge line running backwards almost to the extremity. The fol- lowing two species also are rather closely related, but are readily enough distin- guished by their shorter form and lesser convexity. Since the above was written, I have found among my unworked material from the middle third of the Trenton shales in Goodhue county, two valves that may represent an earlier form of this species. Artificial casts of the interior of these valves closely resemble the Galena shales type of the species, the only difference being that the central part of the casts is not quite so full and the basal line less straightened in the posterior half. There is also a flattened rim along the ventral border that is not seen in the type. In these features the valves remind somewhat of C. oviformis, but they cannot belong to that species, since they are too narrow posteriorly and have the beaks situated more anterior to the center. The hinge is rather well preserved on both the valves, each having about twenty-six denticles, nine of them in front of the beaks. Of the latter the anterior five are larger than any of the others. The hinge, on the whole, resembles that of C. cuneiformis, but the anterior teeth are larger and the beaks situated farther forward. Formation and locality.— The type is from the Galena shales near Cannon Falls, Minnesota. CTENODONTA OVIFORMIS, n. sp. PLATE XLII, FIG. 29. Shell small, compressed convex, transversely ovate, the ends rather narrowly rounded, subequal, the anterior a trifle wider and shorter than the posterior, the base almost regularly convex, the hinge line gently arcuate, and the beaks rather small, scarcely prominent and situated slightly in front of the midlength. Muscular scars comparatively distinct. Number of teeth and surface unknown, but the cast is marked with several obscure concentric furrows. Length, 9.2 mm.; hight about 6 mm.; thickness, 3.8 mm. This small shell is relatively shorter, less produced and wider posteriorly, and more rounded in the basal outline than C. nasuta and C. subnasuta. Collectors will, I think, find little trouble in recognizing it. Formation and locality.— Galena shales, near Cannon Falls, Minnesota. LAMKI.I.IIiKAV 111 s >7 KMODONTA nNHH>l;VI". n. • *. n-m. shell small, compressed convex, transrenely somewhat a •uminate-ovate. tapering • •riorly to a narrow!} rounded extremity; anterior end shorter than the postf hut iniich higher and broadly rounded, except in the autero-cardinal region, where the outline projects slightly beyond the path of a uniform curve; base rather prom- inently rounded in the middle, convex throughout the anterior half, straight or very faintly -innate in the posterior half; beaks small, not prominent, situated about 4 mm. Miin.l the anterior extremity in a specimen 1 1 nun. long; posteriorly from the beaks the cardinal outline is straight, in front of them gently concave. Ilehind the center the shell is more or less distinctly contracted. Surface with obscure concentric M Hinge plate of moderate strength, comparatively long, very gently bent, and just appreciably contracted beneath the beaks, with about twenty-seven nearly vertical teeth in each valve, twelve in front of the beak. The posterior six or seven teeth are stronger than the rest and bent inward. Test thin, muscular scars not observed. The largest -penmen seen, a right valve, i- 1'J nun. lung. 7.1 nun. high ami l.s mm. thick. The contraction and narrowness of the posterior end gives to this species some- what the appearance of C. contrnrtn Salter, but the two species are really widely ditlerent. The Canadian shell is higher, more convex and its cardinal outline much more angular, the hinge plate strongly bent and very narrow under the beaks, the teeth larger and not so numerous, and the shell much thicker. The affinities of C. cuneiform is are probably with C'. nasuta and C. subnnsutn. The former, being a much larger shell, is not likely to be confounded with it. The latter is narrower anteriorly and wider posteriorly, is more convex, especially in a front view, its posterior half is not contracted in the same manner, and the anterior outline more uniformly rounded. tation and locality.— Four -i»rnii.n> were found at • point about fix mile* south of Cannon Falls, Minnesota, wln-n- ttu-y ocourn-d In the upper part <>f th<- middle thin) of th.- Trenton Khali*. The same locality and bed has furnished numerous nth.-r Lamelllbranrhlata. gibbtruln section. \ I.IIIBM. •'/«/-. I-I.ATF. xi.n m; r i trnodonta gibberula SAI.TKI:. IH57. Canadian Organic I)- i. p. 38. T'llinomfa rentrieota Hu.i.. I««I. Itep. Supt. Geol. Sur. WI-, ],. 27: Ivi- Final K.-p..rt of um«, p. 38, fig. 3; MKKK and Wuici HKN. ISJ8, Owl. Sur. 111., •. *r.. Shell rhombic subovate. ventricose, the bight, length and thickness, reap- as seven, ten and -iv. with large incurved l>eaks. situated a little behind the mid- length; antero-dorsal and ventral margins subparallel, the posterior end oblii| 588 THE PALEONTOLOGY OF MINNESOTA. [Otenodonta glbberula. truncate above the narrow and sharply rounded lower part; anterior end broadly rounded and continuing into the basal margin; the latter is straight or very gently sinuate and ascends from the prominently rounded anterior part; posterior umbonal ridge inconspicuous in a lateral view, rather sharply defined, however, in a dorsal view by a narrow furrow which outlines a wide lanceolate flattened area, equally divided by the hinge line, and in the upper part of which (immediately behind the beaks) the ligament is attached to distinct fulcra; anterior dorsal slope abruptly rounded; entire anterior half of valves strongly ventricose, while between this part and the posterior umbonal ridge a slight sulcus crosses from near the beak to the base. Surface marked by rather distinct, closely arranged, subequal concentric strise of growth, tending to irregularity in the basal parts of old shells. Impressions of adductor muscles extremely deep, the anterior pair larger than the posterior. A small, though distinct, pedal muscle scar is always present on the upper part of the strong ridge which forms the inner boundary of the anterior adductor, (in casts it lies at the bottom of the deep cavity produced by this ridge), but the corresponding posterior scar is rarely distinguishable. Hinge plate very narrow at the beaks, but widening rapidly on each side, the anterior half somewhat the stronger and slightly concave along its inner margin, both terminating abruptly at the muscular scars; denticles twelve behind and ten or eleven in front, those near the beaks very small, all interlocking deeply, especially those of the anterior set, which are also somewhat larger than the posterior. The shell is very thick and the rostral filling so considerable that in casts of the interior the beaks appear obtuse and widely separated. I have very carefully compared a large series of the northwestern form which Hall named ventricosa with authentic Canandian examples of Salter's C. gibberula, and I can say, with perfect confidence, that there is not the slightest reason for con- sidering them as distinct species. The only difference that I can detect is that the northwestern specimens grow to a larger size than the Canadian. Tennessee speci- mens also attain greater dimensions than the latter, though their average size scarcely equals that of Wisconsin examples. Meek and Worthen suggested (op. tit.) that Tellinomya ventricosa may be the same as C. contracta Salter, but in this they were mistaken, since that species is certainly distinct and, so far as known, does not occur at any of the northwestern localities. Formation and locality. -In Canada this species occurs in I lie Black River limestone at Pauquette's Rapids. In Tennessee it occupies an equivalent or lower position near Murfreesboro. In Wisconsin, at Ueloit, Janesville and Mineral Point, and ;it several localities in Illinois and Iowa, it forms one of the most striking fossils of the limestones beneath the Galena, particularly the "Upper Buff." In Minne- sota it seems to be a rare fossil, being, so far, known only from 'Minneapolis, where it occurs in the Trenton limestone a few feet beneath the shales. MHX. Reg. Nos. K309, 8316, . •.„„.,.., OUHMAJCBI4 •S I V ' M.IN \ I \. H. «p. «. rather small. gibbous in the anterior ami rostral port inn.-, the ends obtuse in a dorsal view, the beaks large, prominent, strongly incurved, situated near the midlength and turned decidedly toward the posterior end; the outline may be described a- -ul. triangular or obscurely quadrate; anterior margin most prominent and strongly rounded in the lower half, the upper two-thirds more gently curved and sloping hack wan I to the beaks, being continuous with the antero-dorsal margin; vent nil margin straight or l.roadly sinuate, curving al.ruptly into the subtruncate posterior margin and forming, with the latter, an angle of about 80 : cardinal out- line distinctly .-oncave behind the beaks; post-cardinal region slightly produced, though too blunt to be called alate; posterior umbonal ridge prominent, angular, uding to the post-ventral angle; point of greatest convexity on the rounded .interior umbonal ridge; between the two ridges a wide, undefined snlcus, extending from the n ml. ones to the base. Surface marked with distinct and rather irregular "•on.-,.ntrir lines of growth. Hinge plate arcuate, in other respects apparently as in ''•/«vi«/« Salter. Shell thick, muscular scars not observed. ,>il>f>rnil,i i> the only shell known to me with which ('. carinntu might be compared. Although imperfectly known. I am quite confident that its affinities lie chit-fly with that species. Still, though the resemblances are sufficient to prove that the two forms belong to the same section of the genus, it is scarcely likely that any one will fail to distinguish them specifically, the outline in the two species being different in several respects. Thus, in ('. <-.,riwita the posterior end is wider, the post-cardinal region produced and subcuneate instead of flattened, the anterior margin i- more prominent below, and above curves more regularly into the dorsal outline, while the basal margin is not so prominent anteriorly and on the whole more nearly horizontal. The posterior umbonal ridge also is more prominent, the mesial sulcus or flattening is a more pronounced feature and the anterior slope more abrupt. Finally, the hinge plate is less bent and curved rather than geniculated. formation and locality. -Mlddl.- Galena, alx.iii ..n.- mile «ut of Fountain, MlnnmoU. < 'TKNODONTA 1-1. a i \ I '/rich. HI.ATI \\\\il HI.- • > ii Htraight liehiml the lieak-. anterior eml -hort,-8eniicirciil.u ; \entral margin gently convex; r eml ;i little narrow ei than the anterior and morr .sharply roumle-l. Surface with o|,M-inv concentric lint-: -loping ra|ii.lly .it the cardinal margin, i.ut very gently to the ends and ventral edge. Hinge plate of moderate strength, bent a little beneath the beak and with a thickening on the lower side in front <>f same. Posterior to the beak the plate is long, straight and hears twenty or more Miiall teeth, while on the anterior part only nine are to be counted. In the vicinity of the U'.ik the teeth, especially those on the posterior side, are very small. an. I us they are all set at right angles to the hinge plate, the continuity of the series i- interrupted where the two series come together. The interruption is easily over- .'•- Trvnton shales, Ooortbu.- munly, MIooMoU; SMO- 1 with C planadortata, C. romjtrtun, C. toeialif and C. «co C. logani section. t'TKNODONTA LOOAIU Salt- TI.ATF Mil FI08. ; T.lliH,>my,i ,lui- -i II \ i Tenth Ann. Rep. Beg. I ni \ "i ; 183, Kg* 4 aod 5. (Not T. dubia Hall. 1847, F.I «t,,nta ;.v«»« > ALTER. 1869. Canadian Organic He mains. Dec. I. p. 36. (Not C. logani Sailer, 1661, Rep. BriU Aacoc., p. 93, which proved to be the same a* Tellinomga namta Hall, IMT.i Shell of the medium M/«-. rather elongate, sabovate, strong! »x, very gib- bous in the umbonal region, with the strongly incn ik- turned slightly forward and -ituated near the midlength; posterior enulnt.« aiitonv, -animal region, and in the posterior in>toad of anterior position of the beaks. In casts of the interior the beaks are also -mailer ami more prominent. C. nbntpta Hillings, is more ventricose. longer and not so high anteriorly. The two wpecies next described are more closely related. Formation .m-i i,«-,iiity. <;..od specimens nf this species are exceedingly rare, but Illy preferred casto of the Interior, which arc provisionally referred here, are n«it unc-.numonly antedated with C. toeiatit In tii- m..| i ..• thinl i.f Hi.- Tr. -nt. .11 shales at Minneapolis and other localities In the state of Minnesota. ' 'TKNODOXTA MKDIALIS, n. sp. PLATE XLII. riOB. «o-as. This species seems to occupy an intermediate position between C. nitida and C. trori'/'li. 1'rom the first it diflers in having the beaks situated about midway between the extremities, the posterior end longer, more oblique and more narrowly rounded at the extremity, and the anterior end shorter and blunter in the antero- cardiual region. The posterior part of the back is wider, because the umbonal ridge is somewhat stronger and extends farther downward. Finally, the hinge plate is more curved an.l appears relatively wider. From C. xcofieldi it differs in having the beaks centrally situated instead of one-third of the length from the anterior extrem- ity. the umlional ri nton -hale*, Minneapolis and near Cannon Falls. Minnesota. A cast «t th" int*Ti»r fnun the Galena shales of Ooodhue county, probably belongs here. CTRNODONTA SOOKIKLDI, n. sp. I-I.\TK xt. ii nos. m-m. Shell small, strongly convex, transversely somewhat amminate ovate, broadly roumled in front aiul In-low, narrow behind, with small, prominent, incurved beaks, -38 594 THE PALEONTOLOGY OF MINNESOTA. ICtenodonta socialls. directed posteriorly and situated about one-third of the length from the anterior extremity; umbones carinate behind, the ridge having a distinctly concave outline in a side view; posterior end of hinge projecting slightly beyond the ridge, so that the post-dorsal region is not quite flat. Hinge plate comparatively short and weak, widest posteriorly, very narrow beneath the beak and in front of same; denticles small, seventeen or eighteen in each valve, in a continuous series, about eight of them posterior and larger than the others. This neat and constant form is readily distinguished from C. nitida and C. medi- alis, its nearest congeners, by the posteriorly carinate umbones, the less central position of the beaks, its narrower posterior extremity and much weaker hinge plate. The denticles also are less numerous. Casts of the interior of these three forms are difficult to distinguish, but the task is not by any means hopeless when the speci- mens are in a good state of preservation. The species is named for my colaborer on the Gastropoda, Mr. W. H. Scofield, of Cannon Falls, Minnesota. Formation and locality.— Aa entire example and nine valves were collected in the middle third of the Trenton shales in the vicinity of Cannon Falls. Minnesota. A cast of the interior was obtained at Minneapolis from the samq beds. The species has not been observed in the upper third of the shales, but the overlying Galena shales have furnished a number of casts that I have not suc- ceeded in distinguishing. These were collected at Cannon Falls and near Kenyon. CTENODONTA SOCIALIS, n. sp. PLATE XLII. FIGS. 59 and 60. Shell very small, moderately convex, transversely subovate, rarely exceeding 6 mm. in length, the average size about 3.8 mm. high by 5 mm. long; beaks small, turning slightly toward the short posterior extremity behind which it is situated between one-fourth and one-third of the entire length; umbonal ridge inconspicuous, the convexity of the valves being relatively uniform. Surface almost smooth, no markings save a few obscure concentric lines having been observed. Hinge plate narrow, especially so under the beaks, widest posteriorly, comparatively long, arcuate, the amount of curvature varying according to the length of the posterior end of the shell, being greater when this part is shorter than usual; denticles small, nineteen or twenty in each valve, six or seven of them posterior, several of the latter consid- erably larger than any of the others. In a shell of this kind it is very difficult, if not impossible, to decide beyond the possibility of error which end is the anterior and which the posterior. In this case I have assumed that the short side is the posterior, because this end of the hinge plate is the wider and bears the largest denticles, that being the prevailing condition among species of this section. The small size, rather regularly ovate outline, moderate convexity and the I \VU.I ll;i;.\N< IIIATA. Ml posterior position of the heaks ;ire features that render tin- identification of tin- specif- nnii-ually .M~\ . 1 h.'-ii.itrd to gay whether it should be regarded aa nearer ( '. nititl.i or those ovate >hells, like < in which the larger side is undeniably tin* posterior. formation 'll re In certain layen of th«« in thlrtl of tin- Tr.'iii..n shale* at St. I'aul, M -..I .it nor lix-mlltl.- in Hi,- i !.i\. r may IK- .-mi.; I i.\ separated vah i»t- nf UK- mtvrlnr. 'I'll' illlnit one at th<- two locallUe* iir-t merit ii>n't rti/i'i and C. Jilistriata of this report, while it is especially near an unpublished form from the middle beds of the Cincinnati group in Kentucky and Ohio which I shall call C. himida. From these three species C. maduonttuw is distinguished by the more uniform curvature of the anterior margin, the antero-cardinal region in t ho-.- form- being more or less prominent and subangular in outline. and locality. -The specimens upon which the specie* Is founded were collected In the Cincinnati group at Madison, Indiana, where they occurred In association with n tHu rttrota. 598 THE PALEONTOLOGY OF MINNESOTA. [Ctenodontii albertina. CTENODONTA ALBERTINA, n. sp. PLATE XLII, FIGS. 76-80. Shell subovate, widest in the anterior half, 10 to 18 mm. in length; beaks mod- erate in size and prominence, situated about 4.5 mm. behind the anterior extremity in a specimen 16 mm. long; antero-cardinal region compressed, slightly alated, subangular in outline; anterior margin nearly vertical and. rather gently convex above the lower part, where it turns somewhat rapidly backward into the broadly rounded base; the curvature of the basal outline is often not quite uniform, being, in these cases, a little stronger in the anterior than in the posterior half; posterior margin somewhat obliquely rounded-sub truncate; as shown in the figures the width of the posterior end is somewhat variable; cardinal margin nearly straight; umbonal ridge rounded, inconspicuous. Surface almost entirely smooth. In casts of the interior the beaks are prominent, compressed and very little incurved, the adductor muscular scars are distinct, the posterior one being especially prominent and the larger, while the anterior one is drawn out above almost to the point of the beak; the posterior cardinal outline is strongly concave, while the dor- sum in this part is formed by a sharp curved ridge running backward from each beak to the adductor scars and enclosing the area that had been occupied by the hinge plates. The hinge plate is strong, contracted and bent beneath the beak, the posterior part one-third longer than the slightly declining anterior part; denticles strongly geniculated and deeply interlocking, the continuity of the series distinctly interrupted under the beaks by an illy defined pit-like space. In five valves the total number of denticles ranged from twenty-nine to thirty-two, with thirteen, fourteen or fifteen anterior and sixteen or seventeen posterior. In a sixth valve, unusually short and possibly not belonging to this species, there are only eleven anterior and thirteen posterior teeth. Length of an average example, 12 mm.; hight, 9.5 mm.; thickness, 6 mm. In a large specimen these dimensions are respectively 16, 12.2 and 7 mm. The type of structure exhibited in this species and in C. filistriata, C. madisonensis and two as yet unpublished forms from the Cincinnati group of Ohio and Kentucky, stands somewhat apart from the other two types (i. e., C. nitida and C. fecund n) included in this section of the genus. The geniculated hinge teeth and the pit beneath the beak are peculiar features, while another difference, when compared with the C. nitida type, appears in the absence of the small accessory scars over the adductors. That some importance attaches to the absence of these small scars is indicated by their constant presence in the species which pertain strictly to the nitida type in other respects. These scars seem to be wanting in the shell of the •KM.ii:i: \N- in 0M .»!« In typo a-^ well. Imt this, unless we agree that tin- -h«-rt -i'l«- iii those .illy the posterior, doe- not liriu^ them much nearer to the < '. >ill>,rtina type, -UK,- the addm-tnr- an- iv \rrsed, the ariuninate-OVate SCar being anterior ill the latter ami po-ti-rior in the farmer. .I/iff.— A - in tin- iippr: :iati uroup at Clark*vllli- ;iiul i.th.T :I«M -..iiMli-d that ' '!.onwnU, Imt •xl reasons to 1.. .:• \. tliat It may be found In th< II .1- • ata near Spring \ alley. KHODONTA Kll.i-'l i:i ATA, ». •ik-lit side of a cast of UP- inti-rmr of Ctentxlonla flIUtriala, n. up.: band <•, rardinnl and lateral virus ,,i i,-ft valve <>r -ami-: >/, small i>ort!i ./iW^m/.i Salt.-r, fn-m thi' luw.-r Tri-nton ii'-ar Murfr^-sli- >«fle. Tfllinomya Irvata HAI.I. and Wniii IKI.D, 1876. Pal. Ohio, vol. II, p. *_'. (Nut \nruln Imiln HAI.I . p. 150.) Tin may l>e distinguished at once from C. 'illx-rHna, with which it agrees more clo.-ely than any other known, by the delicate, crowded, thread-like concentric lines which cover the entire surface. Twelve to twenty of these lines may be counted in a space 1 mm. wide. The shape and general appearance of the shell is very simi- lar in the two shells, but the basal margin in the present form is always uniformly rounded, while the antero-dorsal angle i- a trifle !>lunter. The latter fact is due to the greater bend in the hinge. The pit beneath the beak is scarcely so distinct as in that species, and as the hinge is a little shorter the number of denticles is less than the average number for C. albert inn, there being usually twelve anterior and fifteen posterior. Finally, in perfect casts of the interior the beaks are not so much compressed and the ridges running posteriorly from them less sharp. This species is generally identified with Mall's \iiniln or Tellinomya kvata, origin- ally described from the Trenton limestone of New York, and closely related t nitiiln of this report. The error of this identification i> so palpable that it is really not worth the while to refute it. Any one at all capable of distinguishing species must, now that attention has been directed to the matter, see at om •»> that the shells are very different. t-.rmation and locality.— In the lower beds of the Cinrinnati k'r •>.!• at numerou* IncalltlM lo and [irinnati. A -m^lo specimen wan col T|« SehocbMt In equivalent beds at Grander, Minnesota. Reg. No. 8378. 600 THE PALEONTOLOGY OP MINNESOTA. ICtenodonta slmulatrix. CTENODONTA SIMULATRIX, n. sp. PLATE XLII, FIGS. 74 and 75. In its general aspect this species greatly resembles- C. albertina, and yet it is a widely distinct form, the hinge being quite different in the two forms. The hinge plate in C. simulairix is much narrower and more uniformly arcuate, the denticles are more numerous and the majority straight and very small. Posterior to the beak, beneath which the continuity of the series is slightly interrupted, there are about twenty-five denticles; in front of the beak the specimen preserves only six teeth, but, judging from other species, their number on this part of the hinge cannot have been less than twelve and probably was quite as many as fifteen, making a total for the entire hinge of from thirty-seven to forty. Comparing outlines, it will be found that in the present species the ends are more regularly curved and the beaks situated a little farther from the anterior extremity. Formation and locality.— Upper part of the Hudson River group near Spring Valley. Minnesota. C. recurva section (Palceoconcha, Miller.) CTENODONTA COMPRESSA Ulrich, PLATE XXXVII. FIG. 29; PLATE XLII, FIGS. 88—90. Tellinomya compressa ULRICH, 1892. Nineteenth Ann. Rep.Geol. and Nat. Hist. Sur. Minn., p. 216. Shell rather small, somewhat oblique, compressed convex, the length and bight respectively as twelve or thirteen is to fourteen; convexity about half the length; upper half triangular, the lower somewhat obliquely semielliptical; beaks small, compressed, acuminate, curving backward; umbones rather flat, the convex part of the valves terminating somewhat abruptly along the anterior and posterior cardinal margins. In the outline these two margins, meeting at the beaks, form an angle of about 85°, with the anterior gently convex and the posterior correspondingly con- cave, or a little straighter. Antero-dorsal edge flattened but unusually narrow, with an obscure furrow on each side of the raised contact line; posterior lunette obscurely defined. Surface with very fine, regular, raised, concentric lines, six to eight in 1 mm. Hinge plate bent rectangularly, very wide in the central part; denticles mostly transverse to the hinge, arranged in two distinct series, increasing gradually in size and curvature away from the beaks, about twenty-two anterior and twelve posterior. A wide crescent-shaped flat space, over which the teeth do not extend, forms the inner border of the hinge plate. Just in front of the point of the beak, and sepa- rating the two series of denticles, is the narrow end of an obscurely defined, curved depression, extending more than two-thirds the distance across the hinge plate. r..\MKl.l.ini: \N< in \ r\ ''."1 OtMMdoaU laUnMMllk.1 Adductor scar- Milimate. situated immdeiately beneath the ends of the hinge, tinct, the posterior one the deeper and margined on the inner Hide by an obtuse ridge-like swelling. Small accessory scars have not heen observed. A .sinirl.' imperfect vahe was all 1 had seen of this species when I first described it. liming tin1 Mimmer of ls'.»'J. however, I succeeded in collecting an excellent - of >p,.| 'iinen-, .-o that 1 am now enabled to present the shell in all its characters and to point out those whicli arc really di-t ine.tive. Compared with C. asturtiformis Salter. of which an authentic example is now before me, it differs externally in its -iv.tter proportion.il wi.lth, somewhat narrow posterior curve, less convex valves, linn- concentric lines and in wanting the coarse wrinkles of growth which seem to be a constant feature of the ventral half in that species. Internally the muscular scars and the denticles of the hinge are about the same in the two species, but the hinu'e plate is considerably wider in the Minnesota form, while the Hat space beneath the denticles of the latter is scarcely represented in Sailer's species. Casts of the interior of the two species are not easily distinguished, the only reliable differences between them, so far as observed, being the lesser prominence and more uniform curvature of the anterior margin and the slightly greater convexity of the casts of C. Furmation and locality.— Upper part of the middle third of the Trenton Abates at Mvoral localities in Ooodhur < •••unty. Minnesota. Casts belonging to this species or to C. (utartiformit, the latter probably, have been found In the upper part of the Trenton limestone at Minneapolis and at Janeavllle, Wisconsin, and I have specimens of a rery similar, though smaller, form from the upper third of th<- Trvnton shale*. KNODONTA INTERMEDIA Ulrich. PLATE XLII. KIOS. 06-07. Trllinomya intermedia I'I.KI. ii. 1882. Nineteenth Ann. Rep. Oeol. and Nat I! - .r. Minn , p. 218. Shell thin, of medium size, moderately ventricose, rather erect, the bight a little greater than the length. Outline subtriangular, at the beaks, which are obtusely acuminate ami incurve'!, forming very nearly a right angle; anterior cardinal margin very gently convex, posterior cardinal edge correspondingly concave, ventral margin together with the curve into the ends forming a semicircle. Knds subequal, the posterior sometimes a little the longest I' in bones full, the remainder of the surface sloping uniformly to the free margin-. An oK-cure sulcu.s may be detected near the anterior margin, ami along the dorsal part of this en>l the surface descends abruptly to the hinge plate. Surface with strong, closely arranged, thread-like, concentric lines, about twelve in •> mm. At intervals of about : mm. generally a fold stronger than the rest. Casts of the interior exhibit a faint rid^e and sulcns in the anterior end, and 602 THE PALEONTOLOGY OF MINNESOTA. (.Ctenodonta alt a. two sharply defined muscular scars and pallial Hue in each valve.* Hinge plate rather narrow, the teeth numerous, over thirty, as usual very small centrally, grow- ing larger gradually towards the ends of the hinge. This species is distinguished from C. astartiformis Salter, by its larger size, greater width, more erect form, and comparatively coarse and regular concentric lines. C. compressa is not so convex, especially in the umbonal region, has more pointed beaks and much finer striae. Formation and locality.— Not uncommon in the middle division of the Galena at WykofT and other localities in Fillmore county, Minnesota. CTENODONTA ALTA Hall. PLATE XLII. FIGS. 03 and 94. Tellinomya alta HALL, 1861. Kep. Supt. Geol. Sur. Wis., p. 27; MEEK and WORTHEN, 1868, Geol. Sur. 111., vol. iii, p. 309. Shell (internal cast) small, rather strongly convex, nearly erect, subtriangular, the length, hight and convexity, respectively, about 11.2, 11.5 and 6.3 mm.; base broadly rounded, semielliptical; beaks elevated, nearly central, arching slightly back- ward; anterior and posterior sides nearly equal, sloping abruptly from the beaks at an angle of about 85°, the anterior dorsal outlines very gently convex, the posterior correspondingly concave; beneath the ends of the hinge the outline on both sides curves rapidly into the base. Muscular scars larg-e and comparatively distinct, the posterior one nearly rounded, the other more oval; the anterior one lies in the wider lower end of a shallow sulcus which may be traced almost to the beaks. The hinge, Prof. Hall says, is marked by from twenty to twenty-five very small curved teeth on the anterior (posterior) side and from ten to fifteen on the posterior (anterior) side. This rare species is a little smaller, not quite as high, more erect and less convex in the basal outline than C. intermedia. In the latter, as well* as in all the other species of this section of the genus, save C. recurva, the anterior half of the outline is more uniformly rounded. Formation and locality .—The specimen described by Meek and Worthen came from the Galena near Mount Carroll, Illinois, while Hall's original type is from, presumably, an equivalent horizon at Dodgeville, Wisconsin. The specimen here used, which is precisely like the Illinois example, is from (.In- shaly lower beds of the Galena near Fountain, Minnesota. •In the original description it is stated that a small pair (if soars is situated above the posterior adduet.or impres- sions. Tliis stateiiMTit I nou helir\e rests upon faulty observation. >OKTA KKriRVA I'lricli. IK \i it } iti* •- /v//i»t>m|ru rrmrtvi UI.HK-II, IHM. Nineteenth An ai. Shell >mall or of medium >i/.e, compressed-convex, slightly oblique. Militriangu- lar. the length and bight almost equal, the thickness equalling al»out one-third of the bight. Knstral portion strongly recurved, ends narrowly rounded, base nearly -emi-elliptical. with more curvature in the posterior half than in the anterior. IJeaks prominent, posterior to the center of the shell; umbones with an mutually -ma II degree of convexity. Cardinal margins sharply inflected, forming an elongate depressed area on the anterior side and a shorter, narrowly cordiform one behind or rather li.-m-ath the beaks. A shallow and gradually widening sulcus extends from the beak along the antero-cardinal margin to the antero- ventral border. Surface !>y several strong lines of growth and between them fine concentric stria-, ten in 3 mm. Hinge plate strong, bent at a right angle, the posterior part nearly straight (gently concave), somewhat shorter than the anterior, with about twenty small, curved transverse teeth, decreasing, as usual, gradually in size and curvature toward the beak; anterior part convex, with about thirty teeth. Consid- ering the strength of the hinge plate, the teeth are very small. Immediately in front of the beak, in the angle of the hinge, a narrow oblique space breaks the continuity of the series of denticles. Hinge plate margined on the outer side by a delicate sharp ridge; just within it a narrow furrow which has considerable width and depth for some distance in front of the beak. In front of the beak and above the marginal line of the hinge plate a small area is defined apparently for the recep- tion of an external ligament (See note, p. 578.) Anterior and posterior muscular scars distinct, though not very strongly impressed; as usual for this section of the genus in size and form. The compressed form reminds of C. comprtusn, but the shape is different, the length being greater, the ends more narrowly rounded and the rostral part more strongly recurved. The surface markings also are coarser and the posterior lunettes much letter defined, while a number of important differences may be observed in their hinges. Hall's <'. altn is similar in the l>a>al part. Imt is a more convex shell and much less curved in the rostral part. •i.ifi'.n and locality. -Upper beds "? th- Hudson Hirer group, at MY«ral localltta* In Plllnon n.unty. Mitiii.— .M It In aMoclated with th- n. xt tpecic* (C. ft"- -pecle* occur*, though *o far a* otwerrnl only In the condition f <-*«U, alv and at Richmond. Indiana. 604 THE PALEONTOLOGY OF MINNESOTA. [Ctenodonta similis. • CTENODONTA SIMILIS Ulrich. PLATE XLII, FIGS. 102-106. » Tellinomya similis ULRICH, March 3, 1892. Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 220. Tellinomya (Nucula) lepida SAKDESON, April 9, 1892. Bull. Minn. Acad. Nat. Sci., vol. iii, p. 339. Shell small to medium size, moderately ventricose, subtriangular, the length and hight respectively as five or five and a half is to six. Umbones full, rounded, the rostral portion rather strongly recurved, with the beaks small and projecting slightly above the hinge. Antero-dorsal edge convex, thick, flattened, but not sharply defined. Postero-dorsal edge rather strongly concave, impressed so as to form an illy-defined imperfect lunette. Anterior outline almost uniformly convex, curving neatly into the well rounded ventral margin; posterior side rather narrowly rounded. Surface of valves almost uniformly convex, highest a little above the center, generally with a few well marked varices of growth and with finer concentric lines in the lower part. Hinge plate of moderate strength, with numerous small teeth (thity-five to forty -two); in the largest examples seen with about twenty-seven anterior and fifteen posterior to the beak; posterior teeth the largest. Muscular scars moderately impressed, always distinguishable. The shape of this shell is exceedingly like that of C. astartiformis Salter, though as a rule proportionally a little longer and scarcely so ventricose. The posterior lunette also is somewhat deeper, but the principal differences lie in the hinge. The hinge plate, namely, in Salter's species, is somewhat stronger, while the denticles are more bent, larger and less numerous. The teeth, furthermore, are largest on the anterior side, while in C. similis the opposite is the case. It is also very much like the associated C. recurva, but is distinguished by being a little higher, more uniformly rounded on the anterior side and without the anterior sulcus. More important dif- ferences are the greater tumidity of the umbones, less prominent beaks, less strongly defined anterior and posterior lunettes and weaker hinge plate. Oasts of the interior are separated chiefly by the greater thickness of the rostral portion. They are also nearly always of smaller size than those of C. recurva. Formation and locality.— Upper beds of the Hudson River group, Spring Valley and other parts in Fillmore county, Minnesota, and at Blanchester, Ohio. CTENODONTA OBLIQUA Hall. PLATE XLII. KIGS. 83-87, . Nucula obliqua HALL, 184r>. AIIKT. .lour. Sci. and Arts. vol. xliii, p. 292. Tellinomya f obliqua MEKK, 187.'). Pal. Ohio, vol. i, p. 139. Palaeoconcha obliqua and P. fabcri MILLEII, 1889. North Amer. Geol. and Pal., p. 498. Shell very small, broadly acuminate-subovate; or, without the triangular rostrum, I \MKI.I. IKKANflllATA. ''•"'' ban' the nut lino may !..« called Mil.circular, the bawil half, as a rule, lu'inn y comparatively strung concentric lines. On casts of the interior, and this is almost invariably the Condition in which the species is preserved, the muscular scars are nearly always distinguishable and the posterior one is often sharply defined and prominent on the upper side. They are situated ju>t within the ends of the shell and each near the wider and lower end of an obscurely defined >iilcns. The two sulci, of which the anterior one is usually the better marked. l>««gin near the beak and extend down on each side to the base of the muscular scars. A small accessory scar has been observed immediately above the posterior add ncti ii. I'allial line simple, rather distinct. Hinge plate comparatively -triiii^. with numerous (at least thirty) small denticulations. The si/e of this shell varies greatly. Many of the specimens found at Cincinnati and localities in the vicinity of that city are less than 2 mm. in diameter, but others are occasionally met with that range from that size to a diameter of 5 mm. In the northwestern localities the species grew to a larger size, specimens having a diameter nf from 5 to 7 ram. being in the majority. Aside from the matter of size, however, the specimens from these two regions are practically identical. I'r. S. A. Miller, in the work above referred to, erects a new genus, Palteoconrlm. and a new family for the reception of the present species, which he divides into two species, giving to the larger form the specific name faberi. But this new genus and family have no right to recognition, since they are based entirely upon erroneous observation, he having come to the conclusion that the hinge in these shells was not denticulated and pml.al.ly edentulous. Through the kindness of Dr. Miller I had an opportunity to examine a number of the specimens (excellent casts of the interior) used by him in defining his genus. Even among these I noticed several that retained undeniable evidence of the denticulate hinge. •ation and locality. Very atuimlant al Cincinnati. < Mil... and numerotu other localities In the ;>.. >. In i h«- nortbwenl It is one of the rare fuMila of the so-called "Nuculm bed" of tin' Mu<|ii»krta »r lluri Kiv.-r shales. :N>NTA HAMBUROEHSI- I I-I.ATI xi. ii KIGB. « tad m. Trllinomgat Hamb»rytn*U WAUtrrr, 1884. Pal. Kurckt I>i»lrt< Shell small, r. >nvex, rounded-snlirhoml>oidal in outline, with the hijrht and length subequal and the beak coni| ly largo, incurved and -nu.it. -I in front of the center; posterior dorsal margin sotnewi tightened. Surface 606 THE PALEONTOLOGY OF MINNESOTA. [Clidopliorus. marked by regular sharp, though fine, concentric striae in the posterior half, the anterior half appearing smooth. Hinge and interior unknown. The single specimen of this form seen from Minnesota, agrees so well in its outline and general appearance with Walcott's figures of T. hamburgensis that I am obliged to refer it to his specieis. It should be remarked, however, that the surface of the Nevada types of the species is described as presenting "a smooth, glistening appearance," giving them "the character of some of the Linguloid shells," and that it is marked by not only concentric lines but also by " very fine, often scarcely per- ceptible radiating striae," — all of which is wanting on the Minnesota specimen under consideration. But, as these differences may all be due to different methods of preservation, I have not taken them into account. Respecting the generic position of the shell there may be some doubt, because we have as yet no knowledge of the interior. Nor does the species seem to fit very well into any of the sections into which the genus has been divided. Certain it is that it is not very closely related to any of the numerous species described. Perhaps it is the most like C. socialis, with which it is also associated, but it will be distin- guished readily enough by its shorter and rounder form, fuller umbones and more distinctly striated surface. Formation aiid locality.— Upper part of the middle third of the Trenton shales, Chatfleld, Minnesota. The types of this species are from the upper part of the Pogonip group, Eureka District, Nevada. Genus CLIDOPHORUS, Hall. Clidophorus, HALL, 1847. Pal. N. Y., vol. i, p. 300. Compare Nuculites, CONRAD, 1841. Ann. Rep. Geol. N. Y., p. 49; and Cucullella, McCov, isr,:,. I prefer not to characterize this genus at the present time, nor to express any definite opinion respecting its relations to Cucullella, McCoy, and Nuculites, Conrad, for the simple reason that I have had no opportunity to study the typical species of the genera. It should be stated, however, that many authorities regard the three names as synonymous and that, unless new distinctive features are brought out, their views cannot be successfully combated. CLIDOPHORUS CONSUETUS Ulrich. ri.Aii: xx.xvn. IMI.S. .1^ uii Clidophorus consuetus ULRICH, 1892. Nineteenth Ann. Rep. (Icol.and Nat. Hist. Sur. Minn., p. 2i'l. Shell above the medium size for the genus, transverse, moderately elongate- ovate, rather strongly convex, the length equaling nearly twice the hight. Beaks small, incurved, flattened. Dorsal line convex, sloping downward behind the beaks Ill A I A t<> the narrowly rounded po-terior extremity. Antorior eml neatly rounded. \s tlian tlio posterior. Ventral margin gently convex in the nii, more strongly and almost e.|iiall\ em-M-l at the ends. An obscure umhonal ridge traceable from the I three-fourth- of the distance to the posterior basal edge. Above it an impressed narrow line, beyond which the -urface descends rapidly to the donal margin, i a-t- of tlie interior with a narrow, slightly curved, clavicular impre— ion ju-t in front of the beaks, extending but little more than one-third of the di-tam-e lie antero-basal margin. Surface of casts with a few obscure growth lines or fold.-. Point of greatest convexity a little above and behind the center of the shell. In a dorsal view the central half of the outline is very slightly flattened. Length. 17.2 mm.; bight. '.».0 mm.; thickness of both valves, 5.8 mm. This shell appears to be related to C. cunealus and C. elongatus, described by Hall from the Silurian rocks of Nova Scotia (Can. Nat and Geol., vol. •">. pp. 14$ and 1-V>. IsOO). It is, however, specifically distinct, the shape being different and the poste- rior sinus situated higher up and very much less defined. C. pliinululus (Conrad) and C. ellipti<-n* Urieh, also have somewhat different outlines and have the cardinal slopes less abrupt, the whole surface, in those species being more uniformly and less convex. formation and focaftfy. -Middle Catena t. ft. MlnneftoU, wlu-iv II IN atMorlaUxl with Cttno- itcmtn intermedia. iiopiiottrri NKULKcrrs Hull. I'l.ATK XI. II KKJd. »-». laphorwt tiralrcfu» II A I.I, I ••*«»-. O«il. Sur. Win., Tol. 1, p. 6i. (Fltfiintl l.ut ti«.t d,~--r; Compare Clidophonu < .Vu. -,,l,it fabxla HALL, 184.1. AIH.T. Jmir. Sri. and Art*, vol. xllll, p. 2B6. Shell varying greatly in size, the smallest observed having a hight of on! mm., with a length of 5 mm., while in the largest seen (from Graf, Iowa,) these dimensions are respectively $.*> mm. am! !•'• mm.: thickness of the latter about 6 mm. Shell transversly subelliptie. rather strongly convex; ends subequalty rounded, the anterior generally a little narrower than the posterior; the outline of the latter, however, often exhibits a tendency to become angular just beneath the middle and obliquely subtruncate above; basal and dorsal margin broadly convex. Beaks small, somewhat tumid, placed about one-third of the length of the shell behind the ante- rior extremity. Surface marked by fine concentric lines and several stronger varices of growth; the latter show through the shell so as to be visible on casts of the inte- rior. Hinge plate narrow, not over half the length of the shell, minutely toothed; denticles twenty or more in each valve, three-fourths of the nun ng post. 608 THE PALEONTOLOGY OF MINNESOTA. [Ly rodesmldSB . to the beaks, placed obliquely and so that they converge inwardly, the direction of the anterior series being nearly at right angles to that of the posterior series. Clavicle strong, nearly straight, almost vertical, sharply defining the somewhat semi- circular and large anterior muscular scar and leaving a strong furrow in casts of the interior just in advance of each beak. The furrow extends beyond the middle of the distance to the basal margin. Posterior scar faint, smaller than the anterior, occupying a central position on the post-cardinal slope. Several small umbonal scars may be observed on good casts, and obscure rays are occasionally visible on their sides. Hall's C. fabula, described from Cincinnati specimens less than 2 mm. in length, seem to me to be nothing more than a dwarfed variety of this species. Formation and locality.— ID the so-called "Nucula Beds" of the Maquokcta (Hudson River) shales at several localities in Lafayette county, Wisconsin; Jo Daviess county, Illinois, and near Dubuque and Graff in Iowa. It is to be found, 1 think, in the equivalent beds in Fillmore county, Minnesota. Mug. Reg. No. 7336. Family LYRODESMID^E, Ulrich. A reconsideration of the genera included in this family, on page 486 of this work, has convinced me fully that they are improperly associated and that the family must for the present rest solely on the typical genus. Dr. S. A. Miller was, I now believe, right in proposing a new family for his genus Technophorus (N. A. Geol. and Pal., p. 458, 1889), but he should have included the closely related Ischyrina, Billings, a genus doubtfully referred by him to the Trigoniidu1. The new genus Allodesma proves to be related to Cyclochoncha, Miller, rather than to Lyrodesma and should therefore be removed to the provisional family Cydoconchidce. The proper arrangement of these three families in a scheme of classification is a point upon which it is very difficult to come to a satisfactory determination. Con- siderable agreement in structure is to be traced between them, and at times 1 might go so far as to say that they should be regarded as closely related. Still, in view of the fact that each in one way or another resembles types classed in such widely distinguished families as the Trigoniidce, Crassatellid«>, Cyrenidw and Myidce more closely than they do known Devonian and Carboniferous forms, it would obviously be an expression of opinion quite insufficiently supported by facts. Genus LYRODESMA, Conrad. Lyrodesma, CONBAD, 1841. Ann. Geol. Rep. N. Y., p. 51; HALL, 1847, Pal. N. Y., vol. 1, p. 302. Actinodonta, PHILLIPS. 1848. Mem. Geol. Sur. Great Britain, ii. Shell moderately convex, larger than high, ovate to subquadrate, rounded in front, usually obliquely truncate behind and more or less angular post-basal ly. 'KM.IIKANrillATA. ''•"'.* 1«*ru* »»'un,ln*i Beaks small, placed in front of the midlength; posterior urabonal ridge generally prominent, often angular; port-cardinal slope frequently with radiating linen, th«> rest of the sm-fai ••• with c..ncentric -trur only. Hinge consisting of from six to eight prominent. Mil>i>.iiial. transversely striated teeth, radiating regularly from the l>eak a ii- 1 placed on a tliick plate, which leaves a large oblong depression in the dorsal edge of casts of the interior. Adductor scars rather faintly impressed, the posterior one larger than the anterior. Two pairs of small pedal muscles, the anterior pair situated immediately above the anterior adductors, the posterior pair on each side of the hinge line just behind the hinge teeth. Pallial line slightly sinuate posteriorly. T\pe: I,, filntimn Conrad. Of this excellently marked genus I know eleven or twelve American specific forms. Kitfht of these occur in the various horizons of the Cincinnati group, the remainder in the Trenton. Two additional species are catalogued by Bigsby among the European Lower Silurian shells. LTRODESMA ACUMINATOM, n. sp. PLATE Xl.ll. riOB. 1-4. Shell obliquely acuminate-ovate, the outline being drawn out to an acuminate extremity posteriorly; in the typical form (fig. 1), the hinge line is arcuate and [in MOB gradually into the posterior margin, which, because of the flattening of this region projects, in a side view, but little beyond the sharply angular umbonal ridge; anterior end broad, regularly rounded; base straight posteriorly. Beaks small, arcuate, strongly incurved, not very prominent, situated somewhat less than one-third of the length from the anterior extremity. Surface with obscure, distant, concentric lines; on the posterior cardinal slope four or five radiating lines. Hinge with six teeth of which the anterior ones are considerably shorter than the posterior one, and the central ones curved backward. Posterior adductor impression unusually distinct; sinus in pallia! line very small. The specimen represented by figures 3 and 4 (plate XL.II), is one of several that I refer to this species with considerable doubt. The posterior end is too short caus- ing the beaks to be more central, and the post-cardinal margin is more prominent and subalated. The nmbonal ridge is even sharper and more prominent, its greater distinctness being due to a somewhat greater flattening of the flanks of the valves. The hinge is injured in the specimen, but it is quite evident that the teeth have not that backward sweep which marks the typical form. Precisely the same form (see 6gure 45-/i, page 611) occurs in the Treuton of Kentucky, hut. ><> faras known. -39 610 THE PALEONTOLOGY OF MINNESOTA. [Lyrodesrna cannonense. not, as is the casein Minnesota, there associated with the typical form. The variety, which may take the name of intermedium, connects L. acuminatum with L. cincinnatiense Hall, being as nearly as possible intermediate between these species. The form of the shell and the prominence of the umbonal ridge will distinguish L. acuminatum from all of the other species. Formation and locality.— Middle third of the Trenton shales, Chatfleld and near Cannon Falls, Minnesota. The var. intermedium occurs at the same localities and in the Trenton limestone near Burgin, Kentucky. LYRODESMA CANNONENSE, n. sp. PLATE XL1I, FIGS. 6-8. Nucula poststriata HALL, 1847. Pal. N. Y., vol. 1, p. 151, pi. 34, flg. 2a, 2b. (Not p. 301. pi. 82, flgs. 10a, b.) This small species of which only casts of the interior have been seen, is similar in shape to L. acuminatum var. intermedium. Critically compared it proves to be longer, and has the beaks farther anterior. The hinge line also appears to have been somewhat longer. Then there is a slight depression on the posterior side of the umbones which is not seen on casts of that species. In all these respects L. cannon- ense agrees very closely with L. subplanum, a new species from the Utica horizon of the Cincinnati group, at Covington, Kentucky, which I am describing in vol. vii of the reports of the Geological Survey of Ohio; and it is with that form that I believe its relations really lie. Comparing it with an excellent cast of that shell, the Minnesota form is distinguished by its shorter hinge line, more oblique posterior margin, more sharply angular umbonal ridge, and wider beaks. Though also smaller it cannot be denied that the two forms are very closely related, and probably nothing more than varieties of one species. The Trenton shell referred to by Hall in 1847 (loc. cit.) to Nuculites (now Lyro- desma) poMtrialum Emmons, is not the same as the Hudson River type of that species, but probably belongs to L. cannonense. Formation and locality.— Galena shales near Cannon Falls, Minnesota. Also in the Trenton lime- stone, Carlisle, Pennsylvania. I ... LAMKI 611 MAJOR /'/r CfrfcJopAortu m.i. r i i M. H, J87». Jour. Cin. Soc. Nat l! p. 36. •I, right valve of Lgrodrtma major Ulrlch; 6, cardinal slope of name, x 2, showing the flap radiating stria-; <-, Interior <>r u right v;il\v: r-harply defined on the inner side by a thin ridge running down from the hinge, narrowing above and surmounted by deep supplementary sears; posterior .cMm-tor elevated 612 THE PALEONTOLOGY OF MINNESOTA. [Technophorus. anteriorly, situated in the cavity of the umbonal ridge about midway between the beaks and the posterior extremity of the shell; posterior pedal muscles strongly defined, situated on each side of the cardinal edge and just behind the hinge plate. Pallial line distinct, especially in front and along the base, sinuate posteriorly. This fine shell is in no wise related to Clidophorus, to which genus I originally re- ferred the indifferently preserved casts upon which the species was founded. Had I been acquainted with the appearance of casts of the interior of Lyrodesma, which are really very distinctive, it is not likely that I should have been led astray by the slit- like vertical depression in front of the beaks. Compared with other species of the genus, L. major is unusually long posteriorly and narrow without running to an acuminate extremity, the radiating lines on the umbonal ridge are finer and the muscular scars deeper. The species is so distinct that detailed comparisons are scarcely necessary. Still it may be well to say that L. acuminatum and L. cannonense are pointed instead of rounded posteriorly and have much stronger umbonal ridges, while they are also less convex in their basal outlines. Formation and locality.— A. small valve apparently belonging to this species was found in the Hudson River group near Spring Valley, Minnesota. Casts of the interior are not uncommon near the tops of the hills about Cincinnati, Ohio. These are proportionally a little longer than the geologically higher form of the species which is represented in my cabinet by excellently preserved testiferous examples from the upper beds of the Cincinnati group at Clarksville, Ohio. Family TECHNOPHORID^E, Miller. Genus TECHNOPHORUS, Miller. Technophorus, MII.I.KK, 1889. North Amer. Geol. and Pal., p. 514. Shell small, equivalve, inequilateral, compressed convex, often attenuate and extended posteriorly; anterior end rather short, wider than the posterior, almost reg- ularly roundgd in outline; beaks very small, scarcely, if at all prominent; one or two sharp ridges, with a furrow above each, arise near the beak and extend in a curved direction to the post-basal margin. Anterior part of surface marked with regular concentric lines, generally separated by rows of minute punctae; on the posterior part, especially the cardinal slope, those lines rarely coincide with the margins of the valves, but assume various arbitrary and sometimes ornamental arrangements. Internally a short and thick rib extends downward in each valve from the hinge directly in front of the beaks, while on the posterior side of same a shorter oblique rib, or a mere thickening of the hinge plate, causes the beaks in casts of the interior to appear much more erect and prominent than they do on the exterior of the shell. In casts the beaks of the two valves are not distinguishable but together form a single pyramidal prominence. Anterior adductor scar small, situated immediately in front of the internal rib; posterior scar and pallial line not observed, although most excellent casts were studied. . Tacaaophorut.) Type: T'-<-hn»ithi>rus faberi Miller. The shells in.-lii.lfcl in this genus are in several respects very remarkable. This i- true in the first place of their xirfaco ornamentation in which they differ more or !<•-- .Ifi-i'le.lly from all known paleozoic representatives of the class, with the possible exception of l-,in/ri,i't Killings, a genus that will be discussed presently. As a see- on. i. though no If-- important peculiarity, we have the character of the beaks as these appear in casts of the interior. In all wholly known Lanellibninchiata, namely, the Ke.ik- of the two valve- are e excavated, and a careful examination of the beaks of casts of T. ertf nun tits brought to light certain faint markings indicating that the excavation was occupied by either a'n internal cartilage or some peculiar type of muscle. The internal ribs are also unusually short and thick, and peculiar in this, that they meet in the center when the valves are closed so as to completely shut off the space occupied by the anterior adductor muscles from the cavity under the beaks. Unfortunately, the hinge proper is not shown by any of the specimens seen by me. Still, one of the casts of T. extenuntus shows a number of very small papilla; along both the anterior and posterior sides of the hinge line that may have been produced by minute denticles on the hinge plate. But we cannot accept such uncer- tain evidence, so that for the present the hinge must be regarded as incompletely known. Ischyrina, Hillings, so far as known to me from the description and figures of the type species, /. winchelli (Desc. Catal. Sil. FOBS. Island Anticosti, p. 16; 1866) seems to be closely related to this genus. The internal ribs are better developed, the posterior one especially. Billings represents the latter as quite distinct from the hinge plate, which is not the case in Technophorus. There are posterior (Billings call- this side anterior) furrows and ridges, but the wing is very short The beaks are stated to be small and obscure, but I have no means of knowing whether they appear in caste as merged into a single prominence or not 7. plicaki, described but not illustrated by Billings on p. 52 of the same catalogue, seems to agree much better with Technophorus /'•//-.»•/. anmt UM b**k« an pr»aiH down to ih« bine* and. Ibough Ib* teprwloa I* of one »»lv* oaly. UM e»ld*w» U fairly c..»ola.lT, that UM b*»k» were uni t«l In raMa a* In TVefcuapfcnnn. Tne *wo«d »p»«la« provw to be. a* I •oaparud. a tn>« IMMopkonu daw raUUooa to T. (MtaoiOu and T. ii»Hi*mlll*m, lu .urfam •arklof* ar* miaul*)/ paaeto-MrUfo. wlib abaat «l(bt of UM tn»lj paitalow eoaoMtrtc HUM In I mm. 614 THE PALEONTOLOGY OF MINNESOTA. [Technophorus extenuatus. TECHNOPHORUS EXTENUATUS Ulrich. PLATE XXXVII, FIG. 34; PAGE 611, FIG. 45-». Ttchnophorus? extenuatus ULRICH, 1892. Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 222. Casts of the interior small, compressed, somewhat elongate, alated and drawn out posteriorly. Beaks small, erect, moderately prominent, together forming a low pyramidal prominence, situated about one-fourth of the entire length from the ante- rior extremity. Just in front of the beaks the casts of the interior exhibit a deep though not very long impression; the posterior umbonal rib left an obscure furrow on each side of the hinge line. Anterior end broad, rounded, most prominent in the upper third; ventral margin broadly convex and slightly produced a little in front of the middle; behind, this point the outline is nearly straight (slightly concave) sloping up toward the narrow (? pointed) posterior extremity. Cardinal line nearly as long as the entire shell, gently concave behind the beaks. A thin sharply defined ridge, slightly curved, extends across each valve from the beak to the. lower side of the posterior end. Surface gently convex in the anterior half, faintly constricted in front of the ridge, and marked with obscure, concentric wrinkles of growth. A specimen preserving a small part of the shell, shows that the external surface is marked, at any rate on the sides, by closely arranged, sharp, elevated lines, separated by rows of small punctae. Length about 21 mm., greatest bight 10 mm., greatest convexity about 3.5 mm. This species, which I now regard as undoubtedly congeneric with the Cincinnati shell upon which Dr. Miller founded the genus Technophorus, is distinguished by the prominently rounded centro-basal margin, and the greatly produced posterior wing. Formation and locality.— Middle third of the Trenton shales, Minneapolis and St. Paul, Minnesota. TECHNOPHORUS SUBACUTUS Ulrich. PLATE XL. FIGS. 33 and 34. Technophoru* subacutus ULKICH, 1892. Amer. Geol., vol. x, p. 101. Shell small, rather ventricose, alated posteriorly, the hight and length respec- tively as two is to three. Cardinal margin nearly straight, anterior end uniformly rounded, ventral edge more gently curved, the posterior straight and sloping back- ward slightly to the acuminate extremity of the hinge line. In a cast of the interior of a left valve, the small beak is erect, projects prominently above the hinge line, and is situated about one-third of the entire length from the anterior extremity. Just in front of the beak there is a strong and deep impression, running almost vertically downward. On the anterior side this slit margins a rather large muscular scar. Extending backward from the beak the cast exhibits another, but in this case, !. \MKU.ir.K\N- III\TA. 116 Tm-hDophorii* SlUirlaiu..] very obscure lim-.i! depre.-Mim. The entire rostrum also is somewhat constricted, presenting an appearance that may have been proanif, will U» found in vol. viii of the reports of the Geological Survey of Ohio. Genus ALLODESMA, n. gen. ). ULKICII, 1892. Nineteenth Ann. Rep. Oeol. and Nat Hist. Sur. Minn., p. 2tt. Slii-11 small, transversely elongate-elliptical, mo«leratoly convex; beaks anterior, small, surface with concentric lines of growth. Hinge apparently with one or two long posterior lateral teeth in each valve, two cardinal teeth in the right valve, and only one in the left; anterior laterals short or wanting. Anterior adductor scar • li-tim't. large, ovate, margined on the inner side by a strong curved ridge extending downward from the hinge at a point immediately in front of the beaks. Just above the adductor. impressions and in front of the ridge, a small pedal muscle scar. Posterior adductor impression faint, larger than the anterior, of rounded form, situ- ated near the middle of the posterior cardinal slope. Pallial line simple. Type: A (Modiolopsis) suMlipticum Ulrich. The species upon which the genus is founded has really no relation to Modio- lopsis with which I provisionally associated it. The original type gave no hint of the character of the hinge, or I would never have thought of the arrangement first adopted. A better specimen, recently collected, at once led to comparisons with the very different genus Cycloconcha. Miller, and proved that the relations of the shell were really with that genus. The only features wherein Allodesma differs from Cycloconcha, so far as data now at hand will admit of judgment, are first, the more elongate form of the shell; second, the anterior position of the beaks; third, the curved ridge forming the inner border of the anterior muscular scar, and fourth, the shortness or entire absence of anterior lateral teeth in the hinge. These differences, though certainly of generic value, are not, as it now appears, of sufficient importance to exclude the new genus from the Cycloconch'uli . Al.LODKSMA SfBELLIlTH I M L'lrictl. I'l.ATH XI.II. Hi.* * Modiolopn* mlxUiptifa in; nil. I- C Nineteenth Ann. Bep.Oeol. an) limy* .Inu.l..] This p-nii- i- I'lareil witli much conKdence into the same family as II. ill'* two Devonian genera riinl>i-i ^rano-lineate and concentrically plicated; but here we timl one of the [iri-uliarit ie> of the Lower Silurian genus. In the latter, namely, the fol.ls are, when not entirely restricted to the anterior end, at any rate always the strongest there, while in Mlorisina they are strongest in the umbonal and central parts of the valves. The hinge and the muscular impressions also, in the absence of any knowledge to the contrary, are believed to be very nearly the same in the two genera. The principal difference probably is the absence of a lanceolate escutcheon in Itlti/lhuya. \ well defined escutcheon is developed also in Pholadella and ('imi- t'lriu and these genera are further distinguished from liht/timya by their large uin bones. In having the concentric surface markings strongest on the anterior end, these -hells agree with Qcdgicickia, McCoy, founded upon Carboniferous species. But after a careful comparison with the figures and descriptions of the species which McCoy himself placed under that genus, I am quite convinced that the Lower Silurian types are not congeneric with the Carboniferous forms. There would be equally good reasons for including them in the same author's genus SanlHes. With the exception of R. sinun/n, which is from the middle Galena of Minnesota and next described, the genus is known only from the rocks of the Cincinnati group. The total number of species known is nine. Of these six are new and three have been described and referred to other genera, namely, S. A. Miller described one under the name of Orthodesma byrnesi, and Whitfield two under the names of Orthodesma mirkleboroughi and Sedgtcickin tuniilnta.* The original of the last species has a well developed lunule and is much shorter than any of the other species. But it is evident that the specimen has been much distorted by pressure. Descriptions and figures of all the Cincinnati species except It. lunnlata are to be published in vol. vii of the reports of the Geological Survey of Ohio. KHYTIMYA SINTATA, n. sp. I-I.ATT. \\XVI. H09. M an.: 11 rather small, about -•> mm. long, l'_l mm. hi^li at the beaks, and 11.2 mm. across the posterior en«l. with the thickness very nearly equalling the hi^i ed, Ix)wer Silurian specific forms, all of which, saving the two about to be described, were found above the top of the Trenton at Cincinnati and other localities wit hin a radius of forty miles from that city. Several of these species are represented by casts of the interior in as fine a state of preservation as could be desired, and yet in no case was it possible to reach any satisfactory conclusion respecting the character of the muscular and pallial impressions. Under the circumstances it is not unlikely that the claim of the authors of the genus that the pallial line is simple, m iY te nothing more than the expression of their opinion and not the record of an observed fact In their description of the genus Hall and Whitfield state also that posterior to the external ligament "the margins of the valves overlap each other to the extent of the cardinal line." This may be true of the specimens studied by them but, except in several cases where it is evidently the result of accident or compres- sion, it is certainly not true of any specimen seen by me that is sufficiently perfect to admit of judgment on the point. The statement, therefore, wants confirmation before it can be accepted as a fact. So far as my own observation is concerned, I am obliged to dissent from such a view, especially as regards C. miamiensis the type of the genus, of which several specimens that seem to have retained the valves in a perfectly normal relation, have the escutcheon divided equally by the straight con- tact margins of the valves. As regards the external ligament, it is preserved by only two specimens seen by me. One of these belongs to C. curia Whitfield, the other to C. coriformis Miller. It is elongate (almost linear), occupies about one-third of the width of the escutcheon ami extends from the beaks backward a little more than one-third of the length of the escutcheon. The same specimens preserve also something like a ligament over the margins of the valves in the lunule. The affinities of the genus are almost certainly with (irammyxin as that genus is defined by Hall in his great work on Devonian Lamellibranchiata (Pal. N. Y., vol. v, pt i, pp. xxx and 358-384.) The principal difference between the genera as now recogni/ed lies in the hinge, this being weak and edentulous in Cutuamya while it is stronger and presents one or two cardinal folds in at any rate the typical forms of i »-.i in in ;/-i'i. Shells probably belonging to this genus have been referred to Sedg- uirki'i and Leplodomus, but as it seems, upon very insufficient grounds, the types of those genera, as defined by McCoy in 1844, (Synopsis Carb. Foss. Ireland) being of a widely different nature. The new genus i he»l by its peculiar hinge, much smaller beaks, and strongly defined anterior muscular scar. 622 THE PALEONTOLOGY OF MINNESOTA. [Ouneamya truncatula! CtJNEAMYA TRUNOATULA, n. Sp. PLATE XXXVI, FIG. 39. Shell of medium size, transversely somewhat elongate, the two ends of nearly equal bight, with broad, compressed, nearly terminal, prominent and incurved beaks; postero-cardinal region subalate, escutcheon less than half the length of the hinge. Cardinal and basal margins diverging slightly posteriorly ; anterior end truncate, almost vertical, the upper two-thirds sharply inflected, forming a rather narrow, deep, and unusually long lunule, from whose lower end the outline slopes abruptly backwards into the basal line; the latter is gently convex in the posterior half, straight or very slightly sinuate in front of the middle, very obtusely angular in the anterior third, and straight again when it ascends from the antero-basal angle to the lower extremity of the lunule; posterior margin somewhat produced and strongly rounded in the lower half, and very obliquely subtruncate in the upper. Posterior umbonal ridge rather prominent, strongly rounded, not angular, curved and becom- ing almost obsolete in the posterior third of the shell; cardinal slope concave, very abrupt near the beaks; a narrow but distinct anterior umbonal ridge descends at right angles to the hinge line from the beak to the antero-basal angle; between it and the edge of the lunule a narrow sulcus; behind it a small well marked mesial sulcus out of which the surface rises more gradually to the summit of the posterior umbonal ridge. The most prominent point of the surface of the valves is situated on this ridge somewhat above the middle of the hight and about two-fifths of the length from the anterior extremity. Surface marked with nearly equal concentric undula- tions or ridges. These are strongest in the mesial sulcus, somewhat flattened yet distinct in the anterior sulcus, and nearly obsolete on the cardinal slope. Hinge and muscular impressions undetermined. This species is closely related to C. coriformis described by Miller from the mid- dle beds of the Cincinnati group of Ohio. So far as known C. truncatula never attains the size of mature examples of that species, while its posterior end is higher, the escutcheon much shorter, the basal outline more convex, and the anterior umbonal ridge narrower and much less prominent. In C. coriformis the point of greatest convexity is on the anterior ridge while it is on the posterior ridge in the Minnesota species. The surface markings also are coarser, and the mesial sulcus deeper in the former. Formation and locality.— Middle Galena near WykofT and Pleasant Grove, Minnesota. LAMKLLIHRANCniATA. ''•-' '•'• jm oblon»» ) CDKKAMTA OBLONOA, n. sp. I'l.ATK \\\V1 lie.!- . This species is very much like C. tnincntnl-i, differing from it chiefly in the follow- in^ respects: The anterior end is more rounded, the lunule shorter and smaller, and the posterior end a trifle narrower and much less oblique, being almost vertical; the Inii^e line is longer, terminates posteriorly more abruptly and is nearly parallel with t he )>as;il margin. The posterior umbonal ridge is less narrowly rounded, the mesial MI lc us about the same or slightly deeper, while the part of the shell in front of this sulcus, is practically without the anterior sulcus which is such a characteristic feature of C. truncatula uiul C. coriformis. This sulcus however is indicated by a slight flattening of the anterior slope. Finally, the surface corrugations are a grade finer. C. miiimifnsis II. and W., is similarly marked but has a different outline and much less distinct mesial sulcus. In the matter of outline C. scapha H. and W., another Ohio species, agrees more nearly, but in that species the lunule and escutcheon are both wider and longer, and the surface markings quite different from those of C. oblotl'J'i. Formation and localitf.— QaU-na lliuexlone, Dlxun, Illinois. Genus SPHEXOUl M S. A. Miller. SphnoKum, S. A. MILLER, 18W. North AIIUT. Gtxil. and Pal. p. 513. Shell of medium size and larger, thin, strongly ventricose, very inequilateral, elongate, occasionally with subparallel dorsal and ventral margins, but usually much the highest posteriorly. Beaks incurved; umbones prominent, large and full; iiniKonal ridge strongly rounded or subangular. No mesial depression or sulcus. Lunule present, usually small and sometimes not sharply defined; escutcheon prac- tically wanting. Surface concentrically lined; occasionally also with radiating . Ligament probably both internal and external. Hinge apparently edentu- lou>: muscular scars very faint, not determined with certainty. Type: S. (Orthodesma) cuneiform* S. A. Miller. Too littl>- i< known of this genus to determine its affinities with any thing like certainty. So far as the known characters admit of judgment they indicate relations with the (irammi/siidtr and the Pholadelliiln . I>r. Miller places the genus near Orthodesma, but in this he is undoubtedly in error. The two Trenton species following are perhaps not strictly referable to Spkttto- Hum. being too narrow posteriorly. In all other respects, however, they agree well enough with the more typical species of the < mcinnati rocks. Besides, I believe I 624 THE PALEONTOLOGY OF MINNESOTA. [Sphenollum parallelum. have evidence to show that this disproportionate development of the posterior end was a gradual process, an undescribed species from the Utica horizon at Cincinnati being intermediate in this respect between the Trenton forms and those occurring in the middle and upper beds of the Cincinnati group. » SPHENOLIUM PARALLELUM, n. sp. PLATE XXXVI, FIGS. 42 and 43. Shell elongate subovate, rather strongly convex, the thickness, hight and length respectively as one is to one and two and one- fourth. Dorsal margin straight, nearly parallel with the ventral, terminating posteriorly in an obtuse angle where it joins the obliquely rounded posterior margin; anterior end short, apparently narrowly rounded; basal line very gently convex; posterior end rather abruptly rounded in the lower half. Beaks prominent, full, incurved; umbonal ridge strongly convex, somewhat emphasized by a slight furrow immediately above it in the cardinal slope; another obscure furrow borders the dorsal edge. A small but well marked lunule in front of the beaks, and a narrow and rather illy defined channel behind them. Central and anterior parts of valves rather strongly convex. Surface marked con- centrically with very fine striae and a few more or less obscure undulations. The latter are more distinct and regular on the umbonal ridge than elsewhere. The subparallel margins distinguish this species from the more typical forms of the species described by Miller from the Cincinnati rocks. Formation and locality.—" Lower Blue" beds of the Tjenton formation, Mineral Point, Wisconsin. Mus. Reg. No. 8346. SPHENOLIUM STRIATUM, n. sp. PLATE XXXVI, PIGS. 44 and 48. The shape and general expression of this shell is almost exactly the same as in the preceding, S. parallelum, yet when critically compared certain differences are observed which render a separation necessary. The specimens are not very perfect casts of the interior and exterior, still they preserve traces of very fine radiating lines on the umbonal ridge and a few coarser ones on the cardinal slope which, if such had been present on S. parallelum, would undoubtedly show on the excellently preserved cast upon which that species is founded. The Galena specimens again present a number of small, regular and short concentric folds on the anterior end, but they are wanting on the sides and posterior end where the folds are rather distinct in the Lower Trenton species. In comparing the outlines a slight difference is to be detected in the postero-cardinal region where, instead of being subangular 1. \M1-.I. l.ll'.l: \\. III A'l \ •II* 1 tin- margin i> rounded iu >'. -fi-inliiin. The four or live I 'inciiiii.it i ipecitt kimun to me arc ail much higher p.Meriorly. ..',"/ \| . i- -ilMHil thin- U > Ml' 'KI'IA. n. :•• Shell rather -mall, tran-ver-ely -uKovate, in Ay convex. e«|iiivalve. inequilateral; hack arcuate. Leak- anterior, not large, curving ohli.[iiely inward ami forward; iiinl.oiial ridge moderate; Let ween the ridge and the dorsal edge a m<" !••>- distinct Milciiv A -harply detined liinule lieneath the ;i|i|iro\iinate lieaks, while i to tin-in tln-ro extend^ to the extremity of tlio hinge an e.jiially eak. l'o>terior half of hinge ci.iiM-ting of a slender lateral tooth in the left valve and a corresponding furrow in the right. Anterior to the center an elongate depression for the reception of an internal ligament. Anterior miHcul.ii -car di-tinct. deep, siihcircular. situated heneath the Itinultv. pallial lino simple, siilmiarginal. posterior scar undeterniined :ier thick in the anterior part. Tyi ••///>•. n. -p. .de the type, the Hudson Kiver >trata of l-'illmore county. Minnesota, contain anotliet having the charactei -ed to this genus. This I puhlisbed .1 ni-w -pecie» of i '•!><• 'iin>i'i. gi\ ing it the specific name siilnn/orsnta. It i- a more e; -hell hut otherwise do-ely related to S. ventralis. A third sjiecie-. thi- one from the y any means identical. In Unimntijsiu nameh. iown in Hall's work on the K-vonian I.amellihranchiata I I'al. New 'I ork. vol. v, part i. plate i.vni. tig. (i). there i< no cardinal tooth in the left valve as in :ider posterior lateral teeth represented. Another di- tingiiishing feature of the latter, and one that is common to many Lower Silurian shelK i- found in the greater depth of the anterior muscular scar. In the genii- /•/ the hiiiL'e. a-i'h- from th«> e-.-utcl:. (iiite ditlerent. the te~t thin, and the muscular impr. .-xi-eedingly faint, while the hack, instead of Keing arcuate, i- conc.i\,- I.ehind the lieak-. the latter I.eing aNo tumid and much more prominent. 62() THE PALEONTOLOGY OF MINNESOTA. |S;iiVordla ventrults. Named as a small compliment to the veteran geologist, Prof. J. M. Saftord, State Geologist of Tennessee. Science is indebted to him for several most valuable woi'ks on the geology of his state, while personally I am under great obligations to him for assistance in the way of specimens and advice. SAFFORDIA VENTRALIS, n. sp. PLATE XLI, FIGS. 3t— 41. Shell transversely subovate, the hight and length very nearly as four is to five; beaks small, declining, situated at the anterior extremity of the distinctly arcuate dorsum, and projecting forward as far as the margin of the shell beneath it. Anterior margin distinctly concave in the middle, the lower part narrowly rounded; ventral margin rather strongly convex, posterior margin subtruncate, a little oblique, the upper half straight or slightly sinuate, the lower rounded. Surface of valves mod- erately convex, with a very inconspicuous umbonal ridge between which and the dorsal edge there is a shallow sulcus. Escutcheon well defined, extending the full length of the hinge, in a dorsal view very narrow between the beaks, wide at the middle, and nan-owing again posteriorly. Lunule sharply defined, very deep, nearly twice as long as wide. Surface marked by subimbricating concentric growth lines. These are rather small but sharp and of nearly equal size for a short distance beneath the cardinal edge, and only a few of them seem to cross the umbonal ridge. Internal characters of hinge as shown in figures 37 and 41. Anterior muscular scar of medium size, subcircular, deep, showing very prominently on casts of the interior; pallial line and posterior muscular impression very faint. This species is distinguished from S. sulcodorsata by its shorter form, terminal beaks, and more rounded ventral margin. Formation and locality.— Upper beds of the Hudson River group ne;ir Spring Valley, Minnesota, ami Iron Ridge, Wisconsin. SAFFORDIA SULCODORSATA Vlrich. I'LATF. XI, I. KKiS. Vi and :tl. Cuneamya sulcodorsata ULiucn, 1892. Nineteenth Ann. Rep.Geol. and Nat. Hist. Sur. Minn., p. 248. Shell small, moderately convex, oblong-subquadrate, with the dorsal and ventral margins subparallel and gently convex, the posterior end truncate, very slightly produced and sharply rounded at the base, anterior end very short (long for the genus), narrowly rounded. Beaks subterminal, declining forward, strongly incurved, projecting forward rather than upward; umbonal ridge moderately prominent, not angular. Dorsal slope with a distinct expanding sulcus; ventral and anterior slopes gently and uniformly convex. Hinge line, posterior to the beaks, long, the edge •!•:!. UI;i;.\M-MI ATA. rdln modi iilfl- '«» form a well marked escutcheon. In front (if ami beneath the I a deep lunule. Surface marked with regular, concentric fold-. oh-oletr on tin ilinal -lope-, ami l-y tw.. ur three times more mimeiou- fine .stri.e, which seem to, ha ded over all part-, of the -urf.i. This neat shell wa- at tir>t de-cril>ed as a Cnnxnni/'i. hut with the disco\ery of the closely all; •//.•.• it hecame evident at once that the specie- had been mi-placed. Compared with the type -pecies it is found to ditl'er in its form, the e the anterior end is very -mall, -harply rounded, aKruptly d.'|,re— ed beneath the l>eak-. projecting very little beyond them, and almost entirely occupied liy a >uhcircular inu.-culiir scar, 1 teaks small, only -lightly incurved, appearing I'rominent. I'mLonal ridge scarcely di-tiii^rui-halile. the cardinal slope faintly concave between it and another low ridge-like swelling that forms the hack of the ca-t. Along the hinge line there is a narrow impressed area. The lunule, like the escutcheon, is proportionally narrower than in the other species. Shell thin: hinge plate narrow, apparently with the characters (as shown by recently obtained material) required l>y the genii-. A- near ieteimined from casts of the interior only, this -pecies would appear to occupy an intermediate po-itioi: !>eing longer t han the tir-t and shorter than ti id. l unth-x, M 628 THE PALEONTOLOGY OF MINNESOTA. [Errata. Errata for the Chapter on Lamettibranchiata. PAOE. 477, 6th line from bottom, for Cluenoilomus read Oymatonota. ' 479, 3d line from bottom, for Clidoporus read Clidoplim-us. '^ 479, 10th line from bottom, for usually road unusually. 479, 12th line from bottom, the variety referred to is described in vol. vii, Oeol. Sur. Ohio, p. 629, as Byssmiychia vera Ulrich. 482. Supply omitted letters S-B to ends of bottom line of cut. 485, 14th line from bottom, for Ectenoptera, Ulrich read Opisthnptcra, Meek. 486. The family LYUODKSMID.K should be restricted to the typical genus, and Allnilxmn. I'lricli, referred to the family CYCLOCONCHID^K ( next page) while T<-<-loi<>i>lif>}-ux, Miller, and /.«•/, i/n mi, Billings. should follow as a distinct family, TKCiiNornoum.K. (See p. 608.) 604, 17th line from bottom, refer M. tnmcata Hall, to Ml14, several instances in third and fourth paragraphs; p. 515, 1st and 6th lines from top, and 4t.h and 5th lines from bottom; p. 516, 5th and 7th lines from top; p. 517, 7th and I7l.h lines from top; p. 518, 16th line from top; p. 524, 8th and 10th lines from bottom; and p. 531, 5th line from top. * 520, 1st line from top, after OKTHODESMA CANALICULATUM add n. up. 563, 19th line from top, for 5100 read 8626. » 592, i!»i.h line from bottom, for CTENDONTA read CTENODONTA. 593, 9th line from bottom, for C. ten In read PLATE XXXV. PAGE. Figs. 1 and 2. AMBONYCHIA BELLISTRIATA Hall ^ 492 1. Nearly an entire cast of a left valve. 2. Anterior view of same, with the right valve supplied according to our idea of the species. Middle Galena, near Wykoff, Minnesota. • . Figs. Sand 4. AMBONYCHIA PLANISTRIATA Hall 491 Left side and anterior views of a specimen preserving the two valves partly opened. "Lower Blue" limestone, Mineral Point, Wisconsin. Figs. 5 to 7. AMBONYCHIA AFFINIS, n. sp 492 5 and 6. Lateral and anterior views of a well preserved fragment of the cast of a left valve, showing very obscure concentric undulations, fine radiating stria; and the sharply defined subrostral lobe. Galena, Carroll county, Illinois. 7. An illy preserved cast of a right valve from the middle Galena at Weisbach's dam) near Spring Valley, Minnesota Survey Museum Reg. No. 8342. Figs. Sand 9. AMBONYCHIA AMYGDALINA Hall : 493 8. The cast of an imperfect left valve. The specimen has suffered from pressure, reducing its diagonal diameter so that the anterior side curves too uniformly into the base. 9. Profile view, the right valve ideal Lower Galena, Goodhue county, Minnesota. Figs. 10 to 14. CLIONYCHIA LAMELLOSA Hall 494 10. A small, but unusually well preserved cast of a left valve showing the impres- sions of the posterior adductor ami pedal muscles, pallial line and ligamental area. This specimen is precisely like those which Hall named A. attenuata, but its less quadrate shape is evidently the result of pressure. Trenton lime- stone, Minneapolis, Minnesota. 11. A left valve of the usual form from the "Lower Blue" limestone at Mineral Point, Wisconsin. 12. Imperfect cast of a left valve preserving the muscular scars and a portion of the • wide ligamental area. 13. Anterior view of same, showing the impressions of the upper part of the margin, the form of the beaks and the pallial line running down from it. 14. Cardinal view of same, showing scars of two small muscles (? pedal) behind the beak. One or both of these scars are present in all the Ambonychiidce. Lower Trenton limestone, Beloit, Wisconsin. Figs. 16 and 16. CUONYCHIA NITIDA, n. sp 495 Lateral and anterior views of a right valve, showing the form of the species and the comparatively fine and regular cencentric lines. Trenton limestone, Min- neapolis, Minnesota. Survey Museum Reg. No. 5099. Figs. 17 and 18. CUONYCHIA EBECTA Hall 496 Lateral and anterior view of a nearly perfect right valve. Trenton limestone, Minneapolis, Minnesota. Figs. 19 and 20. CUONYCHIA RHOMBOIDEA Ulrich. 496 Lateral and anterior views of the specimen described. Trenton limestone, Min- neapolis, Minnesota. Survey Museum Reg. No. 5526. Figs. 21 and 22. CUONYCHIA UNDATA Emrnons 497 Lateral and anterior views of an excellent cast of a right valve. Middle Galena, near Wykoff, Minnesota. Collected by Dr. Bobbins and now in the author's cabinet. Figs. 23 to 26. BYSSONYCHIA INTERMEDIA Meek and Worthen 499 23 and 24. Anterior and lateral views of one of the original types of this species. Galena limestone. 25 and 26. Cardinal and lateral views of a small but typical example from the middle Galena horizon, near Wykoff, Minnesota. Fig. 27. PROLOBELLA STRIATULA, n. gen. et sp 532 The left side of a specimen, showing the form and surface markings. Middle Galena, near Pleasant Grove, Minnesota. Figs. 28 and 29. MODIOLODON (?) OIBBUS, n. sp 522 The left side of a specimen of the natural size and magnified four and one- half times. Upper third of the Trenton shales, near Cannon Falls, Minnesota. Figs. 30 to 89. ARISTERELLA NITIDULA, n. gen. et sp 524 30 and 31. Left and right sides of an entire shell, x 4.5. 32 and .'{.'t. Lateral and cardinal views of the largest specimen seen, x 4 5. 34 and 35. Lateral and cardinal views of an internal cast, in which the hight is less and the inciniality of the valves greater than usual, x 4.5. 36 to 38. Natural si/.e views of three shells. Middle third of the Trenton shales Chatfleld, Minnesota. 39. Outline view of ;i stuill left valve from the same horizon at St. Paul. In this shell the anterior end is unusually narrow. Vol. III. jji ft f H.V f nv.-f 'jjt.v t* tf ;t.v t. : ; t tv»fiji ;t y LaTnellltranchiata J Plate XXXV. PL A' IT. XXXVI. Fig*, land 1 MoiMoi.or-i* SIMILIS Ulrleh ; (to* aU<> pin- xi.ii. HI:. l».i Dorsal and anterior view- of the original type of the specie*. Middle third of the Trenton -h.ile*. Minneapolis, Minnesota. s. 3 to 6. Moi>iI s ANA, n. sp 607 -:•!.• of .1 well preserved cast of the Interior Galena shale*. Cannon Falls, K;K' 8. MOIH..I .• p-i- MYMI."I:>K- Flail 608 Cast of a left valve. M i 608 IlikTht -i.le of a cast of the interior, of the natural size and x 2. Middle third of i n-rrton shales, rii.mietd, Minnesota. Fig*. II and 12. M<'|>II>I.I>P-I- "IMOLHTA, n. sp 609 Testlferous left valve, of the natural size and x 2. Upper part of the middle third .,f the Ti.-titoii shales, Goodbue county, Minnesota. Fig*. 13 and 14. M<>I>X.I <>I-IH RXCRLLENS, n. sp 611 l.'l. Cast of the Interior of a right valve. The specimen Is a little Imperfect In the anterior third. Geol. Survey Mus. Beg. No. 8374. 14. Well preserved fragment (anterior part) of a cast of the Interior of a left valve. Survey Mi. ~. UNI Keg. No. 8375. Hudson Blver group, Granger, Minnesota. Figs. 15 and 16. MOMOUWUI OOMQATA DlfiBh 608 The specimen described, a testlferous right valve, of the natural size. 16 and 16a. Lateral and dorsal views of same, x 2. Upper part of the middle third of the Trenton shales, Goodbue county, Minnesota. Fig*. 17 and 18. WHITRAVRSIA SITBCARIMATA, n. sp 616 The right side and an anttro-dorsal view of a cast of the Interior, showing the f"r n of the shell and obscure trace* of radiating stria; on the posterior part. Middle Galena, Goodhue county, Minnesota. Fig*. 19 and 20. WHITRAVRSIA MODIOLIFOKMIS Meek and Worthen 516 19. left side of an Internal cast, Belolt, Wisconsin. Survey Mus. Beg. No. 8341. 20. View of the original type of the species. In the drawing the base and the ante- rior end is restored and the right valve tilted, so as to give an exact dorsal profile. "Lower Blue" beds of the Trenton formation, Mineral Point, Wis- consin. Illinois State Museum. Fig*. 21 and 22. OOLTOMYA DUOSSA, n. sp 524 The nearly perfect shell upon which this species is founded; of the natural sice and x 4 5. Middle third of the Trenton shale*, Chatfield, Minnesota. Fig*. S3 and 24. ORTHODBSMA SUBNASUTUM Meek and Worthen 618 Lateral and dorsal views of an entire cast of this specie*. Galena limestone, \OD, Illinois. Fig*. 25 and 26. OHTHODESMA SCHUCHBKTI, n. sp 518 ral and dorsal views of a cast of the Interior, which Is Imperfect posteriorly, but In good condition otherwise. Middle Galena, Kill more county, Minnesota. Sir .m Reg. No. 8343. Fig*. 27 an.! J- Kr I:\MYA PLAN \ 11 512 27. Inter . as obtained In a gutta-percha Impression of a cast <>f the Interior. 28. HI nire and anterior muscular scar of the left valve, magnified nearly two diam- eters. Trenton limestone, Minneapolis, Minnesota. Fig*. 28 and 30. MATIIKKI A KUOOSA Ulrleh 663 Views of the exterior and Interior of a large right valve \'\>\»-r part of the middle third of the Trenton shales, Goodhue county, Minnesota. |.,T«K PLATE XXXVL— Continued. PAGE. Figs. 31 and 32. PSILOCONCHA MINNESOTENSIS, n. sp 531 31. The right side of a cast of the^interior, which has been shortened by pressure no less than is indicated by the outline restorations. 32. Dorsal outlines of same. Middle Galena, near Pleasant Grove, Minnesota. Figs. 33 and 34. ENDODESMA CUNEATUM, n. sp 526 Dorsal and lateral views of an excellent cast of the interior. Middle Galena, near Wykoff, Minnesota. Figs. 35 to 37. ENDODESMA COMPRESSUM, n. sp 529 35 and 36. Dorsal and lateral views of a cast of a left valve. Middle Galena, near Wykoff, Minnesota. 37. Sectional view across the shell a short distance behind the beaks, showing the inbending of the hinge plate. Fig. 38. ENDODESMA UNDOSUM, n. sp — 529 Cast of the interior of both valves. "Upper Buff " beds of the Trenton formation, near^Beloit, Wisconsin. Geol. Sur. Mus. Reg. No. 8344. Fig. 39. CUNEAMYA TBUNCATA, n. sp .rf 622 Cast of the interior of a right valve. Middle Galena, near Wykoff, Minnesota. Figs. 40 and 41. CUNEAMYA OBLOKGA, D. Sp 623 Lateral and dorsal views of the specimen described. The imperfect posterior end is restored in the figure. Upper Galena, Dixon, Illinois. Figs. 42 and 43. SPIIENOLIUM PARALLELUM, n. sp 024 42. Cast of the Interior of a right valve, imperfect at the anterior end, but otherwise in an excellent state of preservation. 43. Cardinal view of the same, with the left valve restored in outline. "Lower Blue" beds of the Trenton formation, Mineral Point, Wisconsin. Geol. Sur. Mus. Reg. No. 8348. Figs. 44 and 46. SPHENOUTTM STRIATUM, n. sp 624 Lateral and dorsal views of a nearly complete cast of the interior. Middle Galena, Goodhue county, Minnesota. Flga. 46 and 47. RHYTIMYA SINUATA, n. sp 619 Lateral and dorsal views of an internal cast of a left valve. Middle Galena near Wykoff, Minnesota. 112 DJ>i> »>rn.vr..v.Y.i Lamellitra-nchlata { PLATE XXXVII. PAGE. Figs. 1 and 2. ENDODESMA ORTHONOTUM Meek and Worthen, sp 527 Lateral and dorsal views of the original type of this species. The specimen is a good cast of the interior, in solid limestone, of a left valve. All of it is now exposed, the tough matrix, which covered a considerable portion of the ventral margin when it was used by Meek and Worthen, having been removed before it was redrawn for the present work. Lower Trenton limestone, Dunleith, Illinois. Figs. 3 and 4. ENDODESMA GESNERI Billings, sp 528 Lateral and dorsal views of a good cast of the interior of a right valve. Trenton limestone, Ottawa, Canada. Introduced for comparison with the other species of this proposed genus. Figs. 5 and 6. ENDODESMA POSTLATUM, n. sp 527 Lateral and dorsal views of an internal cast. Upper Galena, Dubuque, Iowa. Geol. Survey Museum Reg. No. 8345. Figs. 7 to 7 and 11. 8. 9. 10. 11. Figs. 12 to 14. 12. 13. 14. Figs. 15 and 16. 15. 16. Middle third of the Trenton shales, Minne- 517 510 ORTHODESMA CANALICUUA.TUM, n. sp • 520 The right side and a dorsal view of a nearly entire cast. Waynesville, Ohio. Well preserved but incomplete cast, showing the anterior end and obscure rays across the central half. Upper beds of the Cincinnati group, Waynesville, Ohio. Posterior two-thirds of a cast from the Hudson River group near Spring Valley, Minnesota. The length of this specimen was reduced by pressure, and to this cause we must ascribe the more crowded arrangement of the radiating lines. View of the broken end of same, showing the natural convexity of the valves and the cardinal depression. ORTHODESMA MINNESOTENSE Ulrich. The left side of the type specimen. Dorsal view of same. Anterior part of a dorsal view, x 4. apolis, Minnesota. MODIOLOPSIS CONCENTRICA Hall and Whitfleld Exterior of the shell as obtained from a gutta-percha impression of a natural mold. Finely preserved cast of the interior. In offering these figures 1 wish it to be understood that the specimens selected are strictly normal for the species as It occurs in Ohio. Further, that the species is very constant, and that all marked deviations in contour which may be observed in a series of specimens are the result of distortion through pressure. Figs. 17 to 19. VANUXEMIA SARDESONI Ulrich 555 (See also plate xxxvm, fig. 45.) Lateral, anterior and cardinal views of the best cast seen. Trenton'limestone, Minneapolis, Minnesota. Figs. 20 to 24. MODIOLODON PATULUS, n. sp 521 20 to 22. The left side and anterior and dorsal views of a cast. Lower or middle Galena, Decorah, Iowa. Geol. Sur. Mus. Reg. No. 8363. 23. The left side of a cast of the interior from the Trenton at Danville, Kentucky. 24. A small specimen from the middle Galena of Goodhue county, Minnesota. Figs. 25 to 28. CTENODONTA PLANODORSATA Ulrich 589 (See also plate M.I i. figs. 38 to 40.) 25. Posterior view of the original type. 26. Right valve of same, with a small part of the surface magnified. 27. Profile in a postero-basal view. 28. Cardinal view of same. Upper part of middle third of Trenton shales, Goodhue county, Minnesota. Fig. 29. CTENODONTA COMPRESSA Ulrich 600 (See also plate M.I i. figs. 68 to UO.) The original type of the species, x 1.3. Upper part of the middle third of the Trenton shales, Goodhue county, Minnesota. Figs. 30 and 31. CTENODONTA LONGA Ulrich 590 Interior of the right valvo upon which this species \v;is founded, nuigriillrd twice and of the natural size. Middle third of the Trenton shales, Goodhue county, M i n nesota. Figs. 32 and 33. CLioopnoRus ? CONSUETUS Ulrich 606 The type specimen of the natural size and magnified twice. Middle Galena near Wykoff, Minnesota. Fig. 34. TECHNOPHORUS EXTENUATUS Ulrich 614 View of the left side of the cast of the interior upon which the species was founded. Middle third of the Trenton shales, Minneapolis, Minnesota. j H. it.v t. i Vol III. I Laonellilranchiaia ( Plate XXXVII. PLATE XXXVIII. PAGE. Figs. 1 to 5. VANUXEMIA DIXONENSIS Meek and Worthen 550 1 to 3. Lateral, anterior and cardinal views of a large cast of the intsrior. In many specimens the anterior sulcus is deeper than in this one. 4. View of the interior of a right valve, as shown in a gutta-percha impression. 5. A small left valve which preserves a portion of the shell. Lower limestone of the Trenton formation, Minneapolis, Minnesota. Figs. 6 and 7. VANUXEMIA DIXONENSIS, var. INSUETA, n. var 551 Anterior and lateral views of a perfect cast of the left valve. Trenton limestone, Minneapolis, Minnesota. Figs. 8 to 14. VANCXEMIA ROTUNDATA Hall, sp 552 8. Perfect impression of the inner side of a rather large right valve. Geol. Sur. Mus. Eeg. No. 8319. 9 and 10. Lateral and antero-cardinal views of an entire cast of the interior. 11 to 14. Respectively, posterior, anterior, dorsal and side views of the cast of the interior of a right valve of a small variety, differing from the usual form of the species In the more evenly rounded surface of the casts and greater incurving of the beaks. "Lower Blue" beds of the Trenton formation, Janesville, Wisconsin. Figs. 15 to 19. VANUXEMIA OBTUSIFRONS Ulrich 554 15 to 17. Side, anterior and dorsal views of a good cast of the interior. Lower Trenton limestone, Minneapolis, Minnesota. 18 and 19. The hinge and an external view of a specimen retaining a large part of the shell. Dixon, Illinois. Figs. 20 to 22. VANUXEMIA SUBERECTA, n. sp 553 Three views, dorsal, side and anterior, of a good, though rather small, cast of the Interior. Trenton limestone, Beloit, Wisconsin. Geol. Sur. Mus. Reg. No. 8328. Figs. 23 to 26. VANUXEMIA MEDIA, n. sp 553 23. An internal cast of a right valve. Trenton limestone, Minneapolis, Minnesota. 24 to 26. Lateral, anterior and cardinal views of a specimen in which the right side is preserved as an internal cast, while the other retains some of the shell. Trenton limestone, Cannon Falls, Minnesota. Fig. 27. VANUXEMIA CRASSA, n. sp 553 A sharply defined impression of the inner side of a left valve. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 28 to 31. VANUXEMIA UMBONATA, n. sp 556 Four views of right valve of this species. 28, anterior; 29, the hinge; 30, cardinal; and 31, lateral. Middle third of the Trenton shales, Minneapolis, Minnesota. Fig. 32. VANUXEMIA HAYNIANA Safford, sp — :...- 557 (See also plate XL, and page 470, fig. 36, iv.) A cast of the interior of a small right valve. Galena shales, Kenyon, Minnesota. Figs. 33 and 34. VANUXEMIA TEUMINALIS Ulrich 556 33. Anterior views of the two valves shown in fig. 34. 34. Casts of left and right valves of this species. The former was found in the Trenton limestone at Minneapolis, and belongs to the collection of the Geo- logical Survey, in which it bears the Mus. Reg. No. 5100. The latter is from the same horizon at Cannon Falls. Fig. 35. VANUXKMIA NIOTA (? Hall) Whitfleld, sp : 560 The left side of an entire cast of a rather small example. The anterior margin seems to be more oblique than usual for this species. Trenton limestone (V "Upper Buff" beds), Rockton, Illinois. Geol. Sur. Mus. Reg. No. 8325. Figs. 36 to 38. VANUXEMIA suBnoTUNDA,£n."sp 559 36. The interior of an imperfect right valve. 37. External view of a left valve, imperfect in the postero-dorsal region. 38. Outline cardinal view of the original of fig. 36. Upper part of middle third of the Trenton shales.near.Cannon Falls, Minnesota. Figs. 39 to 44. VANUXKMIA A iniriTA, n. sp 560 39 to 41. Anterior, lateral and dorsal views of a nearly perfect cast of a right^valve. This specimen is of the average size and proportions. 42. Cast of a large left valve that has suffered slightly from pressure, causing slight differences in the outline and the anterior side to l»' less abrupt than usual. 43 and 44. Side and dorsal views of a smaller cast of a right valve in which the anterior end is very obtuse. Middle Galena, Fillmore county, Minnesota. Fig. 45. VANUXKMIA SARDESONI Ulrich 555 (See also plate xxxvu. flgs. 17—19.) Interior of the left valve as brought out in a gutta-percha impression of the original type of the species. Vol. III. it :t.v t. ;c fcv»'u ;t r 1 La-Tnelhtranchiata ( p|a(t XXXVIH. PLATE XXXIX. PAGE. Figs. 1 to 5. VANUXEMIA DECIPIENS, n. sp 562 1 to 3. Lateral, dorsal and anterior views of the largest cast of the interior seen. 4 and 5. Side and dorsal views of a smaller cast of a right valve. Qeol. Sur. Mus., Reg. No. 8626. Figs. 6 and 7. VANUXEMIA WOBTHENI Ulrich 561 The left side and an anterior view of a nearly perfect cast of the interior. Upper Galena, Jo Daviess county, Illinois. Figs. 8 to 12. CYRTODONTA OBESA, n. sp 542 8 to 10. Three views of a typical shell of this species. Black Elver limestone, Mercer county, Kentucky. 11 and 12. A small specimen of the natural size and x 2, referred to this species with some doubt. Middle third of the Trenton shales, St. Paul, Minnesota. Ji*. FIgS. 13 to 15. OllLUOEOH'l'A GIBBERA, n. 8p 542 Three views of the specimen described. It is a cast of the interior. Base of the middle Galena, Goodhue county, Minnesota. Mus. Geol. Sur. Eeg. No. 8366. Figs. 16 to 19. CYBTODONTA ROTULATA, n. sp 541 16 and 17. Side and profile views of a large internal cast, from the middle third of the Trenton shales near Fountain, Minnesota. Geol. Sur. Mus. Reg. No. 8336. 18 and 19. Two views of the testiferous type of the species. Black River limestone, Mercer county, Kentucky. Figs. 20 to 23. CYBTODONTA AFFINIS, n. sp 540 20 to 22. Side and dorsal views, and the hinge of a right valve. Middle third of the Trenton shales, Goodhue county, Minnesota. 23. A cast of the interior of the var. flllmorenais. Middle Galena, Fillmore county, Minnesota. Figs. 24 and 25. CYBTODONTA PABVA, n. sp 541 The left side of an entire cast of the interior of the natural size and x 2.3. Middle Galena near Fountain, Minnesota. Figs. 26 and 27. CYRTODONTA JANESVILLENSIS, n. sp 637 Casts of a small right and a larger left valve. The central part of the surface in the latter is broken in the specimen, but has been restored in the drawing. "Lower Blue" beds of the Trenton, Janesville, Wisconsin. Geol. Sur. Mus. Reg. No. 8323. Figs. 28 to 33 and ?45. CYBTODONTA BUDOVATA. m op i 536 28, 31 and 32. Three views of an entire and well preserved-shell. Birdseye limestone. High Bridge, Kentucky. 29. An old left valve from the Black River limestone, or the base of the Trenton of Mercer county, Kentucky. 30. Right side of a cast of the interior from the middle third of the Trenton shales, St. Paul, Minnesota. 33. The hinge of a right valve from High Bridge, Kentucky. 45. A cast of the interior of a right valve which is doubtfully referred to this species. The bight of the specimen has evidently been reduced by pressure. Trenton limestone, Cannon Falls, Minnesota. Fig. 34. CYRTODONTA AHPLA, n. sp 538 An Imperfect cast of the interior of a large left valve. Trenton limestone, Cannon Falls, Minnesota. Figs. 35 and 36. CYBTODONTA OBLIQUA Meek and Worthen 540 The left side and a front view of the original type of this species. Illinois State Museum. Galena limestone, Scales Mound, Illinois. Figs. 37 to 40. CYRTODONTA GLABELLA Ulrich 543 37 and 38. Two views of the original type of the species. Middle third of the Trenton shales, Minneapolis, Minnesota. 39 and 40. Two sharply defined internal casts of opposite valves, showing slight variations In the outline. Trenton limestone, Beloit, Wisconsin. Figs. 41 to 44. CYRTODONTA PEBSiMiLis, n. sp 544 41 to 43. Three views of an excellent cast of the interior. "Lower Blue" beds of the Trenton formation, Beloit, Wisconsin. 44. A small right valve from the limestone at Minneapolis, Minnesota. Fig. 46. CYBTODONTA OVIKOBMIS Ulrich 544 (See also plate XL. fig. 1.) Mold of the Interior of a left valve, with a. portion of the shell remaining. "Lower Blue" beds of the Trenton formation, Janusvilli*, Wisconsin. {CMtfUILT Vo| in I LaTnellibra-nchlata { Plate XXXIX. PLATE XL. Fig. Fgs. 2 to 6. 2. 3 to 5. 6. Figs. 7 and 8. PAGE. 544 CYRTODONTA o VIFORMIS Ulrich (Sec also plate .\.\.xi.\, fig. 46.) Anterior view of the type. CYRTODONTA BILLINGSI, n. sp '• 538 Cast of a right valve from the lower Trenton limestone at Cannon Falls, Minnesota. Three views of the best specimen seen. Lower Trenton limestone, Dunleith, Illinois. Another specimen from the preceding locality. CYHTODONTA CINGULATA Ulrich 545 Anterior view and the right side of the original type. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 9 to 14. CYRTODONTA GHANDIS Ulrich, and varieties 547 (See also figure 43, n-l:. p. 547.) 9. Cast of a large right valve of the var. germana Ulrich. Galena shales, Goodhue county, Minnesota. 10. Cast of a small specimen from the middle Galena at Lime City, Minnesota. This specimen agrees better with the var. germana than with the typical form of the species. Geol. Sur. Mus. Reg. No. 4102. 11. A small specimen (cast of a right valve) of the typical form. Middle Galena Wykoff, Minnesota. 12. Interior of the original type of Cypricardites germanus Ulrich. Upper Trenton near Danville, Kentucky. 13. Part of the interior of the var. luculentus Sardeson, as shown in a gutta-percha impression from a cast of the interior belonging to the Survey collection. 14. A good cast of another right valve of the same variety and from the same locality. Upper beds of the Hudson River group, Granger, Minnesota. Geol. Sur. Mus. Reg. No. 8332. Figs. 15 to 19. CRYRTODONTA TENELLA Ulrich 546 15 and 16. Lateral and anterior views of a large right valve. 17. Hinge of same. The cardinal teeth are obscure in the specimen and may not be exactly as drawn. 18 and 19. Anterior and lateral views of another right valve, differing from the preceding in being more uniformly convex. Upper part of the middle third of the Trenton shales, Goodhue county, Minnesota. Figs. 20 and 21. VANUXEMIA IIAYNIANA Safford, sp 557 (See also plate xxxviu, tin. -f'. and text p. 470, fig, 36— iv.) Imperfect interiors of two right valves, showing slight differences in the cardinal teeth. Upper'Trenton, near Danville, Kentucky. Figs. 22 to 24. PLETHOCAKDI A UMBON ATA Ulrich 576 Three views of the type specimen. Upper part of the middle third of the Trenton shales, Goodhue county, Minnesota. Figs. 25 to 27. PLETIIOCARDIA SUBERECTA Ulrich 577 Three views of the type specimen. Galena shales, Goodhue county, Minnesota. FlgS. 28 to 30. WniTEI-LA QUADKANGULAR'S Whitfleld, Sp 566 28. An imperfect specimen doubtfully referred to this species. Hudson River group, Spring Valley, Minnesota. 29 and 30. Lateral and antero-cardinal views of a cast of the interior from Savannah. Illinois. Figs. 31 and 32. WJIITELI-A OBLIQUATA Ulrich 565 31. A cast of a left valve from the upper beds of the Cincinnati group, near Blan- chester, Ohio. 32. The interior of a left valve, showing the hinge with its cardinal teeth, escutcheon and posterior internal ligamont supports, and faint muscular impressions. The outline is imperfect posteriorly, causing the shell to appear less oblique than it should be. Hudson River group, Spring Valley, Minnesnla. Figs. 33 and 34. TKcnNOpnoBus SUBACVTUS Ulrich 614 Cast of the interior of the natural size and twice magnified. Trenton limestone, Minneapolis, Minnesota. Gc.nl. Sur. Mus. Reg. No. 8338. Figs. 35 and 36. TECHNOPHORUS KILISTBIATUS Ulrich 615 Left valve of the natural size and a small portion of the surface enlarged to show the regular character of the flrif concentric lines. Upper part of the middle third of the Trenton shales, Goodhue county, Mirmi'sola. Figs. 37 and 38. TKCHNOPHORUS DIVAHICATUS Ulrich 616 The type specimen, a perfect left valve, of the natural si/.e and enlarged two and one-half times. Upper third of theTrenton shales, near Cannon Falls,M!nnesota. Vol. III. tvxn Mift f >t.v f..v.-f •. .f.vc tf ;<.v t. ; ! LaTnellitra.nchiat& XL PLATE XLI. PAGE. Fig. 1. WHITELLA RUGATINA, n. sp 569 Left side of a cast of the interior. Middle third of the Trenton shales, Minne- apolis, Minnesota. Figs. 2 and 3. WHITELLA CONCENTRICA Ulrich 569 The right side and a front view of the type. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 4 and 5. WHITELLA MEGAMBONA Whitfleld, sp ' — 570 Two views, lateral and anterior, of a good cast of the interior. Trenton lime- stone, Minneapolis, Minnesota. Figs. 6 to 9. WHITELLA COJIPRESSA Ulrich 568 6 and 7. The right side and a front view of an internal cast, differing slightly from the type of the species. 8 and 9. Two views, side and dorsal, of the original type of the species. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 10 to 14. WHITELLA. TRUNCATA Ulrich 572 10 to 12. Dorsal, side and front views of an average specimen. 13 and 14. The right side and a posterior view of the largest cast of the interior seen. Galena shales, Goodhue county, Minnesota. Figs. 15 and 16. WHITELLA PR^CIPTA Ulrich 574 The left side and a dorsal view of a large and well preserved cast of the interior. Galena shales, Goodhue county, Minnesota. Figs. 17 to 21 WHITELLA SCOFIELDI Ulrich 57 1 17. A very large left valve from the middle third of the Trenton shales at St. Paul, Minnesota. 18. Hinge of same. The cardinal teeth are abnormally developed. 19 and 20. Anterior and side views of the original type of the species. Middle third of the Trenton shales, Goodhue county, Minnesota. 21. Hinge of same x 2, showing the cardinal teeth, the striated escutcheon and the posterior internal ligament supports in a very satisfactory manner. 572 Figs. 22 and ? 23. WHITBLLA SUBCARINATA, n. sp 22. A well preserved internal cast of aright valve. Middle Galena, Wykoff. Minnesota. 23. Cast of a left valve, supposed to represent an earlier variety of this species. Lower Trenton limestone, Jo Daviess county, Illinois. Figs. 24 to 26. WHITELLA VENTRICOSA Hall, sp 573 24. Internal cast of a right valve in which the anterior margin is uniformly rounded. 25. Anterior view of same, with the left valve restored from another specimen. 26. Outline of the antero-dorsal part of a left valve in which the anterior^margin is sharply rounded above. Trenton limestone, Watertown, New York. Figs. 27 and 28. WHITELLA STERLINGENSIS Meek and Worthen ". 567 Antero-cardinal and lateral views of the original type of this species. The speci- men is a cast of the exterior. Upper part of the Hudson River group, Sterling, Illinois. Illinois State Museum. Figs. 29 to 31. SAFFOBDIA MODESTA Dlrich 62; 29 and 30. The left side and a front view of an entire cast of the interior, natural size. The specimen isof the average size. Galena shales, Goodhue county, Minnesota. 31. The left side of same x 2. Figs. 32 and 33. SAFFORDI A SULCODORSATA Ulrich 626 Antero-cardinal and lateral views of the specimen described. Upper part of the Hudson River group, near Spring Valley, Minnesota. Figs. 34 to 41. 34. 35. 36. 37. 38. 39 and 40. 41. S.UKOHDIA VKNTRALIS, H. Sp Cast of the interior of a left valve. Spring Valley, Minnesota. Gutta-percha impression of a natural mold of a small left valve in the base of a bryozoan. Hudson River group. Iron Ridge, Wisconsin. Anterior view of same. Hinge of a right valve. A left valve. Anterior and cardinal views of same, with the right valve restored from the 626 original of figure .'17. Hinge of the left valve. Valley, Minnesota. Upper beds of the Hudson River group, near Spring 1125 i Vol.111. ) LaLTnellltratnchlata ( Plate XLI. I I »od ». 1 aid 4 5 Kl««. t to S. PI.ATK XUI LrMMMaMA AtfHIMATCM. n. «p Lateral and cardinal view, nf a large right . »n. . f Hie typical form. OppnlM view*, i -'. of a l«ft valvr of the var. tatemeft*) The hinge of a right valve of the typical form, x :i. .howlng the rrtral *weep of the teeth i-., . I -. Bnmcwhat weathered rant .if tb« InU-rlor. Taad i. Lateral and eardlaal view* of a ca*t preaervlng the muacular .car*. Fig*. • i- U • and 10. II aad U. U aad 14. Flea. I* aad I M>Mi.ijrri< >• lln»l and lateral view* of lb« caul of the Interior up..n which the *pectee waa founded. .1 and .-anllnal view* •bow the muwular eear* and the lining vertical furrow left by the clavicle. The posterior extrem- ity In thla •peclnmn la narrower than usual. »4. An oblique cardinal view of a oa*t of the Interior. X «. .bowing an liupreealon of Ihc ilcnt leu latr.1 lilngn. a. Very perfect ea*tof the Interior (if aa unuiually large right valve, .bowing, he-ldc. the u.ual char- acter*, aaveral obecure ray* on the .Idea and a number of .mall unthonal wan. Minn. Ueol. Hur. MB*. Beg. No. Tat. Fig*. 31 to M. OTMODOVTA UMAjn Baiter • aadtr. Oaatof the Interior of aright valve. Mian. Oeol. Bur. Xua Keg No. Ml*. «. Outta-pereha Impreaalon of came. (Bowing the hinge. Ftg. a. OrooDOwTA oriroBJita, n. ip "** Left aide of a cart of the Interior, .bowing the .trong muecular acan and other character, of the apedea. t -• a. OlMKWOirTA HACCTA Hall Mt A .mall teaUferou* left valve of thl* *pecle* from the middle third of the Trenton .balrm, nrar Cannon Falla. Mlaaeeota. Ftca.II to a. OmoDOBTA oonuroama. a. *p *** 11 aad 8. Two right valve*, the nr»t filti the pnaterior amitrlcllon more dl.tlnct than In the other, a. Binge of aright valve. X X. Flg*.M to a. OrmKoDoirTA «CB*A*CTA. n. *p Three view* of a caat of the Interior. Fig. IT. OTBBDOHTA OIBBBBULA Baiter f (Bee alao text p. too, Ig. 44. f and g) An excellent mold of the Interior of a left valve. Fig*, a U> 40. OrnmDOMTA rt-AKOWIUATA L'lrlch «• (Bee alao plate xxxvu. Ig*. SS-» ) a. View of the Inner .Ide of a left valve. X *. a. Binge of aame. more highly magniaed. 40. Artltolaleastof the Interior of a right valve. Fig*. 41 to 41. OTUODOWTA CAURATA. n. *p. ... <• 41 and n. A right and left valve, both Imperfect aad varying (llgtly In outline. 41. Donal view of the left valve. Fig*. 44 to t». Or*Ki>iH)*ffr>«*yj«, a. *p - • *•** a. BIIMftad right valve of the .peel*, from the middle third of the Treaton ahale*. >l II Inge of aame. x t. U. Oaat of the Interior from the (ialena ahalea. provlelonally referred to thU apedea. Fig*. 51 to 6C. OrannDoXTA icnnti.oi. n. «p a to it. The left aide and posterior, anterior and doraal view* of a .peclmen preaervlng the .hell and .bowing. among other character* of the apMtoa. the .harply angular umlnual ridge. Ml Idle third of the Trenton abalaa. wear Uaaaoa Falla. Mlaaaanl* 57. Hlage of a right valve, xz. a. The right aide of a oaat of the Interior from the Galena ebale*. provtolonally referred to thl* •peeMa. The anterior end I* larger than In the typical form. (Ovca. PLATE XLIL— Continued. PAOE. Figs. 56 and 80. CTENODONTA SOCIAI.IS, n. sp 504 60. Outline views of three specimens of different sizes and showing slight variations in form. CO. Hinge of two right valves, X 8. showing slight differences In the anterior parts. Figs. 81 to 64. CTENODONTA CALVINI, n. sp 596 61. An excellent cast of the Interior of a left valve, showing muscular scars and rays more plainly than usual. In this specimen the length also Is a little greater than in the others. 62. Another cast of a left valve. Minn. Oeol. Sur. Mus. Reg. No. 8028. 63 and 64. Lateral and cardinal views of a cast of a right valve, representing the usual characters of the species. Figs. 65 and 66. CTENODONTA MADIBONENSIS, n. sp 597 The left side and an anterior view of a testlferous example of this species. Pigs. 67 to 73. CTENODONTA FECUNDA Hall r>95 67 and 68. The right side and an anterior view of a cast of the Interior. In many specimens the posterior margin Is more rounded 60. A small part of the external surface magnified to snow the fine concentric and radiating lines. 70 to 72. Cardinal and anterior views and the right side of a specimen preserving the shell. 73. The wavy hinge line as shown on a cast of the interior, X 5. Figs. 74 and 75. CTENODONTA RIMTLATKIX. n. sp 600 74. A cast of the Interior of a right valve, showing the muscular scars and retaining a little of the shell about the beak. 75. As much of the hinge as can be made out from the preceding specimen. Figs. 76 to 82. CTENODONTA AI.BEKTINA, n. sp 596 76 to 78. Three views of a large specimen having the posterior end a little narrower than usual. 79. A smaller specimen of the usual form. 80. Hinge of a large and smaller right valve, showing the subrostral pit and the genlculated teeth. 81 and 82. Cardinal and lateral views of a cast of the Interior which retains a part of the hinge. Figs. 83 to 87. CTENODONTA OBUQUA Hall 604 83 and 84. Lateral and cardinal views of a small specimen of the large northwestern variety of this species, X 5. As usual, the specimen Is a cast of the Interior and shows the muscular scars and impresslonsof the hinge denticles very clearly. ' 86 to 87. Three Internal oasts of a small form of the species from the Cincinnati group of Ohio, X 5. FIgs.88 to 90. CTENODONTA COM PRESS A Ulrlch (See also plate xxxvn, fig. 29.) 88 and 80. Posterior and lateral views of a left valve. GOO 00. The greater part of the hinge of another left valve, X 5, showing the various parts In a beautiful state of preservation. 005 602 Figs 91 and 92. CTENODONTA HAMBURQENSIB Walcott A rlL'ht (?) valve of the natural size and X 5. Figs. 03 and 94. CTENODONTA AI.TA ITall Lateral and posterior views of a cast of the Interior. Figs. 95 to 07. CTENODONTA INTERMEDIA Ulrlch 601 95 and 06. Lateral and posterior views of a right valve preserving much of the shell. The opposite valve Is restored In the profile view. 97. A sharply marked cast of the Interior of a left valve. In this specimen the posterior extremity Is unusually produced. Figs. 88 to 101. OTENODONTA RECUHVA Ulrlch 602 98 to 100. Posterior, lateral and cardinal views of a perfect specimen of this species, showing the usual form, the anterior sulcus and the sharply defined anterior and posterior lunettes. 101. The greater nart of a hinge of a left valve, X 2, showing the arrangement of tin' clrntlrlrs, tin- sharply elevated outer margin and the llgamental area on the right side of the beak. Figs. 102 to 106. OTENODONTA BIMIUB Ulrlch 604 102. Hinge of a left valve of this species, X 2, showing the principal features upon which this species Is separated from ('. reeurva. (See fig. 101.) 103. The left side of a specimen, showing the usual form of the species. Minn. Oeol. Sur. Mus. Reg. No. 8368. 104 to 106. Lateral, cardinal and posterior views of a specimen having an outline very similar to that of C. reeurva. But the absence of the anterior siilcus, the greater convexity of Its valves and the less sharply denned lunettes are all characteristic of C. fimilin and prove its distinctness from C. ncvrva. f r u. Vol.111. p ft it.v t. ; t fvt^a :t r i LeLmelltlrahchlaia I Plate XLII. ««>- I'LATK Xl.lll ! «.. I In Ifur** ara niaflillnl nil. -ii I I . ii. sp Kfi Aril. -.ii and ventral view* of s left valve. L«.« 10 lln)e»t M . Minnesota. Figs. | to I I.- . M.V I-KK-IM II.IH, n. sp. 837 'I'M-' rittht slit.', anterior and ventral views of a rath. -r small specimen. Mi iluril i.' ion shales, Minneapolis. Minn. Flg». 7 ! '' I.i MACKA, n The right side, interior and ventral views of the specimen deKrlbed, showing the re.marknti. ''"MiprwMed character r the larger (right) valve, showing Impression* of the two sets of Internal papilla* along the ventral margin, x 2. Lower Trenton lime- •ton*. Minneapolis, Minn. 11 t'> U. l>"r»al. ventral, right side, and posterior views, x 2, of an excellently preserved test irapace. from tin »aiu<- foroiatlon and locality. The "eye tu- lierrle" |s unusually dlstln Al'AIti IIIIKs ELL1FTH I'*, ii. sp 644 : : I '-t.-rlor and v.-ntral views of an entire carapace. Lower third of the Trenton •hale*, Minn 16. The right side of another specimen from the same locality. Fig*. 1- to 5). Al'ARi HITKS MINUTIMIMU8. var. TKKNTOMENSIS 64« A small right valve from the Trenton shalea, near Fountain. MlnnewiU. 19 ami -X. Lateral and ventral views of a larger valve from the Galena shales, near Cannon Kails, Minnesota. Figs. 21 to 25. CYTHKHKI.I.A? KI-OOSA Jones, and var. AROTA, n var 086 : • Lateral and edge views of two valve* of this species, from the Galena shalea, near Cannon Falls, Minn. 25. A valve of the var. ARCTA. from the middle bedaof the Galenaof GtNtdhue county, ' Minnesota. The generic position of this opeeies la doubtful, and, to facilitate comparison with 0yfAocy;>ru and allied genera, thin specimen has been drawn with the convex margin uppermost. Fig*. 2A to 29. PRIMITIKLLA MJIITLANS. n. »p MX 26. Left valve somewhat doubtfully referred to this species. -'7 to 29. Three vlewH of a typical right valve. Both specimens from the Trenton sbale*. near Fountain, Mlnne«ola. Fig*. 30 to 34. MACHOXOTXLLA SOOFIBLDI, n. gen. et sp 084 30 to 32. Three views of a valve from the lower Trenton limestone at Cannon Falls, Minn. .13 and 34. Two views of a long variety from the Blrdseye limestone at Hitch Hrldgp. ' ntucky. Figs, 35and36. AI-AIK nn» •> AKKBCTUS, n. *p 646 Two views of a left (?) valve. Upper third of the Trenton shale*, St. Paul. Minn. tt and 38. Al'ARCHITK-s CHATKlELDENStS, n. sp. 64« Two views of a left valve the surface of which Is somewhat abraded. Middle third of tin- Trenton shales. Chat Held, Minnesota. Fig*. SB to 41. Si IIMIIITKI.LA I.NCXJMPTA, var. auB^EqcAUB, n. sp. et var 642 <8M »!•<> plaM XLT. flc*. n. a and B.I ws of a right valve. Galena shale*, near Cannon Falls, MlnneaoU. IIMinTKI.I.A PRA!" !l 640 42. F.xt.-rior «.f a ri«ht valve, x 10, showing the broad border. Lower Trenton stone, Mineral Point, Wisconsin 43 and 44. Ventral and posterior views of sa ; Flgfl. 45 to 47. SCHMIDTBLLA AFFIMH, n. sp 041 45 and 46. Anterior and side views of a right valve. Galena shales, near Cannon Falls, Minnesota. 47. Interior of the largest right valve seen. The specimen Is slightly distorted so that the hinge In bent inwardly. IOTMLJ PLATE XLIIL— Continued. PAGE. Figs. 48 to 52. PKI.MITIELLA CONSTRICTA, n. gen. et sp 047 48 and 49. Three views of a right valve; from the base of the Birdseye limestone at High Bridge, Kentucky. In this form the anterior end is rounded and the border scarcely developed. 50. Two views of a right valve, representing the prevailing form of the species in Minnesota. 51 and 52. Lateral and dorsal views of a longer right valve, from the lower third of the Trenton shales at Minneapolis, on which a small raised spot, situated just behind the center of the valve, is barely distinguishable. Figs. 53 to 56. PRIMITIKLLA LIMBATA, n. sp 648 53. Interior of a right valve. 54. Anterior and lateral views of another right valve. 55 and 56. Lateral and dorsal views of a left ualve. Lower third of the Trenton shales, Minneapolis, Minn. Figs. 67 to 59. PBIMITIA OIBBKRA, n. sp 655 Three views of a left valve^ Hudson River shales, near Spring Valley, Minnesota. Figs. 60 to 61. PRIMITIA DUPLICATA, n. sp .".. 654 Lateral and ventral views of a left valve. Middle third of the Trenton shales, Minneapolis, Minn. Figs. 62 to 65. PRIMITIA TUMIDULA, n. sp 655 62 to 64. Three views of the exterior of a left valve, obtained by an impression in gutta percha from a natural mold. Hudson River shales, near Spring Valley, Minn. 65. Cast of the interior of another left valve, from the same locality. Fig. 66. PRIMITIA UPHAMI, n. sp 651 Three views of a right valve. Galena shales, Cannon Falls, Minnesota. Fiifs. 67 and 68. PBIMITIA CELATA, n. sp 653 The exterior and a ventral view of a right valve. Middle third of the Trenton shales, Minneapolis, Minn. Figs. 69 to 72. PRIMITIA MICULA, n. sp 653 69 to 71. Three views of a right valve. Galena shales, near Cannon Falls, Minnesota. 72. Interior of a left valve, from the same locality, supposed to belong to this species. The outline is somewhat different from the preceding, but there is reason to believe that the valve is imperfect at the antero-ventral margin. Figs. 73 and 74. PBIMITIA SANCTI PAULI, n. sp 052 Two views of a right valve. Upper third of the Trenton shales, St. Paul, Minn. Figs. 75 to 77. PBIMITIELLA UNICORNIS Ulrich 649 Three views of a right valve, from the lower or Utica horizon of the Cincinnati group at Covington, Kentucky. The specimen is one of the original types of the species. Ffgs. f8 to 81. PRIMITIA MAMMATA, n. sp 052 Dorsal, lateral and ventral views of a right valve. Lower third of the Trenton shales, Minneapolis, Minn. Figs. 82 and 83. BEYBICHI A INITIALIB, n. sp ; 658 Lateral and ventral views of a left valve. Middle third of the Trenton shales, Minneapolis. Figs. 84 to 88. MOOBEA PUNCTATA, n. sp 682 84. A. right valve. 85 to 87. Three views of a left valve. 88. Another left valve in which the marginal ridge is twice interrupted along the ventral border. Upper third of the Trenton shales, St. Paul, Minnesota. Fig. 89. MOOBKA ANOULAKI8, n. Sp 682 (See also plate XIA'I. tigs. 15 and 16.) Side and ventral views of a right valve. Middle third of the Trenton shales. Minneapolis, Minn. >>*p Mif.f».\f..v.-f,.vf.\M'ff;(.vf. -.'trini vd.in. (OstracodaJ put. XLIM. I'LATK XI. IV All i lie Bgurtwon ihU plaUr »re mMulSwi about twenty dlanMltn. . I. Kri:v< IIII.INA Hrin n.\T.\ I'lrlch. : f,-<-t left valv.- <.f thin species. Lower thlnl «t the Trenton shale*. Fillmorw county, Minnesota. \ UKIK TI.ATA, var v,n. var •n. th<- upper third of the Trenton shales at St. Paul, Mlnne»oU. Fig*. 3and]4. KVBYCHILINA SUBRADIATA Ulrlch :i Interior of a perfect right valve. 4. Nearly perfiTt Ml ralre, showing the usual characters of the species at It occurs In Minnesota. 4o. Section of same across central portion of valve. Lower third of the Trenton shales, Minneapolis, Minn. figs. 6 to 7. EvKYuiii.iNA(t)STincrnucA, n. sp... . Interior of a right valve. 6 and 7. Exterior and anterior views of a more elongate left (?) valve, Upp. r third ..f the Trentob shales, St. Paul, Minn. FlgS. 8 U) 11. CTENOHOLIHNA rCLCRATA, n. Sp B"* 9 and 0. Lateral and posterior views of a left valve, presenting the usual characters of the species. 10 and II. Lateral and dorsal views of a right valve, resembling In certain respects the next -I*-.-,. - r pper third of the Trenton shales, St. Paul. Minnesota. Figs. 12 to 16. CTENOHOLHIX A CKASSA Ulrlch 12 t-i 14. Lateral, posterior, and dorsal views of a left valve. This Is the original type of the species. Upper third of the Trenton shales, St Paul, Minnesota. 15 to 16. Lateral and posterior views of another left valve from the same locality, differ- Ink* In several respects from the type. FlgS. 17 to 19. JOHEOtLLA OMCURA, n. sp Left and right valves and an Interior view of the first. The "horseshoe " ridge Is very obscure In Its lower curved part. Galena shales. Cannon Falls, Minn. Figs. 20 to 22. DREPANELLA BIOENERIS, n. sp • - 20 and 21. Side and posterior views of a left valve. Lower Trenton limestone, Minneapolis, Minnesota. 22. Longitudinal sectional view across the central part of the same. K . 23. DlCRANKLLA SPUfOHA, n. Sp **S (8*e aUo plate * LVI. fig. 41. ) A left valve of this species. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 24 and 25. DICRASELLA (?) SIMPLEX, n.sp 696 (8«e »Uo plate ZLTI, fl*. 41.) Lateral and posterior views of a left valve. Galena shales, Cannon Falls, Minn. In fig. 24 the oblique spine on the left side of the center appears scarcely prominent enough. I.. 26. DICRAMELLA BicoRNis, n. gen. et sp 665 <8*e aUo plate XLVI. fifv t» and 40.) A right valve wanting only the posterior part of the marginal frill. Middle third of the Trenton shales, Minneapolis, Minnesota. Figs. 27 and 28. DICRANELLA MAKWNATA, n. sp 666 Lateral and posterior views of a right valve. Trenton shales, near Fountain, Minnesota. Figs. 29 to 35. BTTHOcrrRis CYLINDRICA Hall, sp 29 to 31. The left side, dorsal, and posterior views of an average example of this species. Lower beds of the Cincinnati group, Cincinnati, Ohio. 33. Yi.'w <>f the Interior of a right valve, showing a slight central thickening of ' test. From the same locality. 33. Yi-ntral view of a complete carapace: also from Cincinnati, Ol. 34 and 35. Lateral and dorsal views of a small right valve, which Is also a little narrower than u-ii:il. Galena shales. Cannon Falls, Minn. [ora. PLATE XLIV. -Continued. PAGE. Figs. 36 to 38. BYTHOCYPRIS (?) CURTA, n. sp 689 Lateral, ventral, and anterior views of a rather small specimen. Middle third of the Trenton shales, St. Paul, Minnesota. Figs. 39 to 42. BYTHOCYPBIS GRANTI, n. sp ussi 39. A large left valve. Middle third of the Trenton shales, St. Paul, Minnesota. 40 to 42. Lateral, anterior and ventral views of a smaller right valve, from the same locality. Fig. 43. CYTHERELLA (?) SUBROTUNDA, n. sp '. 685 The left side of the complete carapace upon which the species is founded. Lower third of the Trenton shales, Minneapolis, Minnesota. Figs. 44 to 46. KRAUSELLA INJSQUALIS, n. gen. et sp 692 Three views of an entire carapace. Lower Trenton limestone, Dixon, Illinois. Figs. 47 .to 53. KRAUSELLA ARCUATA, n. sp... 692 47 to 49. Three views of the smaller (right) valve. Birdseye limestone, High Bridge, Kentucky. Relatively higher than the northwestern specimens. 50. Right valve from the lower third of the Trenton shales at Minneapolis, Minn. 51 and 52. Lateral and ventral views of another right valve. Lower Trenton limestone, Mineral Point, Wisconsin. 53. View of the interior of a left valve. Also a vertical section through center of same. High Bridge, Kentucky. iLLJtiUiiir 3 Hil O.T Jli1 Vol. III. [Ostracodftj Plate M.IV. PLATE XLV. Unless otherwise is stated, all the figures on this plate are magnified about twenty diameters. PAGE. Figs. 1 to 3. EURYCHILINA VENTROSA, n sp. or var 662 1. Left valve, Imperfect at the extremities, yet preserving the essential characters of the species. Galena shales, Cannon Falls, Minnesota. 2 and 3. Lateral and posterior views of a perfect right valve, from the same locality. Figs. 4 to 6. EURYCHILINA (?) SYMMETRICA, n. sp 663 (See also plate XLIV, figs. 5—7.) 4 and 5. Side and end views of a valve, x 28, differing somewhat from the specimens figured on plate XLIV. Upper third of the Trenton shales, St. Paul, Minn. 6. Longitudinal section of same. Figs. 7 to 9. EURYCHILINA (?) SUB^EQUATA, n. sp 663 Side view of a left valve, with vertical and longitudinal sections of same. Upper third of the Trenton shales, St. Paul, Minnesota. Figs. 10 to 12. APARCHITES FIMBKIATUS Ulrich 645 Side, ventral and posterior views of a right valve. Hudson Eiver group, Spring Valley, Minnesota. Figs. 13 to 15. LEPERDITELLA T0MIDA Ulrich 637 Side, dorsal, and posterior views of a typical right valve of this species, x 15, from the Birdseye limestone at High Bridge, Kentucky. Introduced for comparison with L. canalis and L. persimilis, figured on plate XLIII. Figs. 16 to 18. APARCHITES MILLEPUNCTATUS Ulrich 645 Ventral, anterior, and side views of a right valve. Surface punctation omitted except on the antero-dorsal fourth of fig. 18. Trenton shales, Fountain, Minn. Figs. 19 and 20. LEPEKDITELLA DORSICORNIS Ulrich 639 19. A left valve, x 15. Hudson Eiver group, Savannah, Illinois. 20 and 20a. Outlines of same in dorsal and anterior views. Figs. 21 to 23. APARCHITES GRANILABIATA Ulrich 644 Posterior, side, and ventral views of a left valve. The minute surface granules are omitted except on a small space of fig. 22. Upper third of the Trenton shales. St. Paul, Minnesota. Figs. 24 to 26. LEPERDITELLA GERMANA Ulrich 638 Outlines of a left valve in anterior, side, and ventral views, x 15. Lower Tren- ton limestone, Mineral Point, Wisconsin. Figs. 28 f/o 30. PRIMITIELLA FILLMORENSIS, n. sp 649 Three views of a right valve of this small species. Trenton shales, Fountain, Minnesota. Fig. 31. PRIMITIA MINCTI88IMA, n. sp 651 A left valve. Trenton shales, Fountain, Minnesota. Figs. 27, 32—33. SCHMIDTELLA INCOMPTA, n. Sp 642 (See also plate XLIII, flgs. 39— 11.) 27. Interior of a left valve. Trenton shales, Fountain, Minnesota. 32 and 33. Side and anterior views of a right valve; from the same locality. Figs. 34 and 35. SCHMIDTELLA BREVIS, n. sp 642 Side and anterior views of a left valve. Trenton shales, Fountain, Minnesota. Figs. 36 to 38. SCHMIDTELLA UMBONATA, n. sp 641 36 and 37. Anterior and side views of a left valve (opposite valve restored). Upper third of Trenton shales, St. Paul. Minnesota. 38. View of the interior of a right valve, from the same locality. Figs. 39 to 42. SCHMIDTELLA SUBROTUNDA, n. sp 643 Side and end views of a right and left valve. In both cases the opposite valve has been restored. Lower third of the Trenton shales, Minneapolis, Minn. vol. HI. ;t.v (. : t frE»-.u ;t r (Ostracoda) "•«• XLV. ,: 40 3O 34 9 O PLATE XLVI. All the figures on this plat* are magnified about twenty diameters. Figs. 1 to 11. TETRADELLA QUADRILIRATA Hall and Whitfleld, sp. 679 1 to 3. Posterior, side, and dorsal views of a right valve. Middle third of the Trenton shales, Minneapolis, Minn. 4. Another right valve. Birdseye limestone, High Bridge, Kentucky. 5. Inner side of a right valve. Minneapolis. 6 to 8. Three views of a left valve, differing from the usual form in unimportant partic- ulars. Minneapolis. 9 to 11. Three views of a variety, agreeing with var. simplex in wanting the posterior marginal loculi. Trenton shales, Fountain, Minnesota. Figs. 12 to 14. TETKADELLA LUNATIFERA Ulrich 680 Three views of a left valve of a variety of this species. In other specimens that were found with this one the antero-median ridge is more distinctly double. (See cut, p. 680.) Galena shales, Cannon Falls, Minnesota. Figs. 15 and 16. MOOREA ANQULARIS, n. sp 682 (See also plate M.I n. fig. 89 ) Two views of a weather-worn valve, apparently of this species. Trenton shales, Fountain, Minnesota. Figs. 17 and 18. MOOREA (?) PEKPLEXA, n. sp 683 Side and sectional views of the remarkable valve upon which this species is founded. Trenton shales, Fountain, Minnesota. Figs. 19 to 22. CERATOPSIS CHAMBERSI Miller, sp 676 19 and 20. Side and ventral views of a left valve of the usual form. Upper third of the Trenton shales, St. Paul, Minnesota. 21. Inner side of a more elongate right valve, from the same locality. 22. Another right valve from the same locality, peculiar in having the small post- median ridge divided. Figs. 23 to 25. Figs. 26 to 29. 26 and 27. 28. 29. Figs. 30 to 34. Figs. 35 to 38. 35. 36 and 38. 37. Figs. 39 and 40. 669 Fig. Fig. 41. 42. Figs. 43 to 46. 4:i to 45. 46. 669 673 BOLLIA UNOULOIDEA, n. sp Three views of a left (?) valve. Galena shales, Cannon Falls, Minnesota. BOLLIA SUB.SQUATA, n. sp End and side views of a valve of this species. Trenton shales, Fountain, Minn. A small valve from the same locality. Large and relatively high valve from the same position at Cannon Falls, Minn. DILOHELLA TYPA, n. gen. et sp Figures of three valves showing slight variations. Upper third of the Trenton shales, St. Paul, Minnesota. DRBPANELLA BILATERALIS, n. sp 671 A right (?) valve of the usual size and appearance. Ventral and posterior views of a left valve. Interior of a right valve. Upper third of the Trenton shales, St. Paul, Minnesota. DICRANELLA BicoiiNis, n. gen. et. sp 665 (See also plate M.I v. fig. 26.) Side and posterior views of a nearly complete right valve. Middle third of the Trenton shales, Minneapolis, Minn. DlCRANKLLA 8PINOSA, n. sp 665 (See also plate XLIV, fig. 23.) Posterior view of a left valve. |M< ILANKI.I.A (?) SIMPLEX, n. Sp 666 Ventral view of the valve figured on plate XLIV, flgs. 24 and 25. 1 1 \ 1. 1 .n i.i. \ LAUIOBA, n. sp 656 Anterior, dorsal, and left side views of an entire carapace. Galena shales near Cannon Falls. Minnesota. Somewhat weathered and relatively longer left valve: from the same locality. HI. .V f ..v.-f .. \f .v c tr :t.v t. ; i M«>-II it r (Ostracoda) Ptou XLVI. CHAPTER VI TIIK LOWER SILURIAN < >STRA< < >l>.\ •• MI\M->< >T.\. M i. «• 11.1:1 H Thi- order <>f Crustacea compii-e- -mill, generally minute, iniini.il- ha\ing the entire l.o.|y em-lo-ed in ;| -hell or curapice con-i-ting of two more or le>- nearly e.mal calcareou- or corneou- \uhe-. united along the Lack liy a ni.'iiilirane, and capable of being opened at their ventral margin-. Tlie valve.- are clo-ed hy a Mih- central adductor mu-c|e. the attachment of which i- marked on their inner -id. a tn [ pit or a numKer of -mall -pot-. '1'he I tody i- not segmented Imt ha- seven pair- of appendages, of which ' two are antenna-, while they, like the other-, are al-o adapted for creeping ami -wimmiritf. These appendages, together with the caudal extremity of the short abdomen, are protruded along the ventr.il margin of the carapace when the valves are opened. lielmid the tir-t two pair- of appendage- (antennnle- and antenna-), i- a pair of mandilile-, followed hy ;i pair of maxilhe, while the third and fourth pair- may l>e either legs or j i\\-. I inally the last two pairs are leg-like and generally stronger than the preceding pair-. The extremity of the alidomen may lie bifurcated or con- -i-t of a -in^'le -pinous plate. As a rule the eyes are uell developed, with commonly a -mail median and two I'he position of the latter is often indicated on the exterior of the valve> Ky a -mall "eye tulienv ii-tinct heart may l>e present or ali-ent. Imt the alimentary and generative or_'.ni- are well developed. The n,tracoda. or " wa' t hey an- often called, arc repre.-ented l>\ nnmeron- form- hoth in fre^h water and in the sea. Of the families only the t'ljf-i are chiefly fresh-water form-, while mo-t of tlie other families ai I to marine or hracki-h Taken as a whole they are to be considered a- -hallow water inhaliitants. and of -ocial halnt-. I.eing found in great numbers -wimmi the -nrface of tlie water or creeping over the l>ottom. Kemain- of ()-• abound 630 THE PALEONTOLOGY OF MINNESOTA. iostncod» also in nearly all the geological formations, and in some cases so numerously that wholg layers are almost composed of their shells. The fossil forms are furthermore of great variety, since, with perhaps a single exception, all the families which have been established for the recent forms have also been recognized in the fossil state, while many types occur in the paleozoic rocks that seemingly are now totally extinct. With a single exception (Paheocypris), only the carapace valves are preserved in the fossil condition, and as these are often very similar in different genera and even families, it is evident that their study and classification is a matter of exceptional difficulty. To discriminate between these small fossils the paleontologist is obliged to rely on small differences in the shape, the relative size of the valves, the characters of the edges and of the hinge, the thickness of the valves, and the surface ornamentation. Among the paleozoic forms the valves are commonly lobed or sulcate and variations in these are usually counted important. A frequent difficulty is to distinguish between the anterior and posterior extremities. When not alike, the thickest end (it is generally also the highest) is considered as the poste- rior. It must be confessed, however, that this arbitrary determination can be accepted only as provisional. Some working rule like this is necessary until com- parison of other details of structure will have furnished us with more reliable criteria upon which to base conclusions. The carapace as stated consists of two calcareous or corneous valves of compact structure, commonly less than 4 mm. in length, though in a few cases the length exceeds 20 mm. The two valves may be equal (Tetradella, Primiiia, etc.) or more or less unequal, with either the right or left overlapping the other at the ventral border only (Leperditia, Leper ditel la, etc.), or at the dorsal border as well (Bythocypris and Krausella), while in others the overlap is entire (Cytherelld). The hinge or dorsal margin may be straight or arcuate, and, especially among the paleozoic types, is generally simple, though among more recent forms (Cytheridce) hinge teeth and corresponding sockets are not uncommonly developed. The anterior and posterior margins may be broadly or narrowly rounded, pointed or drawn out beak-like; and when the back is straight the ends may join it angularly. The ventral margin is oftenest convex though it is not infrequently straight or gently concave. The sides of the valves in the majority of Ostracoda may be said to be approximately even in contour or convexity but in many cases, especially among paleozoic forms, they are indented and thrown into two or more tubercles, lobes or ridges. The surface of the valves may be smooth and polished or it may be granulose, pitted, reticulose, striated, hirsute or otherwise marked, the effect being in many instances quite orna- mental. Finally many of the paleozoic Ostracoda of the family Beyrichiidce have a wide, frill-like false border, which projects considerably beyond the true contact I I: \< 1 1|. \ - nf tlic v.ihe-. Tin- ir-'iiii- l.iii-ii,-liiliHii alloid- with a "frill." \- !•••_•, ird- tin- ^rnlo^ic.il nr time diution nf the ' ili.it the\ I'.. -in in the upper divi-ion- of tin n. if indeed they ai • be reckoned a in mix the f, ,--il- known. In the Lower Silurian depo-it- ;ili . they iM-ciir in such great numl>er- and variety, tl. doubtful if tin ul.i tion-of the order at any -ul — -.pient time exceeded them in ti The predominant t \ ; ,\ hile holdin;.' their own perhap- through the I'pper Siluria'i. were greatly reduced during |ie\miian an|i.irin^l> .'iite.l. luit taken a> a whole the Silurian ii-ixla fauna i> 'li-ciilfilly |"'ciiliar.* Ill the I |>j>i>t Silurian foniiation^ the '//././• ami /"///•/.•////-A/ -till |.re«lmu- inate.l. luit the fauna \\< \ tied, led accession- in the way of genera re-ai'li"l a- l-eloiitfiiitf to the family ' '///'/•/'•/•/. The 1 > •voinan i >-tracoridli" . 1'hilm :feroii-: /'• Silurian and ('arhoniferou-: Cijll Silurian, t 'arlioniferou- ami IVrmian- Silurian. l>e\onian. i arl,oniferoii- and I'ermian; fii/tli', , -iliirian. I". I'arlioniferou-: ' . Silurian ami • | iurian: i'iil'1. ill ' '.ollifei. •Th HUB pl»c.-d Inlo rrr»nl f*t,. In my THK PALEONTOUHiY OK MINNESOTA. cal inn (if ( ).st rar PROVISIONAL CLASSIFICATION OF THE PALEOZOIC OSTRACODA. Family LEPERDITIID^E. GENKKA: Lrinnliiin. Itonaull; J^IH i-ilitill«, Hindi: J.tiH-liUinn, Jones; Ai>'(// nV/i/n, McCoy; Beyrichidla, Jones and Kirkby; fityrichtopmg, Jones and Kirkby; Klnlln, Ulrich; JJolliu, Junes and IIoll; iiiinn, Ulricli: Ttirmlt tla, Ulrieh; Drepanella, Ulrich: I'luccntulu, Jones and IIoll; Kirkl>i/n. .Iniirs: .l/iKi/vii. JCHH-.S and Kirkby; Strepida, Jones and IIoll; Mm-nmolilhi, Ulrich; Primilii/ln, Ulrich; Ditobella, Ulrich, Family BARYCHILINID^E. GENKKA: llnri/i-liilinu, Ulrich; Kyammodes, Jones. Family ENTOMID.lv GENEUA: Entomin, Jones; Elpe, Barrande; Entomidella, Jones: ? llippu, Barrande. Family CYPRIDINID^E. GENEKA: Cypridina, Milne-Edwards: r///in, Jones: S; .' Yninnjin, Junes and Kirkby: .\mti>lH<>,ini-i'i, .Jones. Kamily CYPRID.K (lENKHA: Aijluin, Brady: <'ni,,li>,,STRA< '< >DA. Family I.KI'MKI U 1TI I am I.I:I'I:I;MTI \ iion.mit. ilMII.I. l-7>. M. in . i lui|i- E \nn. M.ik- N.u Ili-i , ".Hi -.K-iiiKl KtRKBY, 181 -'.'.• .in, I I- i ii, 18M - ipace limit- i,r |e — convex, oft. Ml large, silbobloi. mnu.ite 1 11 i.llt line, with an oblique backward -wing; dor-al edge straight, often angular .it (In- extrem- utr.il outline rounded, -ometimes a little produced at the ini-lillc; ^ivatest tliickin— . in tin- vi-ntral lialf. the lower ••il^l- u-ually I'l-in^alMi Idiint; val\c~ uiif.|iial. tin- n^'lit tin- larm-r an«l overlapping tlic left ; ..\.-rlap cliii-tly ventral, >iinpli-. nr tin- furl ln-r entrance of the ventral eil^e of the left valve i- pre\ent..l l.y two or more |iai'ill.e -et within the overlapping edge of the ri^'ht; hin^o simple. Surface fre- .|iiently horny in api>earan<-e. -.inooth in n • -. ^'lanulose or niinub'ly puoctate in other-; .1 >mall ttiKerele or "eye-8lK>t" is generally pre.-i-nt on the antero-ilor-al fourth, aii'l a larjze. ronmled -nlicentrally situated -miken iiin^e|e-«pot i- seen on the inner side of the valve> ami not iiifr«'c|uently «li-tin^ni>lial»le on the exterior also. T\pe; L. lirittnnnii-'i Konanlt. An excellent account of tin- ^enn- i> ^iven \>\ I'r. 1 i . Si-hmiilt (lor. <-H.) in his t\\.i paper- on the " IIu->icli»-n Siliiriehen I.eper-lit ien." Aeeor-lin^ to I liat author ami to IJoemer. /.. .//-alily the lar-e>t known ostracode. In most of the -lie length \ai> •> mm. ami •_'•'• mm., while inse\ other um|iie.>tional»ly . ric form- the maximum length i- le— than I mm. a niimi>er of minute forms are referred here l.y I'r-.f. JOB68, my-elf others, of which it is at least doiil.tfnl that they really belong to the genu- I'.. -cause of their -mall -i/e and chietly perhaps l.ecanse of the imperfection of t IP the ventral overlap of the right valve has not I.een estal.li-hed for them. Nor has the "eye-tubercle" and other pecnliarititt of the typical -|..-i-ie- .n them. For some at any rate .I/ would otl'er a more natural reception. Finally, a number of comparatively .-mall -p.-.-ie- il -\ n--n. to :!.0 mm I which I have here- 634 THK I'AI.KoNToLOCY OK MINNESOTA. [Lcpl'l'lllliil filljllllles tofore belli as belonging to the genus, are now referred to a new genus on the ground that the free edges of their valves are different and the left instead of the right the larger. Probably seventy-five good species of the genus are known, the greater number of which and all the larger forms, are restricted to the Lower and Upper Silurian deposits. The earliest forms occur in the Taconic, but it is not till we come to the Trenton that the species become numerous.* The Utica slate and Hudson River group species are nearly all small and of doubtful affinities. The same is true of the Devonian and Carboniferous forms, but in no wise of those which are inclosed in Upper Silurian strata, since in this age the genus seems to have attained its greatest development both in the way of size and species. LEPERDITIA FABULITES Conrad. PLATE XLIIL KK;s. 10-14 OytherinafabuKtesOoKR/iD, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 332. Leperditia fabulites JONES, 1856, Ann. Mag. Nat. Hist., 2d ser., vol. xvii, p. 81); also 1881, iilem, .">th scr. , vol. viii, p. 342; also 1891, Contri. Can. Micro-Pal., pt. '.'>. p :•*: WHIT- FIELD, 1883, Rep. Geol. Sur. Wis., vol. i, p. 160; ULHKJII, 1MK), Jour. Cin. Soc. Nat. Hist., vol. xiii, p. 173. Leperdilia cunudensis, var. josephiana JONES. 1858, Ann. Mag. Nat. Hist., ser. 3, vol. i, p. 341; also 1858, Geol. Sur. Can., Dec. 3, p. 94. Leperditia fubulites var. josephiana JONES, 1881, Ann. Mag. Nat. Hist., ser. 3, vol. viii, p :(44. Leperditio. josephiana JOKES, 1881, Ann. Mag. Nat. Hist., ser. 5, vol. xiv, p. 341. SI/.K. — 1. Hcluit, Wis., t(E. C.) Length, 12.4 mm.: bight, 7.!> mm.: thickness :,.() mm. 2. Minneapolis (L. V.) 14.0 " " 8.4 " 3.0 3. (R. V., 11.7 " " 7.5 " 8.0 4. (E. C.) " ll.f> " " 7.4 " 50 5. Dixon, 111. (E. C.) ll!.2 " " 7.5 " 5.5 6. Lavergne,Tenn.(L. V.) 13.8 8.3 " 8.1 7. Lebanon, Tenn. (E. C.) 10.0 6.5 " 4.7 8. (E. C.) 7.5 4.7 " 3.2 9. (K. C.) B.2 5.2 " 3.8 10. (B.C.) ' 7.0 4.7 " 3.3 11. (E.G.) S 1) 5.0 " t 'arapace of medium size, obliquely subovate. comparatively long, widest poste- riorly; ventral curves moderate, strongest just behind the midlength; cardinal line straight, comparing with the length of the valve as 2 is to 3, the two extremities almost equally angular; bight of ends about as 3 is to 4, both obliqely truncate above, the anterior narrowly rounded in the middle; the posterior outline more broadly and evenly curved though having the usual backward swing. Ventral edge of carapace otitiisc, scarcely flattened, with a slight furrow on each side near the edge of the • Consider! ML' tl.:it the ei|iilv;ilent sir:it:i ,,f Kentiieky. Tennessee anil <':in:ul;i. eon lulus no less th;in el<>\ -en -].rri,>< ,,f .1 i kulilr thiil i inly iinc utiiloiibt.'cl speeies of I lie nemis li;is so far IIITTI ill~.-. ivi rnl in t h. Tn'iil.m .,f -ti -it, i of tin- in irlhwi—l ITI, st:iI.->. + In i,'i\ ini lln- -i/i- "f -pi-rlmi'iK. lln-ir rnnilitliin is iniliiMilcil by II" ;iljhn^ ml inns K. O., K V.. unil I, V.. >lKiiiryln^, tlM'ly. < nl ire ra I'll pure, rk'til vulve. :iinl Icfl vulve. Wliei'U tlil'se inlli:ils arr not used, i I is lo lie unilersl I lli;il I lie r.hullUM.) right \.iht- in which a rm\ ..(' minute punct.i- i- gnu-rail y distinguishable; overlap 'I around (In- ' ..-iitr.ill;. ' in ran neither valve ha- a flange or flattened l.order. and when pre-ent it i- in all ca-e- narrow and undefined; ilo: •" -omewhat t hickened. e-p.-cially ni""1 the left -i.l.-. Surface of valve- smooth or .lintly pitted, rather evenly rouvex witli th. -t thickne— -mien hat beneath the center, a low ridge-like tlucken- in- along the po-terinr half <>f tin- d'.r-al margin of the left \.ilve i- to lie noticed. 6 ju-t di-tiiigai-hal>le in m< rely *o di-tinct a- in (lie specimen tijjun'.l, ofton not to be detected. <>n the inner Airfare however it is always marked distim-t pit. Mu-i-le -pot not di.-t in^ni-halile externally except when the specimens are \v I. Imt on the inner -ide it i- often well marked and -urrounded l.y line reticulating radial line-, short dorsally. longest p Tally. On the inner side of theventr oftheri^ht valve there are two row- of small papilla'. three to five in each, the numl»er seeming to increase with atfe. The purpose of these papilla1, one series of which occurs in the anterior third, the other in the pos- terior, evident 1. . preuMit. undue overlapping of the valves l>y presenting an ol«-tacle to the entering vend of the left valve. of tlii- I have l.efort- me i hundred -pecimens, represent- ing twelve localities in the states of Minnesota. \Vi-con-in. Illinois. Kentucky and Tennessee. Considering its wide geographical range and abundance, it is reraarka- l.ly con-taut in all it- character-. T'n.n i( :- so in its outer form is clearly enough >hown liy theali.ixe moasurement>i. taken from representative examples. They show further that the northwestern specimens are on an average about one-third larger than those from Tennessee. In all other respects however they are all practically identical. In 1- (•//.) I Relieved it prol.al.le that /. •-.•/, hi. my Prof, .lone- t hei • '>f minor ilitl.-rence- lietween them, and these will no douht he ad'led to when the later form i- fully known. An. closely related form is the /,. uilm imiidt. from the I'pper Silurian of Hi; It- hinge line is shorter and the antero ventral curve somewhat fuller, hut in other respects, even to the rows of punctae along the ventral margin, the tuo specie- much alike. /.. //mi,/// I' 1 rich from the I'ppcr Trent.m of Kentucky i- more ol.li.|iiely produced posteriorly and ha> a -horter hinge line, a tl.r :itral edge, di-tinct tlanges. and Letter developed tul- 636 'J PALEONTOLOGY OF MINNESOTA. [Leperditella. Pur mat ion and locality.— Lower Trenton or Birdscye limestone, Minneapolis, St. Paul and Cannon Falls. Minnesota; Mineral Point, Janesville and Beloit, Wisconsin; Rockton and Dixon, Illinois; High Bridge and Frankfort, Kentucky: Lebanon, La vergne and Murfreesboro, Tennessee; also St. Joseph Island, Lake Huron, and Murray Bay, Canada. It is said to occur in a similar position also in New York. Genus LEPERDITELLA, u. gen. Leperdilia (part.) Uuucii, 1892, Amer. Geol., vol. x, pp. 263 268. Carapace leperditoid, ovate or oblong, with a straight back; surface of valves without eye tubercle or distinguishable muscle spot, but a more or less obscure broad depression is generally present in the central part of the dorsal half; left valve a little larger than the other, the free edges of the latter fitting into a groove. Length 1 to 3 mm. Type: Leperditia inflata Ulrich (not L, inflata Murchison sp.). Fig. 46. a, small left valve of Leperditella, inflata Ulrich; l>, inner side of a larger valve of same, show- ing the marginal groove: c, vertical section in outline of entire carapace of same: d, dorsal outline of left valve of same: e and/, external and internal views of a left valve of Leperditella, mundula Ulrich: ij and h, outlines in anterior and ventral views of same; t, right side ol an entire carapace of LepcrdilcUn asqwla- I Iricli:./', right valve of Leperditella sulcnta Ulrich; k, left valve of L. aulcuta var. ventricornis Ulrich. All the figures are magnified 10 diameters, and all the specimens from either the upper or the lower beds of the Birdseye limestone at High Bridge, Kentucky. Tliis genus is separated from typical Silurian Leperdttia because the left instead of the right valve overlaps the other, and instead of a simple overlap the ventral edge of the right valve fits into a groove in the left. Furthermore, the eye tubercle and muscle spot of Leperdttia are not distinguishable externally in Leperditella. In certain Carboniferous species of Leperditia (L. carbonaria Hall, L. nicklcsi Ulrich and others) the overlap of the valves, though reversed, is very similar to that of the Lower Silurian species here brought together as Leperditella. Perhaps they also ought to be distinguished from Leperditia. Leperditella embraces L. tumidn, L. mundula, L. ceqitifatera, L. inflata, L.germana, /.. .-/, that ma\ ' ic with tin ////./ / and ls.«-liiline much like /. In,. I.. I'l.XTI M.I I -i. ,illl. . wide-t po-teriorl\. tumid, the puint of greatest thickness hut. little behind aiitr.tight, nut angular in front, and quite ohtu-e Kehiml. po-ferior margin -omeu hat obliquely ronnde-l. y truncated ab< .irthe ventral ed^eof the left valve a di>tinct channel <>r Lfi'<»'\''. deepest centrally. I -.->ted the name. Surface snumtli. Tin- . leing without thi- ,!iarit\ - Miniiiiwiia. i'i i:in iK.i.i.A rKi:-iMii.i>. n. >//. •<>-«. I nun.: hlk'Iit l.i'l nun.: thi.-kn>".s (i - mm i|>ace ovate, moderately convex, with the end- nearly e,(ual: no dor\\\ carefullv compared they prove unite distinct. The outline i- -oineuhat ditlerent being les- wide (high) •••riorly. the dor-al an^le-are rever-e-1. and thO dor-al e.lges much thicker, while the thickness of t e— and the ventral n\- hidi mark.- the left valve in that -pecie-. wanting. Similar ditlerence- distinguish it from 1.. titini'la. hold< about the -aiin- id i- ni>' litlerent in outline. Still a- it- vahe- do not overlap ventrally .n;d a- it ha- no dor-al angles and |. 638 THE PALEONTOLOGY OK MINNESOTA. CLeperdltelhi m;u'r:i. is a very distinct species, there is probably not much danger of confusion between them. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. LEPERDITELLA MACRA, n. sp. PLATE XLIII. FIGS. 7-U. SI/.E.— VE. C.) Length 1.4 mm ., night 1.08 mm.; thickness 0.55 mm. Carapace short, scarcely oblique, subovate; dorsal margin straight, four-fifths of entire length of carapace, angles distinct; ends subequal, rounding almost uniformly into the basal outline; carapace moderately convex except in the anterior third, which is strongly compressed, giving a very unusual ventral and dorsal profile; anterior edges thickened, ventral overlap strong; surface smooth. This species is remarkable for its compressed anterior part, and for its short form, in neither of which features it is equalled by any leperditoid ostracode known to me. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. LEPERDITELLA QERMANA Ulricli. PLATE XLV. FIGS. 24-26. Lepertlit in gemmim UI.KICII, !Wi2. American Geologist, vol. x, p. 2(i(>. SI/.K.— (L. V.) Length 2.17 mm.; bight 1.4 mm.: thickness 0.67 mm. Carapace subovale, ends nearly equal, the posterior somewhat the wider; back straight for about four-fifths of the entire length, dorsal angles well marked; ventral outline somewhat oblique, most prominent just behind the center; edges rather blunt, with a narrow groove or rim along the free margins of the left and perhaps of both valves. Surface with the greatest convexity in the posterior half, and a broad, undefined depression in front of the center of the dorsal slope. This form is closely related to L. mundula and L. in/lata, two species from the lower division of the Birdseye limestone in Kentucky. From the first it differs in having the ends more equal, the edges blunter, and the surface more convex in the dorsal half. The narrow marginal rim is wanting in that species, and instead of a simple dorsal depression, that form has a low elevation in the lower part of it. The second differs chiefly in the greater inflation of the posterior half of its dorsal region. lower third t he outline merge- rapidly into the uni- formly cuir. -in; aiit.'rior end uniformly curved. Surface much the highest in t i rior half, with a part prolonged dor-ally into a short and olitu-ch point.-, I proniiiKMicc that I.einU ,lo\vn dose to the hinfje line and projects somewhat ••nd it. 'I'hi- prom i • deliniti»»n to thr posterior -id.- of a distinct .-iilcn- ,mo-t half acro-v t: frmn the central part of the dorsal edge, and forward alon^ tlie latter. Though having a -ul«Mi<. and therefore agreeing in a general way with I'n'niiliu, I have cho.M'ii t' _-.• tlii- • •. ith /.•/•• i:IH,-ll,i Lecan-e it >eem- to repr. ..... it HUM-. ineiit from -ucli typical -pe_cie> of the L'enu- a- /.. inf/i, •md /. ntUata. Specitically the pr ..... nt form i- readily .'iioii^h di-tin- guislu'd l.y (he concentration of the, dor-al promii -er detinition of t he snlcu-. The form which I called /'/-//////m ///hort. rouii-i. it^ly ronv.-v. more or le-- inflated in the dor-al region, thi- part I.eing the thicke-t ami appeari -ally (in an end \ i. .oulder-like over and out from the -traight hinge line: right valve slightly larger than the left and o\ eriapping it along the ventral margin. No e\e tul-erde nor -ulcii-. l.ut a faint central pit and ••nally present I'lrich. , 640 THE PALEONTOLOGY OF MINNESOTA. i craaslmarglaata. The species which I propose to arrange under this genus might have been placed with Aparchites, Jones, were it not that they have overlapping valves. Even without that difference it may be questioned if such an arrangement would have been strictly proper, since no true Aparchites is strongly developed or gibbous in the dorsal region. As a rule Aparcliites is thickest beneath the middle of the valves. The same is true of Leperditin, a genus that will, I think, be admitted by all to be distinct from Schtni(itdla. Though still somewhat in doubt respecting the systematic position of the new genus, it seems well to place it provisionally between Leperditia and Aparchites. Besides the six Trenton species about to be described, Schmidtella will include Aparchites? obsoletus and A. oblongus of the Upper Silurian rocks of Europe. I refer to the specimens so designated and identified by Dr. Krause* with two British species described by Jones and IIoll under Primitia in 1865, and more -recently (1889) referred to Aparchites by Prof. Jones. While I am inclined to question the identity of the British and German specimens, I can scarcely doubt that the latter at least are truly referable to Schmidtella. SOHMID'TELLA CRASSIMARGINATA U/n'c//. PLATE XLI1I, FIGS. 42-44. Hchmidtella crasvimarginata, Ui.mcn, 1892, Aruer. Geol., vol. x, p. 26!). SIZE.— (R. V.) Length 1.80 mm.fhight 1.45 mm.; thickness O.GOt nun. Valves broadly suboval, very slightly oblique, the dorsal outline more gently arcuate than elsewhere, ends nearly equal though the posterior margin is more curved, especially above, than the anterior, the latter often forming an obtuse angle where it joins the dorsal line; ventral outline uniformly curved, semielliptical; back flattened, slightly convex in a side view, raising very abruptly from and projecting slightly above the nearly straight hinge-line; point of greatest thickness just behind the center of the upper half; a rather conspicuous yet not sharply defined broad furrow around the ends and ventral margin, least distinct posteriorly, produces the thick border that has suggested the specific name. Specimens vary in length from 1.6 mm. to 2.0 mm. The border is more distinct and wider, and the back more flattened than in any of the other species referred to the genus. h':.r,nnti<>n tiii'l lorulili/. -Lower Trenton limestone, Mineral Point, Wisconsin, arid Mixon, Illinois. It- ormriviii-i' In Miis lim.'-ton.'at Minneapolis is not, yet established with certainty. h.'iM.1H>l. |>.492. + Tln- iliinfiislon- L'Ki-n ill tin- iiriL'ln:il cli'srri|it Ion all' loo sinnll. tin- ni:iL'iiili.-:il inn of tin- valvi- nica-iiriMl liiivin'-' IIITII ~ii|i|»>~i.il in !»• i « I, i.n ii «;,. ,,,,|y :i I ii 111 1 Mill hi meters. 641 /-. I'l Ml XI HI 1 Hi- l iiiui.: hltfht n 7J n. Q '11111. Tlif largest valve x-t-n has ;i length uf l.l is 111111. ami a hight of M.'.l mm. This s|., related t.. - //./. ainl at lir-t I was incline. I to -. later \ariety of that >|.i-cic-.. Itnt, considering tin- L'reat constancy which prevails ainmiu' the hundreds uf valves uf > innfn which I have . ami the equal constancy e\hil>ited liy >'. nriini-*, it h.< Miuuglit ln'-t tu hold them a- ili>tinct. I: i fuiin.l it iinl>•;•; equal, with the |>o-U>rior extremity more -tron^ly OH ami the l>a>al outline more proiniixMit in the middle. In an end view the profile is triangular ami the ventral ed^e thinner. The most proininent point of the surface al-o i- ni" riur. while the limad liorder. which is SO con-|>icin> ire for >>h ,le\elu|,ed. For cumi'ari--on with >'. nni- luil 'llji'il. MM' flllll>\\ i lofiilHy.- -*i.i -i, near Cat, n sola. MIDTKI.I.A I MBONATA, ». >/'. I'l.N I K XI \ f II.- ... .- I. V.) LdiKtli »> nun : Inn ili-km-ss o £1 mm. 0.65 " " 0.23 " Valve- ovate, slightly oblique, c-mls sulieqiial. dorsuni unilionato. projecting con.-ideralily aliove the straight hin^e line: free margin with a border, narrower ami less distinct on the le; than on the ri^ht; greatest convexity near the middle of tl .'d, the point occasionally marked hy a very faint depre^jMn Or disc.. |K)t. This almmlant spo« than N. has more nearly equal ends, narrower and hetter defined t>order. and more uniformly coim ••• join the much larger S. ./«'//•/ it dillers too ohvionsly to rpquire '•uniparison. 'innln may i 1 l>ut i< much shorter and almost round. Formation and locality. -l'|-i»T lhir.1 uf ti ky. 41- 642 THE PALEONTOLOGY OF MINNESOTA. LSchmldtella incompta. SCHMIDTELLA INCOMPTA, tl. Sp. PLATE XLIII. FIGS. 30-41. PLATE XLV, FIGS. 27, 32 and 33. S\7.K. — (R. V.) Length 1.1 mm.; bight 0.8 mm.; thickness 0.28 mm. " " 0.9 " " 0.85 " " 0.18 " var. sutow/wah's. Valves moderately convex, dorsal margin straight, about half as long as the valve; ends nearly or quite equal, ventral outline regularly curved; surface highest a little above and behind the center, the dorsal slope convex but not projecting beyond the hinge line, the ventral slope long, gentle and straight or faintly concave, the wide border being almost obsolete. Of this species we have two varieties, one occurring in the lower part of the Trenton shales, the other in the upper part of the Galena shales. The earlier or typical form (plate XLV, figs. 27, 32 and 33), is a trifle more convex and blunter at the dorsal edge, slightly shorter and less equilateral than the other. That the Galena variety constantly developed these minute peculiarities is shown by about fifty valves. Should a subordinate name be desirable, it might be called var. subatqualis. The dorsum is less tumid in this species than in any of the preceding. On the whole it may be considered as marking an approach toward Aparchites. Still, the prominence of the surface in the post-dorsal third, though not strong, indicates a relation to S. affinis. A species occurs in the Birdseye at High Bridge, Kentucky, that seems to be intermediate between this species and S. umbonata. Formation and locality.— Typical form, lower part of the Trenton shales, Fountain, Minnesota; var. mtini-tnlis, upper part of the Galena shales near Cannon Falls, Minnesota. SCHMIDTELLA BREVIS, n. sp. PLATE XLV, FIGS. 34 and X>. SIZE.— (L. V.) Length 0.8 mm.; hight 0.65 mm.; thickness 0.2 mm. Valves short, subovate, the oval being formed by drawing out the anterior end; dorsum short, gently arcuate, and projecting slightly above the straight hinge line; border inconspicuous. In most respects this species is much like its associate, S. incompta, but the valves are much shorter, the dorsal outline is not straight, and the anterior margin is more narrowly rounded. Polycope sublenticularis Jones, from the Anticosti group, has a similar outline, but seems to be uniformly convex which is not the case with the species under consideration. forma/ion ami locality.— Rare in the Inw.-r part, of the Trunton shales near Fountain, Minnesota. i.\ -i n I'l. Ml \l V II..S. linn ; l.ik'lit O.i:i HUM • i. • *iii-ss 0.3 IIIIM. Valves small. short. rounded-ovate, rather uniformly convex. \\itli an obscurely defined, narrow border around the end- and ventral margin; near the center a faint depre--ion. and immediately lifhind it .1 -mall elevation. The generic position (,f thi- -mall i- uncertain. It is placed under •nidfrllti chiefly liecau-e it -eem- to be related to 5. untl>i .' *ulirntnn<{f the ' 'f,i has neither a central pit nor a (.order, I am for the pre-sent obliged to regard them a- distinct. mintion in,'! thlnl of thi-Tri-ntnti - nneapolls, Minnesota. ii- AI'AlirillTKS. Jones. 'NBs, 1W9. Ann. and Ma«. Nat. II -• . » • ••. • ,•;. p. 386. apace subovate, ol>loi >mewhat rounded, with a straight hinge of variable length: valves >ulipqiial; ed^e> tliickened, never overlapping, often beveled ore: in other cases simple, and rarely with a narrow tlattened border. Sin more or less convex, usually smooth, without sulcus tnKereles or lobes. Type: .1. ,/ l,-i,.irfsii Joii' Tiie al>ove definition embraces a number of species that had formerly been ,nder ]'r»inlitt. l.-m-lu'lina and Isjtenliliti. I'mm the first they are distin- guished 1-y the absence of a -ulcu-, from the second by the absence of the eye-tubercle and certain -hallow depressions behind it, and from the third by the nee of the eye-tubercle and the equality of their valves, there being no ventral overlap. From L,^,rU>i they are separated by their equal valves, the left apping the right in that new genus. Finally, the new genus I'rimilirllti includes some very similar carapaces, but these may be distinguished, in most cases very easily, by a broad though quite undefined depression or sulcus in the rentro-dorsal region. The species of Ajmrrli all -mall, the average length being between I.n mm. and \J> mm., while the largest known does not e.\ (| mm. The total number of those known, including several undescrihed species from <>hjo. probably exceeds twenty. These are distributed almo-t equally between the Lower and Upper Silurian n.ck-. though in America they are known chiefly from the Trenton and Cincinnati formati' THE PALEONTOLOGY OF MINNESOTA. [Aparoliitcs ellipticus. APAKCHITES ELLIPTICUS, n. sp. PLATE XLIII, FIGS. 15-17. SI/.K.— (E. C.) Length 1.97 mm.; hight 1.35 mm.; thickness u.'.)f> mm. In the largest specimen the length is 2.5 mm. Carapace rather large for the genus, almost regularly elliptical in outline, the dorsal margin of the left valve more arcuate and projecting above that of the right; edges beveled all around but in the lower part the bevel is turned into a groove by the thickening of the contact edges; surface of valves smooth and rather uniformly convex. This form, though the hinge is shorter than usual, must still be considered as a typical species of the genus. The general expression of the carapace is much as in the associated Leperditella persimilis, but it is somewhat longer, has no dorsal angle, and its valves do not overlap. I know of no American species of Aparchites with which it need be compared, the elliptical outline being distinctive, but there are several in the Upper Silurian deposits of Europe that are not far removed. Particu- larly is this true of the A. simplex, from Gothland, described by Prof. Jones in the Ann. and Mag. Nat. Hist., ser. 6, vol. iv, p. 272. That species, however, is smaller (0.9 mm. in length), relatively shorter, and apparently without bevelled edges. Some of the varieties referred to A. (Primitid) muccoyii Jones and Holl, are very near, if not identical. But I am not willing to admit the latter without a direct comparison of specimens. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. An imper- fect left valve from the Galena shales near Cannon Falls, may belong to this species, but it appears to have been relatively longer and somewhat narrower anteriorly. APARCHITES GRANILABIATUS Ulrich. PLATE XLV. KIGS. lil-23. I. <• I if nl it in grnniluliiata ULKicii, 1802. American Geologist, vol. x, p. 267. SI/.K.— (L. V.) Length 2.1 nun.; hight 1.5 mm.; thickness 0.0 mm. Valves liigh, very little oblique, ventricose in the lower half, somewhat flattened in the upper; outline almost semicircular in the lower two-thirds, the ventral curve being unusually convex; dorsal margin straight, about three-fourths as long as the valve, with angular extremities; border scarcely defined, set with small but promi- nent papilla-; free s Ixivv.lltnl strongly inward. Surface covered with minute, regularly arrangm! granules; mur the center a small raised spot.* Recent comparisons have, demonstrated the necessity of excluding species of this typi-i-t/it! Ini-mn-.'ll} lii^'h than the '•iinil'ilnntiia. the ventral margin I" The anterior end al-o isatritle narrower, and the convexity of (lie valves somewhat less, while none of them -how anv thing of the grannlose surface ornament nor of the marginal papilla'. These -pecnnens may provisionally lie known a- \ar. .NK..I.KI-TI -. The straight l.aek and dorsal an-le- will at once distinguish l.otli the >pecie> and variety from .1. fll'ipti. ' i nneaotA. Var." ntglecttu ir^ In th.' IIIW.T thin! «f tin; slialcs ;ii Mmn.-;i|. AI-.M;. HI: K- Mii.i.KiTM-rvTrs I'frirli. ri.ATK .r«. Ift-W. ••lilin mi! I UlWtOE X, p. 268. <•• '!: \ nun: liitflit 1.0 linn.: Uii.-kn.',M.J-J iniii. Valve> MiMliptical. .lor.-al margin lon^. -trai^ht; ends rounded from the dorsil e<. equal: ventral edges bevelled inw >\nt of greatest convexity a little behind and l-eneath the ini'ldle: surface very finely punctate. This -p, .,•;,.> j. smaller than .1. n shales, near FounUn / 'I rich. I'l.^ U. i ftmhrinln I'I.KI. n ]s;.j. .\II.-T i i: \ i L<'ntfth l.ss mm.: hikrlit l.i'l mm.; thii-ku.>s(i.4» IIIIH. Valves siiUval. moderately and almost uniformly convex; Lack strai-ht. nearly rhirds as long as the valve: dorsal -li.irp. a -liL'ht swelling of the M,, immediately l.eneath them caiisiu- them t. inewhat ].rominei/ 'y equally rounded, the posterior a litt !•• the u i.ler. The entire ventral t... and the end-, excepting the upper third on each -\<\<\ with a frin,.' 3 of long, almost p.iliform. processes, separated l.y intervals of n.l mm. or less. 040 THE PALEONTOLOGY OF MINNESOTA. lAparchites arrectus. The peculiar fringe distinguishes this species from all the Lower Silurian Ostra- coda know to me. Formation and locality.— Hudson River group, near Spring Valley, Minnesota. APARCHITES ARRECTUS, n. sp. PLATE XLIII, FIGS. 35 and 36. SIZE.— (R. V.) Length 0.81 mm,; bight 0.53 mm.; thickness 0.11 mm. Valves compressed-convex, scarcely if at all oblique, semiovate, the ends almost vertical in the upper half, the dorsal edge straight and very long; greatest convexity in the lower part of the valves, a large portion of the central part of the surface appearing flattened; free margins minutely toothed; bevel very narrow. The dentate margin reminds of A. granilabiatus, but as the present form is much smaller and not nearly so convex, and as it has a longer hinge line and is much more elongated, it is quite evident that we are dealing with a distinct species. Its smaller size, erect ends and dentate margins distinguish it from A. millepunctatus. Formation and locality.— Upper third of the Trenton shales, St. Paul, Minnesota. APARCHITES CHATFIELDENSIS, n. sp. PLATE XLIII. FIGS. 37 and 38. SI/.E.— (L. V.) Length 0.76 mm.; bight 0.46 mm.; thickness 0.12 mm. Valves compressed-convex, somewhat elongate leperditoid in outline, being widest posteriorly; hinge line long, straight, dorsal angles rounded; posterior outline peculiar in swinging forward more than backward; ventral edge narrowly beveled inward; surface not well preserved but retaining some evidence of having been obscurely pitted. The posterior outline is different and the thickness of the carapace less than in any other of the elongate species of the genus so far described. Formation and locality.— Middle third of the Trenton shales, Chatfleld, Minnesota. APARCHITES MINUTISSIMITS Hall, var. TRENTONENSIS, n. var. PLATE XLIII, FIGS. 18—20. teperditia (Isochilina) mi nutissimu HALT,, 1871, Desc. N. Sp. Koss. Hud. Riv. Gr., p. 7; also 1872, 24th Rep. N. Y. St. Mus. Nat. Hist., p. 2H1, pi. 8, fig. 13; HALL and Wurr- KIKLD, 1875, Pal. Ohio. vol. ii, p. 102. Apurchites miiintixxiiiuiti Ur.iucn, 1889, Contri. Can. Micro-Pal., pt. 2, p. 49. Si/.K.-rlJ. V.) Length 0.,H.-> mm.; hight 0.54 mm.; thickness O.Hi mm. (R. V.) " 0.49 " •• o.:i:t " Two right valves of the Trenton variety of this species are figured on plate 43. The anterior part is narrower and the dorsal angles duller than in the typical Cin- OSTi; IOODA.. Prlmlilrlla.) cinnati specimen^. Tift lOrflbOO •!•<> IB MATMly M> OODTQJ • iier it i> not thrown up into a j.iiiiit n«>;ir the center. Init i- comparatively uniform in curvature. 'ifrrfllil .Jones (Contri. < 'an. Micro-Pal.. pt. iii. p. • '._': IV'I) from the <'ha/\ at l.ake Winnipeg. i» a clo-eh i. if not identical form. However, as figured liy Prof. .lone-, it appear- to he le- \ ami the outline not so prominent in tin- po-t -ventral region. .in./ i...;iiit-i. Tin- sui:ili •• ilnrii < f tin- Trenton sbaln near Kiiiintaln, ttu- l;irK'-r fnun tin- top of tl, ' nin-sota. Family I5KYKICI1III' 0101 PKIMI rir.l.!.\. n. -on. .ipa<-«' ii-ually olilon^. *«.|iiiv.ilvt"l. moderately convex; surface smooth or finely pnnctato; in tlio .lor-al slope a broad, shallow and quite undefined depression represents an undeveloped mesial siilniv Type: / -•/<•/(«. n. sp. the four new species about to be described, I propose to place in tln- genus Ijrpcrditia unintrnis I'lrich ( A purr liitrx, I'lrich, I'rimitin. .lones^ and I'rimitin trliU /Mil i .lones, from the lower part of the Cincinnati ^roup. I'/hnitin iilrirhi .(ones, I'tica slate, Canada, and prohalily the Kurnpean species, I'riniHia mutiilinii and rirhiumi .(ones and Holl. I'riinitiu minuln Kichwald (as figured by Jones) and 'Hi/nin. var. nmlii. .lone~. 1 am inclined to think that Isocliilinn ? fabacea Jones, from the Hamilton of New York, and Apnrchite* inurnutu* I'lrich also should be placed here. These species constitute a very natural group, distinguished from .!//•//•<•/; /'/-.-• liy the dorsal depression. They are separated from Primitia because they give no adequate idea of that most prolific genus. To be a 1'i-hnifin in my eyes the valves must l>e provided with a well marked sulxvntral pit or sulcus. The Carboniferous genus }',,/<, md K irk l>y, is closely simulated in all respects except the crenulated hinge by I'rimiticllu Innlmtn. Possibly thatgenus is not so far removed from I'rimHiflln as we now believe to be the case. PKIMITIH i.i. \ 001 k, ». >•//. K.-ntu<-ky >] '.''• mm.: thlrkn.--. n 24 mm. Minnesota 0.60 " " " 1:1 " •• .pare elongate, suliclliptical or >ul»i[iiatlrate. the length nearly twice the hight, convex; donwil margin long, .-traight. with both extremities angular, or with the anterior one obtuse or rounded; ventral margin nearly parallel with the do: 648 THE PALEONTOLOGY OF MINNESOTA. Ll'rimltiella limbata. gently convex, or almost straight in the middle; posterior margin somewhat oblique, and subtruncate above; anterior outline always more curved than the posterior; free edges with a narrow border; surface with abroad, centro-dorsal depression. The earliest known occurrence of this species is in the lower part of the Birds- eye limestone of Kentucky. These specimens differ slightly from the later form in having the border much narrower, the ventral margin straighter and quite parallel with the dorsal, and the anterior outline more rounded. The valves seem also to be a little more convex. I'riiiiitiella elongata, var. nudu Jones,* is similar but has straighter ends and sharper dorsal angles. Formation and locality.— Lower and upper Birclseye limestone. High Bridge, Kentucky, and Leba- non and Lavcrgne, Tennessee; lower third of the Trenton shales, Minneapolis, St. Paul, and Goodhue county, Minnesota. PRIMITIELLA LIMBATA, n. sp. PLATE XL1II. FIGS. 63-56. SI/K. — (E. C.) Length 0.73 mm.; bight 0.38 mm.; thickness 0.20 mm. The outline is almost as in P. constricta, only the ends are less rounded, the posterior one especially being nearly vertical, while the dorsal angles are sharper. The most important difference however lies in the fact that the border continues not only around the free edges but along the dorsal margin as well. The thickness of the carapace is somewhat less, and the surface rises more abruptly from the posterior border. Finally, the mesial depression is more obscure, and often scarcely distinguishable. Formation and locality.— Lower third of the Trenton sliales, Minneapolis, Minnesota. PKIMITIELLA SIMIILANS, n. sp. PLATE XLIII, FIGS. 26-28. SIX.E.— Length 0.73 mm.; bight 0.44 mm.; thickness 0.28 mm. Valves rather strongly convex, leperditoid in outline, with the dorsal angles rounded; edges without border; a very faint, broad depression near the middle of the dorsal slope, and occasionally an obscure elevation at its base. In the outline this species is very nearly like P. minuta Eichwald and Aparchites xul,(,r ri'iitni-iliir-al region; edges simple, or with un obscurely defined. narrow border. Though reMMiihling se\> of I'riinitin. fmin which it i- distinguished l.y the wiiltli ami -hallowne-s of the me-ial dcprc— ion. I cannot lind any de-cril>ed OStracode with which it is strictly identical. •.••niiiiii'iii in th>- IIIWIT |>.»rt of tlii- Trcntiiii -li.ili-- ii'-;ir I oinilalo, I'KIMITIKI.I.V 01 I'lrirli. IM.\TI CUB i M lit I 'i.un n. l'7 ii, p. in. pi. vii, UK'. 4. • •n. Is*!'. C'liilri. ' 50. ;rl. Jniir ' rfhtO.59 nun : ihirknr^ o 4 nun. .ipace convex, scarcely oblitjue. oKloni.'. with a long, straight hinge, ami rather wpll-inurkeil 'lor-al angles; ventral margin gently arcuate, nearly parallel with the hack, the anterior In^ht of the valves being but little less than the poste- rior: po-tfi-ior !ii.n_'iii i • iii'lr 1 from the dorsal angle: anterior margin obliijurly triiiicateil in the upper half, sharply n»uii«le joint and follows the outline to the post-dorsal angle; tin- jio-terior extremity of each valve, ii-nally -n: l>eneath the miil-liight, a -tron^r -pine projects outwardly or p.^t.-riorly: in a dor-al or ventral protilc- the end.- are blunt and the side- of i.\\< straight or just appre.-ialily concave: in front of the mi-Idle of the dor-al .-lope there is a wide and ver\ faint depression, and in the lower jiart of tlii- a invariably distinguishable. Speci- mens are usually about 1.0 nun. in length. A small variety occur- at Cincinnati. <»hio. avera^'in^ between 0."> and i».r, mm. in length. All the American -pecimen- of ti .-xceptin^ I lie val\. I \>y me from M.iuitolia i >i}i. rif.) are remarkably con-taut in all their c ha racters. Indeed, out of over tifty free caraj)aces and valve-. I was unable to find one that ditl'ered enough from tis_r. ~tl to make it worth the while to prejiare drawing- of it. I1. :hi- con-tancy in mind it is ratlier surjiri-in^ to learu that ProfLJones fooad Considerable varialiility among the Brit; MICH- n-fcrred by him to the- 650 THE PALEONTOLOGY OF MINNESOTA. [Prlmitia. his drawings (op. cit., pi. iv, figs. 8 — 13), with the figure here given on plate XLIII, it would appear that none of his specimens are strictly identical with the typical form of the species. They are all too narrow anteriorly, and three of the figured ones too long. The other three figures (8, 9 and 10) correspond fairly well with that of the Manitoba specimen already referred to, though the posterior spine in the last is stronger. Possibly some of the variability of the Bala specimens is due to crush, or perhaps their margins were covered by the shale. There remains to be added that in all these foreign specimens the border, as well as the slight elevation in the dorsal depression, seems to be wanting. Under the circumstances it would probably be advisable to separate them, if not specifically, at any rate as a variety, from the typical form of the species. Formation and locality.— Doubtfully identified from a cast of the interior found in a thin bed of shale belonging near the base of the Hudson River group, three miles north of Spring Valley, Minnesota. The typical form occurs abundantly in the lower or Utica horizon of the Cincinnati group at a number of localities in the vicinity of Cincinnati, Ohio. The Manitoba variety is from beds equivalent to the upper divisions of the Cincinnati group at Stony Mountain, while the .British specimens described by Prof. Jones art- from Bala shales, near Welshpool, Montgomeryshire. Genus PRIMITIA, Jones and Holl. Primitia (part.) JONES and HOLL, 1865. Ann. and Mag. Nat. Hist., ser. 3, vol. xvi, p. 415. Carapace small, varying in outline, usually subovate, but the hinge is always straight; valves equal, never overlapping, generally provided with a narrow border; in, or to one or the other side of, the middle of the dorsal half, a well-marked pit or sulcus; the pit may be rounded and situated subcentrally, or it may be drawn out vertically so as to extend from the dorsal margin half across the valve; on one or both sides of the sulcus the surface may be raised into a low, rounded or ridge-shaped prominence. Surface of valves punctate, reticulate, or without ornament; in rare cases it seems to have been minutely granulose. As typical species I will mention P. mundula Jones, P. renulina Jones and Holl, P. variolata J. and H., and P. humilis J. and II., Upper Silurian; P. impressa Ulricb, P. sancti pauli UL, and P. mammata Ulr., Lower Silurian, the last two described in this work. Prior to 1865, species of Primitia were referred to Beyrichia. For more than twenty years after that date, besides the type of structure to which the genus is now restricted, Primitiit included (1) "non-sulcate" forms for which Jones in 1889, pro- posed the genus . I/M/V////V.S; (2) so-called "passage forms" that I now propose to separate as I'rh/ii/iella; (3) forms having the sides of the sulcus elevated into two strong tubercles, for which the genus Ulrichia has been established by Prof. Jones; and finally (4) some that may belong to Eurychilina, Ulrich, because they have the DA. :m«.) broad frill which p greatly beyond the free emit ,•> ()f the- vahe.- m it's of that ^enu-. A- usual. the original conception <>f /ViHiiV/-/ was altoget too broad. ami as. through the iv-tle-< ellorts of collector-, the species began to multiply, it became clear that they fell naturally into several group-, whose import- ance in. \\ith time ami study till then 'ion became, at first desirable. then nece.— ary. Still. 1'i-iiiiitiii retains a l.iru'e number of species, the greater part <>f which are v equally divided l>etween the Lower ami I'pper Silurian ro.-k- Two or three rather ilonhtfiil have been describe.! from primordial strata, hut at least five I'evonian -p.-.-ie< ha\e been discovered and a- many more in the I^>wer ' bon; i fter which the genusseems to have become extinct. With a few except ion- all the-e -pecies were described in papei .lies, Jones and Holl, Krause, and Dlrieh. I'UIMITIA MI.SM TI-siMA, tt. >•/). 11. : linn : hik'ht 0.1U nun. •TJ- small, rather elongate-elliptical in outline, without distinct dorsal angles, the end- rounded and nearly equal, the anterior slightly narrower than the other; valves rather strongly convex; sulcus narrow, sharply defined, extending nearly half across the valve; surface smooth. This i> the smalle-t I'riinltin known to me. It is evidently related to the British \Venloch -pecies. I', hutnilis Jones and Holl, but is smaller, relatively more convex, with the ends more rounded, and the sulcus narrower. It is not very closely related to any of the known American -pecies. awt locality.— Lower part »f th" T .main, ami at Oxf •mi- mine PKIMITIA i MIAMI, n. ,tp. I'l.MK M.lil. 1 Hi. M. I nun.: liitfht 0. H7 nun.: thi.'knev- 0. 1", mm. Valves small, compressed-convex, slightly obli(|iie. -ubovate, without di-tinct dorsal angles; posterior end wider and more broadly rounded than the anterior; ventral margin convex; edges thin, without border: ut in the middle (if the dorsal slope; surface marked by small punet.i . arranged in curved lines radiating from the sulcus; in certain lights each rov irs a- occupying the bottom of a narrow groove. 652 T1IK PALEONTOLOGY OF MINNESOTA. [PriiiiHia m:imm:itit. Though smaller and proportionally higher behind, this neat Primitia seems to be more closely related to P. variolata Jones and Holl, from the Wenloch of England, than to any American species. Still there is a regularity about the arrangement of the punctie that is wanting in that species. In P. trigonalis, of the same authors and formation, the ornamentation is similar, but in other respects the species are quite different Named for Mr. Warren Upbam, of the Geological Survey of Minnesota, whose published work has aided materially in advancing our knowledge of American geology. Formation and locality.— Galena shales near Cannon Falls, Minnesota. PHIMITIA MAMMATA, n. sp. PLATE XMII. FIGS. 78-81. SIZE. — Length 0.51 mm.; night 0.30 mm ; thickness 0.18 mm. Valves suboblong, the marginal portions somewhat depressed, while the central parts are slightly swollen beneath and on each side of the sulcus, the latter narrow- ing dorsally; back straight, dorsal angles rounded; posterior margin strongly rounded in the middle, ventral margin gently convex, subparallel with the hinge line; ante- rior outline most prominent in the upper part, the whole sweeping slightly backward; edges simple, surface without ornament. The slight prominence of the surface about the sulcus gives this carapace an appearance that is not shared by any of the more simple forms of the genus. We are somewhat reminded of P. tumidulu and P. duplicate, — indeed, I at first confounded it with the latter. The first is much more convex, shorter and larger, while perfect valves of the second will be distinguished at once by their double borders. P. cen- tralis Ulrich, of the Utica horizon of the Cincinnati group, is similar in shape, but has a simply convex surface and the sulcus confined to a subcentral pit. Formation and locality.— Lower third of the Trenton shales, Minneapolis, Minnesota. PHIMITIA SANCTI PAULI, n. sp. I'1,ATK XMII. FK;s. ::; :m. deepest in iN loner ji.irt. nai rou HIL' aho\e l>\ tin >|nnont of a low swelling on each side, tliiit i- proliaMy more c|o-ely related to /'. nTilleri I'lnch. from the upper I.eds of the ('inciiiiiati ^roup. tlian to any other known. The si/.e of /'. millrri U somewhat jjreab'r. its length liein^ usually a little more than l.d mm. Hut tin- real ilinVrei. A'een the two form- an- (1) the prnport ioually greater length of the \al\e- aii'l of the liin^e in the Minnesota -|.eei. t* longer ami otherwise ilillerent ->ulcu>. ami i -es«iou of a romi'leu. anter- ly situated tulierele. whieh i- wanting in the ar Canrmn I MlnnoHoUu I'KIMITIA MKI p. .;s. m-n. l.'-iikMli ii '!•' inn, ' i'. nun .: Ihii-kneMa 0.23 nun. Thi- Aperies, though inui-h smaller, seems to be relate.! to /' /muti. It i- however relatively shorter, with a longer hinye line and stronger dorsal angles. The valve is strongly convex, especially in the posterior half, ami the prominences on each -i'le of the curved suleus are «leeidedly higher than in the larger spe' n. that >j.eeies lias a rounded tulierele in front which is wanting in /'. mirtt/n. Filially, the surface i- only ol»curely punctate and not reticulate. It is perhaps more d. I to /'. /itni! much smaller -i/e. it is at once distinguished hy the absence of the narrow curve.! rid^e. running a short di-tance within the ventral margin in that ilooa shales near ( \IinnefloU; a«oclat«d with /'. uphami, llythoryfirii rylin with the hack |i . the dor-al angles di.-tinct though not sharp, the onds ahoiit e.|ually curved though the anterior i> somewhat narrower than the posterior: ventral and anterior margins t. following a -emielliptic curve: free edges grooved, the true contact m.nu'in- >"\ \>\ a 654 THE PALEONTOLOGY OF MINNESOTA. [Primitia duplicate. projecting rim which however is not distinguishable in a side view from the regular slope of the surface except in front; sulcus sharply defined, simple, subcentral, extending less than one-third of the distance across the valve; surface minutely punctate. The widely grooved edges distinguish this species from several otherwise similar forms occurring in the* Upper Silurian of Europe. The projecting rim, which should not be mistaken for an ordinary border, is to be regarded as an undeveloped " frill " and precisely the same as the false border of Ctenobolbina ciliata and Ceratopsis chambersi. It is developed to a greater degree in the next species, but in P. tumidula it appears to have been in a large measure reabsorbed again. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. PRIMITIA DUPLICATA, n. sp. PLATE XLIII. FIGS. 60 and 61. SIZE.— Length 0.70 mm.; bight 0.45 mm.; thickaess 0.35 mm. Valves rounded oblong-quadrate, with a long, straight back, rounded dorsal angles, and a distinctly elevated false border. This border projects slightly beyond and completely hides, in a side view, the anterior and ventral contact margins of the valve. Posteriorly however the true edge protrudes, the border here projecting outwardly much more than backward. Within the border the surface is moderately convex, the sulcus not deep yet distinct, and faintly traceable for about two-fifths the bight of the valve. In front of the lower part of the sulcus a small swelling is faintly indicated, while behind its upper two-thirds there is another but much larger low elevation. Surface without ornamentation so far as known. This interesting species agrees with P. celata in having a false border, but as it is more elevated, especially in its posterior part, and as the two forms are quite different in the region of the sulcus, it is not at all likely that they will ever be confused by a careful observer. I know of no form now referred to Primitia, unless it be P. tumidula, which see, that is sufficiently near P. duplicata to require comparison. Jieyrichia initialis, an associated species, looks considerably like it. It is of about the same size, and has a raised border. A critical examination of the latter however proves that it is not a false border, but the actual margin of the valve bent outward (compare figs. 61 and 83, plate XLIII). Of course the lobing of the valves, though certain similarities may be discovered, is still very different in the two forms. A comparison of their respective figures on plate XLIII will bring out the differences much better than I can define them, Formation and locality- Middle third of thu Trenton shales, Minneapolis, Minnesota. n: IGOD4 I'KIM i : i v i i M i in i \. n . ri vi t MIII i uiB. «-•. •it i) .V> uiin.: thIi-kiieM 0. W nun. Valves strongly convex. subqnadrate-. .,'ht. rather long; posterior dorsal angle strong, the anterior more obtuse or rounded; ends nearly equal in hight, but the anterior margin i- more curred than the posterior, the latter being some- what truncated above; sulcus a little in front of. or quite in the middle of the dorsal half, deep, with a strong rounded swelling on each side; the posterior prominence larger ami higher than the anterior one, but the latter usually somewhat better defined by a forward .-wing of the lower part, of the sulcus; surface beneath the sulcn- prominently convex, and sometimes 1 tearing several small tubercles; a wide ri.in-ave border, defined in the ventral part by a thin ridge, extending parallel with ami some distanre within the edge of the valves. This ridge I consider as the remnant of a false border, like the one which is so strongly developed in I'.tluplicntii. At first 1 thought this -pecie- might be the same as /'. cim-inmitirnxis Miller sp., but a more careful examination proved it distinct, though perhaps closely related. In ti higher, the ventral outline being much more curved. Next, the sulcus is relatively shorter, while the border is not narrow and flat. Hut the most important difference is the submarginal ridge which is distinguishable even on casts of the interior of /'. (unwluln, but of which not a sign is to be seen on Miller's specif-. In /'. >lili> tin- luwer part cif th.- Hudson I i. tlirv.- mi!.- north ••• •illey, Minnesota. I'lMMITlV i.IHHKKA. II. * ii \TE xi. 111. nus. n-m. •n: hitfht ".45 nun.: thic-kneMO.36 mm. Valves somewhat leperditoid in outline, with _'ht hinge line, the distance veen the dorsal angles about five-ninth- of the greatest length of the carapace; ends rounded; valves rather strongly convex, gibbon- in the anterior half of the dorsal region; thi- prominent part i- somewhat tlatt.'iied on the back, and inrlndi- a short and rather shallow notch or .sulcus. In the .-pecimen- at hand the -urfac.- slopes uniformly toward the edges and these seem to be simple and without a border; '656 THE PALEONTOLOGY OF MINNESOTA. [Hallielltt. but, as they are only casts of the interior, a narrow border may have existed on the exterior of the valves. The gibbous character of the anterior part of the dorsal region, and the shortness as well as lateral position of the sulcus, are the principal peculiarities of the species. In other respects it resembles P. mundula and P. simplex Jones. The affinities of this form are rather obscure. There is a suspicious resemblance • to Jonesella ? obscura (plate XLIV, figs. 17 — 19), but very little to ./. crepidiformis the type of that genus. It may also be compared with Placentula inornata Ulrich, a Cincinnati species. Formation and locality.— Associated with the preceding. Genus HALLIELLA, Ulrich. Halliella, ULRICH, 1890. Jour. Gin. Soc. Nat. Hist., vol. xiii. p. 184. Similar to Primitia, but with a thicker shell, thick and bevelled edges, and usually a larger subcentral sulcus dividing the surface into two lobes. Surface of lobes coarsely sculptured or reticulate. Types: H. (Primitia ?) sculptilis and H. retifera, Ulrich. The affinities of this genus are still obscure. Taking H. labiosa, we see Primitian characters coupled with those marking Kirkbya, and I am really quite undecided as to which are predominant. H. sculptilis Ulrich, from the Trenton of Kentucky, is farther removed from Primitia, but its long sulcus produces an effect more like Ctenobolbina than Kirkbya. The same is true, though in a lesser degree, of H. ( ' I'rimitia) seminulum Jones. The Devonian //. retifera, though having something to remind of each, is not a Primitia, lieyrichia, Ctenobolbina nor a Kirkbya. It is these more or less obscure resemblances to a variety of generic types that makes it so difficult to point out the diagnostic characters of Halliella, and I find myself in the somewhat anomalous position of being much better able to say what they are not than what they are. I must admit also that I am not thoroughly satisfied that the four species now constituting Halliella are strictly congeneric. They may be so, but until their natural affinities are better understood, the genus is to be accepted as convenient rather than natural. HAI,LIEU,A LABIOSA, n. sp. PLATE XL VI. Fl<;>. n-40. SI/K. -LiTint.il IP. M; nun.: hijrht . O.dU mm.; thickness 0. -10 mm. Carapace semielliptical, the, lower three-fourths semicircular, the hinge line nearly straight; dorsal edges somewhat thick and bevelled inward; free edges very "1'A. thick, in a ventral view resembling lip-: surface nf valves gently convex within the \side concave border. the central part nf the upp-'r lialf depre>-ed around a narrow pit; in famt Of the pit OOOftttOnally ft digitl roundel elevation. Surf mtifiilly marked witli small pits closely arran^ed-in concentric line-;, usually le»- curved than the ventral outline of the valves. This is one of the prettiest of the niimerou- i Mracoda occurring in the Trenton of Minnesota. It i- al-o one of the mo-t easily n ..... ^ni/.ed. the thick, lip-like . aii-1 the concentric .surface markings being unusually distinctive. tlity. N ;i shales. Goodhiif county, Minm-sota. in I'.KYKIciiiA. McCoy. Beyr* ""'• P- 67- Carapace small, e.|iiivalved. oblong or semiovate, with a straight dorsal and convex ventnil outline. Typically each valve has twosulci and three lobes, of which the- cent nil one is the smallest ; the- two larger lobes often coalesce ventrally. Surface u-iially marked witli pittings, reticulation, papill.f or other ornament. Type: /.'•///•//•/; /'i M.-i'oy. This genus, after /•;. i- the mo>t important of all the generic groups of 1'aleozoic Ostracoda. Many of the species also, those of the Upper Silurian rocks especially, are comparatively large, specimens over 3 mm. in length being not at all uncommon. The individuals, moreover, are generally abundant, layers of rock in many instances being crowded with, if indeed they are not largely made up of their -eparated valves. In the restricted »en-e in which the genus is here defined, the oldest known species is the Minnesota form about to l>e described.* It i- from the middle third of the Trenton shale- ( M'.lack River ^roupi. <>f the Trenton proper. /•'. Mia Walcott. m. iv belong to the genus, and I have a doubtful species from the I'tica hori/.on .it Cincinnati. Ohio; but so far we know of no true Hei/ri<-lii,i from the Hudson Kiveror Cincinnati ^roiip. tln^e referred to the ^enu- from this formation belonging to ;«./. l>rri.-inrll,i. Unlit-' '• •//•/. ++rn+rU,, and / 'rimifi.i. In (lie ( 'linton. however. It. luta Hall iVanuxei .1 good s| ,md from here on to the close of the Carboniferous system the genu- i- more or le-> well rcpre.-cnted in e group of -trata. • Prof. T. Rupert J.mp. bu dracrllMd n^rlrkla Mil from the Mlna-vl»n fliun of Urvil Britain . ii.-.,l MM., n -T . DM. 1 vol. 8. p. JO:1»IV t>ut tin- afflnlllraor thp foMll w«ln to luc »..!-.., Mf.,1. • s • li.Jlla lota J. I. !. 3. The •peclmvno Idrnllllf Joom with II. lain ar* wldflj ilHT.-r.-nt frvm the lypk-«l ( : K ipcvfea. which I. a Irur flryrfeTifci. l.ul I rannoi >1 • hru from Bultla fymmrtHca Rail, ap. M r,:,s THE PALEONTOLOGY OF MINNESOTA. LBeyru'lim iinll.-ihs. BEYRICHIA INITIALIS, n. sp. PLATI-: XLIIJ. FIGS. 82 :uid 83. SI/K.— Length 065 mm.: hightO.41 mm.: thickness 0.30 mm. \';ilves small, somewhat oblong, subqua'drate; hinge line straight, nearly as long as the valve; dorsal angles distinct without being sharp; ventral margin but little convex, nearly parallel with the back; ends subequal, neither much curved; free margins with a distinct border or flange, turned outward. Middle lobe situated just above and a little in front of the center, rather low, rounded, not sharply separated from the anterior lobe; mesial sulcus deeper than the anterior, meeting beneath the small lobe; anterior lobe rather small, coalescing ventrally with the much larger posterior lobe, the junction faintly indicated. In the anterior part of the valve the surface is depressed, but in the upper corner a small tubercle is to be noticed. In this species the isolation of the small lobe has progressed beyond the limits of Primitia, and the result is sufficiently close to Beyrichia to be included in this genus. An approach toward Beyrichian characters is faintly indicated in Primitia duplicata and P. tumidula, while the tendency to vary in this direction is much better expressed in certain varieties of P. cincinnatiensis Miller, and P. ? parallela Ulrich.* The latter might be called a Klu'denia, Jones and Holl, a genus that, with slight peculiarities of its own, seems to be nothing more than a recognition of one of the more permanent transitional types between Pninilin and Beyrichia. Specifically, B. initialis is not likely to be confounded with any Lower Silurian ostracode known to me. Nor is there any pressing need of comparing it with its much larger Upper Silurian congeners. Formation and locality.— Middle third of the Trenton shales, Minneapolis, Minnesota. Genus EURYCH1L1NA, Ulrich. Kurychilina, lU.iurii, 1889. Contri. to Can. Micro-Pal., pt. 2, p. 52; also 1S90, Jour. Cin. Soc. Nat. Hist., vol. xiii, p. 12~>. Carapace with a long, straight hinge line; semicircular, oblong-subquadrate, or somewhat rounded in outline; generally with a well-defined subcentral veilical sulcus and a more or less prominent node immediately behind it. Except at the dorsal side, the valves are surrounded by a wide marginal area, externally either flat or convex and usually marked in a radial manner; on the inner side deeply concave, an outer wall being raised almost to the level of the true or closing edge of the valve; area terminated in most cases by a narrow rim-like border. Hinge simple. Surface beautifully reticulated, pitted, granulo.se or smooth. Typa: K rrH<-nl'.»J 08TRAI 01 The principal peculiarity of l-:,iri/i-h;l;H.i II tin- hollow area surrounding. if nut all. v rate tin- greater part of the free margin-, of the vahe-. In /' .lies, ;i cone. i\e area occir '.nt only at the anterior end. This nundinal area i- n< i with the outwardly >imilar -full" of /•',•///•„ •///../..>/>. .lone- ami Kirkl.y. nor to the " fal-e (.order " <,f » 'ucilWA* ,-fintnl>, .••Ixittt or 1'riinitin c -IIHV ailistinct struct in n outer \\alk want in- in t i .-ie-. i- require. I to form it. Mon>over,an equivalent of the "frill" i- al-o present as a narrow terminal l.or-ler in nio-t of the true -pecie- of /•;«/•_//- /,// , ;me species of Knnj<-liiHn•/lmn ' \ think not. In coming to tin- <-onclu-inn I have in mind the fact th.it a numl.er of "frilled " primitian Ostracoila are known that seem to stand in close relationship with and K. siri-iti>niiir;/ini. One of these is here provisionally referred to /.'«;•//••// ///«»; xul.'iiti K.. Union i if c(,urse. if all or a good proportion of these species pn>\e to !,.• congeneric and are to be viewed as a iiroup liy them-el\e- and a- di-tinct from l'.\inj<-lulin>i . a new ^enii- will have to be ;i-hed for them. I would have propo-ed a name in tin- work had I not l»een •f -ooii recriM :men- of I >r. Kraii- When these arrive 1 hope to enter upon a more thorough iuve-t Ration of the /;. /-/,,„/„ than I have yet been able to gi\e them. 660 THE PALEONTOLOGY OF MINNESOTA. [Euryi'hilhia recticulata. KTRYCHILINA RETICULATA Ulrich, and var. INCURVA, n. v if tin- fact- an- correctly repre- ,-enteil in 1'rof. .lime-' figures it would remove lii- from the typical section of I\tiri/rliilinn. ' ..-urru ocrurs an far Kl K-iCIIII ISA -IHKAD1ATA I'lri'h. PLATE XI.IS : H //. Ai/i.,,1 »ui,r,i>lial,i L'LKK n, 1890. Jour. Cln. Soc. Nat. Hist., vol. xill, p. 128 it marginal ar .-tit " '• nun.: Ihii-knt-s-s 0.50 mm With tnar^'ir j nun.: hiL-Itt l..'t mm. 1'iodv of valves almo-t exactly -I'micirciihir in outline, with the -urface highest along an olitu.-e ridge-like prominence, running lengthwi.-e across the central portion of the valve and from the summit of which the .-urface descends with a distinctly concave slope to the thickened dor-al ed^e; on the opposite or ventral side the slope is more gently concave or Hat: anterior extremity compre— ed; sulcus deep and unusually wide. l.ei:iiining a little within the dor-al margin and extending half way . M the body, it< lower and i margin- thickened and -harply defined: ju-t hack of the -ulcu- a large round tul-ercle; -urface appearing Miiootli in -ome >| mens. l-ut usually it is pitted a- la ) Ki I:M-IIII i VTA. n inn ; hurl U; thlrkm-^0 ..> lulu Wit: -niii. Valve- i|iiadrate--iil'elliptical in outline, strongly convex. \\itli the dorsal angles ol'ttiM', the end- rounded, and the dor.-al and ventral margin- nearly parallel. I'.ody of valve rather uniformly convex, \\ith the anterior end a trille more obliquely rounded than the po-terior. Sulcu- -itnated a little liehiud the center, deep, narrow. .light dor-al border and terminating abruptly at a point le— than one- third of the hight of the valve lie neat li it. On each side of the -nlcn- the -urface rises into a low eminence. one. -uppo-ed to l.e the posterior, a little higher than the other. Central portion of >urface exhibiting numerous, rather irregularly distrihu- ted pn-tiile-. I'.'irder not defined by an impr.- — - I -nture line, flattened except at it- ••me outer edge \\here it liend- -uddenly inward. Its surface presents more or less oli-rure radial «eries of minute granule-.. im.~t distinct on the ventral iiortion whore the horder is al.»o the widi- A- itated under the generic tion. ti ne of a number of species l-elon^iiiL' to an unde-crihed |?enus. Of these form- /. P »tri«ted- of the ( 'incinnati formation, and /-.'. '' i// 1'lrich, from the Hirdseye limestone of Kentucky, are prohaUy the nearest. The first is less convex, ha- a diilerent sule»> and a wider lntnler, marked with fine radiating lines in-tead of n»w> of Crannies. The latter agrees very well in most respects but may i-tingui>hed at once \>\ the alienee of any well defined stilcu-. .'i.'y I !•!•• r ilnr.1 of II . h> ;i..|-,nii.t l»-'li. SI. Paul, MlnnMoU. • Kri:v< IIII.IN i:n v, u r I \ I I h I s inin : liik'tit 1 I i! xur.HiiO-4 t- •hi 7 linn.: hl^tu I ' - mm. Valve- -iiKelliptical or -omewhat ipiadrate. e.|in'lateral. greatly c pressed, l.i'i •_'.<> nun. in length. I>or-al margin -tiaight or slightly convex, a little shorter than the valve; dor-al angle- not very -harp: ventral margin >emielliptical. curving n.-atly into the rounded end-. Mody of valve tlattoned. lnit ri-ing at two points near the hinj?e, each situated aliout midway l»etween the dorsal angles and the center, into two, more or less prominent, large subequal rounded tulx-rde-. These are connected l>yathin ridge, the two bulbs and connecting liar resembling the old "bar shot." Surface broaoly excavated centrally, and marked with obscure pit-. Marginal 664 THE PALEONTOLOGY OP MINNESOTA. [Dlcranella. area convex, about 0.3 mm. wide along the ventral edge, the width decreasing rapidly in nearing the dorsal angles; ventral two-thirds surmounted by a narrow, crescent- shaped thickening, depressed centrally, and marked with rather large elongated and concentrically arranged pits. The affinities of this remarkable species are very uncertain, and it is only provisionally placed under Eurychilina. Perhaps it can go into the new genus with E. ? subcequata and the other species mentioned on p. 659. On the other hand, the two dorsal tubercles may indicate a remote relationship with Ulrichia. Whatever position it may ultimately occupy in classification, it is safe to say that it now stands quite alone. Formation and locality.— Upper third of the Trenton shales (Phylloporina bed), St. Paul and near Cannon Falls, Minnesota. Genus DICRANELLA, n. gen. Valves equal, similar to those of Primitia, excepting that they have " frilled " margins, while each side of the sulcus is raised into a more or less prominent horn-like process. These prominences are directed dorsally and may be subequal, or the posterior one may be much the smaller. Type: D. bicornis, n. sp. Though doubtlessly embracing a good generic type, it is as yet scarcely possible to give a satisfactory diagnosis of this new genus. Two of the following species, the type and D. spinosa, are certainly congeneric, and the third, D. marginata, probably also. But the fourth, D. ? simplex, is one of four species which, while closely related among themselves, are, to say the least, only doubtful members of this genus. Two of these four species Prof. T. Rupert Jones recently described as Ulrichia nicholsoni and U. marrii (Quart. Jour. Geol. Soc., vol. 49, p. 294; 1893) while the third, Leperditia byrnevi Miller, he refers (op. cit., vol. 46, p. 12; 1890) to the genus sEchmina. According to my estimate of these species, they should not be referred to sEchmina because, instead of a single horn-like prominence rising from the center of the dorsal slope, they have two, one subcentral, the other behind it, while between them there is more or less of a notch or sulcus. In Ulrichia the two generic knobs are merely rounded prominences or tubercles on the surface of the valves, never horn-like, nor are their apices turned toward or beyond the dorsal margin. The probabilities are that the affinities of Atchmina and Ulrichia are widely different, and it would be good policy, for the present at least, to restrict their application to forms in which the generic features are sharply defined. As to these four doubtful species, they are, it seems to me, clearly nearer Dlcranella than the other genera to which they have been referred. The answer to < , ,i,.\ the t|iie-tion. are they really congeneric witli tin- typical >pi •< .-pend-. I *hould say, entirely upon tin- -igniticaiice we attach to the presence or absence of the marginal frill. Hclieving that further inve-t Cation- arc de-irable. I -hall not tint to decide tin- .|'i.--i :..i; now. In tin- meantime the now species may be known a- a doubtful l>icrlarrd them. l>i 'i -/-. i i.\ 1 1 \i.i\. i i.. -•• i -j-«. \\ ittiniil I. mil : tln< • nun. ii Ininl.T, l.'UKlli I - nun.: liu-lit 1 i'-J nun. Vahe-ol.l. i^'ht ilnr-ally. roiin«lemooth horder or frill, usually I'ending outward at theed^re; horder narrowe-t anteriorly, widest below. Th i- species is so easily recognized by its "horns," that comparisons are quite unnecessary. ./ locality \. -.-.•• :m mm. This species is similar to I>. A;'«,/-;i/'> hut the valves are a little longer, and the "horn>" hejjin lower down on the valves ami are not carinated, while the posterior one i- shorter, ami >eem- not to extend beyond the rounded swelling. The border al-o seem- not to have been developed anteriorly, while along the ventral edge it i- ii-ually replaced by a >erie- of -pine-. 1'o-teriorly it ha- about the same width as in If. liiriirni*. but i- ornamented with radial furrow- in-tead of I, em;: plain. Formation unit tofilit; third. .f ' il.> (Khinldl neapolU. ^' 666 THE PALEONTOLOGY OF MINNESOTA. I Dk-raiu'llu m;u-i.'in;it«. DlCRANELLA MAROINATA, II. xp. PLATE XLIV, KIGS. 27-28. SI/,K.— Length 1.7 mm.; bight 1.22 mm ; thickness 1.0 nun. In this species the valves are much higher, especially in the posterior part, than in the two preceding species, the border, though wanting anteriorly, is much thicker and projects outward as much as downward or forward, while, instead of horn-like processes, we have two very unequal lobes, the posterior of which is comparatively very small, failing to reach the dorsal edge by a distance almost equalling its length, the anterior one (centrally situated) large, swollen in the middle, high and obtusely pointed above, the extremity reaching the dorsal edge or projecting slightly beyond it. The whole carapace also is thicker and has a more robust appearance. The peculiarities are strongly marked and conspicuous, and it does not seem likely that collectors will experience any trouble in recognizing the species. Formation and locality.— Lower part of the Trenton shales (Rhinidictya bed), near Fountain, Minnesota. DlCRANELLA ? SIMPLEX, H. Sp. PLATE XLIV, FIGS. 24-25. PLATE XL VI, VIG. 42. SI/.E.— Length 0.98 mm.: hight 0.67 mm.; thickness 0.35 mm. Valves moderately convex, subelliptical; dorsal angles rounded, hinge line rather short; ends equal, rounded; ventral margin rather strongly convex; edges simple, without border. A strongly elevated, oblique, conical prominence just within and behind the center of the dorsal edge; another large tubercle, in this case rounded instead of conical and ovate in outline, near the center of the posterior half and like the other reaching the dorsal edge; between the two a rather deep sulcus. A third tubercle, of irregular form and nearly as large as the second, occurs just within the upper half of the posterior edge. This species is evidently related to the Cincinnati form first called Leperditia lijrnesi by Mr. Miller, and recently referred to sEchmina by Prof. Jones. That species however has only one posterior tubercle and a central oblique spine, while D. ? sim- plex has all three. The outline of the latter also is more convex ventrally. Of Minnesota Ostracoda, there is none sufficiently like it to require comparisons. Formation and locality.— Lower part of the Trenton shales (Rhinidictya bed), near Fountain, Minn. 1.4-1 DM .I<>NK>KLI.A Unch. .'»-u.< r. Ml J.'ur • :n;ill. <'<|iiiv.ilve anterior arm is In.ri/.ontal instead (if vertical, while in a third the tun arms arc . Both S^M-I.-.S an- fr..m th,. I..W.T U-dxpf lh.- ruiiiti Knuipa! ..-ky. The atlinities of this genus, which includes so far as known only Lower Silurian species, appear to be with linllin, Jones and IIoll. But the horseshoe ridge in all true species of that genus is suhcentral, while the edges of the valves are thickened into a more or less well-developed marginal ridge, no trace of which is apparent in Jones* lln. The new species aboot to be described is peculiar in the faint develop- ment of the loop, and in the shortness of the horseshoe. In ./. ct mix, as may be seen in the aliove cut, the ridge takes up the greater part of the posterior half. Still, a general agreement of part- Let \\cen the t\\o -|..-cic- i- oLvion>. M. that ./. ient ./.<;/,.>•,//n the other hand, the prominent upper e\t remit ies of the Lent ridge, remind consideraLly of certain species of 1'lrii-hin, Lut as the whole carapace recalls /;„///,/ .puite as nuicli. if not more, it i- to be assumed that these resemblances indicate family relation-hip rather than ric, A- ii-ual with early types ,,f life, the Lower Silurian Ostracoda are apt to be of a composite nature, and the determination of the really significant features of -uch forms, so far as generic and specific alliances are concerned, is never certain except through minute genealogical in lint this touches upon too large a subject for the present work. In the original work on the genus I included a Minnesota species, under the name of J. crassa, that I shall now place elsewhere, because it seems to belong to another line of development, namely, it is closely related to Ctenobolbina r'ulmif.i. Cor further remarks on this and related species see under Ctenob»n>inetween tin' ridges relatively narrow. These specie- pa— over into, ami tin- -ection ought to i nclu. It', some of tin' -n-called i|iiadri j y /•/<•// /,r.* Their relation-; to Titrn nih -- D.L'I: mm. .111 .in. Vahes compre--e 1, suhovate in ontlii _rlit aliove; length of hinge some- what \arialde. shortest, apparently, in old examples; dorsal angles more or less distinct : edge- of valve- thirk. forming a >harpl\ --detined. thin marginal ridge; inner ridjre thin, rather lon^. l"-shaped. one of the arms with a slight swelling near or at ita upper extremity: Mirfaee lietween the ridges Mat and without ornament. The small valves of this >j>ecies remind -omewhat of ' imminln, hut as that, form ha- no inner or horseshoe ridge they are distinguished very easily. 'l>lrl,-ll,i J, Mi K •- 670 THE PALEONTOLOGY OF MINNESOTA. [Drepanella, This species, though smaller and distinct, resembles the Devonian B. ungula Jones, more closely than any other of the genus known. B. persulcata of the Cincinnati rocks is perhaps as near as any of the Silurian forms, but there are so many differences between them that it is unnecessary to enter into comparisons. In B. subcequata, which belongs to another section of the genus, both the inner and outer ridges are much thinner. Formation and locality.— Associated with the preceding in the Galena shales, in Qoodhue county, Minnesota. Genus DREPANELLA, Ulrich. Drepanella (Depranella in error) Ulrich, 1890, Jour. Cin. Soc. Nat. Hist., vol. xiii, p. 117. Carapace equivalved, compressed-convex, somewhat oblong, the outline between subquadrate and subelliptical; dorsal border straight, ventral outline gently convex; ends subequal, the posterior somewhat truncated above, the anterior generally more rounded. Running nearly parallel with and close to the posterior and ventral edges, a sharply elevated, sickle-shaped ridge. Central and dorsal regions of valves with two principal, simple or divided, nodes or ridges. Surface smooth or reticulate. Size of carapace usually about 2.5 mm. long by 1.5 mm. high. Type: D. crassinoda Ulrich, Fin. 48.— a, l>, lateral ami dorsal views of a ri^ht valve of Drepanella crassinoda Ulrich, from the I'.inlseye limestone al. llitili I'.ridtfr, Kentucky; c, a left, valve of D. ampla, van. elvnyatn Ulrich, from the -a formation and locality, introduced for comparison with I), bigeneris; d, right valve of 1>. macra ririrli, from l.he same I'm unit inn at Dixon, Illinois: all x 20. The last probably omirsalso in Minnesota. Of this genus only Lower Silurian species are known. Taking the six species varieties upon which the genus wns founded, we have a sharply defined generic •A. «',7I •all. I grou|>. Witli these we may include, wit limit materially altering our conception of the L'emis. the new I>. bilu' although in tin tin- charactei . -kle- ihaped marginal ridge ifl winting posteriorly. But the other Mianei . /* certainly a n>iiiarkalili> form. In I ireneral appearan well with /' and I>. tim/ifit having tin- sickle-shaped ridge well developed, uixl two lar^'e centro-dorsal node- ted l.y a depression, a- in tin- latter species. Hut the peculiar feature is that t hese nodes are prolonged lielow ami united l>y a -lender connection, ^iviiiy n> precisely the horseshoe ridge of a Ro/lin. The .|iie-ti(.n arising at once i-. why -hould the not \>e viewed as a Bollin, rather than a / 'tit. 1 have decided for />/•»•/»./>*••//// on what I helieve to be good genealogical grounds. In the tir-t place, a-idc from the ventral connection of the nodes, all the characters of ti ••> tlio-e of lh,jin>i>Un. The inar^iiiiil rid^e. it is true, run> farther up on the anterior end than on any of the other species, yet its extremity is thin and the mere fact that it i- a trille loiiL'i'r than usual cannot he of much con-f(|iience. Hut the mnst im|>ortant evidence on the .|iie-tion is furni-hed hy I>. <;;///7 illustrate other types Of the same condition. DISK i- AN KM. A mi. \TKI:AI.I~. //. I'l.ATK XI.VI /lit I '.4 nun : Kmlest 1 ••--. ill. .ml I .limn.; tliirkti--- .lit li.li mm. Valves sul,,,val or ol)lon^-siil..|uadrate. compressed; dorsal margin distinctly aiiu'iilar at the extremit ; a trifle narrower, and the outline less convex than the posterior: ventral margin m iit centrally. Kiiiinin^ parallel with and close to the ventral margin a stron. at thickened at •i end, hut not continuing up the ; this two irregularly triangular and ver\ prominent lar^e no-le- extend to the dorsal edge. U'von-l which their pointed extrem • •nally jiroject. The la-t i- true aUo of a small central tul.ercle. 672 THE PALEONTOLOGY OF MINNESOTA. [Drepanella bigenerls. The form, prominence and bilaterally symmetrical disposition of the nodes and ridge give this species a very distinct and striking appearance, and among all the numerous Silurian Ostracoda not one is known with which it might be confused. Formation and locality .—Upper third of the Trenton shales (Phylloporina bed), St. Paul and near Cannon Falls, Minnesota. DREPANELLA BIGENERIS, n. sp. PLATE XLIV, FIGS. 20-22. SIZE.— Length 2.3 mm.; night 1.36 mm.; greatest thickness 0.95 mm.; average thickness, not including nodes and ridges, about 0.5 mm.; thickness of posterior and ventral edges about 0.6 mm. Valves oblong-subquadrate, longest in the lower half, the ends nearly equal and converging slightly in the upper half; back straight, the posterior extremity suban- gular, the anterior rounded; ventral outline very gently convex; marginal or "sickle- shaped " ridge sharply defined, extending farther up on the anterior side than in any of the other species of the genus. "Two thick nodes or lobes, the anterior one the longer and more prominent, are connected below by a narrow loop-like thickening of the lower border of the median depression or sulcus, the whole producing precisely the effect of the "horseshoe" ridge of Bollia. My reasons for placing this fine species under Drepanella instead of Bollia are given in the remarks following the generic description. The specific characters % are well marked and conspicuous, so that there is little difficulty in distinguishing the species from the rest of the Minnesota Ostracoda. Formation and locality. — Lower limestone of the Trenton formation, Minneapolis and St. Paul, Minnesota. Genus DILOBELLA, n. gen. Carapace small, equivalved, subovate or somewhat reniform in outline, the back straight or faintly concave; valves bilobed, the lobes subequal, very large, and almost completely separated by a deep subcentral vertical sulcus; edges thin, simple; surface smooth. Type: D. typa, n. sp. I find myself obliged to erect a new genus for this remarkable ostracode. A slight resemblance to certain forms of Bollia may be noticed, but the lobes are altogether too large for that genus. That it cannot belong to either Entomis, l-'.ntnmidella nor Ctenobolbina, the only other genera with which it might be compared must be evident to anyone who has paid attention to this class of fossils. As to its affinities, they are obscure. Because of the slight basal connection between the lobes, it may be regarded provisionally as an extravagant development of the Bollia type of structure. \ I >n • n i- v. /- I' I V.I '.«. »-«. •ti I i) nun.: hlK'til • i.-kn.-ss O..VJ n.: hlk'tit ii :'• mm. Va! . .11^ -nine what in Outline, •OB16 being oli-curely quadrate m- -iil»>. other- -Inn t-renifiirm : dor.-al oiitliiii> more or less concave at the middle and rounded or >iihan;,'iilar at the end-: ventral margin -tnni^'ly convex, (lie lower half of the outliue beintf in some cases almost semicircular. A deep, suhceiitral. \ertical sulcu- di\ -id. M info two larp- Milx»<|iK(l loin--. These are very prominent, especially at their center-, and ris«» aliniptly from the flattened horders. At the base an obscure nmne.-ii.in l>et\veen the lol»es may be noticed. When the \al\e- are not perfectly cleared from the matrix, some difficulty may be experienced in distinguishing them from t be associated Ctenobolbinn <;w»w, whicfc also has a deep snlcu^. Hut in that -pecies the sulcus is curved and does not divide the lobes ventral ly, ami the valves are longer and differently shaped. In fact the two species ditler >o greatly that I cannot conceive how good specimens might be confounded. uifi.m md locality.- i'|.|- r third <>r the Trenton shale8 (Phylloporlna bed), SU Paul, Minn.-wU. U ' TKNnl'.nLHINA. 1'lrich. Ct«no6o/6i»'i. 1'i.iui ii, 1*«0. J(.ur. Cln. Soc. Nat. Hist., rol. xlil, p. 108. :iiall, elongate-suboval, strongly convex, the posterior two-fifths more or less decidedly Imlhous or subglobular, and separated from the remainder by a deep, narrow and more or less oblique sulcus extending with a gentle curve from the dorsal margin more (ban half the distance across the valves toward the postero- ventral border. The anterior three-fifths often with another oblique but less impressed sulcus. Valves equal, the dorsal margin straight, hingement simple, the :al edge thick, and the true contact margins generally concealed, in a lateral frill" or fl. false border; surface granulose, smooth, or punctate. Type: ••/<•/. -in •- .-f i :n;ih, Illin..!-. This specie* proba' in the equivalent shale- .-.n Valley, Minn>>- 48- 674 THE PALEONTOLOGY OF MINNESOTA. LOtenobolblna f ulcraia . This genus includes a well marked group of paleozoic Ostracoda, distinguished, in its typical development, from all the other genera of the family by the bulbous character of the posterior end. A small isolated middle lobe, which is the most persistent character of Beyrichia and KUcdenia, is, except in one case, never present, the central lobe or ridge, when one has been divided off from the anterior swelling of the surface, being united ventrally with the large posterior lobe. A small lobe is isolated in C. turnida Ulrich, but as the posterior half is decidedly bulbous in this species it may be advisable to leave it with this genus. Still, I have fully satisfied myself that it is a close ally, perhaps a progenitor of the Clinton Beyrichia lata Vau- uxem, and that is not far from B. kla-dini McCoy. Ctenobolbina has its best development in the Cincinnati group, from which four or five good species and two varieties have been described. Two Trenton species, differing from the Cincinnati types in the lesser development of the posterior bulb, are found in Minnesota. C. punctata Ulrich, of the Niagara, retains the generic characters very well, as does also C. papillosa Ulrich, of the Devonian, while C. informis Ulrich, also Devonian, reminds of the Trenton C. crassa. C. minima, of the Hamilton, is much like C. bispinosn from Cincinnati, and both are almost primitian in their simplicity. Of European species I know of only one that has the characters of Ctenobolbina clearly developed. This is the Beyrichia guillieri Fromelin, as figured • by Jones, in 1890, (Quart. Jour. Geol. Soc., vol 46, pi. 21, figs. 2«, b, c). It is closely related to C. ciliata and occurs in the Lower Silurian strata of France. Another, that is as much of a Ctenobolbina as C. crassa, C. fulcra ta and C. informis, is the Bollia ? iinrifu/iiris Jones and Holl, from the Wenlock of England. Indeed, these four species are closely related and cannot justly be separated generically, so that I propose to refer the Wenlock species also to this genus. Prof. Jones concedes in a letter to me that the auricularis is not a Bollin, and a close comparison with the Minnesota species mentioned proves to me that my former opinion of the British species, when I thought that it might belong to Halliella (Jour. Gin. Soc. Nat. Hist., vol. 13, p. 185), is erroneous. CTENOBOLBINA FULCKATA, n. sp. PLATE XL1V, FIGS. 8-11. Si/i,. l.riii,'Ui 1.2mm.; hight 0.78 mm.; thickness 0.56 ram. Length 1.2 mm.; liitfht 0.80 mm.: thickness 0.00 mm. Valves obliquely subovate, highest posteriorly, with the back straight and the dorsal angles usually well defined. Posterior bulb comparatively narrow ; sulcus deep, wide, oblique, curving backward below; anterior lobe undivided, larger than the posterior, in some specimens less oblique than in others; ventral and posterior sides K <>1»A. of lobes terminating in ;i thin. Mat ..r rai-ed. horder. supported in the hinder part l.y .idi-tant rii N, tliu- forming a- man) -mall cavities in the posterior edge of each valve; surface -mooth. Tlit- -mall cavities in the po-terior half of the edge remiinl of '/'pJ nun : thirkrn-s> n.4i> nun. This species is closely related to ('. riilinitn. and \\ hen the edges are obscured l>y the matrix, it is difficult to distinguish from one of the varieties of that sp<-' But w hen the posterior edge is visible the difficulties vanish, there being no support- nor cavities in the thick edge of C. crassa (compare tigs. 13 and 1G with fig. 9, pi. 1 1 i Aiming other differences I may mention that in ('. i-rnssa the valves are constantly a little smaller, the sulcu< wider, and the lobes more prominent, especially at the ventral edge. The lobes are also more compact and ridge-like, producing an effect that reminds so much of the "horseshoe" ridge of Jonesella. that I at first regarded the species as belonging to that genii-. Hut that was before I knew of its close relation-hip with <\ I'n .11. — AMOClal HlialtW at ' IHIi'SOU. n CEBA.TOP8I8, n. . T.tr,idrlla (|..i •ll.I'W). J.n. Hi Beyrichia (part.) ! : me! Wmi SK>. ;IIK| ..Hi. r :nni. Valves somewhat (.l)li.|iifly BryrirMa fkamlrrti II ui .mdWimi I. li, p. UU. pi 4. ! . 1 lli-r. ,ii an. I i carapace of tln~ \ariety fmm tin- -.hales of the ir Sprint- Mit». • This designation i- prnp, ln'li;in;i. and Kentucky, :ind in tin- .Mjiuvalent IlinUon Kiver group strata of Minnesota. So far as known it is not •e found )>flo\v the hori/on of <>,-tliis .tiifn/iiiiilnifn Hall, and Rlitjni-lintrHn <•ul>aiij/iilar where the contour turns abruptly inward to the false border. anil /n*txfunl, lnilli. .lour-. /,'. li'isnyltipln,-'! Krau-e. /.'. >> Hall, and l\f.,-l,ni-i fcftMMM Kr.m-c. I'pp.T Silurian, ami it i- clear that tin- change from the lir-t in tin- la-t \\.t- nothing more than a gradual coale-cence of the ventral curves of the inner an me. Miice if wniilil I v to assume a division of the small or middle lol.e of t ! which I think I am safe in declaring, never took place. i'lel/n is essentially a Lower Silurian gemis. nearly all the typical |p< I.ein^ re-tricted to strata lielon-ini.' to. or e-|iiivalent to the Trenton and Cincinnati formation-. In America we have '/'. ./i/WnV/'/v/A; Hall and Whit Held, and var. */»»/•/, / I Irich. 7'. lun.ifiirrd and 7'. suln/inKlnil'i Uriel). Of Kiiropeaii species donl.ti. lu'lon^in^ to '/'. ',--i. l,-ll'i I may mention /.V//n'<7j/,/ roin/iHi-.il'i Salter, />'. rilii-iriunn • lone-, li. iijfini.-< .].. II. l>uxiii .1.. /•'. niitii;i K.. /;. /..//MM/.I K . / K. /'. ••'»!'/'•/ K . a:i'l T. ii'ir/." K. As somewhat .h.iil.tfnl l'[iper Silurian representatives, we m ,rd four species figured l»y I >r. Krause, vi/..: It, >/,-!. lllio, Vol. I fl. regulori* Km ). ii. I— ;i Cmilri. • , .;u.i./ri/ir.i/.i I'l.liicil. I "."i. .I-) . I. Hi nun : tii. 'inn. J IMIM.: thickness <).;t* HUM. l.i:i tu HI .: liiK'tit 0.70 IMIM.: tliii-knvmafiS nun. Figures 1 t. from a represent;!' •••inn-n of the specie- a- it occurs in the Trenton shale- of Mimie-ota. I' y nearly identical with the typical form which i- found so abundantly in the up| »f the Cincinnati group in Ohio and Indiana. The original of tig. t i- from the ISir-l-eye limestone at High Micky. Thi- i- -omewhat shorter and more ohli.jue than u-iial. Figur.- a variety, not uncommon at. Minneapolis, in which the aiitero-incdian 680 THE PALEONTOLOGY OF MINNESOTA. LTetradella lunatlfera. ridge has a decided thickening above, and is less distinctly divided below. The two posterior ridges also are not entirely distinct. In the majority of these lower Trenton representatives of the species a delicate ridge or raised line is to be noticed just within the posterior portion of the marginal ridge. This is wanting, as far as observed, in the Ohio specimens, but in the related T. lunatlfera this small ridge is represented by one that is quite as strong as the marginal ridge itself. Figures 9 to 1 1 are taken from a variety of which several examples were collected at Fountain, Minnesota. These are thicker ventrally than usual (see the last of the series of measurements given above), longer, and have an unusually wide flattened border, turned outward at the edge. Some slight differences may also be noticed in the characters of the median ridges, but the most striking of all their peculiarities is the absence of the five marginal cavities. In some respects these specimens agree very well with the var. simplex described by the author from Hudson River shales in Manitoba, but as they are not identical another subordinate name might appro- priately be applied to them. Formation and locality.— Birdseye limestone, High Bridge, Kentucky; middle and upper third of the Trenton shales, Minneapolis, St. Paul, Cannon Falls, Fountain, and other localities in Minnesota; upper beds of the Cincinnati group at Clarksville, Blanchester, Waynesville and Oxford, in Ohio, Rich- mond and Versailles in Indiana. TETRABELLA LUNATIFERA Ulrich. PLATE XLVl, FIGS. 12-14. Strepula lunatifera Ur.iucn, 1889. Contri. to Can. Micro.-Pal.- ii, p. 56. Tetradella lunatifera ULKICH, 1890. Jour. Cin. Soc. Nat. Hist., vol. xiii, p. 112. l-'ig. 51.— Two valves of T. lunatifera from the Galena shales near Cannon Falls, x22; showing differ- ences in the ridges. -Length 1.-.J* mm.; night 0.75 mm.; thickness 0.58 mm. Tliis species is in a general way much like T. quadrilirata but differs more or less obviously from that, as well as from all other species now referred to the genus, in having in all six ridges instead of the usual four. Twoof this number however were produced by division of the posterior and antero-median ridges. All four of the inner ridges may he, as shown in the above cut, separate except at their lower ends where they unite with the marginal ridge. In others (see plate XLVI, fig. 12) the antero-median pair may l)e so near each other as to form practically but a single ridge. In others again this pair is united above and below but bent in such a manner that they enclose a crescent-shaped hollow space. Finally, in a few cases \ f.s I Moor**.) among nliin ami Manitoba specimen-. tin- ventral c ..... lection between tin- in HIT a in I filial !•!•:. Minne-ota specimens. although fri>ni a much lower hori/on than tin- types, cannot be distinguished fn>m them even as a good \ariety. >"f>rimiri,>» nn-t lofaUtg.-t.',., , MlnnonoU; upper • llu. i- .a Ui»T i. • HI Mi"i|;r:.\. -lones ami Kirkl.y. *»"' ~ -""I KniKiiv, !•>• >xlll, p.4W; I8«8. Ann. Ma«. Nat. nl. p. 225, and 1888, «er. !,, v..|. xvn Carapace very small, more or \,<^ uhlnn- nr nvatc. with tin- valves rather thick -helled, smooth, punctate or ^rannlo^e, ami bounded liy . marginal r\>\^\ the ridge may he developed only at each end. or it may continue all around. Within the marginal rid^e. the Mat or gently convex surface shows no trace of a MilciH. pit. nor of Iol>e8. Type-: M. nl>,-sed l.v Prof. T. linpert Jones from the Wenlock. This seems to beaquestion- "'•l'- the carapace being too convex and blunt at the end-, while the ridge, which should he snhmar^inal. is here central and bifurcated posteriorly. A fifth species. M. /.-/>•/%/. de>crihed from the Corniferou- limestone of Ontario by the same author, i- not far removed from M. w of minute papilla'. The original types from the Carl.onifenni- ttX iiern Knglaii-1. •Ml tl" ies are di-tin^uished from Kirl:l»j,i. .lone-, certain species of which they greatly roeml'ly, by the ah-eiiroof a central pit. Some also resemble Placentula • lones and Holl, and certain ^pei-ie- i,f /,'-,/ -he tir-t of these genera hasasmall dorsal loop and ,-nlcns while the latter ahvay- ha- a hor-i-hoe --haped ridge of which no trace is to be observed in M The valves in the new -enn- " ',//,/ an- more convex and without the marginal ri 682 THE PALEONTOLOGY OF MINNESOTA. [Moorea aniruluris. MOOREA ANGULARIS, H. Sp. PLATE XLIII. FIG 89. PLATE XLVI, FIGS. 15-10. SIZE.— Length 0.67 mm.; hight 0.40 mm.; thickness 0.23 mm.; length of hinge line 0.65 mm. Valves compressed, suboblong, slightly leperditoid in outline, the posterior end a little wider than the anterior; hinge line straight, nearly or quite as long as the greatest length of the valve, with the dorsal angles acute; beneath them the outline is nearly semicircular; ridge thin, almost marginal, strongest ventrally, wanting or scarcely distinguishable dorsally; surface smooth, nearly flat. Two specimens only have been seen of this species. Both are figured, the one from Minneapolis on plate XLIII, the other, from Fountain, on plate XLVI. The latter is the larger of the two and differs from the other, which is to be regarded as the type, in several respects. Possibly it is distinct, but as it has evidently suffered from weathering or maceration, the differences may not be normal, hence I perfer for the present to classify it as an imperfect valve of M. angularly. The almost flat, though thick-edged valves of this species, cannot be mistaken, so that comparisons are quite unnecessary. Formation and locality.— Middle third (Rhinidictya bed) of the Trenton shales, Minneapolis, and near Fountain, Minnesota. MOOREA PUNCTATA, n. sp. PLATE XLIII. FIGS. 84-88. SIZE.— Length 0.40 mm.; night 0.24 mm.; thickness 0.18 ram. Length 0.50 mm.; hight O..'i2 nun.; thickness 0.22 mm. Y;ilves somewhat oblong-quadrate, the hinge nearly straight, about one-fifth shorter than the greatest length of the carapace; dorsal angles distinct; ends sub- equal; not strongly rounded, sometimes obliquely truncate above; marginal ridge developed along the anterior, ventral and posterior borders, thinnest and least prominent ventrally, thickest and somewhat club-shaped posteriorly, the ends terminating abruptly before reaching the dorsal, angles; ridge usually continuous, but occasionally incomplete ventrally. Within the ridge the surface is flat and minutely punctate; above it descends abruptly to the hinge line. A neat little species, reminding considerably of Placentula excavata Jones and Holl, and of species of Bollia like B. vine! -I. and II., or It. sttba'quata. It is smaller than Moorea angularis, has less pronounced dorsal angles, a punctate surface, and ililferent marginal ridge. Formation and locality.— Upper third (I'hylloporina bed) of the Trenton shales, St. Paul, Minnesota. 668 v . •. . ..-..•.• M ..... :t v ' • n. >/.. 17 «n«l It. The ti^'iirc- pre-cnt -n.-h ;t reiiKirkaMe valve that I am quite unal>lt> to account for it- peculiarities. I 'nfort unately the original of tin- ilra\vin->. which were nia-le f'»" D niMai.l or lo-t.sothat I am ol,liK,-,| to piil,li>h tin-in without a tinal verification of tin- character* -hou n. It may really In l.ut I «louht. it. Or it may I..- related to I ',,. With more matt-rial it* allinitie- may I.ecome the hope that collectors will -earch for ami p.-rhap- -ucceed in ;iat ha- in.luced me to retain it in my report. Muni (lt>,mi.lirty:i UH|) of th.- Tr.-nt..ii shal.-s, ,,.-:ir Kounialii rienoU. 'i- M \< LA, n. p-n. ,i|.ai-»- convex, semicircular or -.-miovate. with a lon^'. nt-.irly straight, hin^c; valve* equal, full centro-.lur-ally, wit hout ri-l^es or asulcus. hut exhibiting a -moot h -iil.central >|.ot when- the oniami-nt i- omitted; surface, in the only species known. coarsely punctate. Type: l/ . n. sp. I saw no way to escape the responsibility of erecting a new genus for the fol- lowing -pecie* without forcing it into one of several that I am fully persuaded ought not to receive it. The Ion-: hinge, semicircular outline, and almost perfectly equal en. K ren.lerintf it .litiicult to .listin^ui-h one from the other, give it an expression peculiarly its own. A'/>/%« pfrmiunn .lone-, it i- true, ha- a -omewhat similar form, Imt like all the ipeofel of that genus, it has al«> a rnar-inal ri.lge and a subcentral [•it. neither of which are pre-ent in the species umler consideration. Still, the -mooth -p«,t m,.ntione.l al.ove pnil.ul.ly represent* the pit of AV,-/./,,/,/. ;m,| it i- with thi- p-ini- that I think the atlinities of ,/r/A; lie rather than with either •liit.s or Iwhilinn. The 1-,,,-lnlhxi ',,n's ririch (.lour. I'ir Nat '1. 13. |.. IvJ; IV.HI) fn.in the l',-vonian at the falls of the Ohio, may be congeneric with .17 :i. there being >ome similarity in their outline-, hut as the surface of the Hcvnnian form i- tly -mr,oth ami not inllate.l ,-entro- dorsjilly. I hesitate to say it is. 684 THE PALEONTOLOGY OF MINNESOTA. [Macronotella scofleldi. MACRONOTELLA SCOFIELDI, n. sp. PLATE XLTII. FIGS. 30—34. SIZE.— Fig. 30. Length 1.57 mm.; hight 1.05 mm.; thickness 0.78 mm. Fig. 33. Length 2.20 inm.; bight 1.33 mm.; thickness 1.05 mm. Valves varying in length, semiovate or nearly semicircular, the dorsal outline not quite straight, being somewhat prominent centrally; free edges with a sharply impressed furrow, forming a beveled border; surface strongly convex, rather full in the centro-dorsal region, and marked, except on the ends and along the ventral border, by rather large and somewhat distant pits; a row of these pits, more closely arranged than usual, encircles a smooth subcentral spot. Of the two specimens figured, the smaller is from Minnesota, the other from Kentucky. The latter, it will be observed, is not only larger, but also proportionally longer at the hinge line. The smooth spot, furthermore, is less centrally situated. I attach no importance to these differences, believing that they are quite within the ordinary limits of local, if not individual variation. Named for Mr. W. H. Scofleld, of Cannon Falls, Minnesota, to whom not only the author, but the Geological Survey of the state as a whole, is indebted for much valuable assistance. He has been particularly active in the development of the paleontology and stratigraphy of the Lower Silurian rocks of the state. Formation and locality.— Lower Trenton limestone, near Cannon Falls, Minnesota; Birdseye lime- stone, High Bridge, Kentucky. Family CYTHERELLIML Genus CYTHEIIELLA, Jones and Bosquet. Cytherella JONES, 1848, Subgenus of Cythere; Monog. Entom. Cret. Form., p. 28; BOSQUET, 1852, as a distinct genus; Desc. Entom. Foss. Terr. Tert., p. 10. JONES and KIKKBT, 1867. JONES, KIIIKHY and BRADY, 1884. Monog. Garb. Etom., Pal. Soc. p. 70. Carapace oblong or ovate, compressed, especially in front; smooth or pitted; vulves thick and unequal, the right being much the larger and having its edge grooved or rabbeted all round on the inner side for the reception of the edge of the left valve; muscle-spot indicated by a roundish depression near the center of the valve externally, and by a corresponding thickening within. Length 0.5 — 1.4 mm. Type: ('yllnr<'llf the yenn*. 1'rof .lone* has also referred several l.owerand I'pper Silurian >pecie* t«> the p-mi.*. l-ut here, it *oems to me generic relation* arc n >'a*t , \\ith the palcontdlii^ ic ral-lteted edge of the ri^ht valve. This peculiarity, if my memory i- not at fault, has not yet been shown to exi-4 in any of the Silurian ics hitherto referred to the ^'cnu-. It does however exist, and very stron^y !i an iimlescril.c'l -pccic- from the lower beds of the Cincinnati group. In this specie-, ho. unless all the specimens seen (about twenty) are of one valve only, the edges of l>oth valves are about equally grooved. I-'..r remark* on f 'ytlie relit :ntin< tly defined. The outline is broad-oval, almost circular, and as near as can l>e determined, the surface of the smaller valve is moderately and quite uniformly convex, and exhibits neither a central depression, a tubercle, nor markings of any kind. The specimen was found in association with valves described on a preceding page as >VA//i iiltrlln? sul>rutund«. They are distinguished by a small, subcei tubercle, but as they have the same rounded outline, it is possible that a better preserved series of specimens may show them all to belong to one species. That the synonomy may. in case tin lity is converted into a fact, l>e simplified, I have used the same specific name for both. Formation and locality.— L«iw<-r th : .ton shales, Minneapolis Minnesota. 686 THE PALEONTOLOGY OF MINNESOTA. LCyllieiulliiV ruiiosa. CYTHERELLA ? RUGOSA Jones, and var. ARCTA, n. var. PLATE XLIII. FIGS. 21-25. Cytheropsis rugosa JONES, 1858. Ann. Mag. Nat. Hist, ser. 3, vol. i, p. 254, pi. x, flgs. 3 and 4; also 1858. Geol. Sur. Can., dec-ade iii, p. 100. Cytherellat rugosa JONKS, 1891. Contri. Can. Micro.-Pal., pt. iii, p. 99. SIZE.— Length 0.9 mm.; night 0.58 mm.; thickness about 0.34 mm. Var. arcta, length 0.96 mm.: bight 0.53 mm. Prof. Jones' type specimen is said to be 0.83 mm. long, and 0.54 mm. high. Carapace small, blunt at the ends; outline subreniform, rounded at both ends, the anterior one narrower than the other; of the upper and lower margins, one is nearly straight; the other strongly convex. Surface coarsely pitted, the pitting extending over all parts except a small spot situated, if we consider the straight margin as dorsal, beneath the center of the valves. Fig. 25 represents a variety differing from the typical form in having the anterior end drawn out. It may be called variety arcta. The generic position of this species is very doubtful . The typical form resembles Aparchites minutissirnus, var. trentonensis, figured on the ssime plate, but the outline of var. arcta is much more like that of Bythocypris cylindrica Hall (see plate XLIV). It seems very doubtful to me that the species belongs to Cytherella, but as I am unable to suggest a better arrangement, I have adopted Prof. Jones' latest suggestion. Formation and locality.— Top of the Galena shales (Nematopora bed), near Cannon Falls, Minnesota. Variety arcta is from the middle division of the Galena (Fusispira bed) near the same locality. Family CYPRIOTE. Genus BYTHOCYPRIS, Brady. Bythocypris, BKADY, 1880. Kept. Ostracoda, "Challenger," p. 45; JOXES and KIKKHY, 1886, Ann. Mag. Nat. Hist., ser. 5, vol. xviii, p. 250; also 1887, Proc. Geologist Assor., veil, ix, p. 510; JONES, 1887, Ann. Mag. Nat. Hist., ser. 5, vol. xix, p. 184: ULRICFI, 1890, Jour. Gin. Soc. Nat. Hist., vol. xiii, p. 196. Carapace smooth, more or less renifonb ; left valve larger than the right, over- lapping it on both the dorsal and ventral margins; dorsal margin strongly convex, ventral margin usually straight or slightly concave. This is a recent genus into which a number of Paleozic Ostracoda have been placed by Prof. T. Rupert Jones and others. Whether this extension of the genus is justified or not, I am unprepared to say. It seems to me, however, that some of the species might with equal propriety be referred to other genera of the marine Cyprithr. But as I have not given the subject the thought and time which its great difficulty necessitates, my present judgment can have little value when opposed to that of Prof. Jones. Off] Hjl! Respecting tin1 .iliuiit to In- de-cril>ed aiiay that in neaily CM-IT in-tancc they agree • • irith oae or another of the species which I'rof. .inm-- h.i> placed Under tllC geilll-. It may 1-e \ .ill attention tn the fact that the Silurian genii- <'>///« n'/linn, • lones ami Hull.' i- founded upon -pecios very similar externally to some of the Silurian \Vhetlier any of the latter have the obscure internal thirl nf the te-t which are said to characteri/.i- (''/tlien-llinn is unknown, Imt con-tdering the -imilarity of their external feature-, it -eems a little >t range that I'rof. .lone- ha- not remarked ni,,i, it in hi- more recent writings. IM i HIM •» i-i;i- I-M.IMIKII-V E \I.IV F108. . llvi.U 1872, Twi-iily-fniir' I, pi. \ in. •1. il, p. l"l. i r. . tig. 5. /».. Kgti. UGH, I*"'. O.iilri \, UK- 6.) : IOSKS, \9SO. i.in.1- . in, flga. • iln- -1 .1 :u)tuin : hik'lit 0 ,; ne*»0.5 i 1 71 linn ; hitMit " •'•- mm.: tlii'-koew 0.23 in \- the. characters of tin- -|u'cies have been quite generally misinterpreted, I ihle to illustrate them as far as shown in three typical exam; 1 'i the t es of measurements given above, the first may \>e regarded as a fair ap- for fully grown specimen-, while the other i> taken from oue of the smallest seen. The length usually \arie- Let ween 1.0 ami l.'J mm., ami occasionally it in-- \.'t mm. l-'ignri'.N 'J'.t, -\'2 ami :»•. though ilitiering as much in tlieir outlines a- any in hiui'lroin.|>.i|i. had In WS& de*crlbrd fmm c»»u ..f :'..• Interior a* • Or yr if Ilia, mnd lb' « frumlli frniinil rid The u-t :- • ImlUrto/li*""-"-!/!.""-"''1- ' r enJimirr jhrfured ' form of l'. •UtjM'i KTvktly rMeablw B. <«ltedreeimeiis, 2.0 nun. and more in length, occur in the- upper beds of the same formation. These were referred to the species by I)r. S. A. Miller, but are not taken into account here because they are probably distinct. O8TRA«>l>\ •t» I \\\ i ii", rron < PI. A 1 PIOB. n.: hltfht 0 7.') ID in : ihii-knt-s o 4* mm. A larjror S|»M-IIII. ii hata li-rik'th of about I :> nun. Tlii- is an uini-nally short, subovate form, the ends being nearly equal ami, with the dorsal margin, forming an almost regular elliptic curve; ventral outline straight, centrally; surface smooth; valves moderately and uniformly convex, one larger ami strongly overlapping the other above. l,elo\v and at one end. The end having no overlap is slightly narrower than the other. The suhequality of the ends, especially as regards thickness, makes it difficult if not impossible to determine with certainty which is the right and which the left valve. Asa Bytkoqjprittiu larger of the two must be on the left side, and if this is correct for the species, then the blunter of the two ends would be the anterior. ID »•////;•/>•, a genus containing mostly elongate species, the right valve overlaps, but the carapace in the present species is too short for that genus. Of known species Ii. .lone- ami lloll.a Wenlock form originally described as a variety of CytliercUimi * may be nearest, but differs like all other species of Hythocypris in being longer. Formation and locality.- Middle third (Rhinidictya bed) of th<- Treotoa shall*, St. Paul, Minnesota. BYTHOCYH NTI, n. sp. PLATK. XI. IV. F108. L;th 1.40mm.; night 0.68 nun.: thickness 0.7 nun. Length I 17 nun.: bight 0.57 mm.: thlcknetut 0.6 mm. Valves strongly convex, especially so ventrally, somewhat elongate elliptical in outline, the ventral margin convex but not so much as the dorsal, the ends sub- equally rounded but with the posterior one a little blunter than the anterior; surface smooth. This species is readily dfctingnithed from //. rylinr. Ulysses S. (Sraut. of the Geological Survey of Minnesota. Format™* and locality. — Middle third (Rhinidictya bed) of th>- Tr- -nt-.n shales, St. Paul and MINN. - apolls, Minnesota. • Ann M»s. X»l BbU Mr. 4, rol. III. pi. ztr. If 4, 1MB. -44 690 THE PALEONTOLOGY OF MINNESOTA. HYTIIOCYPUIS (?) ROBUSTA, u. sp. [Bythoc'yprls? robustn. C. Fig. 52.— a, a left valve, with somewhat blunter ends than usual, showing position of subcentral spot; b, right side of entire carapace; c and d, ventral and posterior outline views of same; lower Trenton ("Lower Blue limestone"), Dixon, Illinois. SIZE.— Length 2.5 mm.; bight 1.05 mm.; thickness 0.87 mm. Carapace elongate, subelliptical or obscurely triangular, the outline convex dorsally and nearly straight or gently arcuate ventrally; anterior end strongly rounded and somewhat higher (blunter) than the posterior. In a ventral view the outline is wedge-shaped, the higher or anterior end being much more attenuate than the other. Valves rather strongly convex, unequal, the left overlapping the right all around except at the posterior extremity; dorsal edge of left valve some- what thickened; posterior extremity of right (smaller) valve subacute; surface smooth; each valve occasionally showing a small discolored spot a short distance in front of the center. The affinities of this fine species are doubtful. It is not a true Bythocypris, nor is it any more like either Macrocypris or Pontocypris. Perhaps it should be placed under Bairdia since it resembles certain species that have been referred to that genus by Jones and Roll. Yet, after a careful comparison with numerous Devonian and Carboniferous species of Bairdia, I have come to doubt the propriety of recog- nizing that genus in any of the known Lower Silurian species. The acuminate posterior extremity of the right valve reminds as much of the new genus Krausella, and it is an alliance with this genus that I would favor more than with Bairdia. Specifically, B. ? robusta will be distinguished at once from all known Lower Silurian Cypridce by its large size. Fonnition and locality.-- Lower Trenton limestone, Dixon. Illinois, where it was found abundantly •i.iti'in with Kraiutelln incequalix and Schmidtella cratsimaryinata. ,.i,\ Kr»ux.|l>.| .ily r.KKMIKRKLUI'.l M MI \l SKI.l.A. n. gen. Carapace small (I . nun. in length), somewhat elongate, suhelliptical. obscurely triangular ur semiovate in outline, the dorsal margin more coiuev than the ventral, the latter straight or but gently convex; with moderately thick and very une.|iial valves; rL'ht \alve the -mailer, drawn out posteriorly into a strong -pine-like process; left valve overlapping the right all around. Type: AV-/ /*»•//• / iw«/(yii///i.v, n. -p. At ; 1 am ar,|iiainted with only four that should l»e placed in thi- genii-, vi/.: the two about to be described, Hnin/in mificostiensis Jones (Quart. .lour, tieol - . \lvi, p. ~>lx Is'.M)) from the Hudson Hiver or Cincinnati forma- tion of the island of Antieosti, and an unde.scrihed form (near A', .in-milii) which is rarely met with in the upper beds of the same formation in Ohio and Indiana. These !o not agree with /».///•»//// since the spine-like process is not formed by the tapering end- of h,,tl, valves. Imt i- restricted to the right valve, the left valve being rounded po-teriorly and resembling the corresponding valve of a thick-shelled HyHixri/iiri*. We have t here fore t he ditlerence that while the two valves of a Bainl'm are similar in outline, they are quite different posteriorly in A"/ •'. snlitumiil'i we know only the right valve, and this is exceedingly like the same valve of Kr>m*ellmce it may be shown that it, like /.' •/ /-/.////. has the posterior -pine on the overlapping instead of the smaller valve. In the last species namely, the right valve seems to overlap the left, though the overlap is very -light and scarcely di-tingui-hable. Should the relations of the valves (with respect to overlap) in these two species prove to be really the reverse of what we know to be the case in Knium-Un. a di-tii: :i<- grouping for them would probably \«- justifiable. • \!ii<-rto»n G. Till. pp. W7-JO4, pi. t. October. l»l 1.. a ;.;„;,.• • i.e new »eou« BMrfer- tUa. with »ls o«w >Doctn and ooe variety, all derlred fnmi the Ifrmvt HcWt-rlirrx -i r»ia . ' ' 692 THE PALEONTOLOGY OF MINNESOTA. [Krausolla inioquaUs. Beecherella ovata is too imperfectly known to be referred to any genus definitely, but B. naviculn and B. nnyiilnris are generically distinct from B. carinaia as well as from B. sublumida and the species of Krausella. Leaving out B. ovata. we have then at least three and probably four, more or less closely related generic group?, which it seems to me may be justly referred to collectively as the Beecherellida'. KRAUSELLA IN^EQUALIS, n. sp. PLATE XL1V, FIGS. 44-46. SIZE.— Length 2 3 mm.; hight 1.17 mm.; thickness 0.8 mm. Carapace elongate-subelliptical, the ventral outline longer and straighter than the dorsal, the ends, excluding the posterior spine, subequal and most prominent in the lower half; outline in a ventral view elongate rhomboidal, in an end view sub- triangular, the lower part being very thick. Valves thick, very unequal, the larger (left) strongly overlapping the other; basally the left valve turns inward abruptly, causing a decided flattening of the ventral edge; right valve moderately convex, with th« dorsal and ventral margins subparallel, the dorsal edge being less curved than in the left valve; behind it is drawn out into a strong blunt spine-like process, the point of which extends a short distance beyond the edge of the opposite valve. Surface of valves without markings of any kind so far as observed. This is a well marked species, distinguished chiefly by the great ventral thickness and relatively high position of the posterior spine. The latter may be a little lower and the dorsal outline somewhat more convex than in the specimen illustrated on plate XLIV. The inequality of the two valves is so great that, unless found in their natural position, they would scarcely be suspected of belonging together. Formation and locality.— Lower Trenton limestone, Dixon, Illinois. (Stone's River group, Vanux- emia bed). • . KUAI'SKLLA AKCUATA, H. Sp. PLATE XLIV, FIGS. 47-M. M/I:. Length l.'.inmi.: hight 0.82 mm.: thickness about 0.58 nun. Length 1.7 nun.: hight 0.70 mm. Length 1. 8 iniu.; hight 0.70 mm. In this species the outline is nearly semicircular or semielliptical, the basal line being straighter and the dorsal margin more arcuate than in K. iwrqunlis. The po.-tfrior spine also is more slender and situated lower, the point in some instances being almost on a line with the ventral edge of the right valve. Finally, the left vidve is more uniformly convex, the upper half of the surface being fuller, while the •A. r.-.i:: kr»u«-IU »rru»t».l ventral |H.rtioii i> iniicli If-s j.nmiintMit. nfall these .lill'erences tin- nm-t ;in«l |M-rha|» the only itii|.(»r-taiit one i- the hist llninliti, ur 'AS it ^ll(lul(l now In- calif. I. h'r.iusflln anficnstirnsis .lones, 8p represente*! as huving a much l.liiiiti-r ant.-rior outline. Init in tho Cincinnati f«iniia- tion of (ihio and In-liana we have a species that comes much nearer, the anterior end of the ri^ht vaht> UMH^ quite as nam.\\. only the most prominent point i- •A.T ihlr.l.if il. i ihalem Minoeapo : Tn-iUmi n, llUools; BlfdMgw Unwtooe, 11 fb Brides Kentn 694 THE PALEONTOLOGY OF MINNESOTA. [Communication. COMMUNICATION. PROFESSOR N. H. WINCHELL, State Geologist. Sin:— At your request I have prepared the following discussion and illustration of the trilobites collected from the various faunas of the Lower Silurian in the state of Minnesota. In transmitting this paper for publication jn your reports, permit me to record the obligation which I feel to you personally for the opportunity of studying and making notes upon this series of interesting fossils. At your instance only would the work have been possible. My indebtedness to Mr. E. O. Ulrich, the paleontologist of your survey, is also great, as he has placed at my disposal his private collections, not alone of Minnesota trilobites, but of those from other Lower Silurian localities, and this material has contributed substantially to the fullness of these observa- tions. He has also aided me with various timely and apt suggestions of which I have appreciatively availed myself. Several gentlemen have, through you, kindly submitted specimens of these Crustacea for the purpose of this work: Mr. W. H. Scofleld, of Cannon Falls, Dr. C. H. Bobbins, of Wykoff, and Mr. 11. H. Basse, of Granger. By the favor of Prof. C. E. Beecher, some specimens collected by Mr. Charles Schuchert and now belonging to the Peabody Museum of Yale University, have been placed in my hands. To all these I beg to express here my appreciation of their consideration; to Mr. Schuchert especially for his friendly interest in the furtherance of the work. I have the honor to remain, sir, Very respectfully yours, JOHN M. CLARKE. Albany, N. Y., January 2d, 1893. CHAPTER VIII. TIIK LOWEB SILURIAN TRTLOBITI < >F MINNESOTA. MCKK. tNTBODUCTION. trilohites have long invited the attention of observers, the curiosity of the novice, and the mo-t intelligent scrutiny of the student. Murli of this interest lies in the frequent beauty nf their preservation, their abundance, their complication of structure. :ind. no doubt, largely in the fact that the organic plan upon which they are const ni' »n^ -ince extinct or only obscurely recognizable among their living descendants. It has been for the paleontologist to elucidate not only the various modifications of this plan of structure, but to demonstrate the anatomy both of their hard ami soft parts, their ajterations of form in the process of development from infancy to old age, the rise, progress and decline through time of subsidiary structural type-. For this work science acknowledges its obligation to the pioneer investigations of Ihilman, Brongniart, I'rKay, Green, Pander, Kmmrich and Burmeister; to those of McCoy, Salter and Wpodward upon the species of Great Britain: of lieyrich. Corda. Barrande. Ka\-er. .\o\.ik upon those of Germany and Bohemia; of de Verneuil. Houault, I'.ain.i-. . 1st, 2d and 3d lateral furrows. x. fixed cheeks. fc. free cheeks. «• axis- ». facial suture. P pleunr. e. eye. n. palpebral lobe. og. occipital groove. or. occipital ring. b. border. cephalon, C, which corresponds in a certain sense with the cephalo-thorax of the crab and lobster; a median segmented portion or thorax, T, and a tail-plate, or pygidium, P. Each of these parts is in articulation with that adjoining. The central longi- tudinal lobe of the body is called, in its extent over the cephalon, the glabella, g; on the thorax and pygidium, it is known as the axis, a. The lateral longitudinal lobes are, on the OBphalon, known as ti on the thorax and pygidium as the plfu>,i. /i. The two longitudinal grooves dividing the entire test are the y pairs from the anterior backward ( i >f the lobes formed by these furrows the anterior, or frontal loin; I, is large and unpaired; thence backward the lutt-ral lubes are n am be red to correspond with the furrows, each lobe lying behind the furrow with which it corresponds numerically, The posterior end of the glabella is limited by a transverse furrow, the itnl i/ri»>i >, og, behind which lies a distinct segment or occipital ring, or; both of these extend on to the cheeks of the cephalon and form a coalesced segment. The lateral expansions of the cephalon or the cheeks are usually divided into two parts by a f,i,-!al suture, s, which extends from the posterior or lateral margin to the anterior margin. The teat was readily separable along these lines after the sloughing of the integument or the decomposition of the lining tissue. The outer or separable portions are known as the /re* cheeks, fc, the inner portion between the sutures and the dorsal furrows, as the ftted cheeks, x. In a few genera the facial sutures are obscure or not developed, but where they exist the cephalon consists of three plates, two free cheeks and a central intrasutuml plate to which the term cranulium is here applied. The cranidium consists of the glabella, fixed cheeks and a ter or less portion of the occipital ring. The outer lateral margin of the cephalon may lie thickened into a border, b, which meets the occipital ring at the outer posterior angle of the cheek (genal angle). This angle may be obtuse, acute or produced into spines of greater or less length (ut having a very short glabella. The latter had been somewhat al>ra indicate this structure I have introduced an outline figure of the cephalon taken from this cast. It is stated in the original ription that this specimen was labeled in the collection of the Philadelphia Mixeam as from Hamp-lr -mia: the author, at the -amr time speaking of others from the Miami river and near Cincinnati. There is. thus, no doubt of hi^ 'ion to include the well known Ilnd-on Hi\er form under thi- name: 700 THE PALEONTOLOGY OF MINNESOTA. LAsaphus. Conrad's Calymmene senaria* and Green's C. Uumenbachtf from Trenton Falls, N. Y., are distinct from C. callicephala, as shown by the accompanying figure of the cephalon of the latter, which indicates the decided genal spinules and the long shovel-shaped, not abruptly concave, anterior extension. The Cincinnati form may Fig. 3.— Outlines of cephalon of Calymmene senaria Conrad, Trenton Falls, N. Y. also occur in the Trenton fauna of New York as it does in the Hudson River or Lorraine shales of that region, but the usual Trenton species must retain the name proposed for it by Conrad. Among the Minnesota specimens is one to which my attention has been especi- ally directed by Mr. Ulrich, from the Hudson River group near Spring Valley, bearing a cluster of coarse tubercles on each segment of the axis near the dorsal furrows. I am disposed to believe that the original size of these tubercles has been enlarged by a slight deposit of tufaceous matter upon them, but even if this supposition be correct the tubercles must have been larger than usual on this part of the test. The epidermal granulations are seldom well retained in the Ohio specimens but some of the Minnesota examples show them distinctly, while in the New York specimens they are clearly defined over the entire dorsal surface. Formation and locality.— Galena shales, St. Paul, Cannon Falls; Hudson River group, near Spring Valley, Minnesota. Family ASAPHID^E. Genus ASAPHUS, Brongniart, 1822. Subgenus ISOTELUS, DeKay, 1824. The original species of Asaphus, A. expansus Wahlenberg, is of a type which does not appear to be represented in the American faunas. Its lobate glabella, distinctly segmented pygidial axis, and narrow thoracic axis., are sufficiently distinctive to give the term a morphological value when thus restricted. DeKay's term Isotelus, very significant and proposed two years later, includes species with broad axis and obsolete segmentation at maturity. We therefore believe that an excellent purpose •4th Ann. Kept. Pal. IH-pt.; N. Y. Oeol. Survey, p. 49; 1841. tQp. n/., p. 28, cant 1. liutclut fl TRILOni 701 18 subserved in the ratontiOQ Of this nann1. Knr purposes of comparison a copy of l>alman'« ti^nro of As'i^lnis t-j-j»insit^ i- lien- introduced. Flu*. 4. Outline of Atayhu* trpanmt WahU-nU-iy (afu-r Dalnian). ISOTELUS oioAs DeKay, 1824. • luxgigan I>rK \v |8M. AtinaN Ly.-.-uin Nat Hist. N. V., rol. I, p. 174, pi. 12, fitf. I, pi. 13, tg. 1. Ataphut }ilntycrj>halu* (STORKS) of mewl authors. ISOTBLUS MAXIMt'S Locke, 1838. .:, 1838. Second Aon. Kept., Oeol. Surv. Ohio, p. 246, flgn. 8, 9. /•"trim m'aittn* I.IM KK, 1841. Trans. Amer. Aaooc. Oeol. and Nat. p. 221, pi. 6. Ataphu* nuyi*tu* I L\ various authors, Hall.1 Hurmeister,' Meek,1 Miller.4 and others. In the original specimens the conventional distinction l.ctween the species was clearly indicated. DeKay's figures, one of an enrolled example, one of an extended (I»T P«l»OfitoUj«» of N.-w Y.,rk. v.,l [. p ill. pl.tM ».«!.«, O, I- 17 ontanltalloa of tb« TrilohltM < R*r > ..»UHon i. p. 110, pi. 1 •(. U, IMS. (*. Palamatolo«r "' Ohio. rol. I. p. 159. pi. II B. D.-lnn.ti yu.ru Juurn. Scleor-. »ol. I. pp. «7, l> 702 THE PALEONTOLOGY OF MINNESOTA. [isutclus glgas— maxima*. individual, both show that the cephalon was without cheek spines. In Locke's figures (in part a restoration) of his I. maximus published in 1841, the cheek spines are given full importance as a differential character. Writers have found apparently distinctive differences in some other respects; a broader, more obtusely angular head and tail-shield and a relatively wider thoracic axis in I. gigas. Others, again, notably Locke and Miller, ascribe to 7. maximus the broader, more crescentic shields. My observations upon extensive series of these two forms from the New York Trenton have convinced me that specimens of each, preserved without casual distor- tion of the parts furnish positively no basis for a specific distinction in any of these respects, while it is easy to find grades of difference in these features varying with the degree of vertical compression of the test. Normally, in both the spinous and aspinous forms, the cephalon and pygidium are elongate subtriangular, the extremities being subacute, slightly flattened or extenuate. The facial sutures meet at an acute angle at, or just behind the frontal margin. The glabella is obscurely defined and more obscurely lobate, traces only of the lateral furrows being visible in an oblique light. The cheeks bear an intramarginal furrow, above which their general surface is elevated into a more or less conspicuous node, crowned by the eye. The occipital ring and furrow are quite obsolete. The axial furrows of the thorax are distinct, the axis itself broad, considerably more than one-third the width of the thorax. The lobation of the pygidium is very obscure. The dorsal furrows being hardly distin- guishable, The axis is much narrower at its beginning on the pygidium than at its termination on the thorax, but in mature specimens its outline is scarcely discernible. Even a slight compression of the test, bringing the thinner or less resistant portions under strain gives an unnatural distinctness to the lobation of the cephalon and pygidium and likewise an abnormal width to the axis. The specimens of both of these forms from the schistose strata of Minnesota and Ohio more generally evince these effects of compression than those from the purer and more homogeneous limestone of Trenton Falls. The specific type of these forms being in general the same, there are still to be considered the important points of difference at first mentioned. It is, in a general sense, true of the New York examples that the aspinous head shield occurs only in individuals of large size; that is to say, 7. gigas is almost invariably a large asaph. I have not seen a well defined and clearly indubitable specimen of the aspinous head as small as the average spinous cephalon, nor a head of 7. maximus as large as an average 7. gigas. Among the fossils of this region 7. maximus rarely exceeds a length of 60 mm., which would be small indeed for an 7. gigas, of which individuals measuring 200 or 250 mm. in length are not at all uncommon. Among the Minnesota TKII.OI.II i V":; -pi-cimen- t In- -ami- fart hold>; tin- largest , all' I indeed t he only well deli ned -periim-n "f /. 'iiat I have -een lias a length of IMI nun. Tin- smaller >| miens of the -ame type, so far as their preservation permit- the determination, possess cheek -pines. '-.-Itoteltu intJ-imu* L-x-k.-. Hiifl-mi Itiv.-r (jnniji. Granger. It would appear that among the specimens from the Hudson River group of Ohio. Indiana ami Illinois, this is not always the case, as Locke's immense original ami its specific name itself indicate.* Here, locally, the occurrence of large fragments iiiniferou- heads is not altogether infrequent, perhaps even predominant with reference to the aspinous heads; but whether the rule or the exception in that locality, it need not modify the purport of our argument. The morphological significance of the cheek spines in the trilobites has not been demonstrated, nor have they invited especial attention. Undoubtedly their significance varies in different groups. In this group with the evidence now at haii'I. we iiii-1 a suggestion of their meaning. To present these points with the greater lucidity a few general remarks will be appropriate, bearing upon the developmental characters of the species under consideration, and upon the phylogeny of the asaphs. In fxotrlus imuriniHs. amall, ;wuU? tubercle. Tins evidence goes to indicate that the cheek -pine in these a-apliid> is a character of immaturity, diminishing in size as the U'luH romlitinii i» a|i|iroaclu>'l. 7.— O«n«l extremltjr of Itotrltu gigatmaximtu, with pi. ut asjilnous ap«-x. Trentoo X V In the earlier representatives of this generic type where segmentation of the pygiiiium is retaiuo-l at maturity i I'ti/rhopyge), the long cheek spines are also retained, i>hn< mmiiKjfri Walcott, of the Hlack River limestone; and, as observed above, tlir adult fon-lition of sm-h -pi-rif- i< to be regarded as. phylogenetically immature. -pora'iic or restricted local appearance of genal spines in large individuals, an occurrence of rarity, is a natural exception to normal processes, the retention of infantile characters at maturit i n>-umption in the senile condition, occurring alike in individuals, species and races. The / -mnfis \Vliitfield, gp., is an early Trenton (Hirdseye) or Calcifi-roiH form, very closely similar in all >pecific values to /. .V Mining, however, at maturity cheek spines, without the segment- ation of fh»> ivphaloti an-i jiy^idium. < >ur acqiiaintance with this form is essentially restri- t.'.l to the single large, enrolled, distorted and otherwise imperf«" men described Ky Mr. K. 1'. Wliit lieM. Toward tln> close of tlie Trenton epoch and during the predominance of thenorrna! type and with t ho st-nilo decline of the race, the highly segmented and spiniferous type roapp.-ar- in the .1 /M./(//-;I>/> < 'liaprnan and the ' /irx ulrichami gen. et. sp. nov., lioth from the hori/on of the Utica slate, l»«»th recurrent /Vy.7/((yiy7^(ir a senile reappearance of the immature individual type.* id tto opportunity »f ulopi«»ol nf Iti iji In • '••irofif rama (Journal •••" r.i ;.i. -.1 i-.« ,i .1 .1 ...... • ' ••trm»t In Ihc number of IrnMs fn.m li pulled bj ft rrwirplton (»r otorurmlkMI of tlio Itnaf*. And la ooa»«qiM90*. by A ratom .nllto rotidlll.*. Tb«Fcoarliulim*««r«d«rlrMl frum II. . -n ..f » T».I numlwr —45 706 THE PALEONTOLOGY OF MINNESOTA. [Isotelus glgas. The suggestions made here with reference to the morphological significance of the genal spines can be tested fully only when extensive series of specimens are brought under study. That in the subgenus Isotelus, they are infantile characters gradually eliminated in successive moultings of the test, appears to be true, not only of the individual, but of the race. ISOTELUS GIGAS DeKay, 1824. Of late years the name introduced by Stokes, Asaphus platycephalus, for a trilobite from St. Joseph island, lake Huron, has become current for this species, on the ground of priority of description.* None of the figures given by Stokes show the structure of the genal angles, and it is therefore wholly a matter of presumption whether his specimens were of the same character as those afterwards fully described and illustrated by DeKay.f Fig. 8.— Isotelut gigas DeKay. Hypostoma of a large individual, (erratic), central New York. Hudson River sandy shales Formation and locality of Isotelus gigas in the Minnesota formations. Hudson River group, Granger. There is a single nearly entire specimen which appears to have had a spineless cephalon, from the Galena limestone at Mantorville: and from the same locality a fragment of the glabellaof an immense individual, which in its entire condition must have had a length of not less than 17 inches. This is the largest authentic specimen of an asaphid recorded, and I have here introduced an outline figure of the animal in its natural proportions. ISOTELUS MAXIMUS Locke, 1838. This is the name first proposed by Locke, who subsequently changed it, for euphony, to /. megisfos, under which it has usually passed. Formation and locality.— Trenton: Minneapolis, St. Paul, Rochester, Minn.; Mineral Point, Wis. Galena: Wykoff, Warsaw, Konyon, Cannon Falls, Minn. Hudson River: Granger, Minn. •Trans. Geologlr.-il S.K-ii-iy. vol 1.2nd Series, pp. 199,208, pi. 27. 1822. +Thi- Tri'iiinn riH-ksnf New York contain adistinct species known at present only from Its pygldlum. Thishas passed under the n:iuir /. f/ly• •rialh common, though I have seen several characteristic examples. Thespeciea mmy be distinguished 1>% tin term. Imitrlux Jn< •"//>/.-. ln-im; ili'ilirated to Prof. James Hall. Outline of Iso 'JOB OIOA8 l»nl*lu« < !,. II. ) TKll.ul >n- II -p. I.-,IM,I/W WHIM iKi.ii. 18*6. Hull. Am. Mil*. Na' 1. I p. 336, pi. 34, I1|f«. I— «. Atopkui ran.ili* \VimriKi.n. IW.t. Hull. Am. V v.il. It. \>. 61, |.N II. I.1 Tin- nanio. which has I.een ascribed to Conrad l>y both I'roN. HallT ami \\ hit- Held,! and also l>y Mr. Millings,)' had no inirticular meaning until VHlitAold danribad undtM- it a nearly in l>eds on lake Cliainplaiti. To r rod it tl .-s to Conrad is merely a matter «f courtesy, as it was used only in hi- manuscript and even then aj.pliod to a specifically unidentifiable part of thepypdial douhlure. The relation^ uf that fo—i I, or of those described l>y Hall under tin- name from the Cha/y lime-tone, to Mr. Whit lield's -pecies are quite uncertain. There are two extended and nearly entire specimens from the lower or Birdseye hori/on of the Trenton ^rotip in Fill more county, Minn., and a single py^idimn t'\g.9—Itoteluiican from an equivalent position at Stanton. Minn., which may l>e provisionally referred to this species; though it is to be confessed that thoir ditl'erences from /. ;;«/./•/«*»<>• • P»l»«ololo«y of s ^ . ..[ i. p 3.pi 4W». «».. i: rlL •• PtliMMOtc Fo»ll«. T.,| |. p. 164. p. tea. »f. MO, IM&; «nd «!«*..• •x. i. IM. 708 THE PALEONTOLOGY OF MINNESOTA. [Isotelas susiB. are not impressive. The smaller individual has a more decidedly flattened cephalic border than the larger, but this difference is probably due to circumstantial causes; its cheek spines are much the longer, extending to the sixth segment, while on the larger example they reach only to the second. Formation and locality.— Lower Trenton; Fillmore county, and Stanton, Goodhue county. IsoTELue sus-fi Whitfield, 1882. Asaphus susce (CALVIN in MS.) WHITFIELD, 1882. Geology of Wisconsin, vol. iv, p. 236, pi. 5, fig. 3; pi. 10, flg. 8. The features distinguishing this form from its allies in the same fauna lie mainly in the general proportions of the animal. Both cephalon and pygidium are broad and relatively short, their outlines being in contradistinction to the elongate and subangular head and tail shields of /. gigas and J. maximus. In addition, there is a general and very regular convexity of the parts, a sharper definition of the thoracic axis, deeper and more distant axial furrows on the pygidium; the facial sutures, also, on their anterior limb, make broad, sweeping outward curves and a large angle at their union. The description of the species has been given in detail by Mr. Whitfield in the work cited and it is only necessary here to indicate the differential characters. Figs. 10, 11. Two views of an imperfect, partially enrolled individual of Isotelus xusce Whitfleld. Formation and locality. — Specimens having about the same dimensions as the original occur in the Hudson River group at Granger (Museum No. 8434) and two miles east of Spring Valley. Minn, (collection of Mr. Ulrlch). i.i.i TUl oi.ii K> 7"'.t 001 ITYfllnni.r. Angelin. ls:,|. I'M' llnl'V.h I I.KICIII. H. gp. This species is represented in the material liefore me by seven more or less com- plete pygidia: one small and entire. •_'! mm. in length and :::. mm. in greatest width; another, a part of a very large one. fully 1-Jii iitm. in \\idthacrossthetop. The general form of the tir-t i- -emi-oval except alxnit the margins which are broadly concave. Kitf. \-'. An nitir.- i.yjfi.lluin ,,f Ptyehnpyge ulrichi, Cannon Falls. The location is clearly defined, tin- axis Keing relatively narrow, slightly more than one-fifth the entire length of the -liield, and extending for somewhat more than 'liinls the length of the pygidium, ending in a blunt, not elevated extremity. i j - 11— Fragment of a laiv py«i«liuni of ulrichi. wit! ,n ..f <.ut;.ii<-. ( .1 It I >ears eight or nine annulations, only the first three or four being well defined. The pleura* are convex and rather short on account of the broad, concave margin. Besides the articulating segment there are five rids, \\-ith a trace of a sixth; and on the internal cast seven or eight ribs may l>e discerned. Of these the fir*t is the THE PALEONTOLOGY Of MINNESOTA. IGerasaplies ulrlchana. broadest; all are simple, unfurrowed, and all disappear quite abruptly at the marginal border. The posterior portion of the pleurae is smooth, and the extremital area of the border is slightly bent upward. The entire surface of the shield is covered with anastomosing, racemose, elevated lines, which are very conspicuous on the larger specimen, and clearly apparent on the smaller. This ornament is one of the generic characters of the group given by Angelin: "densissime striolatus." This species is not widely different, so far it is known, from Asaphus huttoni Billings,* from the Quebec group of Table Head, Newfoundland, except in the length of the axis, which exceeds that of the latter species. It is an excellent representative of the strongly segmented type of Asaphun for which Angelin proposed the name Ptychopyye. Formation and locality.— One of the smaller specimens is from the lower blue beds of the Trenton limestone at Mineral Point, Wis. (Museum No. 8402), and the others from an equivalent or Birdseye horizon at Cannon Falls, Minn. The latter are from the collection of Mr. Scofleld. GERASAPHES,t n.subgen. GERASAPHES ULRICHANA, n. sp. The form for which this name is introduced, though small, and even imperfectly known in certain respects, is one of no little interest in its relation to the ontogeny of the asaphids. The specimens of the single known species (named in compliment to its discoverer, Mr. E, 0. Ulrich) consist of two cranidia and two pygidia, lying on the surface of fragments of a calcareous shale, from the horizon of the Utica slate, at the mouth of the Licking river, Ohio. Of these four examples, three are on the same piece of rock. The following description embodies not only the distinguishing characters of the subgenus, but also those of the typical species. Fig. 14.— Cranldium of OeratapJus ulrichana, •/, 4. Of the two cranidia, one has a length of 4£ mm., the other of 2A mm. The form of this part is distinctly asaphoid. The facial sutures take their origin on the posterior margin, making an acute angle with it, thence passing inward in a slightly convex curve to the palpebral lobes which are situated at about one-third the length of the cranidium from the posterior margin. These lobes are not large and the course of the sutures in front of them is that characteristic of Isoielus, being a broad • Paleozoic Fossils, vol. I, p. 271. BK. 237,4866. ,*. ..lit: iim/i/ir*. :i-:i|ilms. TUI.oMTKv 711 » J outward curve following the margin- of tin- frontal glabellar lobe, am! recurving anteriorly, tin- branches of the *utnre meeting at an angle in the median line at, or ju*t within the frontal margin of the cephalon. Met ween the anterior limit* of the suture ami the frontal lobe is a smooth, flat area. The glahella is broad and expanded anteriorly, narrowing backwards, it* anterior width being fully twice, that at the occipital ring. Its surface is quite Miiooth ami evenly convex with an olisciire median longitudinal ridge traversing its entire length. The extreme lateral points of the frontal lobe lie about one-fourth the length of the glahella from the anterior margin; thence the lateral outlines converge in nearly straight lines' to points just above the palpebral lobes, where there is a slight inward deflection on each side, which represents the position of the tir*t glabellar furrows. Below this is a pair of more conspicuous depressions, or the id lateral furrow-., which begin opposite the middle of the palpebral lobes, pass directly inward for a short distance and then backward, extending quite to the occipital furrow. These furrow* are not deep but the lobes thus cut off are quite distinct. The posterior median portion of the glabella between these furrows is narrow and the low axial ridge tr.ivereing it terminates at the neck ring in a round, blunt elevation. These features, with the exception of the prominence of the basal lobes, are throughout characteristic of the typical Asaphus, and the accompanying figure may be compared with that of Asaphus expansus given on a preceding page. The occipital ring is arched and moderately prominent. Flga. 15, 16.— Pygldla of Oercuaphei I'ygidium multiM-gmented, outline suhparahnlir. margin entire. Surface very convex medially, lateral i»ortions depressed convex. Horder broad and Mat, being widest at the {Mist-lateral edge?, narrowest at the anterior angles and posterior extremity. At the latter point then i> a slight incurvature of the margin. The outline of the convex portion of the shield i* Mihtriangular and quite diUerent from that of the margin. Axis quite narrow, highly convex, longitudinally arched and extending to the marginal border. It bear< In 11 distinct aiinulation*. the anterior ones being separated by broad grooves. Only the posterior extremity i* unsegmented. The pleura- bear 7 ribs on earh >id.-; these are narrow, straight, transverse. slightly reflected except at their outer extremities on the margin. Kach of these sharply defined ribs is divided by a deep sulcus broader than the interannular 712 THE PALEONTOLOGY OF MINNESOTA. [Nlleus vigilans. grooves which are linear. These sulci disappear at reaching the broad margin, but the interannular grooves are continued upon, and nearly across the marginal expansion. The surface appears to have been quite smooth. The larger of the specimens measures 2 mm. both in length and width. The distinctive features of this subgenus and species are those of early representatives of the asaphid type, which at maturity show a condition of distinct annulation. The form appeared at a period when the true asaphs were on the decline and near extinction. Both structure and size indicate that this was a paracmic modification of the asaphid stock, reproducing in the senility of the race the characters of immaturity. Formation and locality.— Utica shale, mouth of Licking river, Ohio; probably also in the Hudson River shales, Rome, N. Y. Genus NILEUS, Dalman, 1826. NILEUS VIGILANS Meek and Worthen, (sp.) 1875, Asaphus vigilans MEEK and WORTHKN, 1875. Geol. Surv. Illinois, vol. vi, p. 497, pi. 23, flg. 6. lllirnitx (Nileus) minnesotensis, FOEKSTE, 1887. Fifteenth llept. Geol. and Nat. Hist. Surv. Minn., p.,478, fig. 1. The description given by Mr. A. F. Foerste was based upon a single cranidium from the Trenton horizon at Minneapolis. There are before me a number of essentially entire individuals, most of them enrolled but several in an extended condition. Some of these are from Minneapolis but the majority from the Galena beds. Upon comparison of these with the description and original specimens of Asaphus vigilms Meek and Worthen, I find no basis of specific distinction. Fig. 17.— Nilerts vigilans Meek and Wortln'ii. Fi^ ls. -i'r,,|]](. ,,f u,(. Sillll(. Cephalic view of an etindlc-d individual. General form elliptical with subcrescentic extremities; longitudinal lobation very obscure. Cephalon transverse, regularly convex. Margin very slightly thickened by a thread-like elevation. Genal angles obtuse. Frontal slope full but not projecting, terminating abruptly on the margin; lateral surface slightly depressed beneath the eyes; upper surface between the eyes flattened. Glabella, dorsal furrows, occipital furrow and ring not defined. Eyes small for this genus, but prominent; situated at points each one-third of the entire transverse diameter from the lateral margin and one-third of the longitudinal diameter from the posterior Ka 71:', Nllou* vl|til»ii%.) margin, l-acial suture-; making a l.road out ward curve mi th-ir anterior liinli. incurving a^ani near the anterior margin. reaching it in front of the center of tin- eyes and trauM-sintf tin- margin without angulat ion: posterior curves intersecting the posterior margins at lar^o angles not far from flic genal extremities. IK >«• rtgfl«M Meek and W<.rth«-n. An i-ritir.- individual, with c.'phalon iuclln Thorax compiled of ei^ht hroad, flat segments. Longitudinal lobation very > \er.v l.road. covering three-fourths of the entire width of the thorax. The segments are broad in the middle, narrowing somewhat at the axial furrows; on the pleura- they are very narrow, not grooved, and the beveled articulating planes extend for the entire distance from the dorsal furrows. Ps-idimn comparatively >hort, snl.semicircular on the margins. Surface -month, sloping equally to the sides and posterior extremity, slightly concave just within the, margin; wit hout external evidence of lobation or segmentation. On the cast of the inner surface the axis is seen to be considerably narrower at the anterior margin than at the termination of the thorax, and its lateral margins taper regularly to a point not distant from the posterior extremity of the shield; in a favorable light eight animations may be counted on the axis and five on the pleura-. The articulating ring and groove on the anterior margin are broad and conspicuous. l>oul.lnre broad, coarsely striated as in Isotelus. Surface ornamented, especially on the extremital portion-, l.y coarse venation traversing the test transversely. •;ry young entire example has a length of 1C. mm.; the largest extended specimen i- -Jf, mm. in length, and the largest enrolled example 50 mm. in length. evident from certain isolated py^'idia that, th. limeii-ions were frequently exceeded. .-.i/iff. -Lower Tr.-r>t<.ri MiUrk Mirm-ai,.. t,a shales, WyknlT. 1 -ciea was .-riKlnal!y d«-s,-ril--,l from it,,- I; fauna of Carroll anil K. '•:'-' '" 'u* trentoneiuu. with which Ills •>.y tl,.-i-,.ltlnt, ,,r • '.,rrn.,f th.-farlal ihallownw- imdth of tbe thoracic Mgo lifr.nn*. ,/thr.f th.-ir -y.-s. Th!> fralur,- i, -. Dalman. th.- typ,?.,f r,«M Al>, ln th(. Ihr,.,. SJ ;'P- -v- »'•<•«<• £2 Figs. 20— 23.- 1 litmus americanus (aflt:r Hillings). Fig. 20.— Upper side of head. Fig. 21.— Front view of the same individual. Fig. 22.— Pygiclinni of the same. Fig. 23.— A nearly entire individual. to a position in front of the eye. I n others it is behind the eye. The space between the eye and the dorsal furrows is convex, and the eye itself seems to be rather protuberant or subconical. The movable cheek is subtriangular, its width at the posterior margin about onre and a half the distance of the eye from the dorsal furrow, its length along the lower margin a little greater than its posterior width. The anterior margin of the whole head is uniformly rounded, with the exception of a slight concave curve just outside of the suture. In some specimens in which the front part of the head is most abruptly bent down the middle portion of the front margin is depressed convex or nearly straight. Thorax with ten segments. Axis moderately convex, from a little more than one-third to nearly one-half the width of the whole animal, a little wider at the anterior than at the posterior segment; the sides sometimes straight and sometimes slightly curved outwards. On each side of the axis there is a flat •pice between the »lde of th . the h.-ad of tl»- picur.i dth of the space Is between third and : he width of n . Th.- pl.-i, ,t ut the fulcra at an ancl-- which varies ID different inili- and .it ie lU th.-ir length from the side of the I .rtcr than th- •>>: from moderate]* I.. • . and uniformly rounde .::dlum I- well defined at the ai.1 margin l>> wluchd ul at at-Mit one-third orone halMhe]ei,k'th, ••onverglng towards each other, and sometime* . ..-I'.niin: the .1; -oftheci- ir although - .able. The specimen on which th- '-Minded, h.i- th.- R .e head and pytfidmni covered with short !M|iiannis«- .f each fissure lietm.' more elevated than the other, gives to the HUT- : from half a line to two or three linen, all' from one-eighth to one f.Mirth of a line di-tant from each other, t >n the tail they seem to radiate lrr.-k'u- axIsMaccMt- the front margin and parallel with It, arc a number of straight iilou- tl-sures. Tl. r specie* Of tin III other -iM-cimens the ;iar.-..f the name character. Ir n-n In Dr. Grant'* •he middle portion of the front of the head is nearly uniooth, and In addition to the strlas Is coarsely puncture<|. Mr. Hillings also called attention to the close approach of /. «//<./•/<•./«//>• to 7. Ir-iwln Wahlenher^': and 1 am of the opinion that the same fossil had been ' il>ed l.y Hall in 1S47 (loc. cil.) under the latter name. It appears from the ol n- made by Holm* that this species (/. <-nixsiftn'«w/-7i/x tri'titnm-naix and />'. orbicfmifatiit, In finely preserved specimens from the Trenton of New York there is seen to be a smooth interruption of the external ornamentation directly over these spots. The Minnesota specimens are usually in a dismembered state and are frequently some- •Zelurbr. drr d«at»ch. rook*. OmclUcb.. vol. \\\\\. p. iOt. pi a. 1MO. 716 THE PALEONTOLOGY OP MINNESOTA. [Illanius indetermin:iUis. what abraded and in rather an unfavorable condition for study. An enrolled specimen from Kenyon retains the parts better than any other observed. Formation and locality. — Illcenus americanus, like /. crassicauda, has" a very restricted vertical range, though of distinctly later date than the latter. Billings speaks of it as a rare species occurring in the "Trenton limestone only," at Ottawa, L'Orignal, and lake Huron. In the Trenton limestone of Trenton Falls it is not uncommon and is exquisitely preserved. In Minnesota it is known only in the Galena limestone and shales at Wykoff, Kenyon, Old Concord, Cannon Falls, and in Goodhue county; also at Oshkosh, Wisconsin, and Galena, Illinois. ILL^ENUS; compare I. INDETEBMINATUS Walcott. IttcenuB indeterminatus WALCOTT, 1879. Thirty-first Ann. Kept. N. Y. State Mus. Nat. Hist., p. 70. Fig. 24.— Cranidium of Illcenu»; cf. I. indeterminatus Walcott. There is a single cranidium of comparatively large size, from the lower Trenton beds at Janesville, Wisconsin (Museum No. 8413), which agrees very well with the description given by Walcott, and is characterized by the conspicuous development of the dorsal furrows, which clearly define the lateral outline of the glabella. Mr. Walcott's original specimens were from Herkimer county, N. Y. (Black River lime- stone), and from Plattesville, Wisconsin. Subgenus THALEOPS, Conrad, 1843. THALEOPS OVATA Conrad, 1843. Tlutleops ovata CoNitAD, 1843. Proc. Acad. Nat. Sci. Phil., vol. i, p. 332. Thaleops(Illcenus)ovatus HALL, 1843. Palaeontology of New York, vol. i, p. 259; pi. fi7. flgs. 6a, b. Illtenus ovatug WIIITKIKLD, 1882. Geology of Wisconsin, vol. iv, p. 238; pi. 5, flgs. 1-2. Illtenus herricki FOEKSTE, 1887. Fifteenth Ann. Kept. Geol. and Nat. Hist. Sur.v. Minnesota, p. 479, Ilg. 2. This appears to be the most abundant of the Minnesota trilobites; and though I have seen but two essentially entire specimens, separated heads and tails are of frequent occurrence. The species is very characteristic in its structure and was clearly described by Mr. Conrad from entire individuals. The diagnostic features indicated by him, and which lead at once to the identification of the species, are the deep lobation of the cephalon, the attenuate cheeks, divergent, tapering, peduncular eye-nodes, and the complete isolation of the axis of the pygidium. The first of these features varies more or less and is better defined on internal casts than on the external surface. TKII.olUTI 717 ;.- .....l«.l lieneral form ovoid, broade-t anteriorly, attenuate and salient at (lie angles of the cephaloti. Axial length ami: \\ hit h equal. < 'ephalon l.roat of the surface and lie nearly in the plane of the thorax. The free cheeks are abruptly constricted beneath and in front of the eyes and take the form of di\ rrj^ent .-lightly recurved -pines or horns. The facial -utures rise rapidly from the occipital margin to the summit of the eye-nodes, thence rounding gradually forward to the anterior margin which they intersect opposite the anterior extremities of the dorsal fun-' Fig. 25.— Internal cast of Thaleopt ovata Conrad. Thorax subquadrate, tapering; composed of ten segment-. Surface strongly lobed. Axis convex, narrow. I'leuni* geniculated at about one-third their length. Segments Hat and. upon the axis, moderately broad, not furrowed on the pleur.e. recurved toward their extremr 718 THE PALEONTOLOGY OF MINNESOTA. LThaleops ovata. Pygidium short, transversely subquadrate, the posterior margin being a very broad curve; width equal to nearly twice the length. Axis very prominent, much narrower than at the termination of the thorax. It tapers very gradually and Fig. 26.— Pygidium of Thaleops ovata Conrad. Fig. 27.— The same viewed from behind. terminates bluntly in an elevated extremity, which is faintly bilobed. The axis is thus entirely surrounded by the dorsal furrows. Its length is about one-half that of the pygidium and its extremity lies at the beginning of the convex posterior deflection of the shield. Anterior margin of the pleura; straight for one-half their extent, thence deflected at nearly right angles. Surface flat above, curving abruptly to the margins. All annulation of the pygidium is very faint, but in well preserved. Fig. 28. — Thaleops ovata Conrad. Outline of head viewed from the front; showing the terete genal extremities. From an impression of the external mould of the specimen shown in figure 25. specimens under favorable illumination, traces of five may be counted on the axis The surface of the cephalon is covered with epidermal punctae. On the cheeks and over the anterior portion of the glabella these are vertical and isolated; over the posterior surface of the glabella they become oblique and confluent, making an irregular series of elevated anastomosing stria1. The segments of the thorax appear to be quite smooth. On the pygidium, especially over the anterior portion of the axis, the punctations are deep, coarse, and arranged in transverse rows. Formation and locality.— Trenton limestone, Minneapolis, Minnesota; Beloit, Janesville, Mineral Point, Wisconsin; Dixon, Rockton, Illinois; Decorah.-Iowa. Observations.— The peculiar extension of the palpebra and the long, attenuate and projecting cheeks are features which appeared in an earlier species, Illcenus arcturus Hall, of the Chazy limestone, and re- appeared in the /. pterocephalus Whitfleld, from the Niagara limestones of Wisconsin. In the typical forms of Illcenus (group of /. crassicauda Wahl.). the structural those parts is so different (low, sessile eyes and broad, obtuse, unprojecting cheeks) that Conrad's term Thaleops may well be retained for the subordinate type of structure represented by/, ovatus. Mr. A. F. Foerste's /. herricki, was evidently described from an entire head of I. (Thaleops) ovatus, and must hence fall into the synonymy of the species. BUMAKTUS TRENTONENSIS EmmOHS (sp.), 1842. Illcenus trentonensis EMMONS, 1842. (!i:ology of New York: Ut-pl. 2d Dist., p. 390, fig. 3. cf. Illcenus crassicauda (WAUL .) HALL, IT. Pahi-ontology of New York, vol. i, p. 22!»: pi. 60, flgs. 4c, id. Illcenus milleri liiu.iMis, 185!). Canad. Nat. and Geol., vol. iv, p. 37~>. Illcenus milleri WALCOTT, 1879. Thirty-first Ann. Kept, N. Y. State Mus. Nat. Hist., p. 71. Not Bumastus trentonensis K.MMONS. Geology of New York: Kept. Second Dist , p. 390, fig. 1. Not Illcenus trentonensis HALL. Paleontology of Xew York, vol. i, p. 230; pi. 60, llg. .",. Not Illcenus crassicauda HALL. he. cit., pi. 60, flgs. 4a, 46. TIM I." "'•' •n»n.U 1 ;-.». i lullin.- cif hi-;ir. Kmmon- in M'J noticed, under the ii;iine lllnmis tr?n1»n< •». . LM\ ing ;i profile and dorsal view of a -ingle entire -prcimen. Tlif-e tL'inv- .in- here introduced. In the same place he a figure o| a much larger ami quite distinct species, from pre.-umalily the same hnri/iiM. referring to it liy the name Himnix/u* tnntonrnsi*. This use of the same -pecitic naiiu' for ipedet evidently di-tinct. and \\liich the author regarded a?- generically ditlen-nt. ha- l>een tlic -ourcc of tht> «'onfiision of the two. ll/»m<- tr< M/o;i«7i.v/x Kmmoii-. ha- not IHMMI n-cn^iii/i'd liy later writers; litnuusfMit frrntonensis Kmmons was reforred liy Hall (/<>• . '-it.) to IH Kminons' llltrnus trentontnsis was not noticed l>y this writer. This involution of names is the probable cause of both of Kmmons' forms being referred to /. trentonen.ii* in the catalogues of Miller and Vogdes. The Ilumastiix tr> n/<»i> usi* Kmmon- i /. 'i-i-ndinfnsi* Hall), as represented in the original figure, is a large species with /////;w.---like cephalon and broadly lobed thorax and pyjridimn. The longitudinal loliation is so pronounced, and the median lobe of the body so narrow, as to make the reference of the species to Rumastus iiicon^ruon-. It appears from the description of this species given by Mr. Hall (loc. that the original specimen was lost, and that his account, as well as his figure of it, was drawn from a plaster cast. One or the other of these figures must have been quite inaccurate, for the latter represents a fossil in which the lobation is Aether obsolete, except for the faint evidences of dorsal furrows upon the cephalon. The animal. uted thus, would he an excellent Rumnttus. I am -. 30. 31.— B .ind -hall then-fore revive for 720 THE PALEONTOLOGY OF MINNESOTA. [Bumastus trentoncnsis. the smaller, now before us, the term Bumastus trentonensis, this process involving simply the interchange of the generic names originally applied to the species. The original of B. trentonensis was not described, but the wood cuts given of it show in both views only eight thoracic segments. There is no evidence from these figures that any of the segments have been lost or forced beneath one or the other of the extremital shields. Mr. Billings' species Illccnus milleri (from various localities in the Trenton limestone about Ottawa, and also from the Black River limestone in the township of Hull, Canada) is inseparable from B. trentonensis. It was described as having nine thoracic segments; Mr. Walcott, however, in identifying I. milleri in the Black River and Trenton limestone of New York and the Trenton of Platteville, Wisconsin (loc. cit.), suggests that one of the segments of the original was concealed, as his specimens showed ten segments. Before me are two entire individuals of this species from the Trenton limestone of Trenton Falls; one of them shows ten thoracic Fig. 32.— Bumag'.us trentonensis Emruons (sp.). An entire individual with ten segments. Trenton Falls, New York. segments, the other agrees with Emmons' original in having but eight. The latter has been eroded in such a manner as to afford a complete longitudinal section of the specimen, which fully demonstrates that no segment has been lost and that this animal at this stage of development possessed no more than eight segments. An enrolled individual from the Black River limestone at Poland, N. Y., shows nine of these segments. Among the numerous examples of the species which have been received from localities in Minnesota and Illinois, enrolled individuals are common, while but a Fi«. 33.— Bumastus trentonensis Emraons (sp.). An entire but, disjointed individual, with nine segment--. single extended example has been observed. This, from the Galena beds at Pleasant Grove, Minnesota, has nine segments; coiled specimens from the middle Trenton -hales .1 rithony Park ami from .Minneapolis have nine, ami a single coiled example from tin- (Jalena sh.i fan, 'ioodhno. county. Minnesota, haw Imt ei^ht. Theetween the eye and the axial line, and much more clearly apparent on the cast than on the outer surface. It seems aide that -uch cepha •* were areas of insertion of muscular bands •bed to -imilar -cars on the inner surface of the hypostoma. mally there is no trace of longitudinal lobation on the cephalon or pygidiura, and the axial furrows of the thora <'ry obs< ~ light vertical compression, howevt" .mally to ernp! hese features in the head and thorax, and -en- th- \ityoftheformer. Formation uml Icnilil;, n linxtit' . \\ -hales: Pleasai . DUD Fall* 722 THE PALEONTOLOGY OF MINNESOTA. I Hiliii;is1ii-i (ii'ljiciuidatus. BUMASTUS ORBICAUDA.TUS Billings (sp.), 1859. Illtenus orbicaii'l'itu* liir.i.i.vas, 1859. Canad. Nat., vol. iv, p. 379. Illcenus orbicaudatus BILLINUS, ism;. Out. Silur. Foss. Antirosti, p. 27, flg. 10. There is a single cranidium from the Galena shales at Wykoflf, Minnesota (Dr. Robbing' collection), which appears to represent this species, described originally from the Trenton or Hudson 1 fiver horizon at English Head and elsewhere, Anticosti. Fi^. 3G. — Binmtiitiis orlrii-iiiulatus Hillings. Galena shales. Kcnynn. HUMUS/UN orbicaudatus and B. frentonensis resemble each other in many respects, though specimens of the latter are of decidedly smaller size and greater convexity of cephalon. The Wykoff specimen measures 20 mm. in length, and 26 mm. in width across the base. Certain large, smooth, unsegmented pygidia from the Galena shales at Kenyon are probably parts of the same species. Genus BATHYURUS, Billings, ISO!). BATHYURUS KXTANS Hall, (sp.), 1847. Asaphus? extans HALL, 1847. Paleontology of New York, vol. i, p. 228, pi. 60, Iljjs. '2ciiiieiis in lian-l liavt- tin- -arne characters, and the following a«lilitional In spite of the coarse and closely set tubercles, covering tin- upper Mirfare of the gl, '\vn pairs of lateral grooves are -li-ccrnible. Hotli are short, the tir>t ln-in^ tran- M.- -ccoii'l ilin-cti-1 liackwanl. The glahellar • • all iiiilistinrt, tlit> frontal lobe ci>Vfring fully one-half of the ghibella. The •al bonier i- nam>w. but broader than in /•'. fXfolU, eon. ,ut the glabella, and turned up at the edge. The palpebral lobes are moderately large, approximate and posterior. The cwripital ring is tulien-led and it< central spino aliout one-third the length of the glabella. Associated with these cranidia, in both the localities mentioned, are pygidia. entire on tho margin, and having the general form of B. rxtans, but more highly ••on nig unite abrupt. The axis extends to the narrow, • uiiMve margin where it ends abruptly. It bears three di-tinct annulat with traces of a fourth and tifth. The tirst of these has a small median, spinou- tuln'irle: on tlie second the tubercle is not so large; on the third it is again more I'iciiuu-. ( 'lo-e behind this lies the base of a strong, erect or slightly recurved -pine, and with it. in -ome of tin- specimi'ii-. the spinule on the third annulation is merg'-i. Then ill tubercles on each side of the axis. Thepleur.i- bear four t! which il Pigs. 39, 40.— r\k'lM- '. 724 THE PALEONTOLOGY OF MINNESOTA [Haihyimis BChuohertl. BATHYURUS SCHUCHERTI n. sp. This new form is represented by a series of cranidia and a single pygidium. Though I am reluctant to add to the imperfectly known representatives of this genus, these specimens present some distinctive differences from those before described. Fig. 41.— Cranidium of Bathyurus schucherti. The glabella is of rather large size, elongate subovoid, and gently convex, the dorsal furrows broad and shallow, the frontal border narrow, concave and upturned at the edge. The glabella bears the faintest trace of lobation, and its surface is smooth except for a fine granulation toward the posterior extremity. The basal edge of the glabella is straight and its slope to the occipital groove abrupt. Occipital ring broad, smooth and produced into a short median spine. Fig. 42.— Pygidium of fiathyurus schuc.li?rti, partially restored, x 2. The pygidium accompanying and undoubtedly belonging to the same species is rather short, very broadly concave on the pleurae, only the portions near the dorsal furrows being convex. Axis moderately convex, proportionally narrow, terminating abruptly at the concave margin. As far as preserved, it appears to be obscurely segmented on its anterior moiety. The pleurae bear three broad ribs (beside the articulating rib), which are simple, separated by linear furrows extending overHhe concave area to the edge of the shield. Surface smooth. Horizon and locality. — Trenton limestone: Minneapolis, Minnesota: collected by C. L. TIerrick, (Museum No. 5084.) NOTK. In tin' Twelfth Annual Report of the Geological and Natural History Survey of Minnesota (1884), p. 8, Capt. A. W. Vogdes described, under thf name Rtithi/unix slonrmani, a pygidium said to have conn- from the Trenton lime-.tonr at M inm-a pulls. Professor Wirichell informs me that the data concern- ing tin' origin of the spt. cimi'ii when it was placed in Capt. Yogdrs' hands for description were not only vague but misleading, as it had been found by a gentleman unused to careful distinctions in such matters, f'pon re-examination, the pygidium proves to lie that of a Froetus, whose struct lire alone would indicate an early Devonian age, apart from its association in the small fragments of light brown limestone with an Alri/pa reticnlarin and a Cyrtina. It appears to be unlike other known Devonian species of the genus and will hence retain its specific name as I'rnrtii* xtnni'innni. The rock is presumably a fragment from the mirth western drift picked up in the vicinity of Minneapolis. I I;KO.\TKIIM . ana Hl.'MNTKl s. y Hillings, his originals coining from the Trenton lime-tune of nttawa where, as sail I l>y him. it i- not of infrequent occurrence. In thr : Camel • » an excellent wood-cut of an entire individual \va.- given. Thr -iiecimen^ from Minno»ota. while all more or less incomplete, agree throughout with the <'anadian species ami we have therefore introduced Milli HronttH* /mi.. figure a- m to the student than any which might \te derived from the1 1 before u>. The latter <••>: a somewhat hroken individual having tin- part.- togi-ther fnun the Trenton lime-tone near Spring Valley, Minnesota (No. U>71 of the Mii-enm collection), a «-rani'lium from the tiah-na limestone at Wykoti (Mr. I'lrich's collection), and a line external impres-ion of a pygidium from the same locality (I»r. KohhinV collection). Throughout the specie- of - then- is a certain homogeneity in -tructure which rend. ..-neric group more comp;i. -harply delimited than i> n-ual among the trilol>it«-. Hut few sugge>tion- ..f ;t divi.-iou of the genus havi- been made and only one of the propo-ed suliordinate generic term- has met with even a •; al acceptance. Thi- i- 7V, //>. one of COP; •.-, dt-igm-d to include ;es with marginal spines on the pygidium. and which ha.- demo: 'itle to recognition, -ince the group ha- proven to possess a .|iiite definite .-tratigraphical value as a structural variation prevailing in Hercynian faunas. In II. litnntii* the \arion- [lart.s were not irr, ••.opment of any unusual character-. The - >OS8688 a -h> ! tin- cut in* .1111111:1! I iiitni'lurc ;i iL'tne drawn tnun . pecimei. ! i'i 'ii \\'nli-ii/t, (.-p.) 1^77. . tntormeditu \N \ 8f»l ll. -!.. p. «». Mr. Walcnr- ies has not heretofore been figure*!. Imt, after careful compai- i-on witli tin- de-cription. ami with the ;iiil of the original specimen, I have little hesitation in referring to it the commonest of the ••••lining in the Silurian rock- of Minnesota. Without entering intoa detniile'l ilr-crijition of llii^ form, which has been given l>y Walcott, some of its diflerentiul features may mphaoii The outline of the cephalon is rendered sulitrian^ular Ity a slight anterior |inijection of the margin. The facial -utiires al>o 11; -ightly salient angle at thi- ['uiiit, ami fre(|iient ly here the surface of the glabella i> impressed or casually force. I ilown. The anterior limli- of the suture cut oil or traverse the lateral angles of the frontal lol.e. as in all species of / n a.-.-mint of this depression the lol»- ,ite i-o|.ite.l an.) not conlli !i the middle iif the glaliella. The second furrows are linear, deep only at their proximal extrem Imt di.-tim-t ly continue*! to the dor-al furrow-. The third or occipital lol.e- are -mall 728 THE PALEONTOLOGY OF MINNESOTA. I Pterygometopns eboraceus. but clearly defined, not confluent with the second lobes at their outer margin. The occipital ring is moderately broad, considerably elevated and without evidence of spine or central tubercle. At the angles of the cheeks are short, sharp spines, not extending beyond the second thoracic segment. The lateral margins of the cheeks are bordered by a thickened rim. Fig. iz.—Pterygomttopus in- Fig. 46.— Profile of the same. Fig. 47.— Pygidiuni of another termedius Walcott. Cephalic view individual, x 2. of an enrolled individual, x 2. Although the thorax is .preserved in several very neat, enrolled specimens, there is nothing of diagnostic value to add to the description already given. It tapers more rapidly than is usual in the later dalmanitids, but by no means as much so as in Dalmanites achates Billings. The pygidium is eminently triangular in marginal outline, the sides making a sharp posterior angle, which, when the animal is enrolled, projects conspicuously beyond the anterior margin of the head. This is, however, not a spine. The lateral slopes of th.e pygidium are decidedly abrupt, especially toward the posterior extremity. Our specimens agree with those described by Mr. Walcott, in having from 10 to 14 (when clearly retained) annulations on the axis, and 8, with some- times traces of 2 more, ribs on the pleurae. The first three or four of the latter are usually faintly sulcate. The surface of the glabella is very sparsely tubercled ; usually only traces can be seen, and hence the generally smooth aspect of the head. Formation and locality.— Lower Trenton (Black River horizon): Chatfleld; Trenton: Lake Street Bridge, St. Paul; Minneapolis; Galena: Wykoff, Minnesota. PTEBYGOMETOPUS EBORACEUS, n. sp. This is a New York form, closely allied to the foregoing species, though differing from it in some interesting structural details. The glabella is of the same Fig. 48.— Pterygometopus eboraceus. general form in both; but here the median portion between the first and second lobes is decidedly convex and scarcely depressed. The first, second and third lateral raiLOBiro. - li;i\f tin' -.mi.: rel.i'i ii /'. in' 'lit (lit- -epaiatm- fur are ver> -hori. deeplj inoiaed .it their inner extremities, while tin- lol.e- tin are all continent along the dm--al fun. \ ringlt -t«-|. further 111 tin- obliteration of tJ ,il furrow-, causing the Hr>t ami second loin- to iiecomo. wholly continent. \voiilil produce that condition of the glahella which Schmidt has • (.generic value. proposing for specie- of tin- structure the name Mm ( Moiiorm'liux eiueini.). \\ith t he i-vidtMice of closi- specific relationship Between P. >> and /'. intrnitxlius. it would ho ina«lmis..aMo to employ this term here, though the former may l>e reganle.! as a stepping stone from the typical •/>!«? to that condition of extreme ••scence of the glahellar Iol>e8 exempli; >ius. • •'. I'terj/yvutftoptu eboracftu, fnnu th<- san, ii.il rentorcd. The occipital ring of / ler than in /'. i>if?nm;lii« and bears a conspicuous tul-eicle at its center. Genal spines are also present The surface of the glabella is generally tubercled. and on the free cheeks there are faint. ramif\ minutely punctated grooves. The general form of the thorax is somewhat less tapering than in /'. interim •» Sclcnc«» dc 81. •if*. «-»).* 730 THE PALEONTOLOGY OF MINNESOTA. I PtorygometopvB schmnlii. The cephalon is short, but pointed at the anterior extremity and bears a depression at the meeting of the facial sutures, as in P. intermcdius. Cheeks quite narrow and the angles produced into very short, round spinules. Glabella likewise Fig. 50.— Cephalon of Pteryyometopus schmidti. short, the frontal lobe covering more than one-half its length. It is, however, proportionally wide anteriorly, the dorsal furrows approaching rapidly so that the glabella at its base is but one-third its width in front of the eyes. The first lobes are narrow, transversely triangular, their general direction being obliquely forward toward their distal extremities. The second lobes are quite small, transverse and subrectangular, directed obliquely backward; the third lobes are two very obscure tubercles. The general surface of the glabella is regularly convex, there being no depressed area between the inner extremities of the first and second lobes. None of the lobes are confluent. The first glabellar furrows are transverse and concave anteriorly, while in P. intermedium they are convex. All these glabellar lobes are clearly defined and show no tendency to obsolescence. Occipital groove narrow, occipital ring also relatively narrow and not greatly elevated. Eyes proportionally very large, extending from the first glabellar furrows to the occipital ring. The size of these organs renders both the fixed and free cheeks remarkably small. Between the base of the eyes and the lateral margins is a broad, smooth, thickened but not elevated area. The entire surface of the glabella, the palpebral lobes and a small triangular area at the base of the eyes between the occipital ring and the border, is coarsely and abundantly tubercled. More scattered and finer tubercles are seen on the marginal border. The thoracic segments show no differentials of importance, Their extremities are obtusely rounded as in Pkacops. The pygidia associated with these heads are similar to that of P. callicephalua of the Trenton limestone of New York, having a rounded subtriangular outline, narrow, very gradually tapering axis and broad, evenly convex pleura-. There is, however, a difference in the segmentation of the parts, the axis having 8 — 10 annulations which make a double sigmoid curve, and the pleura- having 5 — 6 ribs, which are simple for about one-fourth of their length and then bifurcate. None of the ribs are continued to the margin which is broad and smooth. In sharp internal casts there are but four duplicate ribs, the posterior division of each disappearing toward the margin much sooner than the anterior. Behind these may be seen the trace of TKII.ii three or even four simple ob-cnre rib-. The of the .IMS \\lm-li is -ideral'l v renioM-d from tlir termination df thr -hiei-i. i- also seen to lie faintly bilol Tlir Uon i.f ' . u-idia with tin' fiirin nf cephalon described i- to .-ome ee a matter of pre-umption. though their intiin.iti- i ...... m n the -amc rock- and otiiri '\idence.f.i BB me pleMtm to dadkwte tin- !o in\ frifii'l. Prof. 1 r. Srhinidt. tin- fuuneen kindly placed in my hand- l-y I'rof. I!. 1*. Whittield. has shown that in -tincture of cephalon and pygidinm, /'. cullif-film/iK ditl'i'i- from the form which we have descrilied at length ax /'. < Innidli. mainly in the alismice of genal -pine« on the former. veen the typical -pocimens referred to and separated heads and tail.- from .on. Konntain and Cannon Falls. Minnesota, and county, Kentucky, the "f rt'ryux caUicephulu* Hall. followii,. > of agreement are evident. The cephalon has a short triangular anterior projection; genal an-lc- liroad. roiiml and thick, without indication of >pin •• the occipital . basal glahellar lobes small and - punctated beneath the eyes; surface of glabella • ephnlta I! coarsely tubercled. The a\i- of the py^idium ha- iin-urved m. .ui-l -mnoii- annulations: of the latter there are from Mo Id; on (lie pleuiM- there are.", dup! rili-. with trace of a -i\th. n anil /<«- :iiati«in t: 732 THE PALEONTOLOGY OF MINNESOTA. I' '!> .1 |-\ .11 Ions mi rii:in>|j|il,". OBSERVATIONS ON THE AMERICAN LOWER SILURIAN IMIACOIMD/K. A sufficient number of species of the Phacopida: has now been described from the Lower Silurian of the United States and Canada, to render the discrimination between the specific forms a matter of some nicety. Of these species, some are yet known only from dismembered parts or isolated heads, but of them all the greater number conform to the Pterygometopus type of structure, in the high marginal termination of the posterior limbs of the facial suture, the transection of the lateral expansions of the frontal glabellar lobe by the anterior limbs of the suture, and the usually rounded pygidium without caudal spine. The more typical or normal of these species are P. intermedius, P. schmidti and P. callicephalus. Of the other Phacopidae known from these rocks, Dalmanites achates Billings, D. bebryx Billings, D. carleyi Meek, D. breviceps Hall, Chasmops troosti Saf- ford and Vogdes, and P. eboraceus Clarke, all show transitional characters in one direction or another. Thus we have noticed the difficulty of making a specific distinction between Pterygometopus intermedius and P. eboraceus, except in so far as the latter, by the incipient coalescence of the first and second glabellar lobes along the dorsal furrows, manifests an inclination toward Monorachus, a subgeneric group (littering from Pterygometopus only in the extreme to which this tendency to coales- cence is carried. Dalmanites bebryx and Chasmops troosti* are species of the same character. It would on many accounts be convenient to apply to this developmental (in a phyletic sense) stadium of the early phacopidean type, the term introduced by Schmidt, Monorachus, but such a designation would fall short of its purpose unless accompanied by an equivalent term to designate the same phase of development in those early Devonian species which follow the appearance of typical Dalmanites, namely, such species as those to which the name Chasmops was applied in the 1'alasontology of New York, volume vii, e. g., D. anchiops Green, of the Schoharie grit. The first appearance in the lower Silurian of this phase of partial coalescence of the first and second lobes was simple; its re-appearance in the Devonian was complicated with a variety of ornamental modifications, occurring at a period when the trilobites generally were garnished with all sorts of dermal extravagances. •ThlH >.|>'-' • '"''I M'ror. Acini, Phils.: P. Hi7. UK.::. U " O0< in u r..niliti..n tO r.-.-iinl tin- mini ir i of DM' liciid." Tin- fl'-Mirr, lioni-vi-r. -IIMW-. lln> l hi nl .-mil :i |.:ul of ;i ]:II-L'I- •.n-iinii loin-. Mitli.-i.-nl to il.'iininslrati' Hint II. is nut. :i i '/IIIHIIIIIJI.X; whl l» tin- k in i w n -tru.-nm- of i In- .- peril's in n( h IT ri'spiTis r\ inri-s ;i d'^i- :i pprnai'li to /'. <»'" II '' Hilling--- ' '"- iii"l'' •'' ...... '•'' hy ^^iri>nl |}] >:iiv,,i-,| :1I|(I Vo-"ili". in HMl. .-, fro, n I In- Tn-nl on horl/.ini ;it :inil in :ir M iirfri^-~l)oro. 'I'l-in-- n:ii.onn i •al com -uh^eneric name- ha\e lieen applied to these later foi f>,/(l;i/,i,vy»/i-i/;/v. where the frontal linili of tin- cephalon heard a row of inci-or-like in which similar processes extend to the genal alible-; jidiiim ha- an ediinute margin ami it- posterior extremity • •cted into a -emidrcular collar. The-e names are taxonoinically snlionlinate in the third degree term />/,'/// initf<; that is to -ay. we • • that they all, with the inclusion of those iMvonia1; - referred to above as "Chastnops" (forming a homo! ip) are fulxidiary to a diruion whote diagnostic feature i- the more or If-- ••omjilcte coalescence of the. first and second lateral ^labollar lolies, ami for Mich a >nl>^oncric «livi-ion ;i designation is needed (e. g.. Synph<» : typical cxpros-ion and phylctir nonnai of ltn«niti-s is represented by a series of upper Silurian and rarlir-t l'c\onian form-, in wliich the ^lalidhir location i- i" ml the py^i'li'im caudate. An excellent example is the D. liinuliiriin • Millings, of the Trenton limestone, and perhaps by l>. carlnji Meek, of the Hnd-on Itiver tfroup. . .'/«-x »/.-//f7/«>- still maintains the t'arial suture of 1'tenj- ij'im- •. ith the complete ^laKellar lol.ation. anterior width of glabella and ariiminate iiy^'idium of typical l^ilmnnitcs. The acmic or mature type uf I>>itiny •ate processes on the cephalon. lioth in the later (Waldroni Niagara ( /'. Hull', and in the Lower Helderberg (D. n'ie seems to have abruptly disup[ieurcd. but it reappeared in the Hamilton fauna devoi.l of other dermal ornament than the broad. Hat marginal exten-i"1 the pyL'idium. <*. This i> the last of the race in American faunas. These appear,! :. to be interpreted and summarized as follows: The lobal coalesenee of the lurian sped.-. /' ' '//. trooxti. /'. .dive of immature or epacmic developn 1 lie relation of I/". -e ami probably al. A ftei passing the acmic "d. when phyl- iity manife-t- itself in the variety and extravagance of the dermal ornamentation, tli' on to the epacmic condition of lobation i- Imt an accompaniment of the decline of the metopux :it- but a secondary stage in thi- process, a stage i advanced than that indicated by I>. >•' . I5ut in eertain - ••mi-, there i- a lateral e\pan-ion of the tir-t and .-econd ^lubellur ' iving to the L'lal>ella as a whole a -omewhat ^lol.. ••?. I'mm -udi gp< *he point of 734 THE PALEONTOLOGY OF MINNESOTA. [Ceraurus pleuroxaathentus, departure toward the true Phacops, leading thence through the little Upper Silurian P. trisulcatus Hall, and P. orestes Billings, into the typical forms of the Devonian. Chasmops is a genus abundantly represented in the Scandinavian and Russian Lower Silurian, but with a single American representative, D. breviceps Hall,* from the Hudson River group of Ohio. In this genus the first glabellar lobes are extrava- gantly developed at the expense of the other pairs and extend frequently from the first glabellar furrows to the occipital ring. Family CERAURID^E. Genus CERAURUS, Green, 1832. CERAURUS PLEUREXANTHEMUS (Jreen, 1832. Ceraurus pleurexanthemus GREEN, 1832. Monogr. Tril. North Anier., p. 83; cast 33, plate 3, B&f. 10. Ceraurus pleurexanthemus HALL, 1847. Paleontology of New York, vol. i, p. 242, pi. 65, flgs. la-n; pi. 66, flgs. 1, 1ft. Ceraurus pleurexanthemus WALCOTT, 1881. Bull. Mus. Comp. Zool., Harvard Coll., vol. viri, p. 211 pi. 5, flgs. 1-6. This species abounds at several localities, and specimens do not materially differ in size and habit from those of the Trenton limestone of New York. It has a very considerable vertical range, having been found at the following localities. Lower Trenton, or Birdseye limestone, Jauesville and Mineral Point, Wisconsin; Black River horizon, Minneapolis; Trenton horizon, St. Paul; Galena horizon, Kenyon; Hudson River horizon, Spring Valley, Minnesota. Subgenus PSEUDOSPH^EREXOCHUS, ScHmidt, 1881. 1 'SEUDOSPH.SREXOCHU8 TRENTONENSI8, U. Sp. The remains of this fossil are quite imperfect, but the occurrence of this type of structure in the Trenton fauna of New York is worthy of notice. This division of the Ceraurus group, Pseudosphcerexochus, was introduced for such species as differ from Ceraurus in the subtrigonal rather than subquadrate outline of the glabella, its convex or bullate contour, the posteriorly directed glabellar furrows (the third pair being the largest, but not reaching the occipital furrow), and the very large size of the third pair of glabellar lobes; all of which are features in strong contrast to their disposition in the restricted genus Ceraurus. Our specimen is a single glabella of large size, regularly convex surface, and rather abrupt slopes to the frontal and lateral margins. Its length to the occipital furrow is 19 mm., and the occipital ring is 3 mm. in width and decidedly flat on the axis. The width of the glabella at its base is 21 mm. The three pairs of glabellar » Adv. Sin'.. Is Twi •nli.-lli IN-i't. N :il>. N:it. Hist.. |>. IB, 1M1: 'I' w I'M I V -foil i 'I li '!').. }>. •>%!, pi. viii, fijrs. lf>, ID. IHV.i; •iloli.Uy »f Olilii, vol. II, p. 108, pi. Iv. fl;;s in. 17. 1S7.1. [LOBIT1 furrows are distinct, the tir>t being the -hortest, originating cloee to the fnmt;il JMI. the length <>f each being ju^t about one-half the 1: tance between i •nities i I in a -traight lin«>. The SIM-OIK! furrows are longer, iilcl for about uiit'-lialf their length with tl; /air. thence directed more -trmigly backward. Tlic thin! furrow- an- again louder than t he second. Mibparallel t<> tln'in lint dellccted aliruptly l^n-kwar-l at tlicir extremities where they .m- into a -liirht pit or i-v-'.uat ion. Tlic la-t ilo not reach tin- occipital furrow. frontal loin- i- relatively small ami spherically suUriangular; the first pair of lateral lobes clon^at*- rectangular, the secoml pair -iniilar, though broader and delli'ctf.l -oiiicwhat pnste. (ieneral contour depre—ed convex. Hat.tcned al»>\e. Frontal lol>e lar. .ind >econd lol»es small, obx-iirely deKned. the former ti -angular curving backward towards the dorsal furrows, the latter suhtriaiigular and l.roade-t within: third lobes raodera' form just the reverse of that of the second lobes, and almn-t if not wholly set off from the glabella by the deep bounding fun "'id 736 THE PALEONTOLOGY OF MINNESOTA. [Note on Ceraurus. pairs of glabellar furrows are exceedingly obscure and may be discerned only in an oblique light. Occipital furrow narrow and deeply impressed; occipital ring broad in the middle, highly arched on the axis, which is scarcely as wide as the base of the glabella. On the cheeks the occipital ring gradually widens, at its extremity meets the outer marginal rim of the border, and is continued into a short, outwardly directed spine. The occipital furrow is also sharply defined upon the cheeks. Eyes of moderate size, not elevated to the hight of the glabella. Suture normal ; ocular ridge from the anterior angle of the eye to the frontal margin broad and conspicuous. The entire surface of the shield is minutely and uniformly pustulose over all its parts. This species has somewhat the general aspect of Ceraurus pleurexanthemus, but differs from it characteristically in the obscure lobation of the glabella, the surface granulation, and the shortness of the genal spines. It is, I believe, wholly distinct from any of the various species " Cheirurus" described by Billings from the Lower Silurian, though the usual imperfection of Billings' material renders a decisive opinion impossible. Formation and locality. — Lower Trenton limestone, with Ortiiis pectinella and Strophomenn subtenta, Minneapolis; and the Glades, Lebanon, Tennessee. Collection of Mr. Ulrich. NOTE ON THE SUBGE-NERIC CLASSIFICATION OF THE AMERICAN SPKOIKS OF THE GENUS CERAUHI s. The wide variation in the form and degree of lobation of the glabella and form of the pygidium in species which have been referred to Ceraurus, led Angelin, Schmidt, and some others, to introduce a number of subordinate and useful designations for what appear to be natural groups. The structure of Ceraurus as exemplified by its type species, C. pleurexanthemus, is characterized by its subquad- rate glabella with moderately large frontal lobe, short, subequal lateral lobes .separated by horizontal furrows, the third lobes being apparently isolated by a linear depression extending from the actual inner termination of the furrow to the occipital groove. The surface of the inner cheeks is characteristically marked by deep pittings scattered among the tubercles, while the pygidium bears two or three pairs of marginal spines, the first being of very great length. The principal points of deviation from this type are manifested in the compo- sition of the glabella. The glabella in Cyrtometopus, Angelin, Pseudosphaerexoc//ns, and \ics:/,-tnrs/.-i>i, Schmidt, is subtriangular, broadly clavate or subovoid, the lateral furrows and lobes being directed posteriorly. In Cyrtometopus the glabella is evenly and not greatly convex, and the third lobe is usually not wholly separated from the The ridge extending from the eyes forward to the anterior margin of the •IUI.OMTIC8. 7M7 M..tr on O»r»uru«.| glabolla is eontmuoii* with t!u> l>n>.id frontal margin of t he ri>|>lialon. Of American species representing this suligenns we may cite: C.apollo and C. mercurius Billings, from the Quebec group, < ;-.//•« v \Valcott, from the Trenton limestone and C.scofieldi Clarke, from the Galena shales. In l'*>-n.l».<{>li.rrexochn8 the Isabella is very eonvex, the thinl lateral furrow >tronger than the others, and the third lobe larger and not separated from the body of the glahella. The pygidium bears eight marginal spines of subequal length. Under this division may be \>\. i>r»Hticns Hillings, of the Quebec group, and /'. '/-•i'> Clarke, of the Trenton limestone. :konskin Schmidt, has the glabellar furrows very oblique posteriorly, the glahella m<>~t mnvex In-hind and usually produced into a posterior spine; the third furrow is the strongest and the third lobe is not separated from the body. To this division may be referred Millings' C. ylaucus, and C. perforator, of the Quebec group, C. satyrus, of the Chazy limestone, and C. numitor of the Hudson Kiver group. Schmidt includes among these subgenera. SpAanMOTjpfc Angelin, in which the anterior portion of the glabella, embracing the frontal lobes and the first and second lateral lobes, becomes extremely convex and subspherical, without traces of lateral furrows. The third lobes only are apparent, and these quite obscure. ( if the foregoing divisions, all except Pseudosph-*3nce of negative evidence may provisionally be regarded as a new Fig. 68. — Cranicliiiiii »f l-:»crinuru* rrmtntuji. x 3. The glabella is obconical, its narrow, blunt extremity being directed posteri- orly and conspicuously elevated. It extends almost if not quite to the occipital margin, over-hanging the posterior edge. The dorsal furrows are very deep and constrict the glabella laterally. The glabellar furrows are represented by three deep puix-t.e at the bottom of the dorsal furrows, and these afford evidence of four pairs of lateral lobes; the first very small on the margin and limited by a faint groove extending up wan! over the surface of the glabella; the second and third also narrow and linear, are immediately merged into the median lobe, while the fourth pair is better developed than the rest, extends entirely across the dorsal furrows, connecting the eye-node with the anterior extremity of the glabella. The glabella bears upon its upper surface a few (25) coarse, distant tubercles, which on the posterior portion are elongated, directed obliquely backward and upward, and take on the form of blunt spinules. From the middle point on the anterior margin of the glabella diverges a pair of shallow grooves, which skirt the ante-lateral margins and become obsolete on the lateral slopes. These grooves, which apparently indicate the course of the facial sutures on their anterior limbs, rut off a narrow ridge on each side of the anterior margin and each of these ridges bears a single row of four strong spiniform tubercles. The lateral and posterior concave slopes of the glabella are smooth. The length of this glabella is 5 mm. A portion of the left eye-node is retains 1 and appears to have been moderately elevated though not to the bight of the glabella; the eyes were approximate and posterior. Among the Russian species of Encrinnrus described l>y Schmidt, we find lose ally to /.'. ••/ -i-\. xiv. figs. 16 — 26). In the latter the glaliella i> less convex and more abund- antly tubercled; but the posterior tubercles are equally spiniform. ami tin- anterior row is clearly delimited though not divided in the center. 742 THE PALEONTOLOGY OF MINNESOTA. ICybele wlnchclll. Genus CYBELE, Loven, 1845. CYBELE WINCHELLI, n. sp. There is a single extended individual of this genus, considerably defaced about the head, so that the glabella is wholly lost; but the outline and proportions of the cephalon and the structure of the other parts are preserved. General outline linguate, tapering from the head backward to a subacute extremity; axial length Fig. 59. — Cybele winchelli. 36 mm., greatest width 26 mm. Surface convex, flattened above. Cephalon transverse, broadly rounded at the sides, somewhat concave on the frontal margin which was slightly elevated. Length 10 mm.; width 26 mm. As the structure of the glabella is lost, a figure is here introduced copied from one of Schmidt's drawings of Fig. 60.— Cephaloa of Cybele bellatula (after Schmidt). C. bellatula Dalman. This shows the three distinct pairs of lateral lobes, the rather small frontal lobe and the peculiar projection of that portion of the shield lying between the upper anterior extremities of the facial sutures. Eye-nodes large and elevated, situated near the transverse diameter of the shield and directed somewhat anteriorly. Facial suture taking its origin on the outer margin considerably above the genal angles, whence its course may be traced as far as the eye-node. Margin of the cephalon thickened, convex and somewhat spreading on the ante-lateral limb, receding and becoming concave posteriorly, thence produced into rather short divergent genal spines. Occipital ring and groove well marked. Thorax subquadrate, tapering; 20 mm. in width at the anterior extremity; 8 mm. in width at the posterior extremity; length 20 mm. Composed of twelve segments. Axis proportionally narrow and convex throughout, having about ,i.i one-fourth the width of the thorax at any point The segments are slender and distinctly ^romc'l for their entire length or within a very short distance of their extremitie-. Tin- lir-t five segments appear to be obtusely rounded at their termination-. Imt the last seven are acute. The sixth segment, though no broader than the rest within the articulating lines, is greatly expanded at the line of geniculation and each extremity is produced as a stout spine, consider- ably beyond the termination of the py^idium ; these curve outward at first, thence recurve and approach each other. Though their entire length is not preserved, they could not have been less than 20 mm. long. The last six segments are like the tirst live, except that they are curved more abruptly backward, their terminations being acute. idium short, narrow in front, all the annulations being curved abruptly backward. Anterior diameter 7.5 mm.; length 9 mm. The articulating ring of the axis is very large and conspicuous; behind it is a single annulation extending entirely across the axis, three others which extend from the dorsal furrows partly across, these being followed by five or six rings which do not reach the dorsal furrows and an- -evirated medially l>y a flattened area. like that in Kit'-riimrii-. The axis end- .H-utely and does not reach the extremity of the pygidium. Kach of the pleura bears four or five ribs, the first of which is quite narrow, and in, probably, the anterior moiety of the second, as it does not reach the margin. There may also be seen a trace of a similar intercalary rib between the second and third ribs. The second, third, fourth and fifth ribs end in acute, free points which • were directed outwardly. Surface finely tubercled, the tubercles being coarsest on the border of the cephalon and the ribs of the pygidium. The surface of the free cheeks was slightly pitted or punctated. Formation and locality.— Galena II me* tone (V), Plllmnre county, Minnesota (Museum No. 8436). This specimen was found loose, and Its exact geological position K hence, uncertain. Ot*ervation*—Thl* Is the moat completely known spectra of Cybel- from the American fauna*, indeed the only species of the genus observed here except that iinur.-.l (.-. lillllnics under the namefn- rrinuru* mint*, from the Quebec ,-P.II|. • '. Newfoundland;* and of all the forms of this irenus that hare been Illustrated no speclm. n -:,.«•* I..-U.T the general form .in 1 relation of the parts. Ctfbele is an eminently low.-r Silurian k'enuit, attaining Its maximum development and variat form In the Scandinavian and Haltlc Silurian districts, at an horizon equivalent to that of C.ielnehrlli. Tli-- unfortunate condition of the tflabella of mir -|i.'.-.m--ii precludes a UrirmiKhly reliable comparison with othi-r forms; Imt the ch . ::utu, with short fnt- l«Tiiiinalioii> of Die ribs, SUneaU a specli ••> -hip with c. reraleiui* Shmhli,' from the «tageC,, a somewhat earlier stage of Ihe -i ton |H ri.nl than that represvnl4- Oali-n;i llm<-tonr. None of the Russian speclM posMM the cheek spines of C. POMIU. vol. I. p.M. «».».', IMS. Thenproi.-. w». fnundrd no > (l»lx>lla. wl.lrh I. «u«plclnu«l v I,. ; the pjrfldlum. bowerer. %Moclkted with It In n.. lllu«tr»Umi , the teKriptlOB. l« probably thai of m tlU-.UlooiJero.lU.lt. «lur. TrilobltM. Ablh. I. p. JOJ. pi . xm. Be »: pi. xr. Sf. 6 un.M. 744 THE PALEONTOLOGY OF MINNESOTA. [Odontopleuru parvula. Family ACIDASPID^E. Genus ODONTOPLEURA, Emmrich, 1849. OPONTOPLEURA PARVULA Walcott (sp.), 1877. Acidaspis parvula WALCOTT, 1877. Adv. sheets, Thirty-flrst Kept., N. Y. State Mus. Nat. Hist., p. 16. Acidaspis parvula WALCOTT, 1879. Thirty-flrst Bept., N. Y. State Mus. Nat. Hist., p. 69. Odontopleura parvula CLARKE, 1892. Forty-fourth Kept., N. Y. State Mus., p. 101. The few fragments of this species which have been observed in the Minnesota formations present no differences from the New York form. As the species is frequently preserved in an entire condition in the Trenton limestone of Trenton Falls, N. Y., a figure of such a specimen is here introduced. Fig. 61.— Odontopleura parvula Walcott. x 3. Trenton Falls, N. Y. Formation and locality.— Galena, shales, St. Paul, Minnesota. Family LICHAD^E. Genus LICHAS, Dalman, 1826. Subgenus ARGES, Goldfuss, 1839. ARGES WESENBERGENSIS Schmidt, var. PAULIANUS, n. var. Cephalon convex, subsemicircular in anterior outline, projecting medially; lateral extensions not exsert. Glabella regularly convex, anterior and lateral slopes the more abrupt. Median lobe broadest on the anterior margin where it covers three-fourths of the entire width of the glabella, regularly rounded, most convex just in front of its center. Anterior and posterior glabellar furrows continuous and deep, setting off a pair of simple, rounded, subovoid lateral lobes, bounded on the outside by the dorsal furrows which are somewhat shallower than the inner furrows. The first and second lobes are thus wholly coalesced, the third or occipital lobes being represented by a pair of elongated nodes which at their union with the narrow posterior portion of the median lobe form an obscure annulation. Occipital furrow broad; occipital ring narrow, elevated on the axis and aspinous. The fixed cheeks and eye-node are convex, the latter appressed to the glabella and somewhat posterior in position. _^ TKII.or.ITB8. The outer cheeks are abruptly convex below the eye, are there broadly grooved by a furrow which widen- toward the margin, where it produces a rather deep emargina tH MI of the periphery. Oenal extremities recurved, tapering to an acute angle, I >ut not narrowed on the posterior surface. Occipital furrow broad and distinctly defined. FIffft. 62, 93.— Cranldlutn uf Aryet iretenbergriui*. var. jmulianut. x 3. The i-ephalon is covered with tubercles which are coarsest over the glabellar lobes; on the cheeks they become scattered, vary more in size, and the coarser are gathered along the posterior margin. No single specimen of the head retaining all these parts in apposition has been observed, but in the cranidia the size is about the same, an average glabella measuring 5 A mm. in length; 6| mm. between the eyes. Of the thorax only a few scattered segments have been seen. Fig. «4.— Pygldlum of a somewhat smaller Individual, x 3. Pygidinm short, transversely semielliptical in outline. The axis is convex and has about one-third the width of the shield on its anterior margin. Its sides are straight or slightly incurved, scarcely tapering, for about one-half the length of the -hii-ld. Posteriorly it is broadly rounded and terminates in an elongated ridge which extends to, and is confluent with the marginal thickening of the shield. Three annulations are distinctly defined and behind these are one or more transverse rows of tine tubercles. The pleura1 are depressed convex, thickened about the margins. There are two distinct pleura! ribs, the anterior being deeply sulcate and its two divisions uniting to form a single narrow, acute, moderately long spine. The second rib is also broadly sulcate, is much smaller than the first and its parts unite out- wardly to form a second marginal spine longer than the first. Behind these two ribs there are two tubercled spaces extending to the median prolongation of the axis. On the margin, besides the first and second pairs of spines, there is a third or terminal pair somewhat shorter than the others, and between them and the second I'.nr is a small and short accessory pair, making in all eight short, rounded spines. On the under side or doublure these are more flattened than above. Length of average specimens 4 mm.; anterior width 5 mm. 746 THE PALEONTOLOGY OF MINNESOTA [Plntymetopus cucullus. Hypostoma transversely elongate, subquadrate, anteriorly convex, posteriorly broadly marginate. Central lobe distinctly defined and with two short, lateral, transverse sulci or indentations. Formation and locality.— Trenton limestone, Minneapolis; Galena shales, St. Paul; Wykoff, Minn. Observations.— This' species is quite abundant in the calcareous Galena shales at St. Paul, much more so than at the other localities cited. There can be no question as to the unity of the parts described above as there is no other species in these faunas to which any of them could be referred, and they are moreover closely commingled in the fragments of rock studied. The species is characterized by the lobation of the head in which it corresponds to the type of structure represented by the genus Arges Goldfuss, as interpreted by Schmidt. We accept provisionally this subgeneric reference, though it is to be borne in mind that the type of Arges is a Devonian species (A. armatus Goldfuss). Upon close comparison of our specimens with those described and figured by Schmidt,* I have little hesitation in concluding that the two forms are specifically identical. Slight varietal differences may be observed in the rather more complete isolation of the lateral glabellar lobes on their posterior margin and in the somewhat greater length of the marginal spines of the pygidium in the American specimens. This species from the Trenton-Galena, the Arges phlyctenoides Conrad, from the Niagara, a hitherto undescribed form from the Lower Helderbergt and the Arges contusus Hall, from the Upper Helderberg, form an interesting series in which the subgeneric characters of the cephalon are maintained throughout. Arges wesenbergensis is from Schmidt's etage E, or the Wesenberg zone, associated with Plectambonites sericea and Strophomena deltoidea.t • Subgenus PLATYMETOPUS, (Angelin) Schmidt, 1885 (emend.). , PLATYMETOPUS COCULLUS Meek and Worthen (sp.), 1865. Lichas cucullus MEEK and WOKTIIEN, 1865. Proc. Acad. Nat. Sci. Phila., p. 266. Lichas cucullus MEEK and WOKTIIEN, 1868. Geol. Surv. 111., vol. iii, p. 299, pi. I, figs. 6a-c. This species which was described from the Trenton horizon of Alexander county, Illinois, is characterized by the simplicity of its glabella, there being but a single Figs. 66, 67.— Portion of cranidium of Platymetopus eucullus Meek and Worthen, Galena limestone, Wykoff, Minnesota. pair of furrows, which meet the occipital ring at right angles; and by the slight, concavity of the median lobe of the glabella on its posterior slope, which gives it a •Revision dor intb.il t. BIlur.Trllobltcn, Abtli. 2, p. 44, pi. VI, flgs. 1—4. 1885. t AIUIKK roNSANiiiMNKirs, win. iimim*. This species may lx- best described as ditl'erlnx from A. ii'i-srnlifriirnxi*, var. . In the narrowci and much less convex frontal lobe, . smaller and lc--s elevated lateral lolies. nodlform and not Fig. 65.— Cranidium of Arges consanguineus. annular third lolics. turner and mure elevated ocular nodes, broudor and more highly arched oivlplt.il ring. The glabclla Is notably less convex, and. taken as a whole, proportionally smaller. The t wo specie- a\craurc almut the same si /.r. Knmi the Hhaly limestone of the Lower Helderberg (,'nmp, near Clarksvllle, N. V. The type specimens have been presented by the writer to the New York State Museum. *9ee Schmidt, Ou the Silurian Strata of the Baltic Provinces of Russia: Quart. .l..u> i.e., I. -,„•.. Nov. 1-H'J. p .V.-J. TU II." I: I TBS. 747 IM»lrmri..pu« rwbbln.l 1 peculiar Mil-conical protuberance. It is mainly in the latter feature that the species, If a- it- pirts arc known. dihVrs from the Lidins trtntonensis Conrad. A well preserved glabella of /'. cnrulln* occurs among the material from the Galena lime- stone of Wykotl. Minnesota, loaned by I>r. Kobbiiis, and a fragment which may represent the same species comes from the Trenton beds at Janesville, Wi>con>in (MiiMMim No. M1J) l'i. \TV.M: I: '•/ Schmidt,! rather than with such spinous processes a> tlinx- po^c-M'd hy L. Inrornis IMrich. Hnjtlnlirli,^ Iriru^iidnla Beyrich and //. probosciil"! I 'ames. The character of the glabellar furrows, also, is of importance. These are very narrow and sharply impressed, have the usual degree of curvature anteriorly, but posteriorly become quite parallel and straight, debouching in the equally narrow occipital furrow at right angles. Thus, as in so many of the American Silurian species of Lichas, these grooves represent the continuous anterior and posterior furrows, the median pair being lost by the coalescence of the first and second lobes. The third pair of lobes we regard as obsolete. Fig*. 08, 40.— The crmnUlium of I'latymetopiu robbinti Ulrich: with outUm* Elsewhere we have expressed the conviction that the lobation of the glabHla must be given fir>t importance in the sub.Hvision of the genus /,/>/,. an-1 the nature of this lobation with the total loss of the third lobes places thi- -p-.-ies with the • PaUnntolacia «r*adln»vl<-a. pt- I. p. «. pi. xxxv; *f*. tn-e. MM. d.0.tb»U. Sllor Tr > l.-n. pi I M« IJ. IKM. 748 THE PALEONTOLOGY OF MINNESOTA. [Platymotopus blcornls. subgenus Platymetopus. I regret being unable to concur with Mr. Ulrich's reference of this and the following species to Dames' proposed subdivision Hoplolichas, but in the latter the third lobes are well defined. Dames ascribed much importance to, and indeed, found the suggestion of his term in the stout, sometimes forked spine borne by the occipital ring,* while the possession of anterior extensions of the frontal lobe, though of much the same significance structurally, is taxonomically unessential. It would seem, in fact, that if there is any basis for the admission of the division Hoplolichas, it lies in the presence of this ornamental or defensive character. The original specimen of P. robbinsi is broken near the center of the occipital ring but there is no indication that it possessed a central nuchal spine. In the possession by different subgenera of Lichas, of similar frontal extensions of the glabella, as in L. (Metopias) pachyrhyncha, var. longirostrata Schmidt, L. (Hoplolichas) proboscidea Dames and L. (Platymetopus) robbinsi Ulricb, we find an instance of morphic equivalence in a certain structural character coexisting with subgeneric features essentially distinct. Formation and locality.— Platymetopus robbinsi is from the middle beds of the Galena limestone, at Wykofl, Minnesota. (Collection of Mr. E. O. Ulrich). PLATYMBTOPUS BICORNIS Ulrich, (sp.), 1892. Lichut (Hoplolichas) bicornis ULRIOH, 1892. Two new Lower Silurian species of Lichas (Subgenus Hoplolichas); Amer. Geologist, vol. x. p. 272, flgs. 2a-6. This interesting species has precisely the same character of glabellar lobation as the preceding, and the remarks made upon the generic relation of the former apply as well to this. In the possession of a pair of divergent spines on the frontal lobe it would seem to bear a similar relation to Hoplolichas tricuspidata Beyrich, as P. robbinsi does to H. proboscidea. The characters of the species, as far as known from a single cranidium, have been sufficiently described by Mr. Ulrich, and will be apparent from the accompanying figures. Figs. 70, 71.— Cranidium of Platytnetopus bicornis Ulrich, with outline profile. Formation and loality. Hudson River group; two miles east of Spring Valley, Minnesota. (Collection of Mr. E. O. Ulrich). •See liiiincs. /.-Itschr. d. deutecb. geolog. Oesellsch.. vol. xxix., p. 71)4. pi. 12-14, 1877. I KII.xl.ITR8. n.ul . . |t.n,K->. Is77. CONOLICHAS OORNUTU8 H. *l>. The specimen to be described was entire when found, but before coming into my li:ui'l-. sii tit-red from unskillful manipulation to such an extent as to obscure the lohatiun of the glahella ami the segmentation of one side of the thorax. Notwith- -tamling, the condition of its preservation is much better than can usually be hoped for, in this group of fragile trilobites, for a Lichas with its parts in normal juxtaposi- tion i< a rare occurrence. (Vphalon transverse; narrowed and attenuate toward the lateral extremities; . 72, 73.— OmoifeAo* corn* tut. greatly elevated axially. Length 11 mm.; width 81 mm. Glabella prominent; anterior margin the arc of an ellipse, projecting conspicuously beyond the general outline of the shield. The surface is convex, rising in a deep curve from the anterior margin to a well defined apex, marked by the base of a strong spine. This point is 84 mm. above the horizontal plane of the anterior margin. The lateral slopes of the glabella are less curved, and the posterior slope is long, straight or slightly incurved. The lateral and posterior lobes of the glabella are so obscured that only the delimi- tation of the former can be made out It is evident that no middle glabellar furrow fed, but the anterior and posterior furrows were confluent and continuous. This furrow, originating on the anterior margin, rises nearly vertically along the sides of the glabella, making at first a slight inward curve, and, at about one-half the length of the median lobe, curving outward, terminating near or in the occipital furrow. The lateral lobes thus set off are large, though they were probably not greatly elevated, and represent the first and second lateral Inlies of species in which the median glabellar furrow is developed. Whether the third or occipital lobes existed cannot be ascertained. Cheeks elongate and tapering; but slightly curved posteriorly toward their extremities. Where they unite with the glabella they are so much 750 THE PALEONTOLOGY OF MINNESOTA. [Conoliclias oornutns. narrower than it as to effect an abrupt indentation in the ante-lateral margin. Their posterior margin is slightly concave, and from this incurvature the cheeks are made to stand away from the thorax, as in Arges, etc. Their surface is convex and the slope rather the more abrupt on the posterior side. Thorax subquadrate, narrowing posteriorly, composed of nine segments, the first of which is obscured. Length of this part (entire), 20 mm.; anterior width 30 mm. Axis proportionally broad; on the anterior segments having rather more than one-third the width of the thorax, but relatively narrower behind. Each segment is flat or depressed convex, and there are no nodes or thickenings at their junction with the axial furrow. The axis is regularly convex, and the lateral furrows broad and not deeply impressed. Pleurae flat for about one-third of their width, the outer moiety being evenly deflected. Segments broad, recurved and tapering to acute terminations. Pygidium comparatively large, being 17 mm. in length, which is more than one- third the length of the entire animal. Axis very prominent, tapering gradually to a blunt protuberance at about two-thirds of its length, whence the surface becomes abruptly depressed, and the marginal furrows incurve, meeting on the posterior mar- gin. The elevated portion of the axis bears one distinct annulation, and a second one whose posterior groove does not extend to the axial furrows. The ribs of the pleurae are in three pairs. Each is broad, gently convex, the pleural grooves being narrow and sharply incised. Adjoining ribs are united for rather more than one-half their length. The first two pairs are elongate lanceolate, curving backwards. Both of these pairs bear linear grooves on their surface. The members of the third or posterior pair are rhombiform, still with a slight inward curve toward the axial line. The surface is covered with fine and coarser tubercles or pustules, which are especially conspicuous upon the pygidium and axis of the thorax. There is no evidence of any other spine upon the test than that rising from the apex of the glabella. Formation and locality.— Middle Trenton limestone, Trenton Falls, N. Y. TKI1.0IHTR& Mkl N iiif Si IKIKUINATV 61 NIK AMERICAN SPECIES or Lien \-. Probably in no genus of Trilohites are the characters upon which dependence is usually placed fur taxonomy, so variable as in //iV//./*. Hence arises the fact that essays toward subgeneric division of the very considerable number of known species have been of but very restricted utility. The lichads were thin-shelled Crustacea, and in the tenuity of the test and its read) ;i.l;i|.t;i1ii>ii tn nmdilicat nni- nf t lie int. -nor may In- fi nun I mic rau-c (if tin- \\ide variation in the form of lobes and protuberances, the length of grooves and ridges of the surface. In this respect the genus stands in strong contrast to such compact and thick-shelled genera as I'lmcops where the parts of the test have become rigidly condensed and present throughout the existence of the genus a stable resistance to all modifying agencies. The subdivisions of the genus Lichas which have been suggested by the eminent investigators, Angelin. Fr. Schmidt. Dames, and Hall, may perhaps be character i/.cd as well adapted to the material which the authors had before them, and to strictly typical specimens, but losing a degree of applicability when a more extended use of them is attempted. Such a criticism is easily made of any classification, and it is sufficiently evident that these authors were alive to the difficulties presented by these multiform species. There has been a diversity of opinion as to the best basis of subdivision. The majority of students have, perhaps, made use of the variation in the lobation of the Isabella, as the most conspicuous and essential source of structural difference, and there can be no doubt of the primary importance of such variation in the trilobites generally. Some authors, appreciating the instability of the characters of the head, have had recourse to the differences in the structure of the pygidium; but this is, also, an equally variable, part. It is evident that any satisfactory classification must take into consideration concomitant variations of all the parts, and in this respect, the elaborate work of I'r. F. Schmidt upon the Silurian species of the Bast-Baltic Provinces must be regarded as the nearest appro xi mat ion to a successful classification. Marrande, conservative in his treatment of the classification of all the trilobites, recognized no subgeneric division^, and this is 1>\ far the easiest solution of the taxonomic difficulties arising in the group, hut the strnrtur.il. t'aunal and strati- graphical value of modifications of the generic type are thereby left in obscurity. Subgeneric divisions are iuadmi— al.le or useless in series of compact acmic forms 752 THE PALEONTOLOGY OF MINNESOTA. (.Observations on Lichas. like Phacops, Trinucleus, etc., or a slightly oscillating group like Proetus, but the plastic Lichas, presenting the widest range of variation, affords an excellent opportunity for empiric skill at classification. The typical species of the genus Lichas is the L. laciniatus (Wahlenberg)* Dalman, founded upon a pygidium, an outline copy of the original figure being Fig. 74.— Outline of pygidium of Lichas laciniatus Wahlenberg (after Dalman). introduced in this place. The remaining structure of the species is not known; but the pygidium bears two broadly falciform extensions on each side, and terminates in a single acute undivided median lobe. It is quite similar to the pygidium referred to Platynotus trentonensis Conrad, given by Halljf and if the imperfect cephala from the Trenton limestone of New York given by this author represent the same species as the entire individual quoted and figured in the work cited as from the blue lime- stone of Ohio, the cephalic structure of Lichas in its typical or restricted meaning is very simple, the lateral furrows debouching at right angles in the occipital furrow, there being no middle grooves and no third lobes.J This is the structure of the New York specimens of L. trentonensis, of which the pygidium is not definitely known, that referred by Hall (loc. cit., fig. Ib) to this species, being probably a part of our Conolichas cornutus. This structure, however, is the same as that predicated of Platymeiopus Angelin (as interpreted by Schmidt). We have therefore to face a dilemma in the application of these terms. The precise value of the restricted term Lichas is not yet demonstrated, but knowing the meaning of Platymetopus we may provisionally employ the term while awaiting fuller evidence of its relation to the •Uebcr die Palaoaden, pp. 53, 71, 72, pi. vi, fig. 1, 1828. + Palaeontology of New York, vol. 1, pi. cxiv, fig. le. tTo Illustrate the normal lobatlon of the cephalon In the highest development of the llchad type of structure a figure is here reproduced of the L. palmata Beyrlch. (Barrande, Syst. 811 , vol, I. pi. xxvm. fig. 45,) Fig. 75.— Glabclla of Lichas palmata Beyrlch. (After Barrande.) d. dorsal furrows. a. median or frontal lobe. 1', 2', 3'. anterior median and posterior lateral lobes. J, 9, •). apterior median and posterior lateral furrows. TKII.MMTB8. ' ':; I truo Lichns. A diflicult y, more apparent than real, in assigning the species of lii-lmds to their natural ^n>u|m, arises from the frequent recurrence of extravagant -i > li»s of ornumentution in tfnmp- II.IMHJJ a totally different character of cephalic loli.uion. Tlui> in Mi-infii.is, rinliftndopus and lloplolichaft may occur along, club-like extension of th»> frontal lobe; riatytnetopux and Conolirhas may both have subconical frontal lobes, concave on their posterior slope; I'latymeiopus and Ifoplolichas may ha\c tln> frontal lobe garnished with erect tubercle-spines. These are instances of inoi pine ri|uivalence in diverse groups, which cannot be accorded a high ttignificance in the association <>f the species. \\ •• ni.u Miggeat the following subgeneric division of the North American species of Licha*: AKOKII. Goldfuss -Mulillf glabellar furrows obsolete, posterior furrows mure or low Indistinct; <>ut>T lateral margins of glabellar lobes convex; third lobes obsolete. Pygldlum with 2—3 arm illation son the axis, mad narrow, round spine* on the margin. A longitudinal ridge extend* f ruin Hi'- , \; ri-iniiy of the axis to the margin. Elerated portions of the body often echlnaU*. A . ifftfnt>frgennt Schmidt, var. paulianta Clarke. Galena. pUfeUnoidn Green. Nlaicara. A. cotuamguinfiu Clarke. I. A • 1 1- •Nlcrherg. A. eontufnt Hall. U|ip>-r II>-lderberg. /-. (Conotiehat) hltpidut Hall. Upper Helderberg. /.. (ConoliclHu) eriopit Hall. Upper HelderberK- The last twu seem to be more at home here than In lhi> aubgenuK Vonolirha*, on account of sub«tan- tlal difference* from the latter In glabellar lobatlon and form of the pygldlutn.. PLATYKOTUS, Conrad.— Glabella depressed; middle furrows obsolete; frontal lobe depressed at Its narrowest point; third lobes obscure, but present. I'ygldlum with three pairs of broad, acute, flat spines; axis short with 1—2 annulatlons. /. harriti Miller. Hudson River. /-. Mtoni Blgsby. Niagara. tL. nrrfiu Hall. Niagara. L. brtvicep* Hall. Niagara. PLATYMETOPUS, (Angelln) Schmidt.— Lateral glabellar furrows open directly Into the occipital furrow: no third loben; all loben depressed-convex, all furrows narrow; dorsal furrows con- cave inward. 1'ygidluui with two pairs of lateral spines and a bluntly blsplnou* caudal termination. L juketi Billings. Quebec. L. mittganrntu Hillings. Chazy. L. trrntiinfruif Hall. Trenton. L. eufullut Meek and Worthcn. Trenton, Galena. /~ roMiiMi Ulrlch. Galena. /- bieomii Ulrlch. Galena. Hall and Clarke.— Frontal lobe elevated, lateral lubes large and highly convex, all spinif-T..-.-: third lobes absent. Occipital ring broad, with double axial spine. Dorsal furrows^ • -in. ir n<«le very small. Border broad. C. draeon Hall. Upper IIi-lil<>rl*erg. C. grjfpt Hall. I li-rlierg. TKRATASPIS, Hal!. Fnintal lobe ovoid, constrictnd Iwlow; dorsal and lateral furrows very broad; lateral lobes not sharply f this evidently new form is a part of a cephalon (considerably more than one-half), preserving the outline of the frontal and lateral limb and the confiKiir.it ion of the surface. The anterior curve is subseraicircular, broadly round- ing to the sides where the margin is straight for a considerable distance, thence incurving rather abruptly at the angles of the genal expansions. The outline thus formed may be termed subquadrate-ungulate, and its peculiar curve is a distinguish- ing character of the species. Fig. 76.— Oephalon of Harpimi minnetotenti*. • • General surface of cephalon moderately elevated. C label la subtrigonal, tapering anteriorly to an obtusely' rounded extremity. Length about one-half that of the cephalon axial ly; slightly greater than the width across the base. The top of the glabella is somewhat abraded but its lobatipn is quite distinct, showing that the frontal lobe is long and conical, extending for about one-third the glabellar length, the first pair of lateral lobes faint, the second pair a little longer; the third pair is comparatively large, ovoid, attached by a narrow neck to the basal and most elevated portion of the glabella. Of the glabellar furrows the third are largest and deepest Occipital furrow broad and shallow; occipital ring narrow in the middle widening to the axial furrows. The frontal limb is broad, convex just in front of the glabella becoming deeply concave and elevated at the margin, to the full hight of the glabella. This general concavity of the marginal area is continued over the cheek, to the extremity of the cheek-spine, becoming, however, less, posteriorly. The outer marginal nm '* thickened all around; the inner margin elevated but not thickened except at the continuation of the occipital ring on the cheeks. Eyes situated in a transverse line which crosses the glabella at about one-third its length from the anterior extremity, elevated and widely separated from the glabella by the broad dorsal furrows. A low ocular ridge extends from them obliquely backward toward the posterior extremity of the glabella. 756 THE PALEONTOLOGY OF MINNESOTA. [ llarpinn inlnnesotensis. Surface deeply pitted over the free cheeks and marginal expansions. The punctae are circular, large, attaining their greatest size where the surface is most deeply concave. They appear not to be confluent at any place, but become obsolete on the marginal rim. The single specimen observed has an axial length of 12 J mm.; length to end of cheek spine, 23 mm.; basal width 26 mm. It is hardly necessary to indicate the particulars in which this fossil differs from the described species of Harpes. The character of the ornamentation, the form of the glabella and its lobation, the absence of broad, lobate expansions about the basal angles of the glabella, the oblique direction of the ocular ridges, as well as the curve of the marginal outline, are all distinctive characters. Harpes is a genus which is not abundantly represented in species in any country, though its species are found from the Lower Silurian to the middle Devonian. It is a curious fact that all American species are from the Lower Silurian with the possi- ble exception of the H. consuetus Billings, from the Island of Anticosti, which may belong to a middle Silurian, or a Hudson River-Clinton fauna. In Bohemia none of the forms described by Barrande are from the Lower Silurian but are distributed throughout the Upper Silurian and lower Devonian, while in Germany it ranges through the Devonian faunas disappearing with the fauna of Gonitatites intumescens (Intumescens-kalk). The late Dr. Ottomar Novak called attention* to the intermittent occurrence of Harpes in the faunas of the Bohemian basin. Two of the eleven known species appear early in the Lower Silurian (etage DI), but from that horizon to the etage Ea Fig. 77.— Hypostoma of Harpes venulosus Fig. 78.— Hypostomaof J/tirptnaprifcia, enlarged Corda, enlarged. 'Etage F,). After Novak. (Etage D,). After Novak. including five of Barrande's stratigraphical divisions, there is no evidence of its existence. Novak, suspecting a structural difference between the Lower and Upper Silurian species, which is not apparent from the extei'ior except in a less number of •Sluillrn :m llypostoinun der bOhra. Trlloblten, No. II. p. 4, pi. I, 1884. TI:II.I>UITKS. 757 in the former, investigated the nature of the hypostoma of both ami found therein differences so notable that he introduced the name llnrfiina for the early Silurian species; a terra which we retain as probably applicable to all our American ami Utfaliljf Knun the mlilill.- |K>rVl'm of the Galena HUU-NHI.', lladi-r, Minnesota. Mr. K. <>. Urlch. 1 1. \KI-IWA, cf. H. OTTAWKNsis Hillings (sp.). Among the material obtained from Dr. Robbing is a large horseshoe-shaped impression of the exterior of the submarginal doublure of the head-shield. It is quite Hat and its ornament apparently consisted of a great number of fine puncto of about equal si/e except along the inner margin where they are larger and continent in radial lines, forming a series of short divergent furrows. The marginal :•' ll.irpina, ct. H. oltatcfntit Billings. outline of the shield is quite similar to that of //. vltaicensi* Hillings,* of the Trenton limestone of the city of Ottawa. Indeed, the specimen conforms almost exactly in size and curvature with the original figure of that species. We have above observed that species with a concave cephalon may have a perfectly flat doublure, and I am to believe that this specimen probably represents an individual of //. is, with which it presents an additional point of agreement in the character of the surface puuctte. formation and locality.— Galena Illusion.', Wykoff, Minnesota. HAKI-INA BUTRBLLUM, n. sp. An hitherto undescribed species is represented by a head-shield with the following characters: Size moderately small, outline subsemicircular. Surface convex, somewhat depressed above; marginal border not so broad as in //. min> tensis; deeply concave. Margin thickened, smooth and slightly upturned. Genal extremities not retained. Olabella subconical, extending more than one-half the • FtUmiolo ItoMlta. »ol. 1. p IB. •(. 110. UK. 758 THE PALEONTOLOGY OF MINNESOTA. [Harplua rutrellum. axial length of the shield, anterior extremity narrow and obtuse. Basal lobes very broad and large, together making the glabella considerably broader at the occipital ring than it is long. These lobes are separated from the glabella by short, posteriorly oblique lateral furrows, and from the cheeks by deep grooves which are abrupt and Figs. 80, 81. — Portion of cephalon of Harpina rutrellum, with sectional outline showing the charac- ter of the doublure. ridged on their outer margins. The occipital ring is narrow, elevated and well defined over about one-half the extent of the cheek. Cheeks somewhat flattened above, abruptly deflected to the concave margin. Eyes small, nodiform, distant from the glabella and situated in a transverse line cutting the shield at its center. Surface of convex portion of shield covered with coarse, deep, irregular punctures which are coarsest about the eyes and on the anterior slope of the shield, become finer and more nearly circular about the margin. The glabella is covered with shallow, irregular pits, while the basal lobes and occipital ring are smooth. Doublure flat, its width equalling that of the concave part of the upper surface; thence it is bent upwards at a right angle, its distal portion becoming parallel to the anterior slope of the shield, as in the accompanying figure. The outer surface of the flat area is covered with large and very coarse circular punctae. Length of specimen 9 mm.; probable width at base, 16 mm. Though there is but a single example of the head, the characters above given are sufficiently distinctive. Whether a second specimen showing only the flat portion of the doublure belongs to the same species it is impossible to decide definitely, though the character of the punctation is essentially similar, and the vertical section shows that the upper surface was concave about the margin. Perhaps the species most closely allied to ours is Prof. Hall's Harpes escanabce* from the Trenton horizon on the Escanaba river. This was based upon the marginal rim of a small cephalon described as being strongly pitted with the punctae arranged along the outer and inner edges of the finer and more abundant perforations in the middle. This agrees with the character of the under surface of the second of our specimens, but not with the upper surface of the first and more typical example. Harpina rutrellum may also be compared with H. antiquata Billings, of the Chazy limestone. Formation and locality.— The cephalon described is from the Galena beds at Cannon Falls, Minn. (Mr. Ulrica's collection); and the fragment of the doublure is from the Trenton at Minneapolis (Museum No. 8420). • Fotttr and Whitney's Bept. Geology of Lake Superior, p. 211, pi. xxvn, flg. 2rt, 1861. TKILOIMTBR .'•'.' CypbupU (alcnmuU.1 Genus i -Y I'M. \S1MS. Burmeister, 1848. CTPHASPIS ? OALXNKNSIS, n. sp. This muni' is applied to a single minute cranidium bearing an ellipsoidal, very convex glabella surrounded by deep dorsal furrows and tapering about equally toward Ixith extremities; and with narrow convex fixed cheeks. All evidence of the lobation of the glal>ella is very obscure, indeed consisting only of a slight lateral indentation on one side, at about the middle of its length, and of three equidistant elevated lines on the other. The surface is smooth or very faintly granulose on the glabella and more coarsely papillate on the cheeks. Fig. 81— Cranidium of Vyphtupitf galenenii*. (x S). The fossil evidently represents an undescribed species and may therefore take the name here proposed, but its generic relations remain quite uncertain. In general appearance, form of glabella, convexity of cheeks and curve of facial sutures, it is like Cyphaspis, but it altogether lacks the basal glabellar lobes of that genus. Two other species from the Lower Silurian faunas of America have been referred to Cyphatpis: C. girardeauensis Shnmard,* a normal representative from the Trenton horizon, and C. ? brevimarginata Walcott,f from the Pogonip group of Nevada, a form having characters not unlike those of C. ? galentnsi*. • G«ol. Kept. MlMOurl. p. 197. pi. viu. B(. 11. 1H6. •l-.lB-o.it Eureka DMrl.K.f NI-TMU. p. «. pi. XH. fig. 10. IW. Formation and totality .— The MinnedoU specimen In from the Galena nhalea at Cannon Falln. 760 THE PALEONTOLOGY OP MINNESOTA. [ (Joinrminlcatioti COMMUNICATION. Professor N. H. WINCHELL, Slate Geologist. Sm:— At your request I have prepared the following chapter, embracing descriptions of the Cephalo- poda of the Lower Silurian rocks of Minnesota, which is herewith respectfully transmitted. I have the honor to remain, sir, Very truly yours, JOHN M. CLARKK. ALBANY, N. Y., September 10, 1894. CHAPTKU IX THE LOWER siLt'RlAN CEPHALO I 'ODA OF MINNESOTA. ll\ K.IIN M I I.MIKK. INTRODUCTORY. The Cephalopoda or " head -footed " inollusks are distinguished from the other mnllusran groups by the possession of a circlet of long fleshy tentacles or prehensile organs arranged alxmt the head. This group of animals is a very large one and, from its appearance in the early faunas of the globe to the present time, has been represented by species of limitless • liv.'rsity in form and structure. Those with which we have to deal in this chapter represent only early and primitive types of structure. The two Orders of the Cephalopoda generally recognized are: 1. Tetrabranchiata; 2. Dibranchiata; terms which imply the possession respectively, of four and two gills. The tetrabranchiates are typified by the living Nautilus poinpilius; the dibrauchiates by the Loligo, or squid, Sepia, or cuttle-fish. The tetrabranchiates were wonderfully ahmnliiut throughout the Paleozoic an.l Mesozoic periods of the earth's history, hut are to-day almost extinct, while the ililiranchiates are the predominant cephalopoda in existing seas, and their fossil representatives much less numerous and diverse. The tetrabranchiates possess shells in which the animal occupies only the outer or forward portion, and the rest of the internal cavity is divided into successive chambers by a series of transverse or oblique plates, called septa. These septa are connected with one another and with the outer or habitation chamber by a fleshy tube or sipho passing though a perforation in each septum. This order is usually regarded as divisible into two suborders termed: o. Nautiloidea. b. Ammonoidea. TO 762 THE PALEONTOLOGY OF MINNESOTA. [Introductory. In both of these subdivisions the shell may be straight, arcuate or spirally enrolled; but in the Nautiloidea the sutures, or lines of junction of the septa with the walls of the shell or conch, are, as a rule, simple, without abrupt curvature and very seldom with sharp angles, while in the Ammonoidea these sutures are usually highly angulated or zigzagged; in the nautiloids the sipho is very variable in position, may be small and cylindrical, but is often large and its walls much thick- ened, while in the ammonoids the sipho is always cylindrical, always marginal in position and without a thickening of the walls. In the faunas of the Lower Silurian no representatives of the dibranchiates or of tne ammonoid tetrabranchiates are known. We have, therefore, to deal in this chapter only with the nautiloid tetrabranchiates. As an illustration of the general structure of these bodies and to show the relation of the animal to the various parts of the shell, we have here inserted a drawing of Nautilus pompilius, reproduced from the well known figure by Richard a. Mantle. b. Its dorsal fold. e. Nidauental gland. Shell muscle. i. Sipbo. k. Funnel. :/. Fig. 1.— Nautilus pompilius. n. Hood. o. Exterior digltations. p. Tentacles. ». Eye. x. Septa. z. Body chamber. 7C.3 G0tt*r»l rhtjr»i*t«*r* of r* forms here discussed in which this shell is straight or but slightly curved. QBNKKAL CHAKACTBBS OK THK LOWBR SILURIAN CEPHALOPODH IIKKK DKHOKIHKD. We have observed that the Cephalopoda met with in the early Silurian faunas are mainly of primitive types of structure. Their predecessors existed in faunas before the Silurian but their remains are of infrequent occurrence, and hence our knowledge of them is very restricted. With the opening of the Silurian certain progressed generic types, such as Orthoceras and the shells which must still be referred to Cyrtoceras, became fixed or static in their traits and were continued thereafter for long periods without essential modification. Two structural features in these Silurian nautiloids are especially significant and invite brief attention. 1. The form of the shell. The straight, elongated shell or longicone exemplified in Orthoceras, Cameroceras and Adinoceras, is the prevailing type. It is known from Fig. 2.— An Orthoftrfu represented u rertlrally sectioned for a portion of IU C. body-chamber; r. alr-chambera; x. septa; *. alpbo. the study of some of the later longicones that these shells, from their primitive formation onward through all intermediate phases to maturity, have maintained the straight mode of growth, and we may therefrom infer that such shells have been derived from ancestors whose shell was also straight. The formation of such 764 THE PALEONTOLOGY OF MINNESOTA. [General characters of eephalopods. regularly conical shells implies equal progress in the deposition of the shell-matter on all sides, but when the shell is coiled this effect is due to an obstruction of the shell growth on one side. In certain of the coiled genera we know that the enrolled portion of the shell represents only the immature stages of existence, while during later-growth stages the shell becomes straight. This fact, illustrated by the genus Lituites, does not necessarily imply that such forms have been derived from primitive coiled types, but may with excellent reason Fig. 3.— Lituites lituus. (After Rcemer). be interpreted as follows: The straight conch of the full-grown animal may be regarded as a senile character expressing a return to, or towards a primitive growth- condition not otherwise represented in the individual, but indicating the source whence these generic traits have been derived. In the peculiar genus Ascoceras the early growth of the shell is in the form of a long, very slender, gently arcuate cone with a regular succession of siphonated septa as in Cyrtoceras, but this mode of growth is abruptly terminated in later development by a lapse to a much more elementary condition of development evinced by the suddenly swollen .conch and the incomplete and primitive septa. Several of the genera here considered are characterized by a swelling or expansion of the shell during later growth, and a sudden contraction at the close of the swelling near the aperture. This is observable in Oncoceras, Clinoceras, Poterioceras and the shells referred to Cyrtoceras* The presence of this character in these early types might of itself be interpreted as indicative of primitive structure, as it has recently been shown that in certain Devonian species of the orthoceran genus Bactrites this expan- sion of the shell characterizes the growth stage directly succeeding the formation of the protoconch. Fig. 4. — Ascoceras manubrium. (After Li ndstn'im). •It Is elsewhere observed thai In the Devonian and typical representatives iif tills genus tills swelling of the couch Is uiually absent, but It li more or less distinctly developed In the majority of the early Sllurluu species. 7.;:, Min-li may In- lt>arne> friuii the onianitMitatiuii i>f the external Mirface of the shell. It has, nplt>. IMMMI ilcnii'ii-trat.'.l. .iii.l the fact is illustrated in the following page* l'\ the species Orlhwnix lii/inenlum, that the concentric rin^- nr annulations which are fmm-l in .1 larp> iium!>er of orthocerans, are of secondary growth, the earlier -of the shell heingfree from them; thus indicating that these annulated shells rep- resent a more programed condition of development than those with smooth -m f _. rif structure of the sipho. The sipho is, typically, a cylindrical tul>e connect- ing the air-chambers and continuous from one septum to another. Actually, liuwi'MT. in most of the primitive genera, such as Nanno, Pilocerns, Camerocerns ami it has not fully attained this condition. hut is in formative and longivrimum of the Black River limestone, both very rare species, is said by some investigators to have the place of the sipho tilled by successive sheaths which are posterior continuations of the successive septa; these forms, hence, having no true sipho. This interpretation requires verification. Others have regarded these shells as having a distinct siphonal wall and the sheaths as confined to the siphonal cavity and occurring at intervals which have no direct connexion with the septa. If the former view be correct then Vaginoceras must be regarded as representing a highly elementary condition of development, but the latter interpretation of the structure renders it homologous with Piloceras in which we know that the siphonal «. b.-Cameroetnu Imrchor.li, *h..wii.i: Ki«. *.-Ca*uroeera» proMforme ; »howlnu U.. ,al funnels. (After Dew I U). Hi-' -hf. siphonal funnels. wall i>- .leveloped for at least a portion of its length, as it is also in Nanno and Camtrocera*. In the two genera last named the median and later portions of the sipho are constituted of deflected portions of the septa known as the siphonal funnels. These often extend from one septum to, or beyond the one preceding it, thus separating the siphonal cavity from that of the air-chambers; but not infre- quently these funnels do not completely cross the air-chambers. In either case these funnels form a discontinuous siphonal wall. In I'ilocerM, Catneroceras and .V.i nno the continuous apical portion of the sipho is thickened by the extravagant depo- sition of testaceous matter in the cavity or between the successive siphonal sheaths. I n 766 THE PALEONTOLOGY OF MINNESOTA. [General characters of cephalopods. Nanno this solidified portion of the sipho protrudes behind the septate portion of the shell, indicating a primitive condition in which the inhabited shell was a simple aseptate and asiphonate cone. - c Fig. 7. — Camerocerat protei forme. C. outer shell or conch; s. septa; «/. siphonal funnels; sh. solid apical portion or guard of sipho. In certain more advanced types, Adinoceras and Gonioceras, where the siphonal tube is continuous throughout its extent, as in Orthoceras, the sipho takes the form of a succession of beads expanding into the air-chambers and contracted where meeting the septa. Within the siphonal tube is a thick deposit of shelly matter, leaving a narrow central passage or endosiphon, which may be completely closed in the earlier siphonal beads and quite wide in those of the last air-chambers. The thickening of the siphonal wall is, thus, to some extent, a process common to all lime-secreting organisms, tending to fill up and close deserted cavities. From the endosiphon of Adinoceras are given off series of radiating filaments ''penetrating the thickened walls and reaching the true siphonal tube. In the following pages about fifty species of these fossils are identified and described. The material which has been studied may be regarded as fairly repre- sentative in abundance although its usual retention in the form of internal casts leaves our knowledge of some parts of the species unavoidably imperfect. The identification of some of the species, especially those of Cyrtoceras and Oncoceras has been rendered difficult by the brevity and obscurity of the original descriptions and, in many instances, the absence of illustrations, but, as a careful comparison has been made of the material with the original specimens of such unillustrated species, reasonable security is felt in these identifications. Many of the most interesting specimens are from the collection of the late W. H, Scofield; others have been loaned by Dr. C. H. Bobbins and Mr. E. 0. Ulrich. 7117 Class CEPHALOPODA. Order TF.TK.Mti; \N< II I AT A. Suborder NAUTILOIDKA. • Family KNDOCERATIDJ (Jenus PILOCERAS, Salter, 1859. I'M.OCKKAS NKWTON-WWCHRLLI, 8p. nOV. PLATE XLVII. F108. !-». Two specimens preserved in a white chert indicate a small undescribed species of this genus. The more complete of the two is obliquely fusiform, slightly arcuate on the siphonal side, and bears sixteen septa which are very oblique on the upper part but lose this obliquity toward the apex; the direction of the earliest septum is nearly transverse. The obliquity of the later septa is so great that the last septum exposed, in crossing the shell from the dorsal to the ventral side traverses the depth of five air-chambers on their antisiphonal exposure. The length of this specimen is 31 mm. and its width at the top measured along a suture, 21 ram; the transverse diameter at the top, 17 mm; at the base 7 mm. All the air-chambers are deepest at the antisiphonal edge. At the top of the specimen is the opening of a wide siphonal cavity. A longitudinal section of the specimen along the axis of this ravity shows some interesting points of structure. The mouth of the cavity is broad at the top, covering nearly one-third of the entire diameter of the shell. Its actual and relative diameter lessens, however, toward the apex. The position and relative size of the sipho and the difference in the direction of the septa on the two sides are shown in the accompanying figure. This cavity is not filled by a solid accumulation of siliceous matter, but is more or less cavernous. The siphonal walls, however, are encrusted and
  • tinrtly retained. It is very clearly evident from this section that the septa are not coalesced with the siphonal wall (ton). The edge of each septum lies close against, usually in actual contact with a thickened 768 THE PALEONTOLOGY OF MINNESOTA. [Plloceras newton-winehelli. ridge or annulus on the outer surface of the sipho. The latter tube is, hence, a es Fig. 8.— Median vertical section of one of the specimens described, x 2 Fig. 9. — Enlargement of a portion of the same. s. sipho; ss. siphonal sheaths; ws. wall of sipho; es. endosiphon; sp. septa; a. annulus formed at junction of septum with sipho. distinct sheath of itself, not originating from successive invaginations of the septa. The earlier portion of the sipho (s.) contains two siphonal sheaths (ss.) which are separated from each other by an empty space, and above the first of these sheaths there is also but a partial and irregular filling of silica. Below the second sheath the sipho is solidly filled. These sheaths take their origin from thickened walls of the sipho, the separation of the testaceous wall being very apparent at their origin. When the sheaths become fully free from the siphonal walls, they converge more or less rapidly. The first or uppermost of the sheaths is very plainly perforated at its apex, but this opening is less clearly retained on the lower sheath. These open- ings are undoubtedly to be construed as the passages of the endosiphon, as Hyatt has termed a small tube connecting successive deposits and compartments within the sipho. In the larger forms of Piloceras which have been described by Dawson and Whitfield (P. amplum, P. explanator) and whose siphones have become solid from the more rapid formation of these sheaths and the intermediate deposition of crys- talline calcite, this endosiphon is sometimes very clearly retained,* but here where the chambers of the large cavity are open, nothing remains but the passages of the endosiphon through the sheaths. In this respect the structural difference is note- worthy as the case in hand is the only one observed in which the siphonal chambers •See Dawson, Canadian Naturalist, new series, vnl. \. Nn. 1, 1881, p. 1-4; and Foord, Geological Magazlnn, Dec. Ill, vol. Iv, No. 12, 1887. BALOFODA I'ltiireru r .lie >n larire and have nut Keen rendered more or le^s completely -olid liy the r\ti.i\ ,i-at Km of organic deposits. Tin- M-.'niid and less complete specimen of the species exposes a portion of one -ide d'J septa), toward the lower part of whirl), liy rross fracture, the siphonal tul>e i> left open and shows the terminal extremity of the internal solid cast of one of the siphonal chambers and a considerable portion of another later and enveloping -heath. The apex of this internal cast does not show satisfactory evidence of • •ration. There are seven -leM-ril.ed .species of Piloceraa, six of which are recorded as from American fauna*. All are of much larger size than /'. nrtrton-winchelli, and so far as known, have greatly broader siphones. All are from the early faunas of the Ixwer Silurian: Hillings' species P. cunadense* from the Calciferous horizon, P. wortheni*, /'. tritnn* and P. gracile1 (the last two but little known) from the Quebec -roup: /'. explanntnr Whitfield3, from the Calciferous fauna of Vermont and New Y'ork (Fort Cassin beds), /'. •nnplutn Ihiwson.4 from a corresponding horizon near Montreal, and /'. invayinaluni Salter5 (the type of the genus), from the Durness limestone of Sutherlandshire, Scotland, associated, according to Salter, with Ortln's •• shell piiss from their primitive condition onward, aii-l wi> take the liberty of quoting this passage: "The visceral sac of the animal h;i had secreted a shell of like form. This shell was thu- quite open and of conical shape. It now funned hut a single chamber which was both initial aud habitation chamber, wholly filled by the animal. With the growth of the animal the shell was, naturally, lengthened on the anterior margin. As the animal [shell ! at last became too heavy and had need of a hydrostatic apparatus in order to raise and sink itself, the air-chambers, by which the hydrostatic problem is solved for the tetniliranchiates, were formed. The first of these originated in this way: On one -i>li' * *f the upper portion of the visceral sac a circular and almost enclosed constric- tion was produced. The fold of the mantle thus formed deposited shell-matter making an inclined wall and a division of a part of the originally open initial chamber. The resulting chamber was empty and formed the first air-chamber. . This chamber is, thus, bounded by only one septum and in this case lies behind the w.xll corresponding to the first septum in Nautilus. It therefore corresponds to the initial chamber in that genus. As it here has the same function as the other air- chambers, I have termed it the first air-chamber, although, in fact, it is a remnant of the open initial chamber. Moreover, the second air-chamber is probably formed in part from the anterior portion of the initial chamber. The visceral sac of the animal was now divided by a constriction into an anterior and posterior portion. The anterior portion now forms the actual habitation chamber, but the great visceral sac also fills the posterior portion. The growth of the shell progresses; the shell is again lengthened about the aperture. The animal becomes again too heavy and must form another air-chamber. It loosens itself from the wall of the conch, the visceral sac extends itself along the constriction and the animal moves forward a step in its shell. The mantle surfaces form a new septum and about the elongated portion of the visceral sac the calcareous deposit takes the form of a .sheath or siphonal funnel. Thus originates the siphonal cord of the animal. Hence the sipho of Kndoceras belemnHif'onne must have had its origin in a differenti- ation of the visceral sac." (Op. <-it., pp. 6, 7.) The pneseptal cone of .\ fairly .il>uii. though the evidence afforded by them indicates the probable presence of several species. Of more interest than the variation in specific features is the interesting illustration of the structure of the sipho which is represented by many and various forms of internal casts of the organ. With all that has been written upon tlic relation of the sipho of this genus to the septa and conch, there still remains much to l>e learned in regard to the structure of Catneroceras, and some light is thrown upon obscure points by these specimens. We have here adopted without reserve Conrad's term Cameroctras in place of the more generally accepted name l.mloceras. Whitfield has employed the former term with a suggestion that there may prove to be a generic difference in the two structures, but this seems to us, with the present evidence, scarcely possible. The distinction which has been recognized between the two by Hyatt is that in Endoceras the siphon is not lined by a continuous shell layer but is composed of a succession of septal funnels, overlapping heir edges, while in Cumeroceras (which this author regards as a synonym of Sannionites, Fischer de Waldheim, 1837), the siphon is a continuous layer. The typical species of Endocerus ( /•.'. />rokiforme Hall) is vastly better known than that of Cameroceras (C. trentoneme), and while it has been impossible for me to carry out a generic distinction in the two, the fact must be recognized that the latter term was introduced in 1839 and the former not until 1847. Conrad, also, in 1839 employed the name Diploceras (D. vanuxemi, type) for a shell from Trenton Falls, N. V .. which is unquestionably a Camerocems, and the species probably the same as Endo- /»•<•/• it'nrmt. Hall*, Whitfieldf, DewitzJ, HolmjS, Foord " and others have shown the existence of a continuous sheath situated at, and composing the apical portion of the sipho, often thick-walled, and extremely so about the apex itself. These have been sometimes termed "embryo-tubes" and also "siphonal sheaths," as though they existed within the sipho and were not an integral part of the sipho itself. Such bodies, of which internal casts abound in the Trenton formation of Minnesota, are the thickened extremital portions of siphones; the septa lie against them (or at least, against their upper portions) in a normal position, and above its free edges the sipho is a discontinuous sheath composed of the overlapping and • Bull. Am«r. MM. Nat. lll.i > ..I I. DO. I. pp. 1 • PmlcoMolonr of New York. vol. L, pp. W wr . l-ilh.ololocbciM Abb»ndlun«rn. Hod 111. Heft I. IMA. I Aon. »od M»*. Sat II tot.. DM- W7. pp.1 776 THE PALEONTOLOGY OF MINNESOTA. [OMneroceras. retrally directed funnels of the septa. This is well illustrated by a very large and essentially entire internal cast of the sipho, measuring 3 feet 3 inches in length, a reduced drawing of which is shown on plate XLVII. The principal extent of the surface of this specimen bears traces of the contiguous or overlapping septal funnels which have thus created a discontinuous siphonal tube. The specimen is so drawn as to show the side nearest the margin of the conch; hence the remnants of the septa show a marked angularity due to their concavity. This is a trait characterizing all such siphonal casts in which the position of the sipho was lateral. With variation in the position of the sipho and in the concavity or obliquity of the septa, these siphonal funnels vary in their direction. It will be observed that at a short distance from the apex of this cast is an abrupt contraction in its diameter, which is continued to the apex. This apical portion is the internal filling of the solid and continuous sheath whose probable extent and thickness is indicated by a dotted line which carries the sipho to an apex according to the slope of the discontinuous sheath. The evidence afforded by this specimen is abundantly fortified by others which demonstrate that this solid apical portion of the sipho is but a filling and thickening of the vacated and discarded apical cavity of the otherwise discontinuous sheath. The internal casts of this long apical cone are of far more frequent occurrence than those of the funnel-tube, because the parts of the latter are not often coherent and usually the latter are found to retain the overlapping or approximate parts of the septa upon their surface. The great siphones of the dead shells of these creatures afforded favorite retreats for other and smaller cephalopods, and they are hence frequently found crowded with diverse species of Orthoceras and Cyrtoceras, sometimes three or four being crowded in side by side, or one within another, in such cavities. The material examined does not afford the most satisfactory evidence of the duplication of the siphonal sheath, and it would seem that much of the evidence that has been adduced in regard to the presence of such duplicate sheaths requires re-examination, although it is by no means intended by this expression to cast doubt upon their existence. In some accounts of these fossils a careful distinction between the apical sheath, its filling, and such adventitious or hermit orthocerans as may have got in, has not always been made. Attention may be directed to the internal siphonal cast shown on plate L, fig. 3, which shows a portion of the filling of the discontinuous part of the tube and an acuminate terminal process which indicates a tubular cavity near the apex of the solid sheath. Whether or not this ever penetrated the solid sheath and thus represents a true endosiphon communicating with some other sheath, as in Piloceras, cannot be determined from such casts. CKPHALOPOI \ 777 pr. With all the knowledge that we can derive from th«? works of others ami our own observation* a- to the carls >holl-^n>\vth in this genus, there seems to be no £ ..... 1 IVMOD far MIBining that tlir-oli.l -ln-atli m (.'.'""•""• /••/- -\\a- pn>tni.|r. I Ki-ycui'l the septate portion of the shell, as is the case in our new genus AVi;in». The close relation between \tinn<>. < ' /• It.- I'l.VTI I.I. HI.-. I-I; IM.ATF. 1.1 1 1. FIUK0-&. A,'/i'/ocen« proteiforme, II MI :-»7. rahi-nntolmty <.f New York, vol. I. p. JOB, Pis. XLVI, MKK. In //. \ in. Me- I. ^ ( -I. .1. 4: xi.xi\ tln<. la, «; L, fl»{8. 1—3: LII. figs, la l>; LIII, fin*, lo-e ' (E. maanirrntrumj, Z: LV, flg. 1 ( /•:. licatumf ) ; l.vn, tl»;s. la, 6. To this species, so abundantly illustrated in the work cited, may be referred the majority of individuals of Cameroceras occurring in the Trenton limestone of Minne- ^mce the elaborate account of these fossils given by professor Hall, no attempt has been made to supplement or revise the original determinations, but it iiui-t now be observed that the number of species into which the genus was there divided and, especially, the numerous varieties ascribed to Endocera* proteiforme can hardly be regarded a- wholly valid. At that early date, nearly a half-century ago, the structure of these remarkable bodies was, naturally, less clearly understood than to-day. Professor Ilall'< oloervations were almost the pioneer explanations of the peculiar siphonal structures and are by all means the fullest and most comprehensive illustration of these structures that has been given even to this day. A very natural misconception of certain structural features introduced some errors which, in the 778 THE PALEONTOLOGY OF MINNESOTA. [.Canioroceras proteiforme. light of our increased knowledge, at once correct themselves. The composition of the entire sipho was not then fully understood. We have already adverted to the fact that it consists of a continuous and to some extent solid apical cone followed above through all the mature and later chambers of the shell by a discontinuous tube composed only of the deflected septal funnels. The continuous parts of such siphones were originally regarded and designated as "embryo-tubes" or "shells," and, as an easy inference, all apparently similar internal tubes were thus interpreted. We now refer to the shell of Cameroceras only the internal tube formed by the consolidation of the sipho and its few subsidiary sheaths. All other tubes are adventitious, hermit orthocerans or cyrtocerans of various species, which, as we have already observed, found favorite retreats in the great siphones of these dead shells. Such occurrences are extremely frequent, and the finding of as many as four or five such tramp shells ensconced side by side in a siphonal cavity is not unusual. Hence we are compelled to look upon such species as Endoceras duplicatum of the Trenton limestone of Middleville, N. Y. and E. gemelliparum of the Black River limestone of Jefferson county, N. Y., as based upon unessential and adventitious characters, and the latter as probably a portion of the mature shell of E. proteiforme* Furthermore, the several varieties ascribed to E. proteiforme, such as vars. lineolatum, strangulatum, tenuistriatum, are now known to have been founded upon incarcerated shells of Orthocerrptal animlations U|K)n tliis tube, and the gentle incurvature of the >cptal fimrirU. the annuliition of this tube. There is nothing in the material in hand to indicate any «•-- tMitial 'liitt'ifiirc-. fnMn the New York specimens of this species. Formation and locality.— The majority <-f th< <>xamplrs examined are from tte Trenton llaieatoneof Cannon Falls, Minnesota, and are from th«- roll.vtiun of the late W. II. Sooflcld. Th<- large siphon floured Is from the same horizon at WykofT, Minnesota (collection of Dr. C. H. Bobbin*), and other fragments from Derorah, Iowa. CAMKROCKRAS HENNKIMNI, sp. nor. I'l.ATK Lit. KIOS. l-i; IT.ATK Mil Mc.~ 1-1. Tins a tine large species, the most complete of the fragments which represent it indicating a length of not much less than four feet, with shell very gradually expanding. In a distance of 230 mm. the transverse diameter increases from 94 to 100 mm. In section the shell is subelliptical being perceptibly flattened on the siphonal side, and less so on the opposite side, while the lateral curves are compara- tively narrow and abrupt. The air-chambers are relatively narrow, those exposed averaging about 20 mm. in depth, without increasing in this respect toward the upper extremity. There are fourteen of these chambers in a length of 270 mm. The sutures are not regular and simply transverse in their direction, but upon the siphonal side make a broad retral curve along the median line, bending forward again for one-third to one-half the depth of a chamber on the sides, but upon the antisiphonal side being more directly transverse and without curvature. The septa are very deep, sloping with broad, gently concave, almost, at times, plane surfaces to the sipho, about which there is a constriction. The sipho is very large, measuring 46 mm. in diameter where the septum is 90 ram. In the lower portions of the specimens a distinct and continuous siphonal sheath is retained. The vertical section of a fragment represented on plate LIU, fig. 1, shows the thickness of the siphonul wall, which has been preserved only on one side, the other having been destroyed in the process of fossilization. It is here seen that the mode of union of the septa to the sipho is .1 tirm adhesion of the former to the outer wall of the latter, the septa being slightly thickened at their junction therewith. The structure of the shell substance shows with clearness that however firm the coalescence of these parts the distinction between the two is sharp. The specimen also shows the excent im- position of the sipho, the shell not being much abraded on the siphonal side, but having lost considerably on the other side. 780 THE PALEONTOLOGY OF MINNESOTA. [Ounerooeraa, *ji. This species is readily distinguished by its close air-chambers, regular sutures and the subcentral position of the sipho. Formation and locality.— Thz larger of the specimens here figured is from the Galena horizon, two miles northeast of Spring Valley, Minnesota. The smaller specimen is probably from the same horizon, but its precise locality has been lost. Museum Register, No. 340. GAMEROCERAS, sp. PLATE XLIX, FIG. 1. A single long fragment of a slender sipho, 378 mm. in length, 45 mm. in its circular cross-section at the larger end, has very broad septal funnels, and these make but slightly oblique or undulating ridges about the sipho. These are characters in which the specimen is quite unlike anything heretofore described. The directness of the septal funnels indicates a subcentral position of the sipho, while the length of the funnels is much greater than observed in other species. The length of these funnels is from 18 to 20 mm. and they are seen to very considerably overlap each other. The specimen indicates a distinct species of large size, though this example of the sipho constitutes our present knowledge of it. Formation and locality,— ID the Trenton limestone at Cannon Falls, Minnesota. Collection of W. H. Scofleld. CAMEROCEBAS, sp. nov. PLATE Ll, FIGS. 5-7. Among the figures given by Bigsby in his work on the Geography and Geology of Lake Huron* is one which shows in section a Camerocems with large marginal subtriangular sipho. No name has been applied to this American species, though the peculiar shape of the sipho indicates a form unlike any which bear names with us. Holm has described a species of this character from the Lower Silurian of Esthland (Endoceras gladius.)-\ The specimen figured upon plate LI, figs. 5 — 7, is a very characteristic example of one of these bodies, having one side broad and flat and the other broadly rounded. The siphonal funnels on this cast are broad and distant, distinctly curved upward on the fiat side, but regularly transverse on the rounded surface. From Higsby's figure we infer that in their normal position in the shell these siphones were submarginal, had their curved surface towards the conch and their flat side inwards. Formation and locality.— The specimen here figured is from the Trenton limestone at Zurnbrota Ooodhuc county, Minnesota. Muneum Register, No. 3391). •Trans. Goolog. Boo. London, vol. i, pi. 2«, fig. 1. 1K24. t IMC. cU., p. 13, pi. 2. ( KI'll Al.i'IlM'A A.-lln.p,-«-r». bin-.1 Family ACTINOCERATID 1 ii- ACTINOCEKAS. Brnnn. ls:{7 iN'n'KRAR Blt;-MVi >'/«/•<•«, 1840. I'l.ATE XI. VII FKiS. I*-IT. iiaefnu bigtbfi STOKBM. 1840. Tran*. Qeolog. Soc. London, MC. »or , vol. \, p. 707, (tlif. in , v,,l I, p| xxv, figs. 1—3. 1824). <'"in|»ar«> (frmocerat r>mii>'/»». \\ M.I . PalaNtntoloffy of New Ynrlc, v,.l. I p. R5, pi. xv. lit;. 1 lr; pi. xvi. rigs. 1-1«; pi. xvit, flg8. la. '•. Considerable uncertainty must long remain in regard to the specific values of the various orthoceran shells illustrated by Bigsby in 1824 and obtained from Thessalon and other islands in lake Huron.' Of the several plates of illustrations representing these, names were given only to the Huronias ami those by Stokes. It was only with the publication of Stokes' paper, cited above, that names were pro- posed for some, but not all of the examples of .!.•//' /I/KV/-./V figured by Bigsby. All of these are weathered interiors, and there is an evident agreement among them all, including also those referred to the genus Ormoceras, notwithstanding the fact that later investigations have tended to indicate a more recent age to the species there termed Ormocerns backi and 0. buyfieldi. Actinoceras bigsbyi is safely enough an early Trenton form, with many evident points of relationship to Hormoceras lenuifilum Hull, of the Black River limestone of New York. The two are undoubtedly conge- neric, though the New York specimens are not often retained in such a manner as to show the endosiphon and its radial canals. The Minnesota collections have furnished but two or three specimens which may l>e referred to this species, one exposing in vertical section twelve air-chambers in a length of 105 mm., with a width at the upper end of 36 mm. and at the lower end of 25 mm. The other specimen consists of an internal cast of four air-chambers, showing that the sipho is very large and excentric, extending quite to the margin. The great width, however, is at the lower surface of each air-chamber, its diameter greatly diminishing at the upper surface. The greatest width of the siphonal beads. extending thus into the chambers and resting with a broad base upon the septa, is fully two-thirds the diameter of the shell. The endosiphonal walls are thick especially where the beads are broadest, and the endosiphon seems to vary ID with its position in the shell. The casts of this tube show a wrinkled surface and bases of radial branches. Formation and locality.— \n the Ttvtmm liin.Ktun.- at Mlnin-apnlK and at (Jarrli-k'i -(UArry, Dear Rochester, Minnesota. Muteum Rrgutrr. No. 23, IM. •Thr till.- of Hlf-tijr'. pap- • N !«•» on th« O«nfr*ph)r «nd Oeobwy of !.». • Tr»n« . »U- <••!. I. pp m •-. 782 THE PALEONTOLOGY OF MINNESOTA [Aetinoceras beloltense. ACTINOCERAS BELOiTENSE Whitfield, 1877. PLATE XLVII, FIG. 18. Orthoceras (Aetinoceras) beloitense WHITFIELD, 1877. Ann. Rept. State Geol. Wis. for 1877, p. 97. Orthocera»( Aetinoceras )beloitf.nse WHITFIELD, 1882. Geology of Wisconsin, vol. iv, p. 226, pi. vm, flg. l;pl.x, flgs. 9, 10. Original description: "Shell large and robust, subfusiform, moderately expand- ing to the diameter of about four inches, then more gradually decreasing in size to the aperture. Section oval in all the examples noticed, and usually a little more flattened on one side than on the other, with the siphuncle sub marginal on the flattened side. Septa shallow and not often symmetrically arranged; from seven to eight chambers occupy a length equal to the diameter of the largest of the number measured; toward the outer portion of the shell the septa become more crowded, and just below the outer chamber are sometimes less than half the usual length. Siphuncle large, strongly beaded within the chambers, with an inner core, in the casts, having radiating filaments extending to the center of the bead in each chamber. Surface of the shell unknown." This species is represented in the collections by two fragments, one retaining sufficient of the air-chambers to show the characteristic form, and also displaying the relatively small sipho which serves as a distinguishing feature from Aetinoceras bigsbyi Stokes. The casts of the sipho in both specimens show a highly crenulated, gathered and puckered surface for the interior of the siphonal tube (endosiphon) and a series of fine canals connecting with the outer siphonal wall, below the funnel of each septum, and this possibly forming a means of communication between the endosiphon and the air-chambers. Each cast of the endosiphon bears upon the proximal or siphonal side a deep longitudinal groove, representing a prominent ridge on the wall of this tube. Formation and locality.— In the Trenton limestone at Janesville, Wisconsin. Museum Register, No. 8279. ACTINOCERAS REMOTISEPTUM Hall, 1850. I'LATE LTV. FIGS. 1-3. Ormoceras remotineptum HALL. Third Ann. Rep. N. Y. State Cab. Nat. Hist., p. 173, pi. iv, flg. 3. Original description: " Cylindrical, gradually tapering; septa moderately convex, distant half the diameter of the tube; siphuncle excentric, large, swelling moderately between the septa and but slightly contracted at the junction of the septa; character of the external surface unknown. IIAI.OI ..... A - rr»« The specimen described is a fragment which is worn through the center of the si|duincli>. I lie proportions of this part of the fossil and the great distance of the septa contract very -tron^ly with the Orm 'initiln»i. and with other known -p.-. -if- ..f tin- L'fiiii-. • 1 hi- -].e«-ie- iii-cur- in tlie higher part of the Trenton limestone, near Water- tnwil. .lellersoll COUIltV." A large specimen from Cannon Falls Minnesota, measuring upward of 300 nun. in length, much more complete than the original specimen of Ormoceras remotiscpium, has the dimensional characters of the latter, and upon sectioning a few of the air chambers it shows a sipho in all respects like that of the type. The shell has been somewhat compre->ed. giving it a subelliptical cross-section where it was normally circular. The rate of expansion of the conch is very slow as shown by the fact that at the lower end the diameter is 46 mm., while at the upper end, the length of the specimen being 350 mm., the diameter is 70 mm. The portion preserved retain- no part of the body-chamber, and in this length of 350 mm. there are thirteen an -chain! »ers, which increase considerably in depth from below upward, the lir.-t having a depth of 20 mm., the last of 33 mm. The sutures are normal and regular, possibly a little inclined towards the siphonal side, while the septa are deep and regularly convex. The sipho is large and submarginal. At the 7th septum, counting from below, the tranverse diameter of the sipho is 20 mm., that of the septum 58 mm. In section it proves to be decidedly constricted at the septa and makes a broadly nummuliform expansion in the air-chambers, its diameter there being one- third greater than at the septa. It is very thick-walled and is penetrated vertically through the center by a narrow canal or endosiphon which gives off more or less irregular branches into the substance of the endosiphonal wall. In the relative depth of the air-chambers and the general form of the shell this species presents an external resemblance to Hall's Orthoceras amplicameratum, from the Trenton lime- stone at Middleville, N. Y. In that species, however, the sipho appears to be small and suggests no relationship to Adinoceras. Formation and locality.— The single specimen observed Is from the Trenton llmeatone at Cann M, Falls, Minnesota. Collection of W. H. Scodeld. Family ORTHOCERATID^E Genus ORTHO I I, \s. Hreyn.. 1732. The material representing this genus is measurably abundant, but not in very favorable condition for identification, and probably represents a greater number of 784 THE PALEONTOLOGY OF MINNESOTA. [Orthooeras nicolletl. species than are here made out. The annulated species are more readily distinguished by their surface variations, but among the smooth forms the exterior of the shell so rarely retains the surface sculpture that little basis remains for the determination of specific traits. No attempt is here made to follow the subgeneric distinctions introduced principally by Hyatt among orthoceran shells, as in the first place, the divisions are based largely upon variation in ornament and contour, and, secondly, our material is not sufficiently complete in its representation of the young stages to justify a subdivision of this kind. ORTHOCERAS NICOLLETI, sp. nov. PLATE JtC. FIGS. 1-2. L V, Tube of moderately large size, very gradually tapering, slightly arcuate in the original specimen, but this appears to be, to some extent, casual. Transverse section circular or subelliptical. Surface covered with strong, distant annulations which are sharp, rather narrow at the base, elevated and quite oblique in their direction, curving downward in traversing the shell from the convex (dorsal?) side to the inner side of the specimen. This obliquity increases very considerably toward the aper- ture. The annulations are separated by broad and deep constrictions whose width increases toward the aperture. Sutures transverse and even; septa regularly and somewhat deeply concave, crossing the shell in such a manner as to transect the annulations and constrictions. The interval between the septa appears to be about the same as that between the annulations, but this is not distinctly shown in the specimen, the suture and septum being clearly displayed only at the lower extrem- ity. The finer surface ornamentation, if such existed, is not retained. In a length of 145 mm. the shell bears eleven annulations, the distance between the first two on the outer or curved side being 11 mm., between the seventh and eighth, 15 mm. on the outer side, and 11 mm. on the inner. The depth of the septum exposed is 7 ram. The diameter of the shell at its first annulation is 33 mm., at the last, 36 mm. This species is strikingly characterizad by its strong, oblique annulations and slender tube. It is, perhaps, most closely allied to the Orthoceras olorus Hall, but its difference in the features mentioned serve to distinguish it. Formation and locality.— ID the Trenton limestone at Belle Creek, Minnesota. Collection of W. H. Scofleld. ORTHOCERAS ANELLDS Conrad, 1843. PLATE flMH. FIGS. 22— 2.'). XL. V II Orthoceran annellus CONUAD, 1843. Proc. Acad. Nat. Sci. Phila., vol i, p. 334. Orthoceras anellum HALL, 1847. Paleontology of New York, vol. i, p. 202, pl.'XLin, figs. 6a-/. To this species are assigned two fragments of small conchs characterized by their very gradually expanding sides, sharp, regular, almost imperceptibly arcuate annu- CKPHALOPOl \ Wi • •••ra. p»rr..n | separated by furrows of equal \\i.|tli. sutures regular and lyiuj; in the hori/ontal furrows septa deeply concave and regular. ;in. I -uiface markings consisting of tine, do-ely-set longitudinal linos slightly alternating in size. These are characters agreeing with the early description-. cited, and >er\v to dMinnui-li the species from Orthoceras />ilin<'. nov. I'l.ATE LIV. F10S, 4 and &. Shell moderately large, very gradually expanding. Cross-section broadly MI I. elliptical, nearly circular. Surface covered by closely-set annulations about •J mm. in width, separated by somewhat narrower transverse furrows. Sixteen of these annulations, of equal size and at regular interspaces, occur in a length of 41 mm. These ridges and furrows are crossed by a double series of vertical elevated lines alternating in size, upon the summits of the annulations being very conspicuous and developed into lamellar expansions. This character (one secondary lamella between each two primary lamellae) is maintained over the entire surface, apparently without the intercalation of other series. Where best preserved, the surface affords no evidence of concentric lines. Sutures regular and transverse; septa evenly concave, moderately deep; sipho small and central. The specimen showing the above characters is a well-preserved siliciBed fragment retaining the exterior with unusual delicacy. Its length is 50 mm., its greatest width 30 mm., and its minor axis at the same plane 26 mm. The species is allied to Orihocerns olorus Hall, but its distinguishing features will be found in the closer annulations and the different composition of the ornament. Formation and /oco/Uy.-In the Hudson River group at Granger, Minnesota. OKTHOCERAS LESUKURI, sp. nov, PLATE LIU. no. 4: I' LATE I.V. FI08. » mat 9. Shell rather small, slender: Mil>.'lli[.tical in cross-section. Surface covered with numerous fine, nearly transverse or very slightly oblique unuulations, which are narrow at the base, abruptly elevated, sloping equally above and below, and ~> -para- ted by grooves somewhat broader than the aimulation- themselve-. The latter make a very slight backward curve on the dorsal and ventral Mirfaces, with a broad -50 786 T]IE PALEONTOLOGY OF MINNESOTA. [Ortlioceras hlllneaturn. curvature anteriorly at the sides. They are not crossed by vertical surface lines as far as shown by internal and external casts. Sutures regularly transverse, each lying at the bottom of one of the horizontal constrictions. These appear to follow the curvature of the constrictions and annu- lations, and it may hence be inferred that the latter, which are slight, are to some extent increased by, if not due to vertical compression of the shell-tube. In a length of 31 mm. there are fifteen annulations. Septum moderately deep; position of sipho not known. The species is sufficiently distinguished by the character of its annulations, the position of the septa with reference to the former and the absence of a lineate surface ornament. This seems to me to be the same species as that referred to by Prof. Hall as "Orthoceras (species undermined),"* from the Trenton limestone at Middleville, N. Y. The length of the original specimen is 67 mm.; its diameter at the lower end, 11 mm.; at the upper end, 13 mm. Formation and locality.— In the Trenton limestone, Cannon Falls, Minnesota. ORTHOCERAS BILINEATUM Hall, 1847. PLATE XLVIl, FIGS. 20 and 21; PLATE LIV. FIGS. 6 and 7. Orthoceras bilineatum HALL. 1847. Palaeontology of New York, vol. i, p. 199., pi. XLIII, figs. 2a-d. Shell of rather small size, gradually expanding; cross-section subcircular. Surface for a considerable distance over the apical region, smooth; but concentric annulations gradually develop, those first appearing being very obscure, those succeeding of increasing strength, until they present the aspect of strong, rather oblique or undulating ridges which are not sharply elevated, but become broader and more conspicuous toward the aperture. The constricted interspaces, which are somewhat wider than the annulations, also become broader toward the body- chamber. In one example there are eighteen annulations in a length of 63 mm.; in another fifteen in a length of 50 mm. In a third example the shell is virtually free of annulations for a distance of about 50 mm., and has a diameter of 14 mm. where the annulations are first well developed. The apertural diameter of an average individual is probably not more than 20 mm. with an entire length of 150 mm. These estimates are somewhat conjectural but are based upon the best preserved of numerous examples. • Palm mt-ilojjy of New Yurie, »ol. 1, p. 203, pi. *U|i, flg. 8. . I I'll \l <>I-,,I.\ "Ml,... t .. blhnr.1,1,., ! The Mirf.K •(• i- ornamented l.y coarse ami fine vertical, elevated lines, reticulated by extremely fine hon/unta! linr<. Toward the apex, over the smooth i>ortion of tin- >hell. the vertical lines occur in two >imple series; where the shell has a diame- ter of 7 nun. there are twelve lines of the first order, between each two lying one of • secondary series. As growth advances these lines rapidly multiply by intercala- tion, an. I the alternation in the size of the stria) becomes decidedly less pronounced. Oer the annulated and later portions of the shell the ornamentation becomes proi>ortionally very much finer but the regularly alternating size of the lines is maintained throughout. The horizontal striiu are exceedingly fine and often not retained. Where crossing the other series they are usually elevated into slight nodes or projections. Sipho small and nearly central.* The septa are rather shallow and the sutures regularly transverse and without undulations. They bear no definite relation to the annulations. Over the early, smooth portion of the shell they appear to be relatively distant on account of the narrowness of the shell, there being seven air-chambers in a length of 17 mm., in another specimen five in a length of 12 mm. They do not greatly vary in depth with the increase in the diameter of the shell. The sutures being usually t ran Averse, cross the more or less oblique annulations and constrictions, variously transecting, or at times lying wholly within a given furrow. The original description of this fossil was based upon specimens showing only the adult characters of the species. The existence of specimens in the material in hand, showing in a single example the gradual change from a smooth to an annu- lated shell, brings out an interesting fact in regard to the morphic variation through which other annulated species are known to pass. It has, for example, been shown by Hall' that the embryonic tip of the shell of Orthoctras crotalum, an annulated Devonian species, is smooth, and also that the vertical stria; are well developed much before the appearance of the aim illations. In that species, however, the smooth portion of the shell is very short and greatly abbreviated in comparison with that <>f n. liilinrtilmn. The passage of the shell of 0. crotulum through the smooth stage is highly accelerated, while its longer duration in O. liHim-utmii more forcibly suggests the pbyletic as well as individual relation of the non-annulated to the annulated forms of this genu- It is, however, to be observed that the degree to which the apical smooth shell of 0. bilineatum is retained is in a certain sense an individual peculiarity. Some specimens develop the annulations much earlier than others, and those which retain the smooth shell to a considerably later period preserve for a longer period an infantile character. York. »ol. T. pi U. pi. cam. •«. 11. 788 THE PALEONTOLOGY OF MINNESOTA. lOrUioeeras olorus. Formation and locality.— In the Trenton horizon at Minneapolis (Lake Street bridge), Pleasant Grove, St. Paul, Cannon Falls and Fountain, Minuesota; in the Galena shales at Warsaw, Minnesota. The original specimens were from the lower and middle parts of the Trenton limestone at Middle- ville and elsewhere, New York. Museum Register, Nos. 350, 381. ORTHOOERAS OLORUS Hall, 1877. PLATE LV, FIGS. 3 and 4. Orthoceras vertebrale HALL, 1847. Palaeontology of New York, vol. i, p. 201. pi. XLIII, flgs. 5a-c. Orthoceras olorus HALL, 1877. In Miller's American Palaeozoic Fossils, p. 245. To this species are referred a few specimens with rather distant, narrow and elevated annulations, which are slightly undulating and are traversed by alternating elevated vertical strise and these crossed by extremely fine horizontal lines. None of the material is good and such characters as are retained by the specimens show no great dissimilarity from the original. The septum is moderately convex, the sipho subcentral and the sutures, in the only example where clearly shown, follow the annulations and lie in the bottom of the constrictions. The species has a general resemblance to Orthoceras perroti, but differs in its more distinct and stronger annulations. In one example there are nine annulations in a length of 45 mm.; in another, five in a length of 25 mm. The diameter of the shell in both of these is about 30 mm. Formation and locality. — In the lower blue beds of the Trenton limestone, Mineral Point and Janes- ville, Wisconsin; St. Charles and Holden, Minnesota; Galena shales, at Wykoff, Minnesota Museum Register, Nos. 252, 379, 8291, 8292. ORTHOCERAS TENUISTRIATUM Rail, 1847. PLATE LV. FIGS. 5 and 6. Endoceras proteiforme, var. tenuistriatum HALL, 1847. Palaeontology of New York, vol. i, p. 209, pi. XLV, flgs. la-6; pi. XLVII, flgs. la-6, 2a-c. Shell long, straight, gradually expanding. Sutures direct; septum regularly concave and very slightly oblique. Sipho subcentral, small. Surface of the shell without annulations or ridges; marked by fine, crowded horizontal lines, somewhat undulating or irregular, often running into one another, rounded on the summit and subimbricating, separated by low furrows and divided at irregular intervals by a furrow of more than average width. These horizontal lines and furrows are crossed by extremely fine vertical lines seen only under magnification. Thanks to incarceration in the siphonal cavity of Cumeroceras, one example of this species shows the surface ornamentation in a highly satisfactory manner. It even retains a series of narrow vertical bands which do not in any way 'DA. Ortborvn* •oolalr.) intcniipt the -iirfare sculptim-. luit liav«> the appearance of opaque or dull li upon the -hilling surface of the -lu»ll. These I pro-nine to be traces of color line- Formation ami /...-n/i'/y.- -In tin- Trvnton limestone, Cannon Kill)-. Minnesota. G'll.-i-ii..n of \V II ORTHOCKRAS SOCIAL*: Hull. 1877. I'LATK LV. FIG. T. Orthoetrai grtgarium HALL, 1MI. lU-pt. Supt. O«ol. Surv. Wisconsin. p. 46. OrtHoftrat *•. i - II M i 1ST*. In Miller's North American Palaeozoic KoMlls, 2rt «•i/.e, gradually expanding from the apex. transverse section circular. Septa deeply concave, not very distant, varying from six to nine in the space of an inch, according to age. Siphuncle central in young specimens, often becoming subcentral or quite excentric in old individuals." This species which is better known from the general diffusion in collections of the fine specimens occurring in rocks of the Hudson River horizon in the Maquoketa region of Iowa than from any published accounts or illustration, is represented in the collections of the Minnesota survey by excellent representatives from Graf, Iowa. There are also a few examples from the Trenton and Qalena horizons at Cannon Falls which l>ear very much the same proportions, symmetrical form and general aspect of 0. sociale and hence suggest the presence of that species in these rocks. « ORTHOOERAS BKLTRAMII, sp. nov. PLATE LV. no. 10. Shell very small, straight, very gradually expanding; cross-section subelliptical; external surface smooth, so far as known. Sutures direct, without lobes or undula- tions. Air-chambers very deep. The specimen upon which the species is founded is imperfect at the apical end, but retains most of the body-chamber. It - length is L'D mm.: its lower diameter 2 mm.; its apertural diameter, 3.5 mm. It bears fourteen air-chambers in a length of 21 mm., the body-chamber being 8 mm. in length. Formation and locality. -In the. Galena shale* at WjrkofT, Minnesota. Collection of Dr. ( II Bobbin*. ORTHOCERAS MrLTicAMKRATm Emmons, 1842. Ortkoctrai multieamerattu EMMOMS, 1842. Geology I -rk. Itopt . S. •< -..r..l : '!«, flg. W. OrthceeraM m*lticamrratxm HALL, 1847. Pala-ontolojjy of New York, vol. I, p. »'.. ;.. \i. '..•- Original description: "Extremely elongate, slender, very gra«lually tapering to an acute point: surface apparently smooth or girt with -light undulations; septa 790 THE PALEONTOLOGY OF MINNESOTA. LOrthoceras juneeum. thin, gently arched, distant from one-fourth to one-twelfth the diameter; siphuncle a cylindrical ventral tube; outer chamber very deep." (Hall, loc. cit.) This species appears to be represented by various imperfect examples of some- what smaller size than the New York specimens, but otherwise agreeing with the above description and the original figures. Formation and locality.— Not uncommon in the Trenton limestone at Minneapolis; in the Trenton shales at St. Paul, Eyota, Lanesboro and Fountain, and the Galena limestone at Rockdell. Minnesota. In the lower blue beds of the Trenton at Mineral' Point, Wisconsin, and in the upper buff beds at Rock- ton, Illinois. Also common in the Birdseye limestone at Watertown and elsewhere, New York. Museum Register, Nos. 721, 4049, 4052, 5045, 51 12, 5578, 7927, 8276, 8277, 8278. ORTHOOERAS JUNCEUM Hall, 1847. Orthoceras juneeum HALL, 1847. Pala'ontology of New York, vol. i, p. 204, pi. XLVII, flgs. 3a-/. To this species -are referred a few internal casts of small shells, with circular cross-section, central sipho, regular and equidistant septa. The original description of the species is as follows: "Slender, terete-cylindrical, tapering very "gradually; septa thin, distant from one-fourth to one-third the diameter; siphuncle small, central, section circular; surface finely striated transversely, but without longitu- dinal striae." Formation and locality. — In the Trenton shales at Minneapolis and near Fountain, Minnesota. In the lower blue beds at Janesville, Wisconsin. Museum Register, Nos. 7 1C, 8280, 8281, 8282. ORTHOCERAS compare AMPLICAMERATUM Hall, 1847. PLATE XLVII, FIO. Ifl. , Of. Orthoceras amplicameratum HALL, 1847. Pala-ontology of New York, vol. i, p. 205, pi. LI, flgs. la-p>. There are a few moderately large fragments of orthoceran casts which present an agreement with this species in general aspect and depth of the air-chambers. In the original description, based on much more complete examples than are here afforded, the species is thus characterized: "Teretely cylindrical, extremely elongated, very gradually tapering; outer chamber profound; septa distant about one- third the diameter, very conve, siphuncle ex centric, small; surface ?; section circular." In one of our specimens the external surface appears to have borne fine, equi- distant, longitudinal striae. Formation and locality.— From near the base of the Galena limestone at Preston, Minnesota; in the lower blue beds of the Trenton at Mineral I'nim, Wisconsin. Museum Register, Nos. 8285, 8280, 8287. ii \i.'>rc>i»A. 791 Family EUDOCERATUXA! Tin- -nmp was erected by Hyatt to include ortltocerau shell* having a greatly rninpii'-soil form. broad lol>es ami narrow saddles, with transverse section fusiform ..r -nlitriaiiu'iilar. The family was designed by its author to embrace the genera Kii'l i Hall) Hyatt. '/';•////«-, r.jv. Hyatt. i'.ltocrras, Hyatt, an. I /•.'//. Ai/,,/,,/s-. Meek ami Worthen. Genus TKHTnt'KKAS. Hyatt. KS8. Compressed orthoceran -hells with broad ventral ami dorsal lolw»s and acute lateral saddles; sipho ventral. The shell may be slightly arcuate but is usually -traii_'ht at maturity: in transverse section subtriangular. TRIPTOTERAS PLANOCONVRXUM Hull. 1SI51. I'l.ATK I. VI. KIU J: PLATE I.VII. HI. 1 Ortkoeera* planoeonv&mm MAUL, IW5I. IU-|>1. Supt. (ii-ol. Surv. Wis.,p.47. Orthocenu planoconrfrum WlllTFIELD, 1881 Ueolivy of Wisconsin, vol. l», p. SZ8, pi. vii. lltf. 14. Oriyinul //• .•"•;•//)/ /<»/: "Shell of medium size, gradually expanding from the apex toward the outer chamber, plano-convex: transverse section semicircular or subtriangular, the diameters as five to nine. The convex side a little depressed on each side of the middle, the opposite side nearly flat, the edges abruptly rounded. Septa moderately concave, arching upwards on the sides, somewhat closely arranged, about five in half an inch. Siphuncle small, central. A specimen of the outer chamber, apparently of this species, is a little more than two and a half inches in length, one inch and an eighth in width, the short diameter being half an inch; the septa are about one-tenth of an inch distant." A rather small but characteristic example of thin species presents the convex side exposing fifteen septa in a distance of one inch, the body chamber having about the same length, so far as exposed. The curvature of the septal lobes is perfectly ,ar ami the junction <>f the septa with the lateral margins distinctly acute. A fragment of a mm-h larger imli\ idual has a body chamber measuring 60 mm. in length and ."ii; mm. in width near the aperture. Tn thi- fragment are attached three air-chambers the last exposing a clean septa 1 xirface and showing the ventral position of the sipho. The specimen show- that while the lateral saddles appear to be acute when viewed from the dorsal side, they are actually somewhat obtuse, the obtu-i-- ness of the angle being distinctly manifested only on the ventral surface. A lim- drawn from one lateral angle to the other shows that the dorsal convexity of the shell is about twice the ventral. 792 THE PALEONTOLOGY OF MINNESOTA. fTriptoceras planodorsatum. Formation and locality. — In the Trenton limestone, Cannon Palls, Minnesota: in the Galena lime- stone at Hader and Wykoff, Minnesota. Collection of W. H. ScoBeld. The original specimens were from the Trenton at Beloit and Mineral Point, Wisconsin. Museum Register, No. 8288. TRIPTOCERAS PLANODORSATUM Whitfield, 1882. PLATE LVI, PIG. 4; PLATE LVII, FIGS. 2-4. Cyrloceras planodorsatum WHITFIELD, 1882. Geology of Wisconsin, vol. iv, p. 231, pi. vii, figs. 10-12. Shells small, compressed, slightly arcuate, the incurvature being on the dorsal side. Lateral margins tapering slowly over the mature portions of the shell; ventral side broadly flattened medially, lateral surface abruptly rounded; dorsal side depressed convex. Transverse section broadly subtriangular, the base being the ventral side. Minor and major diameters as 7 to 11. Septa gently convex, with a broad ventral lobe which is much more decided than that of the dorsal side. Lateral saddles obtuse. Depth of the air-chambers near the aperture about 15 mm., five being preserved in a length of 7 mm. Sipho small, situated near the ventral side but not in contact with it. This species is represented by incomplete specimens, one of which, retaining most of the body-chamber and six septa, has a length of 34 mm., a width at the apertural end of 12 mm., and at the lower end of 10 mm. Another example repre- senting only the body-chamber, is 31 mm. long, has an upper diameter of 14 mm., and a lower diameter of 10 mm. Formation and locality.— From the Trenton limestone at Minneapolis, Minnesota. The original locality is three miles above Beloit, Wisconsin. TRIPTOCERAS OWENI, sp. nov. PLATE LVI, FIGS. 5-7. Shell small, unequally convex, slightly arcuate, with the incurvature on the dorsal side; rapidly tapering; ventral side very depressed convex, nearly flat; dorsal side decidedly convex, sloping with more or less abrupt curvature to the rounded lateral margins. This dorsal convexity is rather more pronounced on the earlier portion of the tube. Lateral margins approximating at an angle of about 20°. The external aspect of the shell is that of some large, slightly arcuate forms of Hyolithes. Septa slightly convex, the minor and major axis as 1 to 2. Dorso-ventrally the convexity is very slight. The entire marginal section of the septum is rounded subtriangular, the lateral saddles being narrowly obtuse. Sipho small, ventral and submarginal. Surface of the shell apparently smooth. The single specimen of this very characteristic form has a length of 34 mm. i i:i'H.\i .<>!-, pretty much the entire body -chamber. Its dimensions are 21 by 9 ram. The distal extremity which exposes a septum i> 1" l>y •"> mm. Tlii- -pecies is readily
  • tinguished by its distinct arcuation, rapidly expanding shell ami the great difference in the convexity of the sides. Formation and lo«alitg.—lo the Trenton limestone, Cannon Kail- Mmm-sota. W. II. Srotli-ld. TRIPTOCBRAS «;< There is a single specimen, an internal cast of the deep body-chamber, bearing :i M-ptinn at is distal extremity, which presents differences from any of the foregoing species. The convexity of the septa and sides is about the same as that of T. l>/'inoconvexum but the inclination of the lateral margins is greater, with the sides acutely angled and almost carinate. The body-chamber, also, is distinctly arcuate. It nearest relations are with this species, as it is decidedly less convex and less r.ipi-lly tapering than T. oweni. The single specimen is from the Qalena horizon near Cannon Falls, Minnesota. Hillings described two species of this genus from the Trenton series, vi/.: Ortlimra.* :ifihi upper part with curved outline, beyond the middle the edges are more ne.irly parallel; the length (when entire) having been a little less than twice the •jroato-t di. mietor. I pper and lower surfaces convex, the one twice as convex as the other. tin- two /•/, I'l \ IK I. VII HiiS 7-10. O*eoe«ra* mumitiformr Win IHKLI>. !•>. Ann. I; Surv, Wisconsin, p. 68. Oneoernu m*mia/ormr \\ in 1 1 IKI.D, 1882. Oeolutfjr of Wlnconsln, vol. Iv., p. 232, pi. vn, ttg». • Mascke founded this genus* upon a shell, C. dens, from the Silurian boulders of North Prussia, characterized by its gently arcuate form, the slender proportions of its early parts, the expansion of the body-chamber, and broad, rather deep constric- tion near the aperture. The aperture itself is regular and not contracted. The -ut ures are slightly undulating and are stated to form a minute dorsal lobe although tin- -ipho is not marginal but lies between the center and the ventral side in the adult chambers. The species which is herewith referred to this genus was described from rather imperfect material, virtually internal casts of but parts of the shell. Similarly piv-.T\r-i -pfcimrn- of tin- IpMiM occur 111 t lie Miniif-ota collection-, ami after an examination of the original material, I refer to the species an unusually tine example which, in form and proportions, is almost a replica of Mascke's type. This shell, as preserved, is nearly complete, the aperture and external surface^ being retained and nothing wanting but a small portion at the apex. Its length i- 66 mm.; its original length was probably about 70 mm. Its aperture which is essentially circular has a diameter of 10 mm., and at a distance of 8 mm. below the aperture the broad constriction is deepest. From the aperture to the greatest elevation of the swelling below it is 16 ram. and at this point the diameter of the shell is 10 mm. The distal extremity of the shell measures 3.5 mm. in diameter. The cross-section of the shell is circular at every point The arcuation of the shell or divergence from the vertical let fall from the center of either extremity is 1- mm. The shell is not equiconvex; the swelling just below the constriction is much more consi.li-r.ihle on the outer or convex curve of the shell, and this differ- ence is perceptible though not so distinct over other portions of the body-chamber. No septa are exposed except the terminal one, and that is evenly convex in all directions and bears a central sipho. This, however, is a very early septum, and though the maturer septa are uuexposed, their siphonal punctures may prove to more nearly agree in position with those of the type-species of the gt-nu-. In some of the internal casts the position of the sipho is somewhat excentric and is dis- •Z«lMclir.d«r4Mtnh.|«olo«.OaMUMh. »oJ. iiTllL p.*. pi. u If*. 798 THE PALEONTOLOGY OF MINNESOTA. [Oncoceras exlguitm. tinctly moniliform. The external surface of the shell is covered with very line, slightly undulating concentric lines. Formation and locality.— The most perfect of the single specimens, is in a block of buff limestone of Trenton age, but without precise locality. In association with it are Orthis Jlabellites Hall, O. testudi- naria Dalman, and Plectambonites sericea Sowerby. (Collection of Dr. Robbing). Others are from the lower blue beds of the Trenton limestone, at Janesville and near Bcloit, Wisconsin. Genus ONCOCERAS, Hall, 1847. ONOOCERAS EXIGUUM Billings, 1860. PLATE LVIII, FIGS. 10 and 11. Cyrtoceras exiguum BILLINGS, 1860. Canadian Naturalist and Geologist, vol. v., no. 3, p. 172, flgs. 17—18. Shell small, short, gently arcuate, gradually expanding toward the aperture and somewhat abruptly constricted. Air-chambers relatively deep, septa evenly convex, with regular sutures and central sipho. Exterior smooth. Of six incomplete examples of this little species, some show that the body- chamber occupied from one-half to one-third the length of the shell. Probably none of the shells were more than 30 mm. in length when entire, and the depth of the air-chambers is from 1| to 2 mm. The species is distinguished by its small size, distant septa and gradual inflation. F+mation and locality.— In the Galena shales near Fountain, Minn. The original specimens were from the Trenton limestone near L'Orignal, Canada. Museum Register, No. 8281. ONCOCERAS MINNESOTENSE, sp. nov. PLATE LVI11. KIUS. 1(1-18. Shell moderately large, rapidly expanding, very faintly arcuate, cross-section strictly oval, the major or dorso-ventral, and minor or lateral axes being as 3 to 2i. Septa concave, much more so dorso-ventrally than laterally. Air-chambers moder- ately deep, there being about eight in a distance of 32 mm. The longest example observed has fifteen air-chambers in a length of 45 mm. Sutures regular, with broad, evenly convex lateral, and a rather broad dorsal saddle. The ventral saddle is much the narrower and subacute, the summit of its angle higher than that of the dorsal saddle. Sipho ventral, submarginal, large and moniliform. The siphonal beads are large subrhombic chambers (in section), with thin walls. The opening of the sipho through the septa has about one-half of the diameter of the beads. The siphonal margins of the septa are distinctly calloused. The diameter of the beads equals about one-sixth of the major axis of the septum. Many specimens show <>nor»r» HALO POD A 799 imliration- of ;i linear or t hicki-iie-l oval scar extending from the inner margin of the -iplional lu'inls aloni: tin- major diameter of the septum to near the inner • lor-al margin. KIK- 1" V. rlii-al median section of O. minntnottnix showing the form of tin- siphonal l«-ad-. . I.'. The external surface is covered with numerous low longitudinal ribs, thirty- tive or forty in mi in her on the later portions of the shell. Among a number of -I imens representing this species there are none of the body chamber. The septate portions afford no satisfactory indication of the expansion which charac- terizes the genus Oncoceras; still the material presents many similarities to the -peries ],'-.Til>«"l l'\ \Vliit.M\e-' a- OyrtOOtTtU to the con-friction. Kifioii ami U»-ality.—The specie* appears to )H< unite (•illinium ill UK- lower liinr In-ils nf tin- Trriiton linn-toil.- ut Janesvllle, Wisconsin. It also iKvut-- In th<> Tn-iit-m at PrenU>n and Minneapolis. MiMii.--i>ta. Mtuntm RfffiMter, No. 8300. OKOOO*BAB OARVKRI. -/'• ' . K I.V1II. KliiS. 7-«. An entire hody-chamber, with three air-chambers attached, is characterized by it- l>roa>i -i'lc-. narrow dorsum and compressed, subangular venter. The cross- section of the shell is, thus, elongate-ovate, its major and minor diameters being as 3 to 2. Above the third septum (counting from the aperture) the shell expands somewhat to within the base of the body-chamber and is, thence, gently contracted to the aperture. The latter is more narrowly ovate than the rest of the shell, its lateral margins convex, making a narrow eraargination on the venter. The suture i- transverse on the sides and dorsum, without curvature, but is curved forward over the venter to such a degree that the depth of the air-chambers at the ventral -urface is about twice that on the dorsal surface. The sipho is ventral and is situated within the margin of the septa. The shell is bnt slightly arcuate, being suberect except in the vicinity of the aperture where it is curved inward making the aperture somewhat oblique. Sur- face covered with fine concentric striae which are strongly recurved over the venter, concentric to the outline of the aperture. The length of the body-chamber in the specimen is 20 mm.; the entire length of the body-chamber with three air- chambers, 26 mm.; the major diameter of the third septum, 21 nun .. the minor diameter, 14 mm. formation and locality.— lt> ih<' Tr.-ntoo limestone at Minneapolis, Minnesota. A fragment of a larger obeli hao also been observed In the upper buff beds at Rockton, Illinois. Mtueum RegitUr. N ONOOCERAS DOUOLASSI, sp. • PLATE LXI. FIOB. tt-15. Shell arcuate over the earlier portion, suberect for the greater part of its length. From the eighth air-chamber (counting from the aperture) upward, the shell expands rapidly to the last septum, thence contracts more rapidly, forming a broad and rather deep constriction just within the aperture. The expansion i- S02 THE PALEONTOLOGY OF MINNESOTA. [Oncoceras pandlon. more rapid on the ventral than the dorsal surface and hence the curvature is greater on the outer than on the inner margin of the shell. Dorsal and lateral surfaces very broad; ventral surface narrow and somewhat compressed laterally. The transverse section of the shell is therefore very broadly ovate, almost circular, the dorso-ventral and lateral diameters being to each other as 13 to 12 at the last septum; as 12 to 11 at the first septum exposed (the eighth from the aperture). The septa are regularly and not deeply concave ; the sutures regularly transverse and simple, without lobes or saddles and the air-chambers comparatively broad and of subequal depth on ventral and dorsal margins alike. The average depth of these chambers is 3 to 4 mm., eight of them occuping a length of 32 mm. Surface smooth, covered with obscure concentric lines which follow the outline of the apertural margin and are, hence, bent backward over the venter. The lateral length of the specimen described, from the aperture to the eighth or terminal air- chambei1, is 59 mm., its dorsal length 51 mm. and the ventral length 57 mm. The lateral length of the body-chamber is 20 mm. The transverse section at the eighth septum measures 12 by 11 mm.; at the base of the body-chamber 26x24 mm.; at the bottom of the subapertural constriction 28x34 mm. This species is charaterized by its very broad dorsum, rapid expansion over the later air-'chambers, the regularity and considerable depth of the latter. It is most nearly allied to Oncoceras constric- tum Hall, of the Trenton limestone of Middleville, N. Y., but is less arcuate than that species, and the expansion of the tube is less abrupt and less ventricose on the dorsal surface. « Formation and locality.— In the Galena limestone at Hacler, Goodhue county, Minnesota. Museum Register, No. 243. ONCOCERAS PANDION Hall, 1861. PLATE LVIII, FIGS. 4-6. Oncocerat pandion HALL, 1861. Eept. Supt. Geol. Surv. Wisconsin, p. 45. Original Description: "Shell robust, strongly curved, very rapidly expanding to near the outer chamber which gently decreases in size for nearly two-thirds of its length and then becomes suddenly constricted to nearly one-half its former dimensions ; broadly ovate or subcircular, the [greatest] diameter in the dorso- ventral direction. Septa moderately distant, strongly curved forwards on the dorsal side, the greatest concavity on the ventral side. Siphuncle large, dorsal. Surface unknown." To this species I refer a few specimens characterized by the great inequality in the curves of the ventral and dorsal surfaces, the latter being very gentle, while • i PHALOFODA. • •«•! the former are more abrupt than in any other species of the Ken us here not None of the specimens are very well preserved, but the best of them retains nearly all of the body-chamber and seven air-chambers. The dot-sum is very broad and but -li^'litly arched. The seven aJr-chaml)ers occupy a length of 19 mm. on the venter ami 10 mm. on the dorsura. The body-chamber is 23 mm. in length, 23.5 mm. in major diameter at the base, and 2'J mm. in minor diameter. The great difference in the outer ami inner curves gives the shell a decided ventricose aspect about the base of the body-chamber. Tin- -piM-imens here described are in very close agreement with those upon which \Vhittield based his species Oncoceras brevicameratmn* from the Trenton beds at Beloit, Wisconsin. This is especially noticeable in the subcircular form of the septum. This species is, however, much less ventricose on the body-chamber than those which we here regard as representing 0. pandion. Formation and locality.- In the Trenton limestone at Janesville, Wisconsin, and In the vicinity of Cannon Falls, Minnesota. Uttteum Remitter, No. 8303. Family CYRTOCERATID^. Genus CYRTOCERAS, Goldfuss, 1832. Though fully alive to the fact that the multitude of middle and late Silurian and early Devonian species which have been referred to Cyrtoceras, must eventually prove to be an association of phyletic inequalities, we still feel constrained to employ the term for a considerable number of the species here under consideration. These forms have been studied with care by Hyatt and most, if not all of the species here discussed will probably take their places within the genera intro- duced by him, namely ; Ma-lonocercu, Oonoceras, Cranoceras and Eremoceratf , but it is difficult in many cases to employ these terms with precision. In this author's work Cyrtoceras does not appear as one of the "Genera of Fossil Cephalo- poda.' l >ut the type of this old genus, C. depression, in assumed as the type • if t'ranocerus. Thi*~type-species is a middle Devonian shell, occurring in those later faunas of the Paleozoic where such forms ususully lack any evidence of a swollen body-chamlier. but are likely to possess extended and more completely coiled tubes than in the Silurian faunas. It is among these later forms that the di-tinction between the genera Cyrtoceras and Gyrocerus becm y obscure.t while in'the Silurian shells the presence of an inflated tube is common and the •O*oUxr of Wl«c.m«lii. »ol. Iv. P.M. pi. Tit. >f . t. •I'roc. Burton 8oc. N»t. HUt-. vol. xxll. pp. m-m. tStf Uif ramarki by Jamr* Hall upon «lie luipowlblllt »( • Itrtr nun.t»-r of IVronlin >pr<-lM • III. mrounrj • nu»: l'»la< ni. lif> l.r.ptll- 804 THE PALEONTOLOGY OF MINNESOTA. [Oyrtoceras neleus. affinities of these species are with Oncoceras and Clinoceras. Some light is thrown upon these facts by observations recently made upon the early stages of the shell in the genus Bactrites* where it appears that in late Devonian represenatives of this genus the swollen tube is a growth-stage immediately succeeding the pro- toconch. It is hence a primitive condition, or at least it may be regarded as indicating such a condition in such nautiloids as reveal it at any growth-stage. We find that this inflation of the tube is a normal mature character in many early Silurian genera, but is continued into the Devonian only in the genus Gomphoceras. CYRTOCERAS NELEUS Hall, 1861. PLATE LIX, FIGS. 17-20. Cyrtncerag neleum HALL, 1861. Kept. Supt. Geol. Surv. Wisconsin p. 40. Original description; "Shell of small or medium size, very gradually expanding from the apex and strongly curved, transverse section circular or subcircular, very obtusely subangular on the back in casts, most ventricose on the ventro-lateral region. Septa closely but not evenly arranged, averaging about nine in a space equal to the transverse diameter of the shell, curving forward to the dorsal sides, their margins undulated especially toward the outer chamber where they become crowded. On the ventral side the septa have a broad advancing curve. The exposed surface of the septa shows the greatest concavity a little on the ventral side of the center. Siphuncle dorsal, comparatively large. Surface marked by transverse, slightly undulating annulations, which are strongly and abruptly curved backwards on the dorsum. Diameter of the large specimens five-eighths of an inch," To this species I have referred a number of specimens which conform to the above description, though the surface markings in the specimens are not distinctly annulations but rather strong concentric striae grouped in bundles and presenting the appearance of low and obscure annulations. Some of this material is of good quality, one specimen in particular retaining nearly the entire extent of the shell, showing its slender and graceful form, and making a little less than one volution. The broad, simple aperture (dorso-ventral diameter 18 mm., lateral diameter 21 mm.), rather shallow body-chamber (15 mm. on the dorsal surface) and the numerous septa, which number forty in the entire length, serve to characterize it. This specimen is an internal cant and along the venter the comparatively large siphonal beads are clearly exposed. Other examples, in which there has been no abrasion of the ventral surface, show the strong upward curvature of the septa and •The writer In the American Geologist, vol. xlv, p. 37, 1894; "The Early Stunts of Itact rites ." "DA. s"'' I'jrrtocer*.* •••murum I the slight deopc-nin;,' of tlic air-chamherson the ventral -m-farr and also the recurved surface striic which have a direction nearly the reverse of that of the septa. Formation and /««vi/ify. In thr T:i-nt..i. Minneapolis and noar Fnun- uin, Minnesota, and Ii.-lc.it, Wisconsin; In the Galena shales at WykofT, Minnesota. Muofum Regittrr, Nus. 6S64, 7026. K.RAH CAMCKfJI //'I//, 1S47. ri.\ it i '.. «. Cgrtoeerat eamumm II M.I.. IM; I rk, v..|. i, p. \\*\. pi. xi.n. fl«. 6. Cyrtocmu camurum WIIIIMKLD, 188*. Geology of Wisconsin, vol. Iv, p. 231, pi. vn, UK*. 7, 8, 9. The very gradual expansion, slight arcuation and extreme lateral compression of th: .-s afford a ready distinction from associated forms. The original -pecimen. from Middleville, N. Y., is not very favorably preserved, but that figured by Whit Held serves to establish the characters of the species and with the latter 1 titul a close agreement in the case of a single specimen in the collections in hand. This retains the entire body-chamber and sixteen air-chambers, and also shows the bead-like divisions of the submarginal sipho. Formation and locality.— la the upper buff beds ..f tin- Tr-nton liinentoni-, Samp's quarry, Belolt, Wisconsin, CYRTOCKRAS HAI.UANTX D'Orbigny, 1850. PLATE i.x. no*. 11. 12. "fcra* tinittllo*um HALL, 1847. I'.i! .1 .mt<,loj:y of N. Y., vol. I, p. 93, pi. XLI, BgH. 2o-«. Cfrtncertu kaUianuiu IKII: o. l'r«Kl. de paltktntul. slratlRraph., vol. i, p. I. Cfrtoetra* billing* SALTKK, 1859. PiRurea and Descr. Canad.Org. Rem. Decade 1, p. 33, pi. vn, flK. 5 (non 8). The original of this species was a small, badly crushed specimen distinguished by its surface ornamentation, consisting of "undulating squamose lamellae which are abruptly bent backward on the dorsal line." There are two specimens before me in which this peculiar ornament is retained; one a mere fragment of the shell with these surface markings very sharply defined, the other a considerable portion of a large and more complete example in which the surface is less clearly preserved. The latter shows an arcuate and broad shell with ovate cross-section, the dorso-ventral diameter diminishing, in a length along the ventral periphery of 60 mm. (and dorsal of 37 mm.), from 25 mm. to 16 mm. Septa rather closely crowded, eight or ten on the dorsal surface of 37 mm., inclining somewhat to the venter. Sutures with low, scarcely perceptible lateral lobes. Sipbo ventral, submarginal. 806 THE PALEONTOLOGY OF MINNESOTA. [Cyrtooeras billingsi. The undulations of the surface lamella) consist of numerous small festoons caught up at regular intervals on the successive growth-lines. Over the dorsal and ventral surfaces are traces of low revolving ridges. Formation and locality.— ID the Trenton limestone at Janesville, Wisconsin, and in the shales at St. Anthony Park, Minneapolis. CYRTOCERAS BILLINGSI Salter, 1851). PLATE LX, FIS. 10. Cyrtoceras billingsi SALTEK, 1859. Figures and Descr. Canad. Organ. Rem. Decade 1, p. 33, pi. vn, flg. 6 (non 5). Salter, in proposing, in the work cited, to rechristen the species C. lamelloxian Hall, with the name C. billingsi, overlooked the fact that d'Orbigny had recognized the preoccupancy of that term, and in 1850 had introduced the name C. halliannm therefor. Mr. Salter also figured as C. billingsi two specimens, one of which shows the form and rate of expansion of the shell as we have above given it, and also the peculiar festooned, squamous growth-lines and faint longitudinal ridges of the surface. The other of his figures (fig. 6) represents a more rapidly expanding shell, with laraellose growth-lines which are simple and not festooned, and are strongly retrose on the venter. By finding both forms represented in the Silurian rocks of Minnesota, retaining all the features exemplified in each of Salter's figures, we are convinced that there are here two quite distinct species. As Salter's name, so far as it is based on the first of his figures (fig. 5) is a synonym for C. hallianum the term C. billingsi may properly be employed for shells conforming to the type of the second of his figures. One excellent specimen and fragments of others permit the following descrip- tion of this species. Shell very arcuate and rapidly expanding. A specimen measuring 57 mm. in length on the ventral periphery and 32 mm. on the dorsal, has an apertural diameter of 23 mm. dorso-ventrally and a posterior diameter of 8 mm. The arc traversed in this length is approximately one-third of a volution. Transverse section nearly circular, venter very broad. Surface covered with fine, crowded, subequidistant lamella:, from .3 to .5 mm. apart; these are projected forward or toward the aperture and may be sufficiently long to overlap each other. The interspaces become somewhat greater toward the aperture. On the venter these lamella- make a short, decided curve backward. The form of the septa and course of the sutures are not known. The external characters of this species are such as to readily distinguish it. The single respect in which a difference from the specimen described by Salter |, A .-an .-sted i- tin- M.me\\!iat greater interval between tin- lamell.i- .in. I tl.i-ir Wronger \rntr.il curvature in tin- ( ':ui.i. HIT. PLAT H-tt. >hell .-mall, -Imrt. slightly arcuate, very compressed laterally, the dorso-ventral diameter being from one and a half to twice the lateral diameter. l>m-al siirlacc i ibtusely rounded, ventnil margin su I. acutely convex. Transverse section narrowly ami rather acutely ovate. Greatest diameter of the tube, ju-t Miiml the aperture. a I >< ml twice that at the 16th septum. Hody-chamber moderately deep, not direct luit sharing in tin- general arcuation of the shell. Septa moderately, somewhat irregularly distant. Sixteen of the air-chambers have a length of Hi nun. on the .-ides. with a scarcely perceptible upward curve on thedorsuin, and a broad ventral saddle which may be subacutely angled. Greatest convexity at the base of the body-chamber which is somewhat contracted toward the aperture. Sipho dor-al. -nbmarginal. Surface covered with line -tri.e which over the body-chamber, are curved backward. A specimen 39 mm. in length on the venter has a bod\ -chamber 15 mm. deep. In one 45 mm. in the same dimension, the body-chamber is 20 mm. long. This specimen has the body-chamber entire. In this species the great lateral compression of the shell is the primary dis- tinguishing character. This added to the arcuation of the body-chamber and the very slight convexity of the septa renders the species readily separable from other described forms. formation and tocalitg.— Four -|- .-;in. i,- ••' t). in the Tri-ntoii inn. -!• IM «.f Cannon Fall*. Minnesota, occur In the matt-rial loaned by the lai-- W. II CYRTOCBBAS PKATHKRSTOMI \n.m. >•/.. uov. l-i.ATl I. VIII. II«M. I»-U. 11 small, -lightly arcuate, gently contracted at the aperture, expanded a little on the body-whorl and tapering toward the apex in low, convex curves. Dorsal or inner surf.c depressed convex, rounding rather abruptly at the sides to a somewhat elevated venter. Transverse section broadest laterally. The greatest lateral diameter of the septum divides the major axis into parts which are as 2 to 3, the greater being ventral. Kach septum is gently concave, the concavity being the most pronounced on the ventral slope. Air-<-hambere closely appressed, thirteen of them measuring !'• mm on the dorsal side and 23 mm. on 808 THE PALEONTOLOGY OF MINNESOTA. lUyrtoceras miuiicapolls. the ventral side. This implies that the depth of each chamber on the venter is very much greater than on the dorsum. Each suture makes a low, broad and very obscure saddle on the dorsum, scarcely perceptible lateral lobes, thence sloping forward and making a strong ventral saddle. Sipho ventral and submarginal. Body-chamber large and deep on the dorsum, equalling ten air-chambers in length, and on the venter six. Surface smooth. Dimensions. The specimen upon which this species is based retains the body- chamber nearly intact, and thirteen air-chambers. It has a length of 36 mm. on the outer curve, 11 of which belong to the body Chamber ; on the inner curve it measures 28 mm., of which 11 belong to the body-chamber. Its transverse diameter near the aperture is 14 mm.; at the last septum 13 mm., and at the thirteenth septum 7 mm. Its dorso-ventral diameter near the aperture is 12 mm., at the last septum 11 mm., and at the thirteenth septum 6 mm. This species is well characterized by the peculiar transverse form the shell. Formation and locality.— The type specimen is from the Trenton limestone, and is believed to have been obtained from Madison, Wisconsin. Collection of W. H. Scofleld. CYRTOCERAS MINNEAPOLIS, sp. nov, PLATE LIX, FIGS. 1-8. Shell arcuate, rapidly expanding to the aperture. Body-chamber without con- striction ; apical curvature not known. Surface laterally compressed ; sides broad ; dorsum narrow, venter still narrower and more arcuate. Transverse section subelliptical, the major and minor diameters being as 11 to 9 at the next to the last septum, and as 16 to 11 at the aperture. The lateral margins of the aperture are convex, the dorsal and ventral margins broadly and narrowly concave or re-entrant, respectively. The septa are regularly and evenly, though not deeply concave, the deepest concavity being at about the center. The sutures are transverse and simple, without lobes or saddles save for a slight upward inclination on the venter, which gives to the air-chambers a greater depth on the ventral than on the dorsal side. Sipho ventral, submarginal, expanded in each air-chamber. Surface covered with closely crowded concentric lines, conforming in curvature to the aperture. On the internal cast are traces of longitudinal ridges over the body-chamber. A small and typical example has the aperture 16 mm. in major, and 11 mm. in minor diameter. At the next septum to the last these dimensions are 11 and 9 mm. In a large specimen the aperture is 21.5x15 mm. and at the third septum from the aperture 15x12 mm. This species has some similarity to Cyrtocems camurum .in.) Hall, a* figured liy \Vhittield,* but i- distinguished from that a- from other species l»y the rapid expansion and absence of constriction in the body-chaml>er. Formation and locality.— In th . <• at Minneapolis Xtuntm Rtyitttr, No. 5048. 1 U1TOCKRA8 CtiKM.'t I.I M //•(//, 1V| PI. > l«. Cfrloeenu eomiculum MALI., 1862. Bept. Ocol. Surv. Wisconsin, p. 41, fltfs. 1, 2. Shell -mall, sh-nder. with graceful curvature, making less than one volution. Surface nearly equally rounded, somewhat hroader on the doreura. Transverse on nearly circular. Septa very gently and regularly concave. Sipho ventral. infra-marginal, minute. distant hy twice its diameter from thy margin. Tin-it- are two specimens of this little species, both preserved as internal ra-t- in crystalline calcite. Imt one shows the character of septum ami sipho ami neither indicates the distance between the air-chambers. Knough, however, is retained of tln> form of the shell and its curvature to show its agreement with this species. The larger of the two incomplete examples measures, along the ventral curve. :10 mm.; along the dorsal curve. 21 mm. At the distal extremity of the specimen which is not far from the apex of the shell, the diameters are 2.5 and . mm., while at the proximal extremity the dorso-ventrul diameter is 8 mm. ami the lateral diameter 9 mm. Formation and locality. -In the Ualuna shale*. Warsaw. Minnesota. Collwiion <>f W. II - ..n.-iil. 1 MM'iCBRAS NORWOODI, .-/'. n- 108. 7-». The sperimen upon which this species is based retain- the entire l>oro;nlly an^'lc.i -.i'Mlr. wlndi i> not anitr. t.ut i- -harper mi tin- -opta nearest the aj>erture. The depth <>f the air-chaml-fi- on tin- M.I.- i- about one-half greater than on the doHura. The form of the suture is so rharai-teri.-tir that, taken in conjunction with the form of the shell, I have ventured to regard the specimen as representing a new specific form. IHmensions. Length, 30 nun.; major axis of apertural end, Hi mm.; minor axis 1 •_'-.") nun : major axis of distal en.!•:. Genii- KIIIVSruMli liroeder. IsiM. Kl KYSTOVlTh- I'MIATUS EIHHKIII*. l^l'J. vai. OCCIDENTALIS Hull. 18fil. ••tt* umlatut. var. occidrnt'ili* HAI.I.. 1861. Kept. Supt. <;•••.! Surv. Wix-nnsio, p. 38. This well known f«>rm i- represented by several specimens in the collections before me, some of them of large size, all possessing the broad whorls with flattened dorsum and the simple concave septa characterizing the western variety of this species. The New York specimens upon which the species was founded, seem to be restricted in range to narrow limits within the Black River limestone formation but the specimens from Minnesota indicate a more general distribution. Two large examples have a diameter of about 140 mm.; smaller specimens show the extreme ventral l>nt suhmarpnal position of the sipho and the dorsal depression or groove on each whorl made by contact with that next within. The species has usually been referred to the genus LHuHf*. Hreyn. the t yjte of which is Litnitr* litnu*. It is evident however that the species is not a Lituites, and and I have here followed the recent suggestion of Hyatt* that it be placed with t'r mition and locality.— In the Tn-nl<>n limestone at Minneapolis, Spring Valley, Northfleld. Island, Minnesota: Dlxon and Roclcton, Illin Xu*eum Regitter, No*. 6066.'.: M •Proo. Am«r. Phl»o». 8oc.. rol jzitl. p. Ui. UM. 812 THE PALEONTOLOGY OF MINNESOTA. I List of < lepbslopoda. LIST OF SPECIES OF CEPHALOPODA HERE DESCRIBED. Piloceras newton-winclieUi, sp. nov. .\' i n no aulema, Clarke. ( 'iji-iixxrina. (?) scJioolcrafli, sp. nov. Cwneroceras proteifoi-me, Hall. Cameroceras hennepini, sp. nov. Cameroceras, sp. Cameroceras. s.p. nov. Actinocerps bigsbyi, Stokes. Aclinoceras belvitense, Whittleld. Actinoceras remotiseplum, II all. Ortluxxras nicoleti, sp. nov. Orthoceras anellus, Conrad. Orthocera.1 peiTOti, sp. nov. Orthoceras lesueuri, sp. nov. Orthoceras bilineatum, Hall. Orthoceras olorus, Hall. Orthoceras tenuistriatum, Hall. Ortluxxras sociak, Hall. Ortluxxras beltrami, sp. nov. Oiiluxxras multicameratum, Emruons. Orthoceras junceum, Hall. Ortluxxras cf. amplicamerutum, Hall. Triptoceras planoconvexum, Hall. Triptoceras planodorsatum, Whitfleld. Triptoceras oweni, sp, nov. Triptoccms Iambi, Whiteaves. Triptoceras, sp. ? Gonuxxras anceps, Hall. Gonioceras occidental, Hall. Poterioteras apertum, Whiteavcs. Clinoceras mumiceforme, Whitlleld. Oncoceras exiguum, Billings. Oncoceras minnesotense, sp. nov. Oncoceras lycum, Hall. Oncoceras carveri, sp. nov. Oncoceras douglassi, sp. nov. Oncoceras pandion. Hall. Cyrtoccrus neleus, Hall. Cyrtocents camurum, Whitttold. Cyrtoccras hallianum, D'Orbigny. Cyrtoctras billingsi, Salter. Cyrtoceras hovghtoni, sp. nov. Cyrtoccras feather stonhauyhi, sp. nov. Cyrtoccras minncapolis, sp. nov. Cyrtoceras corniculum, Hall. Cyrtoceras norwoodi, sp. nov. Cyrtoceras shumardi, sp. nov. Cyrtoceras scofieldi, sp. nov. ii'iii-ijceras duplicicostatum, Whitfleld. Enrystomites undatus var. occidentalis, Hall. NOTE IX) PAGK 769.— Since recording the observations given upon the structure of Nanno aulema, the original material has been placed in the hands of Professor Alpheus Hyatt for further elucidation. Prof. Hyatt's conclusions, not wholly confirmatory of my inferences, will be published in the "American Geologist" for July, 1895. NOTK TO PAGE 774. — The Undoceras-aflinities of the ^cims Cijiim-mna have been ronliniiril by Holm's discovery by of large species of this genus witli dorsal sijiliunt's of groat si/e ;IIK| typical structure. (Om tvenne Gyroceras-formight biijda Endoceras-arter; Geol. Fiiren. i Stockli. Fiirhandl. vol. 14, IS!)2). Errata for the Chapter on Cephalopoda- 766, line 14, after./J/awents, insert or can"'*. 1'age 774; the application of the term- ilm-mil and >•,„//•«/ mi tliis page should be reversed. i Page 777, reference to plates, second line omit 4. W Page 784, reference to plates; for LI read LV; for XL11I read XLVIL PLATE XLVII. PAGE. Figs. 1 to 3 PlLOCBRAS NEWTON-WINCHELLI, sp. nOV 767 1 and 2 Inner and profile views of the more complete specimen; showing the form of the shell, the direction of the septa and, in fig. 1, the large size of the slpho. x 1 1-6. 3 A fragment showing a portion of the filling of the sipho with traces of two siphonal sheaths. Shakopee chert, Union township, Houston county, Minn. Figs. 4 to 11 NANNO AULEMA, sp. nov 770 4 Lateral view of a sipho with the aperture completed, indicating its freedom from the septal funnels 5 Longitudinal section of a specimen broken at the top; showing the thickness of the preseptal cone, the convergent lines representing organic deposits. 6 The most complete eiample observed; showing the form of the shell, the position of the sipho, three of the distal air-chambers and the relations of the preseptal cone to the rest of the shell. 7 to 9 Lateral and antisiphonal views of an average sipho, broken at the upper margin. Figs. 4—9 from the Trenton shales, Minneapolis, Minn. 10 Lateral view of a sipho bearing traces of annulations produced by the septa. From the Galena formation, Chatfleld, Minn. 11 A portion of a sipho above the preseptal cone, showing very strong annulations produced by the septal funnels, and retaining a portion of the conch. Probably from near Cannon Falls, Minn. Figs. 12 to 14 CYRTOCERINA (?) SCHOOLCRAFTI, sp. nov 774 Lateral, septal and ventral (anti-siphonal) views of the original specimen. x3. The sutures are shown on one side of the specimen, and in flg. 14. they have been somewhat conventionally extended over the entire surface. Trenton shales near Cannon Falls, Minn. Figs. 15 to 17 ACTINOCEEAS BIGSBYI Stokes 781 15 View of the siphonal side of an internal cast of four air-chambers; showing the great size of the sipho and the filling of a portion of the endosiphon which is somewhat displaced from its normal position. 16 Outline of the distal septum of the same specimen. Trenton horizon, Minneapolis. 17 Longitudinal section of a longer specimen, the upper part through the endo- siphon, and showing the thickness of the siphonal wall; the lower part through the substance of the sipho. From the Trenton group near Rochester, Minn. Fig. 18 ACTINOCERAS BELOITENSE Whitfleld 782 A portion of an internal cast showing the filling of the endosiphon. In the Tren- ton limestone at Janesville, Wisconsin. Fig. 19 ORTIIOCERAS compare AMPLICAMERATUM Hall 790 A fragment which retains traces of a fine longitudinal surface striation. Galena limestone, Preston, Minn. Figs. 20 and 21 ORTHOCEUAS IULINEATUM Hall 786 20 The apical part of a shell which shows very distinctly the gradual development of the annulations. x2. 21 A fragment of a small shell with the characteristic exterior. This specimen is not very well preserved and the apparent absence of annulations on the upper part of the shell is essentially due to imperfect retention. x2. Trenton shales, Minneapolis. Figs. 22 and 23 ORTHOCERAS ANELLUS Conrad 784 22 A portion of a small shell showing the characteristic annulation and surface ornamentation. 23 Outline of the distal septum. Trenton shales, Minneapolis. VOL. III. IM.ATK XI. VI I £ J * * PLATE XLVIII. PAGE. CAMEHOCERAS PHOTEIFORME Hall 777 (See also plates xi.ix, i,, 1.1. 1.11 - An internal cast of a very lonj? siphon, viewed from the siphonal side of the shell; showing the oblique marks of the septa! funnels and the outline of the continuous apical sheath. From the Trenton limestone. Wykoff, Minn. i v a 9 x u 3 a. cd T3 © Q. _© CCS fi~ SI (D c cu \ \ PLATE XLIX. PAGE. Fig. 1 CAMEROCERAS, sp 777 A long cylindrical sipho, with very broad septal funnels; representing a distinct but otherwise unknown species. From the Trenton limestone, Cannon Falls, Minn. This specimen may be advantageously compared with the figures of Orthoeeras simpsoni Billings, given by Whiteaves. (Orthoceratidas of the Trenton lime- stone of the Winnipeg basin; Trans. Boy. Soc. Canada, vol. ix, sect, iv, p. 80, pi. vii, flgs. 2, 2a, 3; pi. viii, fig. 1, 1891). Fig. 2 CAMEROCERAS PHOTKIFOBME Hall 777 (See also plates i.vm, xi» XLI, XLII.) A portion of a large individual, showing the extent of the solid apical end of the sipho, and the abrupt increase in the depth of the air-chambers above the distal extremity of the body. Where the apical sheath is broken, at the lower extremity of the specimen the cast of the internal cavity and the thickness of the sipho are exposed. Cannon Falls, Minn. J X ta J a, od cti js: Q. (D H X Hi •J > 'IMNMi^l tvas • PLATE L. - PAGE. Figs. land 2 CAMEROCERAS PHOTEIFORME Hall 777 (See also plates i,vm, MX, i.xi, i.xn. i 1 Cross-section of the continuous apical sheath (E) in the filling (e) of which are three small orthoceran shells (x). Trenton limestone, Cannon Falls, Minn. 2 Fragment of a large internal cast with the filling of the air-chambers embracing the cast of the continuous apical sheath. Cannon Falls, Minn. Fig. 3 CAMEROCKRAS, sp 777 Cast of a slender CoZpoceros-like sipho, with broad septal funnels and a narrow acuminate extremity which may indicate the filling of the endosiphon. From the Trenton limestone, probably at Cannon Falls, Minn. •.•rr.-nnr.rr Xtf v.tf.v.'f ^'/^v. \... Ill I'LATB L. PLATE LI. PAGE. Figs. 1 to 3 CAMEROCERAS PROTEIFORME Hall 777 (See alHO plates LVIII, LIX, uc, uci, LXU.) 1 The exterior of a sipho, showing the short septal funnels. 2 The same specimen longitudinally sectioned and showing one, and traces of a second siphonal sheath. 3 Portion of a larger siphon; showing more distinctly the septal funnels. Trenton limestone, Cannon Falls, Minn. Fig. 4 CAMEKOCERAS, sp? 777 4 A specimen whose specific relations are uncertain, having a narrow, cylindrical sipho and relatively short septal funnels. Cannon Falls, Minn. Figs. 5 to 7 CAMEROCERAS, sp 780 5 and 6 Two views of a subtriangular sipho with broad septal funnels. Its specific rela- tions are not known. 7 Outline section of the same. From the Trenton limestone, Zumbrota, Minn. Jl> \..i in. 1'I.ATB LI. PLATE LII. PAGE. Figs. I to i: CAMEROCERAS HENNEPINI, sp. nov 779 1 and 2 Two views in outline of a very large fragment. 3 The form of the;terminal septum, showing the size of the slpho. From the Galena limestone, near Spring Valley, Minn. H 4 I 3 aJ I ti * a si CD o PLATE LIII. PAGE. Figs. 1 to 3 CAMEBOCEEAS HENNEPINI, sp. nov 779 (See also plate LII.) 1 Longitudinal section of a small fragment through the sipho; showing a portion of the thick continuous wall of the tube and the annulations formed at the junction therewith of the septa. On one side the siphonal wall is but partially retained. 2 and 3 Two views of the same specimen. Fig. 4 OBTHOCEBAS LESUEUBI, sp. nov 779 (See also plates XLVII and i.\ . p A portion of a shell protruding from an internal cast of the siphon of Cameroceras proteiforme. From the Trenton limestone at Cannon Falls, Minn. Fig. 5 CAMEBOCEBAS PBOTEIFOBME Hall 777 (See also plates xi.vm, XLIX, i.. JA.) Longitudinal section of a siphonal cast enclosing two individuals of Orthoceras or CWnocercw. Trenton limestone, Cannon Falls, Minn. VOL. III. (@ephal®p©da.) I'LATS I III PLATE LIV. PAGE. FigS. 1 tO 3 ACTINOCERAS REMOTI8EPTUM Hall 782 1 Outline of a large example. 2 The form of the transverse section. 3 The first two air-chambers, longitudinally sectioned: showing the bulbs of the sipho, their thickened walls and endosiphon with its ramifying branches. xl 1-6. From the Trenton limestone at Cannon Falls, Minn. Figs. 4 and 5 OBTHOCERAS FERROTI, sp. nov 785 4 A view of a silicifled shell, showing the closely annulated exterior and the strong alternating vertical strise. 5 Transverse section at the terminal septum. Figs. 6 and 7 ORTHOCERAS BILINEATUM Hall 786 (See also plate XLVH.) 6 View of an internal cast showing the relations of annulations and septa. 7 Another specimen illustrating the same features. From the Trenton shales at Minneapolis. w t p- 9 a S i P >< p oj Q. JST Q. CD ft! PLATE LV. PAGE. Figs, land 2 ORTHOCERAS NICOLLETI, sp. nov 784 1 View of the portion of the conch of the original specimen; showing the strong, distant annulations and the obliquity of the septa, x 1 1-6. 2 Outline of a septum; showing the position of the sipho. From the Trenton limestone at Belle Creek, Minn. Figs. 3 and 5 ORTHOCERAS OLORUS Hall 788 3 A portion of an internal cast referred to this species. 5 Outline of septum, showing position of sipho. From the Trenton limestone, Minneapolis, Minn. Figs. 4 and 6 ORTIIOCERAS TENUISTRIATUM Hall 788 4 A portion of a conch protruding from an internal cast of a Cameroceras-sipho, and retaining the surface ornament, x 1 1-6. 6 An enlargement of the surface; showing the fine concentric lines crossed by longi- tudinal bands which appear to be traces of color-streaks. Cannon Falls, Minn. Fig. 7 ORTHOCERAS SOCIALE Hall 789 An internal cast apparently entire at the aperture; showing the form of the shell, length of the body-chamber and the distances between the septa. From the Maquoketa or Hudson River shales at Graf, Iowa. Figs. Sand 9 ORTHOCERAS LESUEURI, sp. nov 785 (See also plate LIII.) 8 An Internal cast with \ery regular annulations. Trenton limestone, Dixon, 111. 9 An internal cast having the annulationc slightly undulating and the septa lying regularly in the intervening furrows. Trenton limestone, Cannon Falls, Minn. Fig. 10 ORTHOCERAS HELTRAMI, sp. nov 789 The original specimen, natural size; showing the body-chamber and thirteen septa. Galena limestone, Wykoff, Minn. ».v c^w ;<.v t. •.'rr.-mi ;t y VOL. III. PLATE LV. PLATE LVI. PAGE. Figs. 1 and 2 TRIPTOCERAS LAMBI Whiteaves 987 1 View of a large specimen. 2 One of the septa; showing the form of the shell in cross-section and the position of the sipho. From the Galena limestone, Stewartville, Minn. Fig. 3 TRIPTOCEBAS PLANOCONVEXUM Hall 791 (See also plate i.vn < View of an internal cast. Trenton limestone, Cannon Falls, Minn. Fig. 4 TKIPTOCERAS PLANODORSATUM Whitfleld 792 (See also plate Lvn.) View of the flatter side of an internal cast; showing the curvature of the septa. Trenton limestone, Minneapolis. Figs. 5 to 7 TKIPTOCERAS OWEXI, sp. nov 792 Three views of the typical specimen, showing the contour of its surfaces. Trenton limestone, Cannon Falls. u.v t. un \..i in. I'LATB LVI. PLATE LVII. PAGE. Fig. 1 TRIPTOCERAS PLANOCONVEXUM Hall 791 (See also plate L.VI.) A partial internal cast of a large shell Galena limestone, Hader, Minn. Figs. 2 to 4 TRIPTOOERAS PLANODORSATUM Whitfleld 792 (See also plate i.vi. i Three views of an internal cast of the body-chamber. Trenton horizon, Minneapolis. Fig. 5 GONIOCERAS ANCEPS Hall 794 A partial internal cast; showing the form and depth of the air-chambers, the size of the sipho and the filling of the branches of its internal canal. Trenton horizon, Minneapolis. Fig. 6 GONIOCERAS OCCIDENTALS Hall 795 A weathered specimen, showing the double curvature of the septa, the size of the lateral flange and of the slpho. Trenton limestone, Dixon, Illinois. Figs. 7 to 10 CLINOCERAS MUMI^EFORME Whitfleld 797 7 An internal cast of the body-chamber. 8 A nearly entire individual retaining the shell. 9 An enlargement of its surface. From the Trenton horizon, locality uncertain. 10 An internal cast of a portion of the conch; showing the depth of the air- chambers, the position and form of the sipho. x 1 1-6. Fig. 11 POTERIOCERAS APERTOM Whiteaves 796 A view of the best specimen observed, retaining most of the body-chamber and eleven air-chambers. Galena limestone, St. Paul, Minn. VOL. III. PLATB i.\ n a PLATE LVIII. PAGE. Figs. 1 to 3a ONCOCERAS I.YCUM Hall 799 1, 2, 3 Views of the body-chamber and a few air-chambers; showing the form of the aperture and contraction of the conch. 3a Outline of the septa. From the Trenton limestone, Minneapolis. Figs. 4 to 60 ONCOCERAS PANDION Hall 799 4 Side view of an internal cast retaining the body-chamber and its apertural edge. 5, 6 Ventral and lateral views, showing the course of the septa. 6a Outline of the septa, showing the ventral position of the sipho. Janesville, Wis. Figs. 7 to 9 ONCOCERAS CARVERI, sp. nov 799 Dorsal, lateral and ventral views of an internal cast; showing the lateral com- pression of the conch, the slight constriction of the body-chamber and the form of the aperture. Trenton limestone, Minneapolis, Minn. Figs. 10 and II ONCOCERAS EXIGUUM Billings 798 Two imperfect internal casts. From the Galena horizon at Fountain, Minn. Figs. 12 to 15a CYRTOCEKAS FEATHERSTONHAUGHI, sp. nov 807 12, 13, 14, 15 Lateral, dorsal and ventral views; showing the characters of the species. 15a Outline of a septum; showing the ventral position of the sipho. Cannon Falls, Minnesota. Figs. 16 to 18b ONCOCERAS MINNESOTENSB, sp. nov 798 16, 17, 18 Dorsal, ventral and lateral views of a specimen leading to the body-chamber; showing the longitudinal ridges of the surface. 18a, 186 Outlines of septa, showing the ventral position of the sipho. From the Galena beds at Lime City. Minn. \.l III. .i.vt. LLtLhi'iXiLr iflLLl YJ? Jf ili' ^ILUi' [@ephal©p©da.) I'LATB I.\ III. PLATE LIX. PAGE. Figs. 1 to 8 CYRTOCEKAS MINNEAPOLIS, sp. nov 808 1, 2, 3, 4 Lateral, dorsal and ventral views of a small specimen retaining the shell aud preserving the apertural margin. 5, 6 Ventral and lateral views of another small example with the aperture entire. 7, 8 Lateral and ventral views of a larger specimen which is a partial internal cast; showing faint revolving bands interrupting the concentric striae, and the position of the sipho. 7a Outline of a septum. From the Trenton shales at Minneapolis. Figs. 9 to 11 CYRTOOERAS SCOFIELDI, sp. nov 810 Dorsal, ventral and lateral views of the typical specimen. From the Trenton horizon at Janesville, Wisconsin. Figs. 12 to 15 CYUTOCERAS HOUGHTONI, sp. nov 807 12 Lateral view of an internal cast of large size. 13, 14, 15 Lateral and ventral views of an average specimen. 14a Outline of a septum, showing the position of tbe sipho and the great lateral compression of the conch. From tbe Trenton limestone, Cannon Falls, Minn. Figs. 16, 16a CYRTOCERAS CORNIOULUM Hall SOP 16 Side view of a specimen, showing the form and curvature. 16o Transverse section. Galena shales, Warsaw. Figs. 17 to 20 CYRTOCERAS NELEUS Hall 804 17, 18, 19 Lateral, dorsal and ventral views of a specimen having the body-chamber nearly entire, and showing the nearly gyroceran curvature, the closely set septa and the position of the sipho. 17o Outline of a septum at the point of greatest curvature of the conch. From the Galena limestone at Wykoff, Minn. 20 Lateral view of a less complete specimen. In the Trenton at Beloit, Wisconsin. \..l. 111. • rrtvKir.tr FLATK LIX. •• RF * O" /6 PLATE LX. PAGE. Figs. 1 to 4 CYRTOCERAS 8HUMARDI, sp. nov Dorsal, lateral, ventral and septal views of the typical specimen; showing its robust form, broad venter, outline and convexity of septum and position of sipho. Trenton limestone, Cannon Falls, Minn. Figs. 5 and 6 CYRTOCERAS CAMURUM Hall 805 Lateral and ventral views of two fragments believed to belong together and drawn as one. The lower portion shows the position of the sipho and the narrowing of the conch is due to compression. Figs. 7 to 9 CYRTOCEKAS NORWOODI, sp. nov 809 Lateral, ventral and dorsal views of a specimen showing the body-chamber, with a number of very narrow air-chambers, the fine undulation of the sutures, position of sipho, broad and obscure longitudinal bands and the almost impal- pable incurvature of the conch. In the Trenton limestone at Eockton, Minn. Fig. 10 CYRTOCERAS BILLINGSI Sailer 806 A portion of a shell showing the finely and sharply lineate exterior of the conch. Trenton limestone, near Cannon Falls, Minn. Figs. 11 and 12 CYRTOCERAS HALLIANUM D'Orbigny 805 Lateral views of a specimen, showing the undulating lamellae and some of the septa. From the Trenton limestone at Janesville, Wisconsin. Figs. 13 to 15 ONCOCERAS DOUGLASSI, sp. nov 801 Lateral, ventral and dorsal views; showing the rapidly expanding conch and the contracted body-chamber. These figures are not wholly satisfactory, flg. 13 being slightly oblique in position and not affording an exact profile; the lower septa in figs. 14 and 15 are too oblique. From the Galena beds at Holder, Minq. V..i_ III. Seph:: i) HLATK l..\. CHAPTER X TIM: L<>\VI<:R SILURIAN GASTROPODA OF MINNESOTA. i <, I. o. ri.Rli'H ANI> \V II INTRODUCTION. The Gastropoda are Mnlltixca with a more or leas distinct head and a well developed tongue which as a rule is armed with a plate or band set with teeth. The body is nearly always more or less unsymmetrical, the mantle never divided into two lobes, and the shell, when one is present, is univalve, except in the chitons in which it consists of numerous pieces. The "foot" is generally well developed, broad and horizontally expanded, being used by the animal in creeping about; or it may be variously modified to adapt it for swimming or burrowing purposes. The eyes and organs of feeling and hearing are contained in the head, while the viscera (organs of alimentation, reproduction, etc.) are found in the posterior portion of the body. Three principal portions are distinguishable in the body, — head, foot :mr a tin-like tail, by means of which the animal swims, the back down wards. The head is usually very distinct and is generally provided with tentacles and eyes. Within the pharynx is found the singular dental apparatus known a- tin- • Beforr my part of the work on UM Lower Silurian Uulrvpuda of Minnesota could be InUbxd. my friend »nou«b loo modest, worker, the Geological and .Natural History Survey of Mlooeaoia one of lu beat friend*, and the wurl.l a true man. In Inlahlog Ike work with. aeahrtuce. I may here awl there hare taken a Maud that he mlf ht DO* hare auctioned. Boon- of the material • > deecrlbed a* lew. he ne*er «aw. and. a* It would be unju.t to tuakr him bear half Hie mpniMlblllty In theee ca»». I have thought It right to dUtlnguUn neh tpeelea by placing my own aante la parentheata after the propoMd oan.p. wUh It ui be nndentood Uiat whatever credit may attach to the foil.,, n..- w..rk Mr. Sooncld baa erery right Ui chare It • M I. me. On the other hand, permit nte aloeie to bear the blame tor the error. iu:;. n -1 • 814 THE PALEONTOLOGY OF MINNESOTA. [Introduction. "odontophore." The principal portion of this is a chitinous band called the "radula" or "lingual ribbon." This is beset with minute, regularly arranged teeth, and, as it is supported on a cartilaginous cushion, which can be given a rotary motion by a special set of muscles, the ribbon is made to act as a file or saw. The arrangement of the teeth in the radula, taking the whole class into consideration, is subject to considerable variation; yet, within narrower limits, their form and disposition are so constant that they afford one of the most reliable aids to classifi- cation. As a rule they are disposed in a medium series, flanked by two or more lateral rows. Two principal modes of respiration pertain to the Gastropoda,ihe first by means of gills variously constructed and adapted to breathe air dissolved in water, and the second by means of a pulmonary chamber which is adapted for aerial respiration. The alimentary canal, nervous and vascular systems, and some of the senses (seeing, feeling and hearing) are well developed. The sexes may be separate or united in one individual. Generally the young are developed in eggs laid in horny capsules or in the form of a string or band. With very few exceptions the young when first hatched are provided with a shell, which in some cases may subsequently entirely disappear through resorption. Very commonly the embryonic shell forms a nucleus at the apex of the fully-grown shell which is often very different from the following portions. Most of the Gastropoda are water animals and a large proportion of them are inhabitants of the sea. Only the Pulmonata and certain groups of the Prosobrancliiata are terrestrial in habit or live in fresh waters. The pteropods and heteropods of the present day are oceanic in habit and are found swimming in the open sea, near the surface and far from land; but the majority of the marine prosobranchs and the opisthobranchs live in shallow seas, many of them between tide-marks. In depths exceeding five hundred fathoms the number of Gastropoda is greatly reduced; still a few forms are found to inhabit depths of two or three thousand fathoms, or even more. The shell, with which, for manifest reasons, the paleontologist is chiefly concerned, is a secretion of the mantle. It is wanting in the adult stages of the nudibranchs, while in other cases, notably the slugs, it is very minute and hidden in the mantle. In its chemical composition carbonate of lime, either in the form of calcite or aragonite, constitutes 95 per cent, or more of the whole. The inner layer is often nacreous (PleurotomariidiF), but as a rule the whole shell, aside from the horny epidermis, consists of an apparently homogeneous porcellaneous mass, which when carefully examined is seen to be made up of three layers composed of parallel ', those in the outer and inner layers having the same direction, i. e. perpen- OPODA Inlr. - dicular t.. the Mirface :iinl mostly at right angle- to the externul lines of grow t h I lie lamell.e of tin- inner layer, which i~ commonly tlu> st congest of the three, are also perpendicular Imt their direction is opposite. Tertiary Gastropoda often retain the miciox-opic structure of the shell ina very satisfactory manner, but as a rule the minute details arc oli-curc. when not entirely old iterated, in fossil species. The i»nn of the shell varies greatly, yet within the limits of genera ami -pecie- remarkably constant. Three types are distinguished,— the tnlmliir, of straight or only -lightly curved form and occurring only among the .sV,/yi/i(iy;«./'/ and /' ln; the .-.-//HI// in which the shell is either conical or patelliform (An-liinn- or involute i lljilion); and the spiral. Tli- y far the most common type, and may in fact be looked upon as the typical form of the shell in tin >poda. In it the shell is essentially a spirally wound, elongated, conical tube, the coils or " whorls " being in most cases in contact and tightly cemented or amalgamated where they join. Sometimes the whorls are coiled nearly in the same plane, when the shell is said to he "discoidal." as in many of the i'.nninfiluilili . More generally, however, the whorls are wound al'i.ut the axis in an oblique manner, a true spiral being formed, the shell becoming "turn-ted." "trochoid." "turhinated," etc. Occasionally the last whorl rises above the first or apical portion of the spire (Ophileta, Maclurea), but usually the embry- onic shell or "nucleus" is at the top of a cone formed by the gradually enlarging and descending whorls, the mouth or "aperture" occurring at the extremity of the last ami largest whorl, termed the "body-whorl." The whorls above the last constitute the "spire" of the shell. The line or groove marking the junction of the whorls is called the "suture." A shell is said to be "im perforate" when the axis columella" is solid (Fusispiru), or it is "perforated" when the axis is hollow (Trochonetna), the axial cavity itself being known as the "umbilicus." The "peris- tome" refers to the margin of the aperture; it is composed of an outer and an inner olutnellar) Up. of which the former is often expanded (Bucanospira, Salpingos- ) or fringed with spines. The peristome may be continuous or "entire" or it may l>e interrupted or "incomplete," in the latter case the left side of the aperture lii-ing formed only liy the l.ody-whorl. Not infrequently the aperture is drawn out and notched below, or there may be two notches, the second being above near the suture. These serve to protect the respiratory siphons. The posterior (upper) notch i- prolialdy represented by the median slit and perforation in .SV/.V.SH/V//./ and / relln, and the same perhaps is true of the slit or notch in the outer li; •'• /•••/•/»«IM and I'lfurotomarin. In mo-t spiral shells the whorls normally are wound to the right the aperture when in \iew heingon the right hand. In others, as for instance the recent 816 THE PALEONTOLOGY OP MINNESOTA. rintrodtietton. and the Lower Silurian Clisiospira, the volutions proceed in the opposite direction with such constancy as to be eminently characteristic. The apical part of the shell, which is directed backwards in all except some of the Patellidce, presents important characters, as it contains the nucleus, or part formed in the egg, and the primative whorls, which are often very different from the succeeding turns. Careful investigation of the apex is likely to throw very reliable light upon the evolution of the fossil types. In a large proportion of the Gastropoda the posterior portion of the foot secretes a calcareous, horny, or fibrous plate called the "operculum," which serves to close the aperture. Its inner surface is marked by a muscular scar whose lines bear no relation to its external lines of growth, nor is its form like the muscular scar in the shell. It begins its development in the embryo, the point from which it commences its growth being called the nucleus. Further growth may take place around the nucleus in a concentric or spiral manner, or the nucleus will be marginal the additions occurring on one side only. The spiral forms may make only one or two turns, or there may be as many as twenty. Opercula that were fit for preservation as fossils seem to be comparatively rare in Paleozoic rocks. When they are found it is nearly always as separate pieces so that it is in most cases very difficult to decide to which of the associated shells they really belong. Still, some of the early Paleozoic forms are interesting, being of unusual types, that of Maclurea especially being remarkable for the strong internal process to which the muscle was attached. Regarding the markings of the external surface of the shell, the "lines of growth," which are more or less fine lines or stronger plications running parallel with the edge of the apertural lips, are nearly always distinguishable. Their importance to the paleontologist, who only too often must be satisfied with imper- fect specimens, is obvious. Sculpture and color markings are longitudinal or vertical when they take the direction of the axis, and revolving when they follow the spiral. Of the more common varieties of sculpture we may mention the striate, in which the surface is covered with fine lines either longitudinal or revolv- ing; the carinate, when the revolving sculpture is prominent and sharp; the plicate referring to a vertically ribbed sculpture; the cancellate, in which fine and straight vertical and revolving lines cross each other nearly at right angles; the reticulate, in which the decussating lines are not straight; the punctate, granulose, nodose and spinous, referring to conditions sufficiently expressed by the terms applied to them. Finally, as regards the application of measurements, the distance between the apex and basal extremity of a gastropod shell is termed the hight, while the width or diameter of a spiral shell is the distance through the body-whorl at its OASTU"! • >l>\ periphery. Ismjth should U> applied only to patelliform -h«>lls in which it refers to the di-tanc.> from the anterior to the posterior margin. A whorl represents a sinKrl,> .-oinplete revolution of the spiral cone; its periphery is an imaginary spiral upon the outer wall corresponding with the line of greatest width. In counting the numlier of whorls we begin with the apertural margin from which to a point on the suture next above it constitutes one whorl. Repeating this process to the apei gives the total number. The apical angle, which i> t lie angle formed by the di\ fr^iii^r sides of the conical spire, is determined by means of a goniometer. CLASSIFICATION. It is very difficult to decide which of the numerous systems of classification that have been proposed is the most convenient and at the same time the most natural. The old school of naturalists paid little attention to anything save the shell. Another and later school bases a classification almost solely upon the modi- fication of the lingual dental apparatus. As neither method has proved entirely satisfactory, the most recent authorities are seeking to frame a system that will combine the best features of previous classifications. Hut it cannot be denied that the system that will do full justice to the evolution of the class is still a thing of the future. Ontogeny and chronogenesis will have much to do with it, from which it is obvious that a large proportion of the work must fall to the paleontologist. The classification adopted by Zittel in his "Handbuch der Pahi-ontologie," embraces all the Mollusca which are provided with a tongue in one class, the Glossophora. These are divided into four subclasses, the Seapkepoda, I'lucophora, Gastropoda, and Pteropodn. Nicholson retains the first two of these subclasses as distinct classes, and unites the last with the third. The Gastropoda he divides into two primary groups or subclasses, the Bnmeluef&tropoda and the I'ulmogastropoda. The ItrnnchtiHjitstropoda again he divides into four orders, the Prosobrnnrhintn, OpistliolmiiH-hiiifii. I'lernfnula and Heteropoda. Try on, in his great work on "Structural and Systematic Conchology." arranges the same organisms as follows: class 1'trro- poda; class Gastropoda, subclasses Prosobrnnchiatn, Opi$titobnuidliata atnl 1'nhnnnifera; class Scaphopoda. Fischer's arrangement again is different: class I'teropoda; clam Gastropoda; subclass Uni «;/rm, orders /'M/< Oputkobnutckiata, NucUobruw' and Prosobranchiala ; subclass Miillii 'nt as his scheme is not as well balanced as it might be a few changes are suggested in the following brief characterization of the principal di\i-ion- Perhaps a more M 818 THE PALEONTOLOGY OF MINNESOTA. [Classification. acceptable subdivision of the class would result if the various groups were reduced in rank, the subclasses to orders, the orders to suborders, and the suborders to superfamilies. The divisions a and b would in that case take the rank of subclasses. Though inclined to favor such a proceeding, we refrained from carrying it out because it entailed more responsibility than we cared to assume at the present time. Class GASTROPODA, Cuvier. Division a. I. Subclass SCAPHOPODA, Bronn. Mollusks having neither eyes nor a distinct head, yet with the lingual armature. Sexes separate. Foot vermiform, lobate. Shell a hollow cylinder, open at both ends. Dentalium is the principal representative. II. Subclass POLYPLACOPHORA, Blainville. Symmetrical mollusks having a distinct head, but neither eyes nor tentacles. Foot broad. Shell consisting of eight moveable calcareous plates arranged in a row. This division includes the chitons. III. Subclass PTEROPODA, Cuvier. Head and organs of sense rudimentary. Foot modified into two lateral wing- like expansions used in swimming. Animal naked er protected by a shell. Order Thecosomata, Blainville; with mantle and external shell. Order Gymnosomata, Blainville; both shell and mantle wanting. IV. Subclass DOCOGLOSSA. (Provisional.) Approximately symmetrical gastropods, provided with dish-shaped or conical shells, or with spiral shells coiled in the same plane. A very primitive group of which the Patellacea and Bellerophontacea, comprised in the provisional order Proteobranchia, constitute the bulk, if not the whole. V. Subclass OPISTHOBRANCHIATA, M. Edwards. Branchiae more or less free, behind the heart. Animals rather highly developed, naked or with a shell; the sexes united in the same individual. Order Nudibranchiata; without a shell. Order Tedibranchiata ; with a shell. a*.) •; /'. VI. Sulu-la» I'KOSOBKAN. in M \. M. IMwank •. nd organs of sense well developed. A uimals breathing by means of gills .11- l.r.in.-lii.i -ituatt'.l in front of the heart; mostly marine, and provided with a -piral >h«»ll. and generally an operculum. Sexes separate. This is the largest and ' 'h\ i-i"ii of the class. Order Xuckobruw r Htteropoda; foot laterally compressed, with fin-like -wimming lobes. Shell sometimes wanting; when present it is more or less symmet- rical, involute and very thin. Order /V//ni7;r.in<-/nVi/.i.- branchia> pectiniform, better and more constantly developed than in preceding order; shell spiral, not symmetrical. VII. Subclass PULMONATA, Cuvier. Annual breathing by means of a pulmonary chamber or lung instead of gills. Sexetf united in the same in-livi-lual. A classification of the Paleozoic genera of the Gastropoda and remarks on their geological distribution, especially of the Lower Silurian types, followed by a summary of the principal results of our work, will be found at the close of the chapter. Ob* GASTROPODA. Subclass DOCOGLOSSA. Order PKOTEOBRANCH I A . Suborder PATELLACEA. Family PATKLLIDJB. The Paleozoic shells which are usually placed in this family are an exceedingly • iithVult group. While we may be reasonably confident that the relations of some of them are not far from the recent genus Patella, there are many others that remind one quite as much of Lepeta and Acmata. These difficulties are of com -•• largely due to the imperfect condition in which the shells are preserved. But, even when the muscular scars are retained. any any means easy to decide ju-t what affinities they indicate most, because these scars, like the whole form of the shells, are in a general way very similar among the twenty or more recent patelloid genera and subgenera. 820 THE PALEONTOLOGY OF MINNESOTA. [Patellida;. When, however, we consider the great diversity of structure of the soft parts that can exist in shells looking so much alike, it surely seems highly improbable that any of the Paleozoic types could have continued on till the present time without being materially modified structurally. And yet it is most difficult to sustain this supposition by a comparison with the fossils. While the latter, so far as known, can in no case be said to be strictly identical with any of the recent genera, the resemblances in several instances are still very striking. Thus, while Tryblidium differs from Nacella and the other Patellidcv chiefly in having the mus- cular scars separate, the otherwise very similar proposed genus Archinacella approaches the recent forms even more closely in having the scars indistinguishably merged into a continuous narrow impression. Little is known of the muscular scars of Scenella and Helcionopsis, but comparing external characters they agree very well, the first with Acmcea or Lepeta, and the second with Helcion. While we admit freely that it may not be possible to prove that the Paleozoic Patellidce are in all cases generically distinct from living types of the family, we are nevertheless fully convinced that such is the case. This conviction, as will be shown in the next paragraph, has something to support it besides the mere improba- bility of their identity. Obviously then we consider ourselves justified in proposing two new names and in retaining those which have already been proposed for those groups which it is convenient to distinguish. We were really forced to these views by the miserable failure of our efforts to distribute the Paleozoic species among the recent genera. After repeated endeavors, the results being different every time, we gave it up as being, to say the least, impracticable. The distinctive evidence referred to in the preceding paragraph is shown in three specimens before us. It consists namely of a pair of rostral muscular imprints which seem not to belong to the usual ring of scars and which we do not find Fig. 1.— o, dorsal view of a cast of the interior of ArcMnacella powersi U. & S., showing the rostral scars at A; b, dorsal view of a partial cast ol the intt-rior of Tryllidium unguis Lindstroru; c, apical portion of same in a direct view to show the rostral scars; d, dorsal view of a cast of I^jietopsis, sp. undet., from Kansas City, Mo., showing muscular imprints very satisfactorily. IPODA, • represented aiinni^ n-r.-nt forms. Tin- first of these specim of the acn.m- panying cut i belongs to our new genus Ar> -Innacflln; the second (fig. 1 & and c) is of the type species of Tri/Mi'lium; while the thinl (tig. 1 •/.-•. The first, then, is a Lower Silurian fossil, the second I'pper Silurian, and the third Darboniferouv The recent l\i(rUi>ln are distributed into generic groups according to the anatomical peculiarities ..f the animals, the characters of the shell being considered as of mil. MI- importance. Obviously such a rale cannot be applied to the fossil ••sentatives of the family, seeing that their shells only are preserved. But that »hntiM not prevent the paleontologist from attempting a classification of the numerous species that have been discovered in the rocks. The geologist requires some convenient means of H M. Lind>trorn. Shell patelliform, obovate, narrowest anteriorly, forming a very low cone; apex anterior, nearly marginal. Mucular scars in seven or eight disconnected pairs, arranged in an oblong circle, the anterior pair drawn out aip I meeting in front beneath the beak. Surface usually marked by concentric lines of growth only; occasionally also by obscure broad radial plications. Type, '/'. MfMM LiixUtn-m. n. jjen. Shell patelliform, ovate to subcircular, usually widest anteriorly, forming a low cone with the apex in front of the center and often sub- marginal. Muscular scars forminp a continuous l>anly in the -lark as to its probable affinities. The other species referred to this genii- l>y Billing fall more or less naturally into one or the other of the generic groups above outlined and will be referred to in discussing the genera further on. \\ - ought perhaps to have included the illy characterized genus Conchopeltis, \V;t. •iKin^r the I'iil. ••./nil- I'.if./li'l.r, especially since the types of the second species described by the author of the genus came from the Lower Silurian of Minnesota. As neither is illustrated, we must rely upon Walcott's description of the genus. That gives us to understand that it is founded on conical patelliform univalves having the apex subcentral and the surface radially striated. So far as it goes it agrees with Scentlla and that indeed is the position we assign to C. minneso- •T considerable trouble Prof. N. H. Winchell succeeded in having drawings prepared of C. ,houM mention, however, that a similar peculiarity occurs in three new species of an undescribed genus of patelliform shells, two of them from the Cincinnati rocks, the other from the iMvonian. In these there is a strong transverse division passing immediately above the beak and separating a lobe corresponding to the upper one in our figure of Conchopelti*. l>ut the rest of the shell is not lobed. The outer layer of these shells is minutely and beautifully punctate. 824 THE PALEONTOLOGY OF MINNESOTA. LTryblidium. Genus TRYBLIDIUM, Lindstrom. Tryblidium, LINDSTROM, 1880, Fragmenta Silurica, p. 15; 1884, Silurian Gastropoda of Gotland, p. 52. Tryblidium (part.), WHITBAVES, 1884, Paleozoic Fossils, vol. iii, p. 30. WHITFIELD, 1888, Bull. Amer. Mus. Nat. Hist., vol. i, p. 303. Metoptoma (part.) of BILLINGS and other authors. For generic diagnosis see page 821. Our description of this genus does not agree in all respects with that given by Lindstrom. This is partly because we believe his to be incorrect in several partic- ulars, and partly because we have seen fit to leave out as unimportant one or two features, and to mention the style of surface markings. Of the three species described by Lindstrom in his last work (op. cit.), T. reticulatum, T. unguis and T. ? radiatum, we would strike out the first and the last, while to the second we would assign the rank of type of the genus. This proceeding is not strictly in accordance with usage, since when, as in this case, no type is specified, it is custom- ary to regard as such the first species following the generic description. The rule is both a good and a necessary one, yet there are cases, and we believe this is one of them, where it is best not to follow it. The species reticulatum and unguis, of which we have through the kindness of Dr. Lindstrom good examples before us, represents according to our views two generically distinct types, of which the first is limited to one or possibly two species,* while the second is recognized in numerous Lower and Upper Silurian species. Herein lies the reason for the course here pursued with respect to the type of the genus, for, should our view of the generic distinctions of the two species available as types prevail, the greater justice and credit would accrue to the learned author.of the genus if his name is adopted for the more abundant group of the two. As to the third species, T. ? radiatum, we refer it with much confidence to our new genus Helcionopsis. T. unguis and all the other species which we leave under Tryblidium have a concentrically striated thin shell composed, as far as known, of thin glossy lamellae which are never porous. T. reticulatum, on the contrary, has a thick shell, especially at the edges, the external layer is minutely porous, and the surface strongly marked by salient oblique concentric laminae, which in the anterior part cross each other, producing an "engine turning" style of network. Lindstrom is inclined to regard the porous character of the outer layer as produced by some parasitic organism. Such an explanation of the origin of the pores would no doubt be a good one if they occurred only occasionally, but considering the fact that they are always present in the Gotland specimens, and what is more, that they seem to be uniformly distributed over the whole exterior stratum, we may well question its sufficiency. The view • LlndstrOm mentions a Lower Silurian species from E«hoala which he says Is closely relatea to T. retieulatum. OAvn:«>ii>i>\ Trjrblldlum ) that those pores are really a normal feature of the external layer receives strong -npport from the fa<-t that a porous outer layer occurs also in other patelliform shells. We have, namely, specimens before us of two shells belonging to an unde- srril>t>j>. rit.. p. 31), he subscribes to the suggestion of Mr. hall < . \nit-r. .louni. ('ouch., vol. vi, p. 281, 1881) that none of the nineteen -pecies provisionally referred to Phillip-' genus Mefoptoma really belong to that genus as now understood. Continuing he says that in his judgment " M>iin>na quebecensis Hillings, lielongs to the genus r, which we owe to the kindness of hr. Lindstrom himself, enables us to show that there is no essential difference between the niu-cnlar scars of this Gotland type of the genus and those shown to exist in the i ort Cassin beds species by Whitfield. The fact i- that '/'. //wyu/v has eight instead of six pairs of scars, and the narrow ends of the anterior pair, which is smaller than 826 THE PALEONTOLOGY OF MINNESOTA. [Tryblidiura modestum. usual, curve around in front to meet beneath the apex. (See fig. Ic, p. 820.) Lindstrom probably overlooked these anterior pairs because he noticed a slightly elevated, transverse, medially disconnected band just in front of the sixth pair. But this band is really the posterior boundary of the scars of an umbonal pair* of muscles which we have shown to exist in a number, if not all, of the Paleozoic PatellidcK. As already stated, we regard T. conicum Whitfield, as a Scenella, while Metoptoma simplex Billings, which Whitfleld places under Tryblidium, and T. piliolum Whitfield probably belong to Archinacella. T. ? acutum Whitfield, with its flattened area-like slope beneath the projecting apex, seems to us to indicate an undescribed generic type. TRYBLIDIUM MODESTUM, «. sp. PLATE LXXXIl, FIGS. 1 and 2. Shell small, somewhat acutely ovate in outline, the apex being pointed, scarcely incurved and projectly slightly beyond the narrowly rounded anterior margin of the aperture; the latter is scarcely, if at all, arched. Surface not well preserved, apparently marked by faint lines of growth. Internal characters unknown. Length 10.3 mm.; width 8.5 mm.; hight of apex about 2 mm.; greatest hight (near center of length) about 2.8 mm. This species is founded upon a single imperfect shell. As the muscular scars have not been observed the generic reference is perhaps a little doubtful. Still, the form of the shell is such that we are fairly confident that it will prove to be a true Tryblidium. Of described species T. erato Billings sp., from the Black Kiver lime- stone of Canada, appears to be the nearest. On comparison with the description of that species (it has not yet been figured) it is evident that T. modestum is much smaller, relatively wider posteriorly and not so convex. The fact that the shell is narrower in front than behind will distinguish it at once from all the species of Archinacella. Otherwise it looks very much like A. patelliformis. It also resembles Stenotkeca unguiformis, but is wider and the beak is not so prominent in front, while the surface markings are quite different. Formation and locality.— Black River group, Ctenodonta bed, near Cannon Falls, Minnesota. Collection.— E. O. Ulrich. Oenus HELCIONOPSIS, n. gen. For generic description see page 821. Of this genus we have at present only three species, the two about to be described and an Upper Silurian one from Gotland, which Lindstrom placed doubtfully •These umbonal scare are shown In fig. 37. pi. i, of LlndstrCni's "Gastropoda and Pteropcda of Gotland," OASTROI-OI'A v-'7 in his genus Tryblidium with the specific name naH'itum. It is very closely related to our // I ii fortunately we know very little of the muscular scars of these species, so that it is difficult to decide whether their affinities are nearer Tryblidium 'In. What is known of them agrees better, as does also the form of the shells, with -i ..... ics of the former genus, while they are distinguished from both by the distinct radial sculpture of their surfaces. The marginal position of the apex separates them from Scenclla, Billings. Stenolheca, Salter, includes laterally compressed and much higher shells. The generic name is from the external resemblance which the species bear to the recent species of the genus Helcion, Montfort 1 1 H.riONOPSIS 8TRIATA, ». */). (UlHrli.) PLATE (.XI. FIOS. 39 »ndaO. Shell rather strongly convex, acuminate-ovate in outline, broadly and regularly rounded behind, pointed in front where the apex projects slightly beyond the margin of the aperture; apex incurved. Surface marked by distinct, rounded, radiating lines, which in the outer half maintain an approximately equal size through In furcation; about ten lines in 5 mm.; whole surface with very fine concentric lines; at intervals of 1 to 3 mm. irregular wrinkles marking stages of growth. Length •Ji •'. mm.: width about 19 mm.; greatest bight 9 ram.; bight of apex about 4.5 mm. This species is quite distinct from all American patelliform shells, but is closely related to the Upper Silurian //. r Also, though of smaller »lz»-, in th«- L«.raln<> jfroupat Cincinnati. Ohio. CWtatfoi».-E. O. I 'I rich -TBCAKINATA. ;/. sp. ATt i \! no. a. il Miiall. MiLovate in outline, the anterior and posterior margins subequal and sharply rounded in the middle. In the cast the apex is depressed, small and not quite marginal; an olitu-*; (-urination extends across the length of the shell. Surface of cast showing remains of very fine radiating lines, scarcely visible without a magnifier, and a few obscure lines of growth. Length 10 mm.; width 8 nun.; greatest hight -V» mm.: hight of apex l.."i mm. We have only two specimens of this interesting species. Both are casts and show impressions of the rostral muscles. One exhibits besides a series of muscular scars similar to those of Trybli-linm. The lines converging from them towards the • SlluriM O..lropod» *»d PUroptxU of GoiUnd. p. M; IM. 828 THE PALEONTOLOGY OF MINNESOTA. [Archill acella. apex are a peculiar feature, though probably of the nature of "progressive tracts." The obtuse angulation of the back of the shell distinguishes the species from all the Paleozoic forms of this family known to us. When not in a good state of preservation it might be confounded with Archinacella patelliformis Hall sp., but in that species the angulation of the back does not extend to the extremities of the shell, while the anterior end is wider, the apex higher and the surface without radial markings. Formation and locality.— Trenton group, Clitambonites bed, Goodhue county, Minnesota. Colkction.— E. O. Ulrica. Genus ARCHINACELLA, n. gen. Metoptoma (part.), BILLINGS, 1865, Palaeozoic Fossils, vol. i. WHITFIELD, 1878, Geol. Wis., vol. iv. Tryblidium (part.), WOITEAVES, 1884, Paleozoic Fossils, vol. iii, p. 31. WIIITFIELD, 1886 and 1889, Bull. Amer. Mus. Nat. Hist., vols. i and ii. For generic diagnosis see page 821.* The shells which we propose to refer to this genus are decidedly like those of Tryblidium, especially so far as the position of the apex and the surface markings are concerned. Their internal markings, however, are readily distinguished, that genus having the muscular scars in eight detached pairs, while they form a continuous band in Archinacella. Unfortunately the muscular imprints are in most cases very faint, even on well preserved casts,' so that we are generally obliged to rely upon another character in determining the generic position. Namely, in all the species of which the muscular scars are known to occur in detached pairs the anterior outline is acuminate, or at any rate more narrowly rounded than the posterior margin. On the other hand, the anterior margin is as broadly rounded or wider than the posterior outline in all the forms of which it is known that their muscular scars are not detached. We have, therefore, considered it good practice to assume that when the anterior end is narrowly rounded the species is a Tryblidium and when this end is the wider the species belongs to Archinacella. There may be some doubt about the affinities of that group of shells in which the outline, as viewed from above, is almost circular or regularily elliptical. In no case have we been able to make out the muscular scars, although we have studied some well preserved casts. Still, as the form of these shells agrees best with Archinacella, and as we know nothing seriously opposing our view, we think it best to arrange them, at least provisionally, under this genus. Besides the species of • We omitted from the generic diagnosis one feature that ought perhaps to have been Included, namely, a pair of scars i'- muscular) occurring one on each side of the apex. They lie on tin- outside' of the usual muscular band and have been observed In two species, A. poutent and A. (Tryblidium) canadensi* Whiteaves. The latter Is a CJuclph species and, as shown In Whlteaves' figures n'al. FOBS., vol. Ill, pi. v), haa these scars more strongly impressed (in the cast) and further forward than they are ID A. powertl. CBOPO Ar>-hln«.-olU powcr»l 1 thi- type .leM-rilie.l in the following pap's, we refer)' " '"///" /n>/.//.;7ix Hillings (Quebec gronpi. I/. .-nnj.!..r Hillings i» '.ilciferous group), M. tr<-nt»n,-nsis Hillings (Trenton group) ;in«l M. tatrlln Hillings (Hudson River group). In addition to the species of which description.- follow and those mentioned in the preceding paragraph, we regard Tryl>liili<>luni Whitfield, T. canadetue Whit eaves, Metopioin'i i>liillif>si Walcott, and M. >•/• Whitfield, as belonging to tliis genus. Ai:i IHSACKLLA POWKRHI, ». »/). 3-8. II large for the genus, moderately convex, subovate, widest in the anterior half; anterior outline semicircular, the posterior semielliptical; margins of aperture r.ither -tnmgly arcuate; apex rather blunt, slightly incurved, the extreme point just over the margin and at least two-thirds of the greatest hight of the shell above it. Surface with fine, distant, impressed lines of growth; near the margin the markings become somewhat lamellose. Length 29 mm.; width 25 mm.; greatest ln^lit In mm.; hight of apex 6.5 mm. Impressions of the interior markings are excellently preserved on the cast figured on plate \.\ I. The loop of muscular scars forms one continuous narrow band curving distinctly down in front so as to pass beneath the apex. The posterior third is somewhat wider and prolonged on the outer side into numerous irregular processes. Within the anterior end of the loop we see the pair of rostral scars, and just behind them a narrow pair lies close to the band. Finally, we observe faint impressions of a larger anterior pair without the band, which may be called antero- laterals. This fine species is readily distinguished from all described heretofore. Collec- tors seem to have confounded it with A. perovalis Whitfield sp., which occurs in the same strata, but is smaller, decidedly narrower — in front especially — and has the n not quite marginal. Formation and JoooWy.— Stone's River group. HHi.lt, Wisconsin, where the types were collected by Mr. II ' !' .w.-rv r»r whom the species Is named. a>Oeettoiu.-Unlverelty of Wisconsin; E.O. I'lridi. ARrHIN \rn.l.v . iN.ii'I.ATA, ». gp. (I'lrich.) 1 and J. Shell large, rather strongly convex. -nl>ovate in outline, very broadly roun-li^l in front, more narrowly behind; hight, width and length respectively as 4.5 to 10 to I'J; margin of aperture hori/ontal: apex Muntly pointed, curved downward to about 830 THE PALEONTOLOGY OF MINNESOTA. [Archluacella depressa. half the hight of the shell, projecting distinctly beyond the margin. Surface with well marked sublamellose lines of growth, averaging in the outer half about 1 mm. apart. Length 32 mm.; width 26 mm.; greatest hight 11 mm.; hight of apex 5 mm. This species resembles A. powersi, but may be distinguished at once by the contour of its aperture, the margins being strongly arched in that species while in this one they are horizontal. The surface markings are also stronger in A. cingulata, while the anterior outline is broader, the apex projects farther forward and the transverse section of the shell is more convex, especially in the post-central region. A. patelliformis Hall sp., and A. simulatrix, though much smaller, are probably more intimately related to A. cingulata than is A. powersi. Formation and locality. — Trenton group, Amygdalocystites bed, Mercer county, Kentucky. Collection.— E. O. Ulrich. ARCHINAOELLA DEPRESSA, n. sp. PLATE LXI, PIGS. 8 and 0. Shell of medium size, depressed-conical, the outline almost regularly oval, rather wide; the width and length about as seven is to eight; apex situated about one-seventh of the length from the anterior margin; the point, which is a little imperfect in the specimen, seems not to have been much elevated or incurved; apertural margin arched. Surface exhibiting a few obscure concentric lines. Muscular scars not observed. Length 20.5 mm.; width 18 mm.; greatest hight (at apex) about 5.2 mm. This shell agrees with A. powersi in the arched apertural margin and broad form, but differs decidedly in having the apex situated some distance from the margin. As the convexity of the shell also is somewhat less, the profiles are different. There is also a slight difference in the outline as seen from above. In all these features the species approaches A. perovalis Whitfield sp., but it is readily distinguished from that species by its greater width and lower form. Formation and locality.— Stone's River group, Vanuxeruia bed, Minneapolis. Collection.— Geological and Natural History Survey of Minnesota. Museum Register, No. 5523. AKCHINACELLA PEROVALIS Whitfield sp. PLATE LXXXII, FIGS. 3 and 4. Metoptoma perovalis WHITFIELD, 1878, Ann. Kept. Geol. Surv. Wis., p. 74; 1882, Geol. Wis., vol. iv, p. 211, pi. v, flgs. 13 and 14. Metoptoma explanata SABDESON, 1892, Bull. Minn. Acad. Nat. Sci., vol. ill, p. 336. This species agrees very closely with A. depressa, the only difierence of any consequence that we can now point out being the greater width of that shell. In s:u .1 i*r.n•/-,/. The apertural margin is slightly arched, and the surface appears to havo been nearly smooth. U Inui.'M describes and figures this species as being flattened and truncate in front, and the absence of anything of the kind in the Minnesota specimens led Mr. Sardeson into giving a new name to the latter. We also failed to notice such a feature in any specimen, even those from Beloit, Wisconsin, the typical locality for the species, being without it, though agreeing in every other particular with Whim. •!•!'- ti-mv-. It seems, therefore, to us that the slight anterior truncation exhibited by the type specimen may be due to some abnormal cause. Fnrmabo* and locality.— Stone's Rivor group, Vanuxemla bed, Minneapolis, Minnesota, and Beloit, Wisconsin. ARCHINACBLLA DBLKTA Sardeson sp. 1-I.ATE I.XI. FI08. !•-«. Cnri*rmis, ah of them having a nearly smooth surface, while Mall's species according to his figures and descriptions has the surface marK--alellifiiniiin. we refer to the Trenton form only, and, as wo have not seen I hr original types, we are obliged to depend solely on Hull's azures and description for our conception of their chara<-ti-i>. • in >i.\ i ii k'n.ii|i. ciil.iint-.nilrs Nil. n. MI- < i ill- an. I E« - fMlonc«oU;Geolin{lcal iK-partnu-nt, University of M r. '• \i: MICAKINATA, «. >/'. I'l \u I \l I I'.- u .t Shell -in. ill, olilii|iifly MI!T.. mr;il. rliiptical in outline; apex submarginal, small, scarcely incurved in the cast; dorsum obtusely carinate for a short distance from tin- apex, lateral -lope- slightly Matt«npil; lii^lit of shell (the jwsterior part especially) 1688 than tiMial, i'i|iiallin^ about two-lifth- of the \vi-ltli. the lii^hest point just iHjhiml tin- ^nrface nearly smooth. Length 12.5 mm.; width 10mm.; bight < in in Five specimen Tlit; dorsal angulation allies this species t<> I. /..//.///'••/•/;!/%• Hall sp., but it does not extend liarkwaol so far, the apex is much smaller and less incurved, and the whole *hcll more depressed than in that species. It is distinguished in a similar manner from 1. formation and locality.— Trriiimi k'n-up, CliUmUinltti* ami KiiHlplrm beds <;'M«lhui' county, Mlnne*oU. OoUeeHnu.-l R B • i.l. Ai;< HINACKI.I.A SIMl'LATRIX, H. 9p. I'l.ATK I. XI. KIOS. 10 »i,.l II 1 -m. ill. aperture hori/ontal, subovate, somewhat wider in front than behind; »{>ex incurved, just al»oveor projecting slightly beyond the anterior margin; back high, -harply round. -d. the lateral slopes flattened. Surface markings obscure, concentric. Two specimens, one from Minnesota, the other from Kentucky. The dimensions of the former are as follows: length 10.5 mm.: width 8..") mm.; greatest bight :U mm.: bight of apex 1.7 mm. In the other the same measurements give !•"•. 1 -'.."». "...') and 'J> mm. This species is di-tin^iii-hed from .1. /.'. i. .1. /a//» iV,//-//i < Formation a*d localitg. Hlark 1. !,yll,,p.,rina I- . Mlnn.-v.U: Tr-nl-,. Mollnlodonbed, Frtnkfort. K.-nt OoUeetitm.— K. O. Dlrl. U 834 THE PALEONTOLOGY OF MINNESOTA. [Archlnacella Bubrotunda. AKCHINACELLA SCBROTUNDA, n. sv. PLATE LXI, FIGS. 26 and 27. Shell rather small, strongly convex, broadly oval, or nearly circular, obliquely conical, with the apex obtusely pointed, not incurved, and situated close to the anterior edge; aperture slightly arched; beneath the apex, in a side view, the anterior outline is scarcely concave; backward from the apex the outline is gently convex, the highest point being about midway between the apex and the middle of the shell. Surface nearly smooth, exhibiting in the best specimens only three or four, distant, impressed concentric lines. Length 13 mm.; width 11.3 mm.; hight 5.5 mm.; hight of apex 4.5 mm. This species is associated with A. deleta Sardeson sp., and A. instabilis var. incurva. From the first it is easily distinguished by its rounded (much wider) form, while in the second the apex is drawn out into a small involute projection, giving it a very different outline in the side view. The species is related probably also to A. (Tryblidium) pileolum Whitfield, A. (Metoptoma) simplex Billings, and A. (Metop- toma) estella Billings, but we cannot consider it identical with any of them. Formation and locality.— Black River group, Ctenodonta bed, Goodhue county, Minnesota. Collection.— E. O. Ulrich. AKCHINACELLA RICHMONDENSIS, n. sp. (Ulrich.) PLATE LXI, FIGS. 6 and 7. Comp. Tryblidium indianetux MILLEK, 1891, Adv. Sh. 17th Rep. Geol. Surv. Ind., p. 85. Shell above the medium size, subovate in outline, obliquely conical, with the apex obtusely pointed, not incurved, and situated about one-sixth of the length behind the anterior margin; in a side view the anterior slope is slightly concave, while the slope backward from the apex is correspondingly convex, with the highest point near the apex; aperture nearly or quite horizontal. Surface marked by rather distant concentric lines. Length 24 mm.; width 20 mm.; hight 6.5 mm. This species reminds one considerably of the geologically older A. depressa, but the arched aperture, lesser convexity and somewhat different outline of that species are sufficient proof of their distinction. It is probably more nearly related to A. subrotunda, but in this case we have obvious differences in outlines and in the position of the apex. We could come to no positive conclusion respecting Miller's Tryblidium indianense, but if his description is reliable it is certainly distinct. Formation and locality.— Richmond group of the Cincinnati period, Richmond, Indiana. Collection.-^. O. Ulrich. BM In..-- l!» II. Sj>. I /7nY/l.> 1-1 \ I I I \\XII I II.- 1 .oil «. T!u> -i>«M-ie8 agrees closely with A. rii-limnmleiuu Ulrich, but may be dis- l.y it- mon> distinct and slightly incurved apex, somewhat arched apertun- and -trimmer >urfart> markings. The latter are coarsely lamelliform in the outer third. Formation and locaUfy.-Ill<-hm>>iiil croup of tli.> Cincinnati period, Mlddlctowo, Ohlu. L-K. O. Ulrlcb. IHUimjx, var. INCPRVA, n. var. 11 \ri i \ i. nos. Ji-n. MtaMto IIM.I is.;*, 1865, Pal. Fossils, vol. I, p. 251. Original Description: "Shell small, depresed conical; apex acute, slightly iin-iii".'- 1. -ituated over the anterior margin; aperture circular; surface finely striated parallel to the l>a-»-. Width of an average specimen, 8 lines, height 4 lines," \ -ingle imperfect specimen, from the Black River group of Minnesota, agrees 80 well with Hillings' description and figures of this species, that we hesitate to give it a distinct specific name. The specimen, it is true, is smaller than the New- foundland types and shows besides certain peculiarities that, if they could be proved to be constant, might justify a separation. The apex, for instance, is more incurved in the Minnesota specimen, — indeed it curves inward sufficiently to form a complete volution,— and the whole dorsal outline is more convex in a side view. Provisionally it may be designated as var. incurva, and it should be added to the list of Black Kiver species mentioned by Billings on page 372 of his 1'al.i ozoic Fossils, vol. i, that are represented by closely allied species in divisions I, K, L and M of the Quebec group in Newfoundland. •t and lufiility 'I':. •.[-•- <>r ih. -|M-CI.-- ,ir. fmm ilivisi.in L. Quebec croup. Table Head, • .-(• .1 l.y I h ii>-ar C;mnmi family is not recognized by some couchologists and OH it is highly prohuMe that tin- 1'aleo/oic |iat«'ll<>i.l -hells are more intimately related among themselves than to it-rent type-, it, has seemed t«> n- tin- widest to embrace them all I>n>\ isionally in one Imiad family, the /'.//»•// iW./. I'M »•*• y i: v in HIM-. //. ^//. i I. \ ii i \ i. I n. s ift-M. Shell depressed rimif.il, rather small. broadly subovate, the anterior part of the outline siMiiifirfular. the posterior -lightly prolonged and more narrowly rounded centr.ilh ; apex pointeil. not quite erect, leaning slightly for wan 1 and situated a abort di-taiice iii front of the center. Surface marked with obscure, fine, concentric lines and usually with seven 1 strung wrinkles or undulations of growth. The latter are more or less variable and irregular, and in some cases may !»• wanting. On caste of the interior they are very faint or .piit«- indistinguishable. Muscular scars not well preserved 1>y any of the specimens seen, apparently detached and forming an oval band about the apical tliird of the Cast. length (-mall -pecimen) 12 mm.: width 10.7 mm.; bight 4."i mm. In a larger specimen these dimensions are respectively !*>.*). 14 and "> mm. The absence of radial surface markings will distinguish thi- -p.-.-ies from the following forms of Scenella, and the subcentnil p»Mtion of the apex renders equally good service in separating it from the preceding species of Archinacella. As to /''//-/ it is certainly distini t from all other forms known to belong to the genus. Formation and locality.— Ston<-s Hiv.-r group. V.unix. -1111:1 U-.I, Minin-:i|Milis: Illack River gr«'iip CteoodooU bed, ml several localities In G<»"lhu.- roimiy. MlnoeauU. CWItdioM.— G«ok«iaU and Natural II -oU; E. O. Ulrlch. Mtueum Remitter, No. 6104. NKI.I.A. Hillings. Setnttta. ISM : loss., vol. li, |. :: t generic characters see page S This genus has never been properly defined and it is perhaps impo—ible to do SO even to-day. Still, we are convinced that, with >'. retimlutu Millings as the type, it may be made to include an easily rr •':<• and thoroughly natural group of patelloid shells having relations to /'••• on the one -ide, and to Strimtlieca on the other. As understood by us the v • liaractei i/ed l>y the -ul. central aj»ex and the radial stri.f. The latter vary in strength, being sometime, rather but in most CMOS very fine. When the radii are d they -how 838 THE PALEONTOLOGY OF MINNESOTA. IScenella superba. through the shell so as to be visible on the outer half of casts of the interior, but usually the casts are smooth, or exhibit only a few obscure concentric wrinkles. The muscular scars of the typical species, — it is a Cambrian fossil, — are unknown, but in several Lower Silurian forms, which with our present light on the subject must be regarded as congeneric, they are very much as in Palccacmcea. Though they have not been observed very clearly, it is almost certain that they are imperfectly coherent and form a sort of wreath about the apical portion of the cast. The number of the scars is not established. Whitfield says that there are eight pairs in his Tryblidium conicum, a species which we believe to belong to this genus and very near S. (Metoptoma) montrealensis Billings. In our S. beloitensis the scars seem to have been divided into four sets of which the two in the posterior half appear to consist each of four almost completely coherent imprints. When the surface markings are not preserved species of Scenella are dis- tinguished from those of Palwacmwa by their higher conical form. In Stenotheca the shell is still higher and the apex curves far forward, projecting in most cases considerably beyond the anterior margin of the aperture. While these characters will suffice ordinarily in discriminating between the genera, there are still several forms of which it is difficult to decide whether they should be placed under Scenella or Stenotheca or arranged by themselves. Metoptoma venilla Billings, Quebec group, and M. alia Whitfield, Calciferous group, are examples of these doubtful species. Scenella probably ranged through the greater part of the Paleozoic rocks, the oldest occurring in the Lower Cambrian, while the most recent known representative appears to be the Devonian species which Walcott has described from Nevada as Metoptoma devonica. SCENELLA SUPERBA Billings. PLATE LXI, FIG. M. Metoptoma superba BILLINGS, 1865, Pal. Foss., vol. i, p. 172. ? Conchopeltis minnesolensis WALCOTT, 1876, 28th Rep. N. Y. Mus. Nat. Hist., p. 93. Shell large, subconical, the hight usually equalling somewhat more than half the diameter; aperture broadly ovate or circular, slightly arched in front and behind; apex subcentral or a little anterior, obtuse, inclining gently forward. Sur- face marked by radiating striae, 1 mm. or less in width, and concentric lines and obscure wrinkles. In casts both sets of striae are usually very obscure, while the radiating lines are seldom shown and then only for a short distance above the margin. Dimensions of an average example: length 64 mm.; width 58 mm.; hight 32 mm. In the largest specimen seen the aperture is nearly circular and between 85 and 90 mm. in diameter, the hight about 45 mm. m.f M«o« 1 Wo ly .loul't tliat the Minnesota specimens above described really belong to Billinj-' V- '..<•'•""" suptrba. They agree exactly with his figures and description except th:it we see nothing of the "obscure carination" which he says "runs from the apex to tin- margin on one side." Perhaps itisan abnormal feature. n<-h»i»'lli< minnesottnsis, Walcott's description, in the absence of figures, is too indefinite for identification.' Still we do not think it likely that his types, which we sought to see but. failed, are distinct from the specimens here referred to Nor do we believe thsit they are strictly congeneric with his ('. '•i. the type of his proposed genus ConchoptHis. (See ante page 323.) and loo: - n.-t Riv.-r ifr.mp, Cmnnon Fall*, MlnncsoU. Walcott's locality for his •tMMteiw '..ur mil.- innoti Hlv.-r, Minn." Kllllnga' type Is fr.mi tin- HI*-. mectooeat Pftu<|Uctt<-H rapid* <>n th.- Ottawa rlv.-r. OoUteUont.— Oootoglcal and Natural Hi*t >f Minnesota: \\ II. S.-..(l.-lil; K O. Ulrlch. Mtufum Rrgitter, N."• mm. •W»l^.u-. dwerlpUoa read* M follow*: - Shell obtawly eoaleml. (MM ^ ptlcal: ap»i ciwotn dlV>rMtladlTldaki<:hlfbt<«f^k«lf U»CTMlM»4UlM«w. Hballo. unduUt not to of tk« •toll not 840 THE PALEONTOLOGY OF MINNESOTA. (.Sceuella compressa. This species resembles S. superba Billings sp., but is readily distinguished by its more depressed form, horizontal aperture and finer surface markings. The muscular imprints also are much stronger than in that species. Formation and locality. — Stones River group, Vanuxemia bed, Beloit, Wisconsin. Collection.— University of Wisconsin, No. 307. SCENELLA COMPRESSA, tt, Sp. PLATE LXI, PIGS. 38-41. Shell small, compressed conical, the bight exceeding the longest diameter of the aperture, while the shortest diameter is to the hight as three is to five, or as two is to three; apex subcentral, laterally compressed, inclining forward slightly; back and sides of shell obscurely flattened, anterior part sharply rounded; aperture subovate, narrower in front than behind. Surface with fine radial lines, three or four in 1 mm., and somewhat irregular transverse lines and wrinkles. The shell seems to have been rather thick and the surface markings are not visible on the cast. Length 13 mm.; width about 9.5 mm.; hight 14.5 mm. This peculiar species reminds one somewhat of the much larger S. magnified, but we do not think its relations to that species are very intimate. Its affinities are probably nearer to S. montrealensis Billings sp., yet not enough so to render confusion between them at all likely. The narrowly rounded anterior slope and the flattening of the sides and dorsum are obvious peculiarities. Formation and locality.— Stones River group, Vanuxemia bed, Minneapolis, Minnesota. Collection.— E. O. Ulrich. SOENELLA AFFINIS, n. Sp. PLATE LXI, PIGS. 36 and 37. Comp. Metoptoma montrealensis BILLINGS, 1885, Pal. Foss., vol. i, p. 394. Comp. Tryblidium conicum WHITFIELD, 188G, Bull. No. 8, Amer. Mus. Nat. Hist., p. 306. Shell small, conical, with the apex subcentral and directed slightly forward, the anterior part compressed, especially for a short distance beneath the beak where it is almost angular; aperture somewhat irregular, subovate, narrowest in front; in a side view the anterior outline is slightly convex in the middle and correspondingly concave above to the apex; behind the latter the outline is gently convex to the margin. Surface exhibiting very fine, easily abraded, concentric and radiating striae, and some irregular wrinkles of growth. Length 10 mm.; width 9 mm.; hight 7.5 mm. This form is probably a variety of S. compressa, distinguished by its lower and wider shell and finer surface markings. It seems also to be very closely related to I* ..MUM.) , ,„„„/, Milling, and 7'n//.//.//i<»// f.>ni-nm Whitficld. but neither of th.-M- -p.vi.'- h.i> tin- ant.Ti.'r llopi -harply rMiiii-l."l .1- in 8, 'i'Jini< an. I J, OPMpWM, \\-\n- which we regard as a true Scwlln. seems to be more closely an.l X. l,,!,,it,'n tin- typical specimens of X. ,///////*• we have before us six others from tin- ::••< -logical 1\ higher » 'litamlM.mtc- ami KnM-pira lied-. In these the anterior cal ridge is less developed and the outline of the aperture more regularly elliptical. The shell also seems to have been thinner and smoother externally. If a Mil.unlinate name i- d.-in-d for this later form of the species it might l>e called var. Formation antl I«runly, MlnnetwiU: I mil WykulT, HlnnctHita. UoM.— Geolofflcal and Natural lli-i..ry Sur\.-> ..f MlnnenoU; K. <>. llri.-h; \V. II >.-..ileld. Mtuenm Kr,j> i I. A UHTI-A I'l.ATK I.XXMI. 110. 10. OmctofMitw oMma SARDEKOM, 18«2, Bull. Minn. Acad. Nat. 8cL, vol. Ill, p. 338. Having seen no specimens which we could refer to this species, we reproduce the original figure and description without expressing any positive opinion as to its validity. So far as Mr. Sardeson's figure of the specimen upon which he founds the species permits of judgment, it seems to us to be a Scenella in which the apex is farther removed from the center and the apical angle wider than usual. /inal description: "Shell large, patelliform, or subconical, apex excentric, apical angle 110 degrees. Aperture subcircular, about three times as wide as the shell is high. Cast marked by four or five concentric furrows and by numerous elevated radiating lint'-, from \'> to ~2^ in one centimeter." •nation and ioeaKty.— Black Uivcr Knuip. Uhinldlclya bed, Minneapolis. Minn.- * M H.I. A KAIMAI.I-. H. Sp. ri.A I I I.M. I l..- 31 and 8. Shell large, depressed conical, hight slightly greater than one-third of the diameter; apex subcentral, obtuse; aperture almo-t circular, the margin apparently a little irregular though nearly hori/.ontal. Surface with di-tmct lines radiating from the apex, five or six in '• nun. These show through the outer parts of the 842 THE PALEONTOLOGY OF MINNESOTA. IStenotheca exsorta. shell and produce corresponding lines on the cast. Diameter about 55 mm.; hight about 21 mm. This species is not nearly as high as S. superba and S. magnified,, while it differs from S. beloitensis in having coarser radii, and from S. obtusa in the more central position of the apex. Formation and locality. — Trenton group, Clitambonites bed, St. Paul, Minnesota. Colkction.— Geological and Natural History Survey of Minnesota. Museum Register, No. 5535. Genus STENOTHECA, Salter. Stenotheca, (SALTEK) HICKS. 1872, Quart. Jour. Geol. Soc., vol. xxviii, p. 180. For generic characters see page 822. The typical species of this genus are from the Cambrian, from which horizon some ten or twelve species have been described. From these it would appear that the generic type is distinguished from Scenella chiefly by the curved form and stronger concentric marking. The genus seems, however, even among the Cambrian forms, to be subject to considerable variation in the matters of form and surface marking, and in such ways that we consider ourselves justified in placing the two species about to be described within its limits. Neither of the latter is greatly different from certain varieties of the Cambrian S. rugosa as figured by Walcott. Stenotheca, as is the case with Scenella also, is often placed with the Pteropoda. We fail, however, to see anything in these shells to justify such a view, at any rate nothing that is not overcome by evidence favoring an alliance with the Patellidce. We must admit that Stenotheca is not a good member of this family, but it most probably represents an offshoot from Scenella, which is a better example, toward certain bellerophontoids (e. g. Cyrtolites). STENOTHECA EXSERTA Sardeson. PLATE LXXXII, FIGS. 11-15. Tryblidium exsertum SARDESON, 1892, Bull. Minn. Acad. Nat. Sci., vol. iii, p. 337. Shell high, laterally compressed, curved, forming one-third or more of a volution; aperture subovate, the length and width about as three is to two, more narrowly rounded in front (beneath the apex) than behind. Surface marked with fine radiating lines, increasing in strength with the growth of the shell, with, so far as known, not less than two in the space of 1 mm. Obscure transverse markings are also present and on the basal half of a large cast several broad folds. On the specimen referred to we fail to see any signs of the radiating lines, but on the other • I-OI'A casts, both from Mmn-.ii'oli-. tln-y are f.iintly indicated. Muscular scars not observed.* Length of apcrtmv -_'n nun.: width of same 1:1. •"> nun.: length of shell from apex to pn-t.M ior margin •_'<; mm. These dimensions in a large and a very -mall -.pecimen are respectively al.out '.!'.», 10 and 4'J mm.. and 1.".. :: and '>.'• mm. The large specimen has -.uilered from pressure so that the width is less than normal. io from the fact that it grew to a much larger si/.c, this species resembles S. rugosa var. /• Walmtt (Tenth Ann. I.Vp. II. S. Geol. Surv., pi. LXXIV. figs. 5, 5a) more closely than it does any Lower Silurian shell known to us. Formation and loea/tff.— Stones Hlv.-r krn.up. Vaniixenila Ix-d. Minneapolis, Minnesota, and Ib-lolt, WUoooftln. CbUMtioM.— Geological and Natural History Survey nf Minnesota; University <>f Minnesota: Univ.T- \ M-nn-lll. Kfffitltr. ' suiMH \ i Ni.riKORMIS, «..•>•/). (f'lrii-h.) ri.vTK I «-«. Sli.-ll nn^niform. acuminate-ovate from above, rounded posteriorly, narrow in front when- the ai»«>\ curves more or less strongly downward, sometimes nearly to the plane of the aperture and projects considerably beyond the anterior margin; aperture horizontal, ovate, usually much more broadly rounded behind than in front. Surface with distinctly elevated, regular, sublamelliform, concentric lines, from 0.2 to 0.6- mm. apart, the distance between them increasing with growth; crossing them very fine radiating lines; test rather thick; surface of cast smooth. Three specimens have the following dimensions: length of aperture 6.5, 10.2 and 11 ."> mm.: wi. 1th of same 5.8, 9 ami 'U mm.; length of shell 7.7, 12.8 and 15 mm.; hight of same 3, 4.5 and 6 mm. Old specimens have thick edges and are relatively longer than medium and young examples. This is because the increase of the shell, after a certain stage, takes place prim-i pally at the posterior border. For the same reason the beak appears more strongly incurved in old shells. This species is clearly may be some doubt about the generic position, tho anterior hight being !»•>- than it should be in a true v Tin' < 'amKrian >'. ' r/<»nct. while in its younger stages it is decidedly like some of the forms referred to S. rugosa by the same author. We believe, therefore. that we cannot be far wrong in placing it un-icr Formation and lor»n that UH>T " »«* n ' "« the CMU bat tlwra >pp»*n to b» m row of •boat M pMBln* »nM*d tb» tbvll from 3 to S mm. »boT« UM Up of MM *prrtur« ' THE PALEONTOLOGY OF MINNESOTA. [Bellerophoutaoea. Suborder BELLEROPHONTACEA. This suborder is proposed for the reception of a type of Gastropoda that seems to be totally extinct. The elements to be comprised in it have heretofore been referred partly to the prosobranchiate order Pectinibranchiata, some to the Heteropoda, and others to the Pteropoda. They are all symmetrical shells and in this respect agree with the Patellacea. We believe that they are either descendants of the same unknown stock from which that suborder was derived, or that they represent an early offshoot from it, differing in the strongly involute (instead of patelliform) character of their shells. From recent Heteropoda they differ in having a stronger shell and in their habits, which evidently were literal and not pelagic. Systematists have experienced great difficulties in assigning this well-marked group of shells to its proper place in nature. Montfort, who was the first to attempt it, originally considered his Bellerophon as a cephalopod because he believed it to possess a number of septa pierced by a siphuncle. Although the total absence of anything like septa was soon demonstrated, Montfort's view was still maintained in the modified form necessitated by the monothalamous character of the shell. Blainville placed Bellerophon with the Ophisthobranchiata, but received very little support for his view. Not so however with the idea first advanced by Deshayes that these shells were Heteropoda. This view seemed to be so well established by the external resemblance of certain bellerophontids to the recent genus Atlanta that it became very popular. But it also has almost disappeared from modern literature. The position to which they are now almost universally assigned is among the pectinibranchiate order of the prosobranchiate Gastropoda. This arrangement was inaugurated by De Koninck in 1843, when he drew attention to certain similar- ities existing between the shells of Bellerophon and Emarginula. His view was adopted by Pictet and Geinitz, but its general adoption was interfered with in 1866, when Meek seemed to prove that their affinities were even nearer Pleurotomana and llaliotis. Since this date Meek's view of the natural position of this group of symmetrical involute shells has gradually gained many supporters, so that now it may be said to be the one that is generally accepted. In our opinion the systematic position of the Bellerophontacea is at least approx- imately determined. All three of the views now current, Deshayes', De Koninck's, and Meek's, perhaps contain an element of truth; the second because Emarginula is either a direct descendant of the ancient type under consideration, or a reversion from the pleurotomarian type; the third because the Pleurotomariidai probably sprang from the same ancestral stock; and the first because there are good reasons , s s I :. to Mieve th.it tlif // have been derived from tlM pleim.tomai i.iu line of development. In other word- tli«- /.'r//.r.»/i//»" /.'/«•-nr»t,»ite regarded as only provisional, -im-e it does not take into account the grand divisional line which ought to be drawn lietween the symmetric anil asymmetry /•.../,<. according to which the class may he divided into two great groups, witli tli»> Nr rli//itii<'n/,lin>-/>»i/f»m »ho. ronclo.iTi.ljr that th« early or Paloocote r»pnn«UUT«» of the Qooogto»«i. Ptmpota und 8ea|Aopod'* and perhaps of other genera. They usually occur associated with large number- of c>fl»ni, another genus of minute gastropods, the specie- of which again may l)e but dwarfed forms of Holopea or Cyclonema and and with very small species of Ctenwlonta and Cinlophorus. :TINA, n. gen. (t'lrich.) (CyrtolHe* [part.|. Lindstrnm, 1884.) Symmetri- cally involute, small thin shells, consisting of one and a half or two rapidly ml., < mtiguous or free volutions, with rounded sides and a more or less well developed slit -band: aperture higher than wide, sinuate dorsally and somewhat deeply emarginated in front of the slit-hand; marks of growth curving strongly backward, more or less distinctly lamellose, with crenulated edges and, when distant enough, traversed by small wrinkled longitudinal riblets. Type, Crytolites I'lmellifrr Lindstrom. In the same work (Silurian Gastropoda of Gotland, pp. 82-84) Lind-tfin de-cribe- three more - belonging to this genus, vi/.: Crytolilrs l>li-i> v and C. oMitjuus. In America the new genus is represented by ••I///™ nitiilitlus I'lrich (Jour. Cin. Soc. Nat. Hi-t.. vol. ii, p. 12; 1879), a species of the upper part of the Trenton group. Family I'll" »T< >\Y \ IM'II 1 1 1 M mietnc. involute -hell-: aperture not abruptly expanded; outer lip ami line- of growth with a broad or narrow dor-al -inn-: -lit and band wanting. n. gen.' Shell thin, -uhgloliose, closely coiled; volutions compressed • lor-o-ventrally. moderately embracing, rounded on the back, enlarging gradually. not abruptly expanded at the aperture, umbilicu- open: aperture transverse, the outer lip with a rather broad and not very deep median insinuation: >l it -band wanting. i- known the surface markings con-i-t of t ran -verse or growth line- only. Type, / :<- thispMne w;is in type we IIMVC. ihrijiijrli (he kindness of I'ruf. K. W. Olaypole ami Mr. Aug. P. Foerste, hoen enabled to sec specimens nf It. li ile comparatively thick, and marked externally with very fine revolving lines. The lines of growth are very faint and they form a broad sinus on he central lobe of the back about as In I'rotowarthla. There Is no slit-band. OAVM. Har.olia. I description.. l\ -tin-part which relates to the absence of a slit and dorsalband, we place the genus near Otctnella and rrotomirtlii-i, and consider it as well dis- tmpiishfd from those genera by the trilobate character of its shells. Koki«n i>xix. For further discussions see remarks specially devoted to the genera named. Family BUCANM1' 1 . :iinetric. involute shells; whorls rather numerous, merely in contact, or embracing slightly, all visible in the umbilicus; aperture often expanded abruptly; dorsal slit-band di-tinct, the slit itself generally very long and narrow, some- times represented by a row of openings; surface with transverse lamella- or lines, n-nally crossed at right angles by short ribs. TKTKANOTA, n. gen. (Hucunia [part] of Hall and other authors; Bucanella • .\. K uken, not Meek.) Shell thin; aperture moderately expanded, laterally chiefly; inner lip without callosity; sinus more or less deep, terminating in a short -lit; whorls generally compressed so that the transverse diameter greatly exceeds the vertical; umbilicus open, large or of moderate size; dorsal band very wide, margined on each side by a strong ridge; about midway between these ridges and the narrowly rounded or angular sides of the volutions there is another ridge on each side, making in all four constant revolving ridges; aside from these the surface markings consist of rather delicate, sublamellose, regular lines of growth, each crossed at right angles by its own set of minute ribs. The revolving ridges, the lateral ones especially, are best developed on the inner whorls and may become indistinguishable near the aperture. Type, Bucania bidorsatu Hall. <' KOKKNIA, n. gen. (liucanelln [part.]. Koken, 1889, not Meek, 1870.) Volution- depressed; slit-band wide. Hat, elevated, with a broad concave space on each side; umbilicus open, rather lar^e: a^rture not expanded, lips thin, the outer one deeply emarginated. Surface with straight, uninterrupted revolving ribs, strong on the lateral parts of the dorsum, fine on the slit-band: growth lines very delicate. Type, Buranelln tsthonn \\ Nrues .lahrbucli fur Mint-ralo^it-. etc.. Itfilagebainl \ i. p. 389; 1889). Ix>wer Silurian drift, Berlin. One American A'. r«w/u//.s- I'. A -64 850 THE PALEONTOLOGY OF MINNESOTA. LBuoanlldae. MEGALOMPHALA, n. gen. (Ulrich.) This name is proposed for the widely umbili- cated group of species which Koken has provisionally designated as the "Gruppe des Bellerophon contortus." The general form of the shell and volutions in these species is precisely as in the typical section of Bucania, as here restricted and defined. They may, however, be distinguished at once by the total absence of revolving surface sculpture. The apertural slit also appears to be much shorter, though the slit-band is well developed. In the last respect they agree with our Tetranota, but the expression in general is different, while the absence of the four revolving dorsal ridges, which are such a striking feature of that genus, must, for the present at least, be regarded as forbidding their reference to Tetranota. Again, they remind one of Owenella, but the presence of a distinct slit- band, which is wanting in that genus, is sufficient to distinguish them. These varied resemblances, however, probably give us a reliable clue to the developmental history of the Bucaniidce. At present the line of evolution appears to be from Owenella to Megalomphala to Bucania to Salpingostoma to Tremanotus. Tetranota to Kokenia and Oxydiscus to Conradella are separate lines. Eichwald's Bellerophon contortus may be regarded as the type of Megalomphala. Excepting the doubtful Chazy species which Hall in 1847 called Bucania rotundata, and which may belong in this connection, the genus is not known to occur in American strata. In Europe, according to Koken, it is represented by Bellerophon contortus Eichwald and B. vaginati Koken, in the Lower Silurian, by B. taenia Lind- strom, in the Upper Silurian, and by B. macromphalus A. Roemer, in the Devonian. That the last really belongs to Megalomphala requires confirmation. BCCANIA, Hall (restricted). Shell consisting of three to five more or less depressed volutions coiled in one plane, with generally a wide umbilicus and not greatly — never abruptly — expanded aperture. Surface markings consisting of equal or unequal revolving riblets and lines of growth, together producing a more or less cancellated appearance. Revolving lines wavy or wrinkled, oblique, especially in the umbilicus, crossing from the ventral side of a whorl to the dorsal slit-band in the space of about one half a volution. Frequently they are interrupted by strong lamellae, the wavy edges of which are parallel with the lines of growth and the apertural margin. Aperture transverse and somewhat reniform in the typical section, higher and relatively larger in the B. nashvillensis section. In the former the lips are thin, the outer one sinuate, and the sinus prolonged into a rather long narrow median slit; in the latter the inner lip is rather thick and the slit shorter. Slit-band distinct, raised or depressed. Type, B. sulcatina Emmons sp. 1>A : HECTION. • utatttiMi Kim. i*jr. • ultlata U . & S. Stone's Hirer group. uitl HU.-k Kiv. grs. B. , k 8. fill .up. (Wptfoa IT. \ S. Trent. m gnmp. :.et Hlv.AWkRT.gr>. Awtortaeta Hall. Trenton group f B. jwMt0vn« EmnioDS. Trenton group. Foreign species.— B. (wdfeanomUi Schmidt, Lower Silurian, Russia. B. NASIIVII.I.KNSIB SECTION. •MuAwVkiifM Ulni-h. Trenton group. /•' fxracuta Ulrl.-li. Trrnton group. mibfeyiS.. B. linyularit Ulrlch. Trenton group. ririch. Tr.-ntoiiKroup. rirh. Trvnt..n group. B. nana, var. fubpatuln I'lrlch. Tr.-nlon group. .irrontnwi Ulrlch. Trenton group. B. rimulatrix Ulrlch. Richmond group. numi I'lrlch. Un-aliKiiiil •M K. l{«x)mer. (Leth. Geognostica, 1876.) Shell symmetrically coiled in <>!!«• plane; volutions numerous, enlarging gradually, scarcely embracing, the •• )>eing a large open umbilicus. Aperture abruptly expanded at maturity, tnnniK't like; peristome thin, the outer portion slightly sinuate. Inner volutitm- with a slit band as in lin<;iniu|>. 8. imbricatn U. & S. Richmond group. S. biK/Ji, rar. Jvntudbouu Ulr. Black Rlv. group. S. rirhmondentit Ulr. Richmond group. S. crpaiuo Hall sp. Trenton group. S. caiMdenfi* Billings. Hudson River group. H tculptilit U. & S. Trenton group. S. /ralernuj Billings. Hudson River group. :OI'EAN SPECIES. & meyalottama Eichwald. Lower Silurian. 8. locator Eichwald Bp. Lower Silurian. 8. comprtua Eichwald sp. . Hall.* In all respects like Salpingostoma excepting that an expanded aperture is developed at frequent and regular intervals, and the dorsal slit closed at corresponding periods, so that, instead of a continuous long opening, there is a series of small, elongate elliptical perforations. Type, T. alpheus Hall. AMERICAN SPECIES. /AftuHall. Niagara group. T. triytmottoma Hall& Whltfleld. Niagara group. T. eMco0MMit McCheaney sp. Niagara gr> T. anguttata Hall sp. Niagara. 7'. pro/undu Conrad sp. Lower Helderberg group. T. lonyihuUnaki Llndstnmi. Up. Sllur., Gotland. T. eomprettut Llndstnim. Up. Sllur., Gotlaml. T. mmdeni Kth.-riilge. Jr. ?TrlaMlc, New Smth Wales. CONRADKI.LA. n. gen. (Vhr'njmolittjt, Conrad, 1838, Ann. Geol. Rep. New York. p. ll'.i.i Shell coiled symmetrically, general form as in Cyrtolites and Oxydiscus, the volutions enlarging gradually and being strongly keeled dorsally. Aperture oval or • Tweotl.U, R»p. S.-« York St. Mu«. N»t. Ill.t . p. MT; IS*. 852 THE PALEONTOLOGY OF MINNESOTA. [Bellerophontlldse . subcordiform, widest in the middle or below, without callosities of any kind, nor with a sinus in the outer lip. From the aperture to a point about half around the dorsal circumference of the last volution there is a narrow open slit lying between two sharply elevated edges; behind this point the slit is closed over and forms an ordinary slit-band with distinct lunulae. Surface with close or distant transverse imbricating lamellae, the anterior edges of which are zigzagged and sometimes greatly spread out. Lamellae plicated, the successive folds often arranged so as to form small revolving ridges; over all very fine lines of growth. Type, C. obliqua U. & S. C. flmbriata U. & S. Stones River group. (7. imbricate Meek & Worthen sp. Trenton gr. C. triangularis U. & S. Stones River group. C. eltgans Miller. Loraine group. C. grandis Ulrich. Stones River group. C. bellula Ulrich. Loraine group. C. obliqua U. & S. Black River group. C. dyeri Meek. Richmond group. C. oompressa Conrad sp. Trenton group. C. dyeri, var. cellulosa U. & S. Trenton. C. similis Ulrich. Trenton group. C. pannosa Billings. Hudson River group. OXYDISCUS, Koken.* (Tropidodiscus, Meek,f Waagen^:, not Steininger, 1855.) Strongly compressed, disciform shells; volutions embracing very little, expanding gradually to the aperture, sharply keeled; aperture somewhat lanceolate or subtri- angular, without an inner callosity; outer lip with a deep V-shaped excision, continuing in the dorsal keel as a long and very narrow slit; behind the slit the summit of the keel may show a more or less distinct band with lunulse, or merely a delicately bordered raised line. Surface markings consisting of growth lines only. These bend strongly backward in passing from the ventral side of the whorl to the keel. Type, 0. imitator Koken. A M 1:1: ii • AN SPECIES. O. acutus Sowerby sp. Lower Silurian. O. cristatus Saflord sp. Trenton. O.disculus Billings sp. Black Riv. and Trenton. O. magnus Miller sp. Cincinnati. O. subacutus Ulrich. Trenton. O. curvilineatus Conr. sp. Schoharie grit and Up. Held. According to Koken Euomphalus strongi Whitfield, a " Lower Magnesian " fossil, probably belongs here. EUROPEAN SPECIES. O. (Euomphalus) planissimus Elchwald. Low. Silur. O. (Cyrtoliles) orbiculus Lindstrom. Up. Silurian. U. (1'orcellia) scutigerus Eichw. Upper Silurian. U. (Cyrtolitts) delanonii (Ehlert. Low. Devonian. O. (Cyrtolites) discus Lindstrom. Upper Silurian. O. imitator Koken. Middle Devonian. Family BELLEROPHONTIID.E. Symmetrically involute shells, the whorls enlarging rapidly, the mouth gener- ally expanded laterally and ventrally, not dorsally, the umbilicus mostly small or closed. Inner lip more or less thickened, the outer sinuate and centrally emarginate, • N. Jarlibuch f. Mlneralogle. etc., Belluneband vl, p. 390; 1889. t Proc. Chicago Acad. Sci., vol. I. p. >J; I860. t Pal. Indira, s.-r. 13. pt. 2, p. 131; 1880. 868 MIUropko.HM.-l tlu> -lit short; slit-band always present Surface with lines of growth only, or cancellated, the revolving lines straight and never oblique with respect to the longitudinal axi- of the volutions. HH.I.KKMHI..N. Mont fort (as restricted by Waagen). Symmetrically involute, subglobo.se shells, with or without an umbilicus, the latter never very large in the typical section; volutions more or less rounded on the back; aperture generally expanded, usually with a callosity on the inner lip; outer lip with a more or less deep central emarginution behind which there is a well developed slit-band or an elevated blunt keel: surface s.-ulpture con-Ming of more or less strongly developed striae of growth onh P] >ilit?s Montfort. AMKKI. • l-'i'KKK.N SPBCIKM. nrlstr.mi. Upper Silurian. 'niiulia Lindstrom. Upper Silurian. /;. uphnri-ii Llnnin<-k. CarbonlfcrouK. •>nUfer DeKonlnck. Carboniferous. B. martini I >•• K'.nlnck. Carboniferous. B. ntlcatulug DeKonlnck. OarboDlfcrm^ II. ferruuaci d'Orblgny. Carboniferous. R. toweHiyi d'Orblirny. Carbon I feroua. />'. ranaltferui OoldfuM. Carboniferous. "(i/oKia Sowerb. Carbonlf« • B. kiuleui Sowerby. Carboniferous. B. cantata* Sowerby Carboniferous. B. plieatui Ryckhold. Carboniferous. B. tongmtialit Phillips. Carboniferous. B. jonetianta DeKonlnck. Permo-Carh. B. oriental* DeKonlnck. Permo-Oarb. It «ffini$ Waagen. Permo-Carb. •iiprtMiut WaaRen. Permo-Carb. B. tqitamatia Waagen. Pcrmo-Carb. />'. I'landfurdinwu Waa«.-n !'• rrno-Carti. 11. irianijularit Waagen. Permo-Carb. n. gen. flinch.) (Bellerophon [part.) of authors; Bucania [part.], Waagen, 1880, and Koken, 18S9.) This name is proposed for shells agreeing in all respects with />//#•/•••/'//<>« excepting that their surfaces are cancellated by regular revolving and transverse striii1. The volutions enlarge rapidly, giving a broadly expanded aperture: the umbilicus is of moderate size and may be closed entirely, while the inner lip is always somewhat thickened. The revolving lines are never oblique nor wrinkled. Type. />'. '••!>• in if era, n. sp. (I'lrich.) AMKKICAN M-WIKB.* HON B. rarinifem I'lrirb : B. coma Foerste. Clinton. 'yorictu White. yuebec >rr. .-iron KIlllnKs. Black Hiv,-r, Tri-nlon. •ntti (d'Orl.ikMiyi Safford. Tr«-nton. -««'. var. buryinentu Ulrlch. Tn-nton. .••MM* I'lrlrh. Tn-nton. B.aityioftM/w t'lrlrh. Tr.-nton. It. WiMatu* Ulrlch. Trenton. ityttoma Meek & Wiirth.-n Trenton. .iJi. D. & "on. «?*u* Emruonv Loral ne. R. newriu Dlrlch. Lorain--. i-ii I'lrlrh. I'tica, Lor . uikri Miller. Richmond group. B. mbangulari* I'lrlch. Richmond group. i.«rr Hlllmtfs. HudAon Klvi-r Knnip. B. *p. undet. Nlagmra. B. ple*>u Mllllnip. Gup*'. B. jxlopt Hall. Schohari.-k.Ti!. Up. Hi-Id. mpinq Mia Meek. Upper Helderberg. It raciii£ so that there is no umbilicus; aperture not abruptly expanded. with the outer lip hilohed. the central insinuation moderately deep and rat I: ml wide, defined mi each side by a thin or thicker ridge; inner lip -nnii'what calloiH iii it- hiteral parts, while the central portion spr. e.lf as a thin, loii;_'itii'lma!l v folded sheet over the inner volutions. These revolving ridges, or. as \Vaagen calls them, columellar folds, extend a greater or less distance beyond the aperture, in some cases reaching a point half around the last whorl. Ueyond them to tln> outer edge of the aperture the surface usually appears smooth, but in perfectly preserve'! specimens it presents very fine lines of growth running parallel with the outline of the aperture. Type, K. urii Fleming sp. Both McCoy and Waagen deny the existence of a slit-band, but Koken maintains (op. '-if., p. :!!(3) — and, so far as the American species are concerned, we have material before us which permits us to sustain his assertion with absolute certainty — that it was always present. That it often, indeed generally, appears to be absent is due to the extreme liability of the outer or sculpture bearing layer of the shell to destruc- tion, while on the inner volutions it is covered by the revolving columellar folds. For further remarks see under Mogul ia ( page 856. ) AV K. (BtUenptum) carbonariu* Cox. Coal Meas. E. (Bellerophon) modocarinatui Hall. Coal Meas. FOREIGN SPKCLEH. E. (BtUsrvpton) mrtoiynyamu Portlock. Carboniferous. Europe. :ng«p. Carboniferous. Europe. idicut Waagen. !'• rui'.-Carbonifrrniis. India. JR. npertut Waagen. Pertuo-Carb<.nifonlf«Tous. India. X. Imtifulari* Waagen. Permo-Cart* India. WABTHIA. Waagen. t Smooth glolmlar non-umbilicated shells, with a broad and rather deep rounded sinus in the outer lip, but without either a slit or slit-band. Inner lip only very slightly thickened, not extensive nor spreading (as in Prototcurthin) over the umbilical regi""-. Aperture without lateral expansions. No revolving 1 m> of growth very indistinct. Type, W. polita Waagen. This genus is readily ; MO. THE PALEONTOLOGY OF MINNESOTA. [Bellerophontlldee. Permo-Carboniferous of India, W. polita, W. brevisinunta and W . lata. To these he adds three Australian species, Bell, undulatus Dan., Bell, strictus Dan., and Bell, micromphalus Morr. MOGULIA, Waagen, (Pal. Indica, ser. 13, pt. 2, pp. 181, 156; 1880.) General appearance of shell as in Bellerophon, from which it differs in having no slit nor slit- band, and only a shallow angular emargination in the outer lip. Surface markings consisting of lines of growth only. These are broad and strong and cross over the dorsum without further interruption than is occasioned by the sharp central bend. Only known species, M. regularis Waagen, Permo-Carboniferous of India. This and the two preceding genera, Euphemus and Warthia, are of unusual interest because we believe they show that in the decline of the family it actually retraced its steps by the adoption of primitive characteristics. In other words we regard them as atavistic types in which the progressive development of the indi- vidual was arrested in the embryo, and in which, because of the failure to develop the adult features of their immediate ancestors, certain characters that under previous conditions were larval only became permanent. In the Devonian and Carboniferous Bellerophontiidce the suborder obtained the hight of its development, and this was not reached until after the extinction of all the other families. The decline, which obviously was very rapid, took place during the time immediately preceding the close of the Paleozoic age. Facts like these permit us to assume that the three genera under consideration are retrograde descendants of Carboniferous BellerophontiidcK and not remnants of types that flourished only in Cambrian and Lower Silurian times. Besides, this idea is entirely harmonious with laws that have been shown to operate in other branches of zoology, and according to which the earliest and latest representatives of a group of organisms may be more like each other than either is like intervening stages in the rise, acme and decline of the line of evolution to which they belong. Mogulia, in the absence of a slit-band, the shape of the outer lip, the form of the aperture, and even in the strength and course of the lines of growth on the dorsum, compares closely only with Owenella, that most ancient of all the Bellerophontacea. Warthia, excepting that it has no spiral surface lines, nor those grano-lineate exten- sions of the inner lip, is precisely like that important group of Lower Silurian shells which we have called Protowarthia. Euphemus, again, in its broad and ridge- bordered slit-band, in the shape of the aperture, indeed in the form and characters of the whole shell, recalls the Lower Silurian genus Tetmnota probably more than either Owenella and Protowarthia. But in the spiral columellar folds which spread over the umbilical regions and a large part of the dorsum of the last volution, we >IIM>A 867 have an extravagant development of the delicatf j,'rano-lineate extension of the iniHM h|> which i> tin- principal difference between /'• "hi" and \\'tirllii>i. 'I'li.« point- linuight out in the foregoing paragraph an- significant and indicate, we believe, that l>viously progressive. The first has no slit-bund and only a very shallow sinus, the second is still without the band but has a broad and deep sinus, while the thin! and f.mith have a narrow and very deep parallel-sided sinus or slit which with the .\th of the shell causes the formation of a slit-band. •IIKI.I .v. Waagen. (Pal. Indica, ser. 18, pt 2. PP. 132, 171; 1880.) Shells agreeing in all respects with Mlrrnphon excepting that they are smoother and some- what unsymmetrically coiled, there being an umbilicus on one side and none, or at any rati« a shallow one, on the other. Type, .S'. bifrons Waagen. So far as known no shells of this type have yet been found in American deposits. Two species occur in the Permo-Carboniferous of India, and five in the Permian of \ '.p-. 'I'll.- latter are described by Stache in his monograph of the fauna of the r».|loroj>hon limestone. Regarding the genus, it seems to mark an important departure from the ordinary types of the family. We suspect that Sbirhelhi may be the radical of the ophisthobranchs, but this is a mere suggestion. The Cretaceous liellfrophina, d'Orbigny, is a similarly unsymmetrical shell, but has no slit-band and only a shallow omar^i nation of the outer lip. Family CARINAKOPSII' 1 1 metrical, almost patelliform shells, the .aperture being greatly expanded; apex small, involute, overhanging the posterior margin, consisting of no more than volutions. Within the aperture abroad concave septum. Anterior lip with a 'nil eniar^rination. This family embraces a small group of Lower Silurian shells that is readily dis- tinguished from other bellerophontids by the internal septum. \Ve believe that it should include also the genus Pftrotheca, which is now almost universally referred to the / \ li-cussion of the affinities of this genus will he found under Carinaropsif. CAKUTAROPSIS Hull.* (PAruyMMtaNo, H*U,-| not Waagen.J) Shell consisting of little more than two volution-, the inner one very small, scarcely embraced by the outer, and shown in the umbilicus; outer volution greatly expanded, the whole shell appearing somewhat patelliform: dorsum carinate, the carina sharp on the inner «w York. TO), l. p. HO. • PourtN-nth (Up. X. Y. 8u Mum. Nat. HI«U p. M : t P»l«wotolo«lc. Indlc*. wr. U pi. 2. p. 1X1; MM. 858 THE PALEONTOLOGY OF MINNESOTA. [Cyrtolites. whorls but becoming less angular if not quite obsolete in nearing the apertural margin; slit-band occasionally distinguishable; outer lip of aperture thin, sinuate and notched centrally; inner lip entire where it touches the preceding volution; within the edge it is first deeply concave, then produced into a broad thick flattened plate or septum, which extends a considerable distance into the aperture; upper surface of septum with a low but well defined median ridge; inner aperture covered (always?) by a triangular flat operculum. Type, C. carinata Hall. C. acuta U. &S. Black River group. C. carinata Hall. Trenton group. C. minima U. & 8. Black River group. C. cunulce Hall. Trenton group. C. phakra Sardeson. Black River group. C. explanata Dlrich. Top of Trenton group. C. cymbula Hall. "Hudson River group." Genus CYRTOLITES, Conrad. Cyrtolites, CONRAD, 1838, Ann. Rept. Nat. Hist. Surv. N. Y., p. 118. Cyrtolites (part.), Hall, 1847, Pal. N. Y., vol. i, p. 187. MILLBB, 1874, Cin. Quart. Jour. Sci., vol. i, p. 308; also 1889, N. A. Geol. and Pal., p. 401. WAAGEN, 1880, Pal. Indica, ser. 13, pt. 2, p. 132. LINDSTROM, 1884, Silurian Gastropoda of Gotland, p. 81. For generic characters see page 846. Restricting this genus to species of the type of C. ornatus Conrad, we have an isolated group of a shells that we find most difficult to classify satisfactorily. Despite the fact that authors have so generally agreed in uniting with the group that other peculiar type which we separate as Conradella, there is in reality but very little reason for considering them as related and much less as identical. ' In discussing that genus on a following page it is shown, we believe, to the satisfac- tion of every fair-minded student that Conradella, with its long dorsal slit and imbricated lamellae, is nearer Bucania, Salpingostoma and Tremanotus than to Cyrtolites. Indeed, we cannot see how an unprejudiced comparison of Conradella and Cyrtolites can fail to impress the observer with the conviction that the two groups of species are not only generically distinct, but not even closely related. Cyrtolites has been loosely employed by most authors for symmetrically in- volute, disciform shells, having the dorsum carinate or angular and the umbilicus broad so as to expose the inner volutions. These characters pertain to several widely distinct genera, and to use them as characteristic of a single genus is to bring together a most heterogeneous assemblage of forms. Thus we have among the species that have been referred to Cyrtolites several belonging to Oxydiscus, Koken (Tropidiscus, Meek), a genus that is nearer Bucania and Bellerophon ; several of Conrndella, which, as we have said, is nearer Bucania; and all of the species com- prisod in the new genus Cyrtolilina. Lindstrom and others have thought that PorceUia, even, is the same as Cyrtolites. With equal propriety we might refer to the same generic group also the recent genus Atlanta! . v •'•' IIW.1 Hut thi> will not do, for it would he nothing le>s than ignoring mo-t palpahle We mu-t return to the original t\pe. t\ ,,,-nMHK' essentially tli.- -aim- generic peculiarities. A Her « lie character- mentioned in tlie tir-t -entence of the preceding paragraph, which brings u- d..wn in the ident ilicati.m of the genii- to four or live similarly constructed types, these peculiarities con-i-t of il) the subquad i angular cross-section, of the whorls, lie simple and sharp edged or minutely serrated character of the dorsal .•anna. <:'.' the total absence of a slit-hand and (4) the pattern of the surface marking whieh. with a -ingle exception, differs from that of all other beller- ophontid.-. The second and third of the features is shared by Oxydiscus, but as the latter has more numerous and more compressed volutions, a much deeper •rural emargination and slit, and lines of growth only, there is little trouble in M-paratiiijj it from Cyrtolites. Conradella is distinguished by its slit-band and remarkably long apertural slit, by the rounded or cordate section of its whorls, and hy its strongly imbricating and wavy surface lamellii-; I'orrelliti has a long ulit like Conradella, rounded volutions, the inner ones unsymmetri. -ally coiled, and different surface markings. For comparisons with Cyrtolifiim, which of all the Hfller>,j,hrd. to Osy-lisou; C. «///•//<> I'lrich, to Ci/iinlitiiin ; C. -nl><;irinnfus Kninion-. pr-il-alily to Cnrinaropsit. C. filosux Kminons and C. crisis Conrad are halopoda; while the remaining forms, C. desidtrntns Billings, C. expansus Hall. C. yill.tnu* White A- St. -iohn. Hall \ Whittield. and < '. >/>m...x-M.v Hall, are too little known to 1)6 placed with anything like certainty, "f Knropean -pecie- that have heen referred to Cyrlni. • iiap- none n-ally l»elcniLr tin-re. <'. tr. .in doul>tless Itelong to (h-i/>lixi-ns, to which we are inclined to reft «> Lindstrom as well, although it ha- a di-tinct slit-band 860 THE PALEONTOLOGY OF MINNESOTA. [Oyrtolltes ornatus. which should not be the case in a true Oxydiscus. Perhaps it would be better to place the last species, together with C. euryomphalus Lindstrom, into our new genus Cyrtolitina, which is more especially intended for the reception of four other Gotland shells described by Dr. Lindstrom as Cyrtolites lamellifer, C. pharetra, C. arrosus and C. obliquus. . CYRTOLITES ORNATUS Conrad. PLATE LXII, PIGS. 27-31. Cyrtolites ornatus CONRAD, 1838, Ann. Geol. Rept. N. Y., p. 118; Ibid. (1839), p. 63; Ibid. (1841), p. 37. VANUXEM, 1842, Geol. Rept., p. 65, fig. 2. EMMONS, 1842, Geol. Rept., p. 402, fig. 2. HALL, 1847. Pal. N. Y., vol. i, p. 308, pi. LXXXIV, figs. \a-g. MEEK, 1873, Pal. Ohio, vol. i, p. 148, pi. xm, flgs. 3a, b. MILLER, 1874, Gin. Quart. Jour. Scl., vol. 1, p. 308. And of many other authors. Shell varying in diameter between 12 mm. and 30 mm., with the average at about 23 mm. Volutions two or three, rapidly increasing in size, strongly and sharply carinate dorsally, rhombic subquadrate in section; sides prominent and subangular or narrowly rounded along a line about three-fifths of the hight of the volution within the dorsal carina, the dorsal slopes gently convex and distinctly undulated by strong slightly curved transverse furrows and subangular ridges, the ventral or umbilical slopes almost flat and usually without undulations; ventral side with a sharp central furrow for the reception of the dorsal carina of the preceding volution. Umbilicus well defined, wide and deep, the edge wavy. Aperture a little wider than high, the hight equalling usually a trifle more than half the greatest diameter of the shell, more or less rhombic-subquadrate, the outline often becoming a little rounded with age. Entire surface covered by a delicate network formed of raised lines running almost straight across the whorls and short connecting lines arranged alternately, the result being somewhat similar to the pitting of a thimble. In a good light the network is generally distinguishable without the aid of a magni- fier, and, excepting three specimens, quite uniform in strength in different shells, there being on the outer half of the last whorl nearly always seven or eight of the transverse lines and eight or nine of the short lines in 2 mm. In the excepted specimens the network is more compact, there being over the outer part of the last whorl from ten to twelve of the transverse lines in the same space. On another, with the reticulation unusually coarse, the number averages between six or seven. On the last specimen a good magnifier brings out some very fine lines of growth running through the network. It is important to note that there is no perceptible backward curvature of the transverse lines in nearing and crossing the dorsal carina. The above description applies to the species as it occurs in the groups of the Cincinnati period wherever these are exposed in the United States and Canada. In .«•.] .tl form tin i- nut known to o.vut in the Trenton, hut a variety has been found in the < 'litainbonites bed of the Trenton group '" Minnesota. For this we propose the >ul>ordinaU> name »iin pecimens being unusually small, none exceeding 11 mm. in diameter. The volutions seem also to he narrow, the hight at the aperture in the specimens at hand exceeding the width by about one-sixth. The surface markings are precisely as in the typical form of the species excepting that the trans\erM' -tru- in crossing the dorsal carina are sometimes bent slightly backward. The variety is of consequence chieHy because it proves the existence of the orw//n.v type at nuite as early a time as that in which the C. retrorsus lived. Anil tli , unities us also in denying that C. ornatus was evolved from C. Formation and locality.— The typical form In a common fossil of the Lormioe and Richmond groups at numerous localities InOhlo, Indiana, Kentucky. IVrmsylvaiila, New York and Canada. At Cincinnati the »1< n covered by a parultlc bryozoan ( Leptotrypa ornata Ul rich) which, when carf ully chipped •way, generally leaves a good cast of the surface markings and not Infrequently the test Itself. The species has not yet been certainly Identified In tin- I'Ura group, ),ut we suspect that one or two casts ;.-.! in the lower part of this group at Oovlngton, Kenim-ky. may IH-II.IIK t<» It. Variety minor was i. O. Ulrlch In tli.- Clltambonltes bed of the Trenton group, near Cannon Falls, Minnesota. On RETRORHU8, n. -;-. I-I.ATI: i. MI. no*. »-w. 11 rather small, the diameter rarely exceeding 15 mm., in one case 20 mm., in others mostly from 12 to 14 mm.; in general appearance decidedly like C. ornatus, the dorsal slopes being strongly undulated, and the surface distinctly reticulated. Carefully compared, however, it is found to differ in the following particulars: the keel is more prominent, the dorsal slopes are more concave, the sides sharper, the transverse section of the volutions more distinctly quadrangular, and their rate of increase greater. The most important difference is in the form of the mouth and the direction of the transverse surface lines. The mouth namely is deeply cut out ami the lines instead of passing directly across the back are strongly curved back- ward. Finally there is a small ridge along the suture line that has not been observed in C. < The retral curve of the transverse lines is slightly greater than in C. e-irinnhis Miller, with the typical form of which C. retrortus agrees very closely so far as the inner volutions are concerned. But mature specimens of the two species cannot be confounded, the dorsal slopes in Miller's species becoming Hat with maturity, while undulations are not developed except in the oldest examples. In C. retrorsus, on the contrary, they begin very early, while the con- cavity of the dorsal slopes continues through all stages. There can be no reasonable question about the specific distinctness of this shell, nor do we doubt that it will include, if not all, at least a part of the Tennessee 862 THE PALEONTOLOGY OF MINNESOTA. LOyrtolites retrorsus. specimens referred to C. ornatus by Prof. Safford. If any are in doubt, then it is those which he obtained from his "Orthis bed," which, like the Clitambonites bed in Minnesota, we place at the base of the Trenton group. The same form occurs also in equivalent strata in Kentucky, but none of the specimens seen by us are suffici- ently perfect to permit of a positive decision in the matter. So far as the form of the shell and volutions is concerned, the specimens in question certainly agree very closely with C. retrorsus, and, if appearances are not deceptive, they are like it also in the backward swing of the surface markings. The evidence at hand, therefore, seems to indicate that all of the Tennessee and Kentucky Trenton specimens hitherto referred to Cyrtolites ornatus really belong to C. retrorsus. .Formation and locality. —Upper part of the Trenton group between Burgin and Danville, Kentucky, and Nashville, Tennessee. Probably also In the lower part of the group near the same localities. About ten specimens, mostly casts of the interior, have been found by one of the authors in the upper part of the Trenton group and in the lower part of the Utica group at Cincinnati, Ohio, and at Covington and Newport in Kentucky. Collections.— E. O. Ulrich; Prof. J. M. SafforY CYRTOLITES RETRORSUS, var. FILLMORENSIS, n.var. PLATE LXII, FIGS. 38 and 39. Under this name we propose arranging provisionally a form occurring not very rarely in the shales of the Black River group at localities in Fillmore county. Unfortunately, none of the specimens before us are in a good state of preservation, all excepting three being more or less distorted casts of the interior. On two of the excepted specimens the shell is preserved on the inner volutions only, while the the third retains a few lines near the aperture. So far as can be determined, the variety differs from the typical form of the species only in having the sides of the inner volutions almost rounded, the form of the outer volution and the surface ornamentation being apparently as in C. retrorsus. The rounded character of the sides of the inner volutions in this, the oldest known variety of the genus, is a noteworthy feature, since it may give us a clue to the origin of the genus. .Formation and locality.— Black River group, Ctenodonta bed, Chatfleld and near Fountain, Minnesota. Collections.— Geological and Natural History Survey of Minnesota; E. O. Ulrich. Museum Register, Nos. 4051, 7535. CYRTOLITES OARINATUS Miller. PLATE LXII. F1G8. 50-52. Cyrtolites carinntus MILI.KH, 1874, Cin. Quar. Jour. Sci., vol. i, p. 311, fig. 32. Coiup. Cyrtolites conradi HALL, 1862, Geol. Rep. Wis., p. 55. (Figured only.) Smaller than C. ornatus, the size being about as in C. retrorsus, the average diameter about 13 mm.; in two of our specimens it exceeds 20 mm. Sides sharply OASTROPO1>\ ir« rarln.iu- > i MI mat«>'l like tlit> >l<>r-uiii, the dorsal .slopes strongly concave on the first ami second \\horls nearly Hat «m flu- la-t, without undulations except near the aperture of the largest exsun !•'••-: transverse lines sweeping backward from the edge of the umliilicu-. ^tnmger than the connecting lines, the diHerence between the two sets increasing with age. The original description of the species is not entirely correct, Dr. Miller daimiriK' tliat the surface "never presents a cancellated appearance," but he seems to have doubted the correctness of his observations since he adds, "at least not on any ^nM-mien observed." Out of more than twenty specimens belonging to the cabinet of one of the authors several preserve the surface markings in a fairly satisfactory manner. These show that on the inner volutions the surface is minutely though distinctly cancellated. The short connecting lines are delicate, and as growth proceeds they become relatively more so, a short exposure to the weather sufficing in many cases to efface them entirely, when the specimen will appear to have transverse stria; only. Generally, however, when the stronger set of lines is preserved, more or less convincing traces of the other set also are retained. Compared with (-. ornntus the present species is distinguished by its sharper lateral carinie, flatter and more concave dorsal slopes, almost total absence of surface undulations, and by the backward sweep of the lines of growth. From C. retrorsus it differs in being practically without dorsal undulations, in having a less prominent dorsal carina, and in the flattening of the dorsal slopes of the last volution. So far as the two species mentioned are concerned, C. carinnlus is clearly di-tim-t. hut we cannot say as much when we compare it with C. conradi, a species named and figured by Hall (Inc. cit.), without a description, as one of the fossils of the Hudson River or Mu<|uoketa shales of Wisconsin and Iowa. Hall's illustration represents a small Cyriolites very similar to C. carinatus, and, as the geological horizon is about the same for both, it i* not unlikely that the two names apply to the same species. To establish this as a fact would in our opinion necessitate a comparison with Hall's original type of C. conradi, and if that is no longer possible, it would be well to drop the name entirely. Formation and locality.— Not uncommon in \\.- I'tlca group at Cincinnati, Ohio, and a nunibcrof localities In the rlclnlty of that city. Th« species occur, probably alno in the lower shah- m-ln- n.iti i» rlud In Wisconsin and Iowa, In which caae it may U- loolml fur In soiitlnTO Mlonoota as w< 864 THE PALEONTOLOGY OF MINNESOTA. [Cyrtolltes parvus. CYRTOLITES PABVUS, n. sp. (Ulrich.) PLATE LXII, FIGS. 45 47. Shell small, about 7 mm. in diameter, 6 mm. wide at the aperture, consisting of about two rapidly enlarging volutions, subquadrangular in section and somewhat wider than high; dorsum carinated, the keel not very prominent, minutely wavy in a side view; sides narrowly rounded, scarcely angular; dorsal slopes gently convex, with- out undulations except near the aperture where several obscure ones may be noticed. Surface with comparatively coarse lines of growth, curving strongly backward from the edge of the umbilicus to the dorsal carina which they cross without interruption. These lines are connected by more closely arranged and very delicate obliquely revolving lines, which, being lower than the transverse set, might easily be overlooked. On the last turn seven or eight of the transverse lines occur in 2 mm. Considering the size of the shell, the surface markings are stronger than in any of the other species of the genus. From C'. carinatus Miller, which it resembles most, it differs also in having the sides of the volutions narrowly rounded instead of sharply angular. In C. retrorsus and C. ornatus the surface ornamen- tation is much more distinctly reticulated, and, while the former has a much stronger keel and concave dorsal slopes, the latter is especially distinguished by the absence of a sinus in the outer lip and consequently in the more strictly transverse course of the surface markings. Internal casts of Cyrtolitina nitida resemble testiferous examples of this species; but if this fact is borne in mind, and further that in the former the back is flattened, the volutions more compressed laterally, and the surface markings of the cast thicker and wave-like rather than thread-like, it is almost impossible that confusion between them can ever occur. Formation and locality.- Near top of Trenton group at Covington, Kentucky. Collection.— E. O. Dlrich. CYRTOLITES DISJUNCTTJS, n. sp. PLATK LXII, PIGS. 48 and 49. Shell about 24 mm. in hight, consisting of about two entirely free or disjoined whorls, coiled very nearly or quite symmetrically; volutions strongly and sharply carinated dorsally, the sides somewhat narrowly rounded within the center, and strongly undulated transversely; ventral side less convex, with two abruptly elevated narrow central carina}, forming a groove with raised edges or what is commonly called a "saddle"; hight of volutions increasing with age more rapidly than the width, the transverse section, excluding the dorsal and ventral carinse, changing from transversely subelliptical to almost circular at the aperture of a fully :ir« dll»t»tu. ) tfrn\\ ii -pct-mien. Surface markings on the whole nearly the same as in C. ornatus, only the transverse ridges are not confine.! to the dorsal slopes !>ut continue down- wan! with a -li^'ht retral curve over the ventral slopes as well. The reticulation of the surf:tr«> also changes with growth in a manner not olwerved in that species. Thus on the minute inner whorl the surface is almost smooth, only a few ohscure revolving lines being visil.li> on this part. With the beginning °f th* second turn the sculpture changes abruptly to the usual style of reticulation, but for some .nee the tran-ver-e ime- curve backward towards the dorsal carina as in C. retrormw and ' «>. Tlii- retral curve, however, is soon lost so that on the greater part of tin- -hell they pass directly over the carina as in C. ornntns. The peculiarities of this beautiful shell are so obvious that comparisons are quite unnecessary. It is the only species of the genus in which the whorls are not in contact. Formation and totality.— Richmond tfroiip »( the Cincinnati period, near Sprint; Valley, Minnesota, where two specimens were found In aMoclatlon with (M/u'.< sutyuodrato tod IIUIIHTOUS nthi-r llrarhiopoda character!/ 1 1. k1 th>- horizon. CWbettm.-B. O. Ulrich I:TOLIT«S(?) DILATATIIS, n. sp. I I. ATE LXII. FI08. »-«. Shell 15 to 30 mm. in hight, the inner volutions unknown, the outer expanding I rapidly in width, sharply carinated or alated on the sides, more obtusely upon the back, transversely triangular quadrate in section; dorsal slopes flat except near the prominent lateral edges where they are concave; ventral side nearly flat, with a central groove probably for the reception of the dorsal carina of the inner volu- tions; aperture nearly or about twice as wide as high, subtriangular, the width slightly exceeding the hight of the entire shell, the outer margin with a broad, centrally angular sinus, the inner lip with a small "saddle." Surface markings unknown: outer part of a large cast of the interior with a few faint transverse wrinkle> of growth. Of this remarkable species we have seen but two specimens, one, a large cast of the interior, belonging to the Powers' collection of the 1 niver-ity of Wisconsin. the other a smaller testiferous example collected by I-!. <> Ulrich in Minnesota. The latter exhibits no signs . To this statement we may add the suggestion that Cyrtolitina may have been derived from some form of Bucania like B. subangulata. Comparing Cyrtolitina with its possible relatives we find that it diifers from Cyrtolites in having a slit-band, less carinate dorsum, an apertural emargination, higher (more compressed) volutions, and surface markings that are to be called lamel- lose rather than reticulated; from Bucania in having fewer and laterally instead of vertically compressed volutions; and from Conradella in having fewer and more rapidly enlarging volutions, much shorter apertural slit, no distinct dorsal keel, and the subimbricating surface lamellae curved strongly backward on the dorsum. CYRTOLITINA NITIDULA Ulrich. PLATE LXII, FIGS. 53-55. Cyrtolites nitidulus ULKICII, 1879, Jour. Cin. Soc. Nat. Hist., vol. ii, p. 12. Shell small, 6 to 8 mm. in diameter; volutions about two, rapidly increasing in size, the outer embracing quite a half of the inner; dorsum blunt, thick, flattened GASTR<>mi>A. in casts; sides gently convex to the edge of the umhilicu> into which they descend ;it lir>t nither abruptly, then gently, the ventral part spreading saddle-like over the inner volution. \i>erture subcordate, notched below; outer lip rather broadly and deeply emarginatod. Umbilicus about :•."» nun. wide in a specimen 8 mm. in diameter, narrowly rounded at the edge. Surface of casts with distinct, subregular, lly curved, transverse stria-, aveni^in^ about live in 2 mm. on the sides and Lark. Tin- stria- continue over and are quite distinct and curved on the flattened dor-inn or slit-band. On the latter some very fine revolving lines are faintly dis- tinnuMiahle. Somewhat oblique and stronger revolving lines, about four in 1 mm., occur on the sides of the volutions. Greatest diameter of a large specimen 8.3 mm; wi.it li of aperture 5.0 mm.; hight of same 5.0 mm. The original description ami figures are incorrect where they differ from the present work on the species. It is scarcely necessary to go into details. i if American fossils we can compare this pretty shell only with species of •elites and possibly of Iliicani-i. < ijiiolUes retrorsus and C. carinatus are found with it. Imt 1'ntli have more volutions, are sharply keeled and without a slit-band. The new < 'ijrtolitts jMirvus is also associated and, because of \\< small si/e and relatively coarse markings, is more likely than any other fossil known to us to be confused with C. nid'liiln: still, they may be readily distinguished, C. parvus having the usual sharp dorsum and wider subquadrate aperture. Besides, it should be borne in mind that they are testiferons specimens and not casts of the interior of the species of CyrtolHes mentioned that look like casts of Cyrlolitinn nHimu- deep, tin- Inl.c- not rounded hut bending at almost a right angle in tlio middle: inner lip slightly re flex ed and thickened on each side; test thin, rnmpoM'd apparently <>f two layers, tlie inner nacrous. Surface of specimens marked l.y more or less nl.M-ure, lines of growth. These are usually the strongest on the dor- suin, where they may l>o seen also on some casts of the interior. The latter, however, are in most cases quite smooth and without a trace of markings. External layer of shell not seen in good condition, so we cannot say positively, though we suspect it to be so, that it was marked near the umbilicus, as in the following species, hy tine granulose stri.r. Might of shell 20.5 mm.; median hight of aperture iin.: width of same 1'.' nun.: \\idth of inner volution 7 mm.; depth of sinus 8mm. In two other specimens, one very large, these dimensions are respectively, 24, 10, 23, 7 and (.i nun., and 30, 13.5, 27, 8 and 12 mm. This species is often met with in collections under the name of Bellerophon liilotxitns, hut it is really quite distinct, as anyone may see by comparing the accompanying figures of that species with those of B. rectanyularia given on plate I. Mil. L' 1. A and H. tw. vn-wsnf l-r,,t,«r' hilnhuiHx, or 1'rutnimrtkia bilobata as it should now be railed, is a more ventricose shell, causing the back to be fuller and much more broadly rounded, while the apertural lobes, are, as usual, rounded in front instead of angular. The rectangular outline of the apertural lobes which has suggested the specific name, dMinguMie^ /'. ncfmnjuliiris from all the other forms referred to Prolotcarthiu. Indeed, it is a peculiarity that is not possessed by any other species of the whole suborder. We have before us three specimens of a variety of this species from the Trenton limestone at Trenton Falls, New York. s.. far as this material at hand shows, the variety differs only in having the apertural lobes less angular than usual. We have also a number of internal casts from the Black River and Trenton shales and 870 THE PALEONTOLOGY OF MINNESOTA. [Protowarthla granlstrlata. limestones of Minnesota which may represent other varieties of the species, but as we cannot be certain about them we prefer to leave them unclassified for the present. Formation and locality.— Bather a common fossil of the Stones River group, at Mineral Point, Janes- ville and Beloit, Wisconsin, and Dixon, Illinois. In Minnesota it occurs, though not abundantly, in the Vanuxemia bed at Minneapolis, St. Paul and Cannon Falls. Collection.— E. O. Ulrich. PROTOWARTHIA GRANISTRIATA, n. sp. (Ulrich.) PLATE LXIII, FIGS. 28-30. Shell scarcely reaching the medium size, closely coiled, leaving no umbilicus; center of dorsum raised into a low broad ridge, defined on each side by an obscure wide furrow; with age the outer boundaries of the latter increase gradually in distinctness, the back of the outer half of the last volution in the largest specimens presenting a flattened appearance; but the central ridge, though decreasing some- what in bight, continues to the aperture. In casts of the interior there is a small umbilicus, while the central ridge is nearly as on the shelf itself. Aperture trans- verse, about twice as wide as high, the width generally equalling the hight of the shell; sinus wide, only moderately deep, the margin of the lobes bending rather sharply where the apertural margin is intersected by the faintly raised boundaries of the flattened dorsum. Except in the umbilical regions the test is thin. Out of nearly thirty specimens, only two preserve anything of the external layer. These show that it is marked by fine lines of growth and by very delicate revolving lines. All of the other testiferous examples preserve only the inner and middle layers, the latter appearing in every case quite smooth. Most of the specimens preserve what may be called a fourth layer. This seems to have been deposited by the inner mantle over the inner volutions, including the smaller half of the outer, while on each side it extends around the callous filling of the umbilicus. The whole of this layer is finely granulose, except the lateral extensions and these are covered by wavy revolving striae. Hight of an average shell 19 mm.; width of aperture 19 mm.; median hight of same 9.3 mm.; width of inner volution 6 mm.; depth of sinus 5 mm.; width of same about 10 mm. In this species the sinus is only about half as deep as in P. rectangularis, the apertural lobes are not rectangular, the umbilicus is closed entirely, and the volutions rounded rather than subtriangular in cross section. It is nearer P. cancel- lata Hall, but that species has a slightly deeper sinus, and a rounder back, the back never being flattened, nor is there ever a sign of the low dorsal ridge and obscure furrows characterizing P. granistriata. QA8TBOPOD4 Fort. -in U,i> s|».,-irs i, known lu. i. OWIerti>n.-E. O. Uln l'l:i'Tn\V\KTIII V I'l ANM|"r|;,ATA, W. Sp. (Hindi.) uaa i ins. n-a. i >f tlii- form we have six specimens. These show that it is of the type of P. •/ninisti-int'i, perhaps it should be called a variety of that species, — differing in having the tlattfniiiL' <>! the back of the last volution much more decided, while the nil rnl^' i- wanting entirely, at any rate it is so for the outer volution. The donon of the, volutions seems to be rather narrowly rounded. The surface kings are essentially the same in the two forms, as is also the form of the aptM-tun- ami the dimensions, the largest specimen being about 24 mm. in hight. The broad dorsal flattening will distinguish /'. plitnotlorxnta at once from all other -i-f.-if- of the genu> ami family known. formation and locality.— Utlca group, CtivifitMmi, K.-ntuckjr. CbibctiM.-E.O. Uln.-h. I'KOTOWAKTIIIA PKRVOLPTA, n. *p. I'l.ATK LXIII ST. This also may be only a variety of /'. granistrinfii, but it is one well worthy of a name. It is almost constantly smaller, the hight in the majority of the specimens being less than 15 mm., and in only one out of over fifty is it 20 mm. < 'omparing the two forms we find that /'. penoluta is more closely inrolled, giving a more globose form. The aperture also is relatively wider and the umbilical callosity has a t-olumel la-like twist that is not seen in P. granistriata. The volutions further are nearly uniformly rounded dorsally and never show anything either of a central ridge or a flattening. Though some of the specimens before us are tolerably well preservc.l. none of them exhibit any - it i-f irtory evidences of external markings save the granostriate marking of the inner volution. This is more extensive, but in other respects essentially ;us in the two preceding species. Here and there a small patch of the external layer is retained and these sometimes exhil.it taint traces of exceedingly delicate transverse and revolving lines. Formation and toealiig. In K.-niiirky this specie* occu'nln the Klark Klvi-r uroup anil in ih.- lowest bed (Orthlt or Modlolodon b^li ..f tin- Tr.-ntn>us eumplea arc rmr • furth.-r ir Catimm Fa IN .in. I .1! Chattl.-id th.-y ar.- aluindant. Colltctiont.-} h; W. H. Scofleld. 872 THE PALEONTOLOGY OF MINNESOTA. [.Protowarthia cancellata. PROTOWARTHIA CANCELLATA Hall. PLATE LXIII. FIGS. 1-14. Belterophon cancellatus HALL, 1847, Pal. N. Y., vol. i, p. 307. Compare Beltei-ophon bilobatus of Hall and other American authors, not of Sowerby. The general form of this shell is much as in P. rectangularis and P. planodorsata, the average of characters being about intermediate between these two species. From the first it is distinguished by the more rounded back of the volutions and the rounded instead of angular outline of the apertural lobes. The sinus in the outer lip also is less V-shaped. From the second it is sufficiently distinguished by the rounded instead of broadly flattened dorsal region of the last whorl. Young speci- mens, especially if casts only were compared, would perhaps prove inseparable. We refer here a large number of casts from the Black River and Trenton groups of Minnesota and elsewhere, as well as casts and testiferous specimens from the Utica, Loraine and Richmond groups of the Cincinnati region. The specimens from the Trenton period might be separated as var. trentonensis, as they are almost constantly a trifle more narrowly rounded dorsally than is the geologically higher typical form of the species. And yet we have specimens from the Black River group at Chatfield, Minnesota, that are, so far as it is possible to determine, precisely the same as the common variety of the species found in the lower part of the strata at Cincinnati, and which we regard as typical of the species. Specimens preserving the shell in a satisfactory manner are everywhere rare. The outer layer which carries the transverse and revolving lines is nearly always gone, and, so far as our observation is concerned, this layer is retained, if we except two or three instances, only by specimens that have been removed from the solid limestone. These show that the perfect shell was ornamented with fine lines of growth, generally a little unequal, and even finer (just visible to the naked eye) revolving lines. The former may be obscurely visible on the inner layers of the test, but the latter are entirely superficial. Now, while most of the testiferous examples are almost entirely smooth, the greater number preserve the irregular or wavy revolving lines which surround the umbilical regions. This is true not only of this species but of the preceding forms as well, and proves that these thin exten- sions of the callosity of the inner lip are composed of a more durable substance than is the usual sculpture-bearing layer of the shell. So far as observed the inner whorls are not granulose dorsally as is the case in P. granistriata, P. pervolufa and P. planodorsala. The umbilical callosities of the inner lip are shai-ply defined, oblique and somewhat flattened, though always more or less excavated. We have not seen the original type of this species which Hall sought to separate from the specimens which he regarded as Bell, bilobatus. But we have little or no -i MI -A Pralowartkl* »ab .loiil.t of tin- rorrectti.'-- nf inn identitiratimi. nor of tin- -perilir identity of a large proportion of the -pei-mien- th;it American authors generally and erroneously place under Sowei by'- Ii,llfi;>i>li/««•//(//•( is the commonest by far of all the Ix)wer Silurian bellerophontids. •o /'. bilobata Sowerby, the original figures of which are reproduced on page 869, we have not the least doubt that it is specifically distinct from P. cancrllulu, that species being a larger and more globose form. Indeed, we doubt very much that Sowerby's species occurs in America. Formation and lotalUy.— Hot uncommon in th>> Hl:u-k Klvcr group, principally In the Ctenodonta bed. at Mlnm-.r I'aul, Canonn Fulls, Chattleld and other ltx-al!ti<> In Minnesota. Also In Mercor r.ninty, K.-ntii'-k> . and In Canada. It is very aVfcndant In the Trenton, Utlca, Loralne, and Richmond ttroiip*, in th.-ih-t ihr.-v especially, at numerous localities In Minnesota, Wytontln, Iowa, Illinois, K.-n lucky, Ohio, Indiana, Tenneuce, New York and Canada. PBOTOWARTHIA SUBCOMPKESKA, n. sp. (Ulridi.) I'LATK I.XIII. KI08. »~U. II large, compressed-subglobose, the greatest bight and width about as six is to four; back broadly rounded, sides somewhat flattened, umbilicus closed, wanting; aperture semi-ovate, outer lip thin, inner lip moderately thick and reflexed in the umbilical regions; callosity extending over the whole front of the inner volution, apparently smooth; sinus broad and about as deep, the depth decreasing slightly with age; apertunil lobes rounding very gently to the sinus where the outline makes a rather sharp curve. Surface marked by fine lines of growth and near the aperture by some obscure wrinkles. The callosity which extends over the inner volutions exhibits the usual fine irregular revolving lines in the umbilical • I!-. When the shell is removed, the cast shows a narrow furrow down the center of the bark and several more faintly on each side. Greatest diameter 41 mm.; smallest diameter 'J'.t mm.; width of aperture 27. "> mm.; bight of same (central) mm.; width of inner volution K! mm.: depth of -inus 7 or 8 mm. This fine species, besides attaining a greater si/.e than /'. <-nn<-i-ll,iiii, differs from it in being narrower and in wanting. - known, the delicate revolving line- of that species. The umKiliral callo-ity of the inner lip i- also less and does not slope outwardly, the edge only being reflected. Ilrllcrophon tnnrruii-ensi* Miller and I»yer. whirh also may belong to Protoii-'irthin, i> in-utliciently known. According to the descriptions, it seems to differ in having the dor-al -i'lr -h.trply angular. /'. pltinodorsata has a wider aperture, revolving lines, and a flat dorsum. 874 THE PALEONTOLOGY OF MINNESOTA. LProtowarthia conclnna. Formation and locality.— Richmond group of the Cincinnati period, Versailles, Indiana, and Butler county, Ohio. Collection.— E. O. Ulrich. PROTOWARTHIA CONCINNA, «. sp. PLATE LX1II, FIGS. 36-39. Comp. Bellerophon mori-owensis MILLER and DYEK, 1878, Contr. to Pal., no. 2, p. 8. The specimen upon which this species is founded has, although it is much smaller, relatively nearly the same dimensions and form as P. subcompressa. The dorsum however is narrowly rounded instead of broadly, the aperture is triangular rather than semi-ovate, and the sinus is narrower, while the thickened base of the lip forms a small sharply defined and shallow umbilical depression which is not seen in that species. The surface of the specimen is without markings of any kind save on the small end of the visible volution where some traces of minutely granu- lose lines are to be detected. Greatest diameter 18 mm.; transverse diameter 13 mm.; width of aperture 11.5 mm.; central bight of same 8 mm. It is possible that this is not distinct from the Bellerophon morrowensis described by Miller and Dyer from about the same horizon in Ohio. If they prove to be the same then their type specimen must be considerably crushed since it is described as "lenticular in form" and with the "dorsal side sharply angular." Under the circumstances we are obliged to consider our species as distinct. Formation and locality.— Richmond groups of the Cincinnati period, near Spring Vailey, Minnesota. Collection.— E. O. Ulrich. PROTOWARTHIA OBESA, n. sp. (Ulrich.) PLATE LXIII, FIGS. 45-47. Shell rather large, obese, the greatest diameter between 30 mm. and 45 mm., the greatest width of the aperture usually about one-tenth less; volutions ventricose, almost uniformly rounded, the center of the dorsum just appreciably elevated; umbilicus covered by the reflexed or thickened lip, small in the cast; aperture transverse, the central hight somewhat greater than half the width; apertural lobes rounded, sinus very broad and comparatively shallow, but the depth seems to be somewhat variable; test thick. The specimens are all casts of the interior and exhibit merely obscure traces of the lines of growth. A small patch of the shell on one of the specimens shows that the growth lines are fine and unequal, and that revolving lines are wanting. Two or three broad transverse furrows cross the back of each of the five specimens before us. These furrows were produced by thickened bands upon the inner side of the shell, passing almost directly from side ; >.\ s< •"' i to side,— at any rate they are much less sinuate in the middle than is the margin of theaperturr The ventricose volutions, shallow sinus and broad transverse furrows (on caste) are tin- -li-tiurtive features. Very young specimens may look much like the largest <,f /'. },,-n:,lnt,i. luit the adult form, which is all we have seen, is certainly quite distinct. /'. obesa should be compared with the British /'. bilobatu Sowcrby sp. (see lig. ;5. p. sf»'.») because it is, according to our opinion, the nearest known American representative of that much (mis-) quoted species. And still the American form is distinct if only for the reason that the apertural sinus is deeper in the bilobata. Formation and locality.- Lower beds of Ui. Tr.'nt<.ii k'ruup. Bunfinand Danville, Kentucky. CMHNM.-B.aUM*. Gemi* Ti: I i:\NOTA, n. gen. ftur>initru crossing from line to line. This style of sculpture, excepting that it is much finer, is essentially the same as that marking the H. lindxleyi section of /•';<•••/«(./. We attach great weight to this point and believe that it proves our association of the genus with the Huraniiiltr to be well fouml»"l. The four revolving dorsal ridges, which we regard as the principal peculiarity of the genus, are always distinctly developed on the inner volutions. In T. sejxar- 876 THE PALEONTOLOGY OF MINNESOTA. [Tetranota. they continue also over the outer volution quite to the margin of the aperture. In T. bidorsata and T. wisconsinensis the two central ones become more prominent toward the aperture, and on casts of the interior usually appear as a broad and more or less flat-topped single ridge. In the former the lateral ridges, though much less distinct, are still distinguishable in the outer half of the last whorl, but in the latter not a trace of them is to be seen on any part of the outer volution of casts of the interior, the only condition ki which the species is known. The same is true of T. obsoleta with the addition that the double central ridge also is much less developed than in the other species. The unusual width of the slit-band, which lies between the two central ridges and is more or less concave — never much so, — is another important characteristic, though not entirely confined to Tetranota. Briefly the new genus differs from all the other genera of the suborder in the possession of four dorsal ridges. In most other respects we find that Tetranota agrees closely with Bucania and Megalomphala. Still there are some good additional differences. Thus, Bucania has a narrower slit-band and longer slit, besides stronger revolving surface sculpture, while Megalomphala agrees in all respects with Bucania excepting that it has no revolving lines. The Cambrian Owenella, though reminding one in a general way of Tetranota, is distinguished at once by the absence of a slit- band. It is scarcely necessary to extend our comparisons to such widely different types as Bellerophon, Bucanopsis and Protowarthia. As to the shells of Euphemus, about which genus we have already (see page 856) expressed the opinion that it is an atavistic type of Carboniferous Bellerophontidce, they have no umbilicus and their apertures are even less expanded. Further, they have an inner lip slightly thickened laterally and its central portion, which bears more or less numerous revolving folds, is spread as a thin sheet over the inner volutions and part of the outer. These folds may recall the ridges of Tetranota, but are in reality quite different, being a feature of the ventral side of the shell in the one case and of the dorsal side in the other. Koken (loc. cit.) connects several Silurian and Devonian species of Europe with T. bidorsata. In this he has doubtless committed an error, while his proposal to use Meek's Bucanella for the group seems to us quite unwarranted. In the first place hi.s Bucanella esthona and B. stibtriata Krause sp. (we are not sufficiently acquainted with the others to include them in our opinion) are not congeneric with T. bidorsata, being without the characteristic dorsal ridges, while they have uninterrupted straight revolving lines which do not occur in a Tetranota. Where the subtriata belongs is most difficult to say just now,* but of the esthona we may say that it is kept out of • We refer to this species again In our remarks on BucanojMl*. I»A. T.ir.noi* MdofMta 1 Bucania by its wide -lit-!>and ;in«l -traight revolving lines, while the first character, together \\itli it- different (Hn<;inin-\\\n>) aperture excludes it from liuranopgis. Having to describe a similar species from Minnesota, we have concluded to establi-li a new genii-. /\'"'<;im, for their especial benefit. The vertical range of three of the species of Tefninnfn is more extended than innal witli II»H(U<;;I. T.obsolda occur- in tlu> Vanuxemia bed of the Stones Kr.er group, in the t 'tenodonta bed of the Mlack Kiver gronp, and reappears; appar- ently very slightly modified, in the Utica group at Cincinnati: '/'. 1>\iilnrxntn\ and the others are still farther removed. Good adult specimens cannot be confused, only the young being sufficiently alike to render separation difficult. Formation and locality.— Stoat* Kiv.-r trroup (Vanuxemla bed), Minneapolis, St. Paul and Cannon Palls. Minnesota: Beloitand Jan. ^ ill.-. Wis.-..n*in: ln\.,n. III.; Lebanon and Lavergne, Tennessee. Tren- ton gruup (Fuslsplra bed), Kf Union- county, Minnesota. O9Bert4 Ulrlch. 880 THE PALEONTOLOGY OF MINNESOTA. [Tetranota obsoleta. TETRANOTA OBSOLETA, n. sp. PLATE LXV, PIGS. 19-23. This species differs from T. bidorsata in several obvious respects. Chief among these is the fact that the revolving ridges are much less developed, especially on the last volution, the centro-lateral pair being quite obsolete except on the inner volutions, while even the central pair does no more than to merely maintain the same strength relatively that it held in earlier stages. Interior casts of mature shells exhibit a broad, comparatively low and more or less distinctly grooved central ridge, beyond which the surface is first shallowly excavated and then gently convex to the lateral boundaries of the volutions, which again are not angular but narrowly rounded. The exterior of the shell looks the same, only the ridges bordering the slit-band appear thinner and sharper. Continuing our comparisons with T. bidorsata we find that the umbilicus is smaller and less abrupt, and the volutions more rounded on each side and therefore elongate-reniform in cross-section. The form of the aperture and the surface markings seem to be very nearly the same in the two species. The latter were easily abraded, and on only a single specimen, — it is from the Utica group at Cincinnati and doubtfully referred to the species, — have we been able to make them out at all. In this specimen they are imperfectly preserved near the aperture. Here they appear to be somewhat finer than in T. bidorsata and each seems to have borne a row of minute prominences. It is scarcely likely that any one will ever find it difficult to separate T. obsoleta from T. sexcarinata, the apertural sinus being deeper and the revolving ridges even more prominent and constant in that species than in T. bidorsata. The largest specimens of T. obsoleta occur in the Vanuxemia bed of the Stones River group at Minneapolis. One of these has a hight of nearly 30 mm. The others range from this size down to about 15 mm. The average hight of the specimens from the Black River and Trenton groups is less, being only about 15 mm., while in the largest it did not exceed 20 mm. In the Utica group however the average was increased again to almost 20 mm. Formation and locality.— Stones River group (Vanuxemia bed), Minneapolis and St. Paul, Minne- sota; Janesville, Wisconsin. Ulack Kiver group, Mercer county, Kentucky; (in Ctenodonta lied) Chatfleld and six miles soiitli of Cannon Falls, Minnesota. Trenton group (Kusispira bed), Goodhue couty, Minne- sota. Utica group at Cincinnati, Ohio, and localities in the vicinity of that city. Collections.— Geological and Natural History Survey of Minnesnta: E. O. Ulrich. Museum Register, Nos. 610, 5109, 7294, 7405 TltTKANol \ \\IM-ONSINKN8IR WllUliclil. MJB. : vwnmn>i'n.>i'> Win 1 1 IKI.H. :-> Ann. Rept Oeol. Surv. WIs., p. 76; alao 1882, Oeol. Sunr. WU., TO). Iv, p. 223, pi. vi, fig*. 15, 16. ••ato.-t lii^lit (if >hfll varying in the material l>efore us from s mm. to 37 mm.; closely coiled for the genus, subglobular in form when young, but becoming strongly i. with the last volution less inrolled and the lips greatly expanded laterally | :i:it al-o above (yet not materially thickened) in the adult form; in the latter the outer lip is deeply notched in the middle, the notch spreading anteriorly more slowly than u-u.il. the lobes on each side rounded-triangular in outline. Dorsal periphery of casts with a broad, revolving band, the top of which may be slightly convex, Hat or concave, the whole increasing in elevation with age; on each side of the central band the inner volutions (as seen in fractured specimens) have tir-t a concave space and then a ridge, but these pertain chiefly to the exterior side of the shell, being only in rare cases, and always with difficulty, distinguishable on casts: inner volutions elongate-reniform in section, outer volution more triangular; umbilicus comparatively small, the width only about one-fifth of the greatest •<•„;»> ;/n that the mouth i- abruptly expanded, but in tin-; doubtless he was influenced by hi- /. which now is not a Ilwinin hut a X'il}'ingostoma. The name of the genus was most probably inspired by the same species, and if it bad been customary at that time to designate the type of a genus his 884 THE PALEONTOLOGY OF MINNESOTA. [Bucanfa. choice would, we believe, have fallen upon the expansa, — and it would have made a good type of a good genus. But, since Roemer has described a genus that will include the expansa, and both Waagen and Koken take B. sulcatina, the first species following Hall's description of the genus, as the type, — a course that is fully justi- fied,— it would not be good policy, and only add to confusion where there is too much already, if we were to revert to what evidently was Hall's original intention. Nor can we blame either Roemer or Waagen for overlooking or ignoring his intention, since in the absence of a more complete knowledge of B. expansa than was furnished by Hall, they would not have been justified in departing from the rule which, when the type is not designated, gives that rank to the first species following the generic description. As we are all agreed to adopt B. sulcatina as the type and to restrict the genus to species having essentially the same characters as that species, the first thing to do is to determine exactly which are the essential peculiarities and which are not. This may not have been possible for either Waagen or Koken, and we are probably the first having sufficient material, both in the way of species and individ- uals, to do it in an approximately satisfactory manner. The amended description of Bucania given on page 850 rests on no less than twenty Lower Silurian species. These show that the umbilicus is nearly always large, certainly never small. The outer lip has a broad V-shaped sinus and a central slit, the slit-band is narrow and slightly elevated, flat, or channel-like. The surface markings run in two directions, transversely and spirally, and both sets cross the volutions obliquely from the umbilicus to the slit-band, the degree of obliquity of the spiral lines depending iipon the rate of increase in size of the volutions, being greatest in those in which the expansion is the most rapid. The transverse (growth) lines are oblique because they curve in directions parallel with the margin of the aperture. But the feature of the surface sculpture that deserves the most attention, and this applies to the Bucaniidce as a whole, is that the intersections of the two sets of lines are nearly always rectangular. According to the remaining characters, the species fall into two groups, the first or typical section, containing the type of the genus and seven other species, being characterized by a thin shell, very broad umbilicus, slowly and gradually enlarging depressed volutions, relatively wide yet not expanded aperture, thin lips, and long slit. In the second or B. lindsleyi section the shell is thicker, the umbili- cus smaller, the volutions enlarge more rapidly and are higher, the inner lip is thicker and slightly reflected on each side, and the slit shorter. These differences will be better understood after a comparison of figures 1-12 with the remaining figures on plate LXVI. ::intf tli»> -lit. perhaps not OD6 specimen in ;i thon-aiid of the li. sulcntina section preserve- it entirely. As a rule the delicate apertural portion of the shell i- i.niki-n .iu.iv quite to the posterior end of tln> -lit. In tlie other section a complete aperture i- a much more frequent occurrence, l>oth because the slit is shorter and the » hf 11 -tronger. It will l>e noticed that the characters brought out in the foregoing paragraphs are different from those pertaining to much the greater part of the genus as defined A'aagen and Koken. They derived their ideas of the genus chiefly from Upper Silurian, Devonian and Carboniferous spirally ribbed species, which with few exception- (none of them true liucairia) will fall into the genus that we propose to call , M.S. It is to be noted, however, that Koken with his usual acumen draws attention (op. ••',(., p. 380) to differences in the aperture and surface sculpture between the " ^nlr,itinn-\\\<\\^" and the Devonian and Carboniferous species. I iifnrtiiii.it. 'ly ho did not, or for want of material could not, carry his comparisons to their logical conrln-ion. According to our opinion I>n<;inia, as here restricted, is (1) strictly a Silurian genus and possibly not even represented in the Upper Silurian, (2) it is the stock from which .^nlpingostoma. and later Tremanotus, was derived, and (8) it is not genetically related to AV- //<• •/««'.«. In support of the first statement we have the that while the twenty known Lower Silurian species fit closely together, not one of the succeeding forms could be included without materially altering the generic diagnosis. The truth of the second statement is but too apparent to those who are obliged to discriminate between imperfect specimens of associated species «{ S'llfrinnnstoma ami />'i«. /„/,/. Casts of the former from which the abruptly expanded aperture has been broken away, and on which the dorsal fissure is not clearly represented, are most difficult, if indeed it is at all possible, to separate from casts of liii>-.vto»i« here since we shall do so quite fully some pages hence in our remark- on that p-nns. The third statement refers t< Tlii- ^enn- was evolved, we think, not from Hn"inia but from Ibllfrophon. No better description of the genus could be given than that which says that it includes species agreeing in all respects with l:Jl.;-ujihon excepting that t Ill-s- hare revolving stri.r which, with tin- transverse lines, produce a cancellated sculpture. Without the revolving lines Huranopsis would be nothing more or less than /.V//<'/M/I//O;/. Not so, however, with /. -ince that genus would still IH> distinguishable. Again the spiral lines are not the same in numni-i and hucanopsis, bein^ -tr.uj/lit in the latter and not oblique nor wrinkled nor ever interrupted as in the former. 886 THE PALEONTOLOGY OF MINNESOTA. IBucanla lialli. Among the species of the B. lindsleyi section it is common to find that the obliquely revolving lines are sharply interrupted by the regular development of lamellae whose wavy anterior edges are decidedly elevated and parallel with the margin of the aperture, of which indeed they represent previous stages. The effect is considerably as in the otherwise widely different genera Conradella and Cyrtolitina. The surface sculpture of Tetranota also, though of a finer pattern, is essentially of the same type. Of the species originally referred to Bucania by Hall,* B. sulcatina and B. inte.rta are typical of the genus; B. punctifrons Emmons sp., though provisionally retained in the genus, is a peculiar form having a reticulated surface sculpture very much like that of Cyrtolites ornatus; B. rotundata, if correctly described, belongs to Megalom- phala; B. bidorsata is the type of our new genus Tetranota; and />'. r.rpunsa belongs to Salpingostoma . BUCANIA HALLI, n. sp, PLATE LXVI, FIGS. 4-8. Shell 20 to 30 mm. in hight, consisting of about three and a half depressed volutions; volutions increasing in size gradually to the aperture, gently convex on the back, subangular at the sides, slightly concave in the middle third of the ventral part, acutely subelliptical in section, and about twice as wide as high; umbilicus large, deep, well defined, with flattened slopes, and equalling nearly two-thirds of the greatest diameter of the shell. Aperture transverse, the hight usually not exceed- ing half of the width, acutely subelliptical, angular and narrow at the lateral extremities, and slightly indented below by the preceding volution; outer lip very broadly sinuate, medium slit not fully seen, probably a half volution in length. Sur- face with subequal revolving wrinkled ribs, averaging about seven in 5 mm.; the total number increasing with age by bifurcation and interpolation; in the umbilicus, especially behind the anterior half of the last volution, the ribs are decidedly oblique, but on the back of the volutions they are nearly longitudinal; at intervals of 2 or 3 mm. they are interrupted by more or less distinct transverse lamellae, running obliquely backward from the edge of the umbilicus to the slit- band which they join at an angle of about 65'. Slit-band narrow, in some specimens appearing as slightly elevated; in others the center is excavated. Casts of the interior are quite smooth. A small specimen is 20 mm. in hight; the aperture is 15.5 mm. wide and 7.5 mm. high; the greatest width of the inner volution (at edge of inner lip) 5.5 mm. The surface markings are not perfectly retained by any of our specimens. • Pal. New York, vol. I. 1847. 3TBOFODJ Ku.-»n[» One seems to show obscure traces of very fine spiral lines between the stronger ones, and it is pos>il>le that Mich line- will he found on the perfect shell. .(/// i- i-li.-ely related to B. suloi/inn. hut that species has wider volutions, and. although they do not enlarge any more rapidly, the proportional width of the aperture i> greater. being quite equal to the hight of the shell, wliirh is not the case in the pre-ent species. The whole form of that shell is also more globose. Ii. in ia a smaller and lurr-mer shell, and has more closely arranged revolving ribs and less depressed volutions. \\ •• have four fragmentary casts of the interior, collected in the Fnsispira bed of (ioodhue and Killmore enmities. that may belong to this species. formation and lotaUty.— Stone* River group. Cannon Falls, Minnesota (six specimens); Black River i-ii{ht •>!•• UoUtttim*,-*. O. Dlrich. \V II BCCANIA MINNEHOTENSI8, n. Sp. I'LATE I.XVI, FIGS. 9 and 10. This is associate*! with and probably closely related to H. //•////. Still there should be no difficulty in distinguishing the two forms since this grows to much greater size and yet has the same number of volutions. The last whorl especially enlarges rapidly, though relatively more in bight than in width. The sutures are deeper and the slope of the umbilicus, taken as a whole, is not so flat. Still the flatness of the slope increases with growth until on the last third of the outer whorl it has become decidedly concave; causing the sutural portion to appear swollen. The surface markings seem to be about the same in the two species. Formation and locality. — Yanuxemla bed of the Stones River group, Goodbuc county, Minnesota. CWfcdi.rn.-E. O. Ulrica. Hn-AMA 1MMON8I, n. 8p. i.xvi nog. i-i. This -peries ditler> from /;. linlli, which it resembles closely, in being smaller and in having on the whole narrower yet more speading volutions. The volutions are more rounded in the uml>iliru«. causing the suture line to be deeper. The latter is peculiar in being deepened at regular intervals by the development of short, wave-like dents in the ventral side of the volution-, similar dents are to be seen also on the sides of the volution in the Fountain specimen-, hut they cannot be seen on the even better preser \. i T.-nnessee shell. These sutural indentations dis- ii-h the species not only from /;. lialli but from the even nearer H. inttsta and all the other species now known of the genus. In a specimen 18 mm. high, the THE PALEONTOLOGY OF MINNESOTA. LBucania elliptlca. width of the last volution increases from 5 mm. to about 17.5 mm. The hight of the aperture is about 10 mm. .Formation and locality.—'1 Central limestone" of the Stones River group, near Murfreesboro, Ten- nessee. Vanuxemia bed, Cannon Falls, Minnesota. Black River group (VCtenodonta bed), near Fountain, Minnesota. Collection.— E. O. Ulrich. BCCANIA ELLIPTICA, «. Sp. PLATE LXVI. FIGS. 11 and 12. Of this species we have only three casts of the interior, and all are more or less incomplete. The best is figured on plate LXVI. In this, as in the others, the apertural portion is broken away quite to the posterior end of the slit. In the figured example the last volution appears as though it had been free and possibly expanded at the aperture, in which case we would have to call it a Salpingostoma. But the slight expansion shown by the specimen is most probably the result of crushing. The volutions, as far a sobserved, are elliptical in cross section and enlarge slowly, the last in width from 6 mm. to 14 mm. On the whole the cast of the interior resembles B. halli U. & S., B. emmonsi U. & S., and B. intexta Hall, the last in partic- ular, but a distinct species is indicated by the rounded instead of angular sides of the whorls. Detailed comparisons with the species named will bring out several other differences. In the Kentucky specimens the volutions are less convex in the back than the Minnesota type of the species, and it is possible that more perfect material will prove them to belong to a distinct species. Formation and locality.— Lower part of Fusispira bed, Trenton group, three miles south of Cannon Falls, Minnesota; base of Trenton or top of Black River group, Mercer county, Kentucky. Collection.— E. O. Ulrich. BUOANIA 8UBLATA, tt. Sp. PLATE LXVI, FIGS. 16-10. This is a small subglobose shell, with wide volutions, broadly rounded on the back, flatly sloping in the umbilicus; and sharply angular on the sides. The umbil- icus is sharply defined and deep, but comparatively small, its greatest diameter equalling only about half of the hight of the shell. The volutions increase gradually in size to the aperture, are acutely subelliptical in section, about twice as wide as high, and two and a half or three in number; the width of the aperture equals the hight of the shell. The surface markings are preserved on only a very small part of the shell. As near as can be determined they appear to have been about as in B. halli. The slit-band lies between two thin elevated lines and is a trifle wider, and 3TROPODA Buraul* lind^cjrl ] the slit shorter, than u-ual. Hightof shell 1- nun.; width of aperture 12 mm.; of same about »*> mm.: \\nlthot uml>iliciH (',.:. nun.; \vi-lth of inner end of last volution about 4.7 mm. The form i- more globose and the umbilicus relatively smaller than in any of tin- piv.v.img species of the genus. In both of these aspects it remimls one strongly of B. sulcatina, of which it is probably a dwarfed descendant. Formation and loeatfly.— The trpet arv from th<- uj.|--r part ..' th. Tn-nton jrrmip. n.-.-ir Bunrin, Ky. A cut of the Interior, agreeing In ever/ renpect with tin- typo, wasfoutul in thr Ct<>n>Hi<1 i.r tin- •.tain. Minnesota; another (tit. I'.'t i- fr""> '>!.• St«nn". Kivr \ir, at Mlnne- apol. . small specimen, presumably of the uue specie*, occurred In tin- Ku-ispira Nil at Wykoff. Cbtlirtfan.-KO.Ulri Hl.-AXIA I.INMSI.KYl I. I.\\ !. HUH. M ami SS. H»d»fcyi SAFFOUD, 1888, Oeol. of T.-nn., pi. «. , t\^. 3a, b, ,1 and r. (:(c doubtful.) Not described. •11 30 mm. to 40 mm. in hight, the width of the aperture slightly less than the greatest hight of shell; volutions about three, embracing less than a fourth of the next within, rounded on the back, somewhat semi-circular in cross-section, narrowly rounded beneath the middle line of the sides; umbilicus moderately steep, of large size considering the rapid expansion of the volutions, its greatest width equalling about one-third of the hight of the shell; aperture somewhat expanded in the lower part, semi-elliptical in outline, the lateral angles narrowly rounded and scarcely reflected, the center of the lower outline very slightly indented by the preceding whorl; lower lip entire, thickened inwardly; upper or "outer lip thin, the margin sweeping backward to form a broad shallow sinus, the center continuing backward as a narrow slit, the latter having a length of at least 10 mm. in a speci- men 38 mm. in bight. Surface coarsely lamellose, the lamella,*, which indicate the margin of the aperture at previous stages, occurring at intervals on the back of the last volution varying from less than 2 mm. to 4 mm. or more, the average being about 3 mm. Usually the lamellae are crossed approximately at right angles by more or less unequal and irregular ribs, seven to ten in the space of 5 mm., and these again by tine lines of growth. Often the ribs are irregularly broken up and sometimes they combine to form an obscure network reminding one of the surface sculpture of It. i>uncti front Kmmons. (See pi. LXVII. fi^. }|>. Slit-band distinct, -lightly concave, margined on each side by a sharply elevated, thin line; lunula* somewhat unequal luit always clearly defined, rather crowded. This fine shell is readily «l from all of the preceding species of the genu- !'\ th*> i.ij-; : rvpansion of its wliorU. 890 THE PALEONTOLOGY OF MINNESOTA. LBucanla rusatina. Formation and locality.— Trenton group (Middle Nashville), DeKalb county. Tennessee. A small imperfect specimen, possibly of this or the next species, occurred in the Clitambonites bed near Cannon Falls, Minnesota. Collections.— Prof. J. M. Safford; E. O. Ulrich. BUCANIA RUGATINA, W. Sp. ( Ulrich.) PLATE LXVI, PIGS. 13-15. Resembles B. lindsleyi closely, but is smaller, the hight of what appears to be a full-grown individual being a trifle less than 20 mm. Of other differences we may mention that the whorls are more tightly enrolled, causing the umbilicus to be appreciably smaller, the transverse markings are relatively stronger, more equidis- tant, closer, averaging 1 mm. apart and appear more like waves or wrinkles than overlapping plates. A slight groove on each side of the slit-band occurs on the specimen illustrated. The other specimens are not in condition to permit us to decide whether these grooves are characteristic of the species or not. At any rate nothing of the kind has been observed on good specimens of B. lindsleyi. Formation and locality.— Upper part of Trenton group, near Burgin, Kentucky, Collection.— E. O. Ulrich. BUCANIA NASHVILLENSIS, n. sp. (Ulrich.) PLATE LXVI, FIGS. 36-40. This species is based on six specimens received from Prof. J. M. Safford and supposed by him to belong to his species lindsleyi. A careful comparison with the original type of that species, good figures of which are given on plate LXVI, proves that they represent a closely related yet distinct species. In the first place the volutions expand more rapidly, two and a half turns making as large a shell as three whorls in the lindsleyi. Next the umbilicus is smaller and more abrupt, the sides of the volutions being more sharply rounded. Again the dorsum is more prominent along the central line, causing a more or less decided flattening of the dorso-lateral slopes. The slit-band also, instead of being sunken, is slightly raised. Finally, as regards the surface markings, the transverse lines are much less regular, and crowded rather than distant, while as a rule they would scarcely be described as lamellose. They are also much less distinct except near the aperture of large specimens where they are strengthened and emphasized, as usual with old shells, by irregular wrinkles. The oblique revolving lines also are little more than half as strong, while in the umbilical cavities, where these lines are usually very conspicu- ous in Saflord's species, they are scarcely distinguishable. After adding to these differences that the shell of B. nashvillensis is thicker, we believe we have given ample reasons for the creation of a new species. STROPODA fr»nkforl«Mta.l >Vrm/i'».. • it-.i, nnm|,, [V K:iU> '-..unly, and ,*WU.-Pr,,f .1 M Saffur.l: K. O. flru-li. I'.i.-ANIA HRANKKOKTKNS1-. //. >/'. (I'lrirll.) I l.\ . I K1OB. Tliis species is related to both />'. //«'. nl>tusely angular. Still, where good ventral - ran l>e compared (see plate LXVI, figs. 32 and 37), showing their different im nit h- aii.l the more rapid lateral expansion of the outer volution of II. naxIn-HUnsis, a glance -liould suffice to separate them. Formation and locality.— Near Uip of Trenton k'r'.np. Frankfort, Kentucky. CbUtrftoit.-K. O. Ulrlch. KM \M\ 8UBANOULATA, W. «/). (Ulrich.) PLATE LXVI. rioa. »-». In this well marked species the dorsum is obtusely angular, the slope of the -in fare from the slit-band to the edge of the umbilicus somewhat flattened, and the -harply rounded or subangular, these features imparting a widely triangular, perhap- it would be better to say rhomboidal, section to the volutions, which of itself i> Mittirient to distinguish the species from the associated H. rugatina. Con- tinuing our conipanxm- with that species, we find that the surface markings, though similar in pattern and strength, are not so regular, and the umbilicus is a little •r aii'l better defined, while the slit-band forms the flat summit of a low keel fl i>f a smooth groove. Both n.frnnkfortensis and K. nashvillensis are probably -ly related, though readily distin^ni-hed by their greater size, relatively smaller umbilicus, and more rapidly enlarging volutions. At maturity, however, the ventro-lateral angles are more abruptly expanded in 11. subangulata, giving the aperture a more broadly triangular form than i- the case in either of the larger species. It is to be borne in mind, further, that these large shells require no more turns to attain their full growth than do specimens of the present species less than half their size. In the largest of eight specimens the hight is about 23 ram., the width of the aperture about 25 mm., the hight of same (in a side view) 17 mm. In a Miiall specimen the same measurements resulted respectively in '.» mm., '.) mm., an. I ". mm., 892 THE PALEONTOLOGY OF MINNESOTA. IBucanla micronenia. showing that the aperture is relatively larger in adult examples. The small specimen, which is one of several, was at first believed to be distinct, but a careful comparison of the whole series resulted in the conviction that the small examples were merely immature. Formation and locality.— Upper part of Trenton group, Mercer and Boyle counties, Kentucky. Collection.— E. O. Ulrich. BUCANIA MICRONEMA, tt. Sp. (Ulrich.) PLATE LXVI, FIGS. 26-29. Of this form we have but a single example. Although closely resembling B. sublata, B. lindsleyi and B. rugatina, in one or another feature, we are fully persuaded of its specific distinctness. The specimen, which has the appearance of being mature, is so much smaller than the second of the species mentioned that further comparisons with it are probably unnecessary. As to B. sublata, the present shell has it volutions narrowly rounded on the sides instead of sharply angular, its aper- ture is relatively larger, and its surface markings, which are not visible to the unassisted eye, are much finer. Compared with B. rugatina, with which it was found, its volutions expand more rapidly, giving a wider aperture, and its surface markings are much finer. Besides the transverse lines are much less distinct and not wave-like, while the lines running in the opposite direction, of which there are about five instead of two in 1 mm., are not only finer but more continuous, appearing like irregular wavy, knotted lines, running obliquely forward from the umbilicus to the slit-band. Formation and locality. — Near top of Trenton group, Danville, Kentucky. Colkction.— E. O. Ulrich. BUCANIA SIMULATEIX, n. sp. (Ulrich.) PLATE LXIII, FIGS. 48 and 49; PLATE LXVII, FIG. 45. Shell large, known from casts of the interior only. These consist of three or four comparatively slender and loosely coiled volutions, leaving a large umbilicus in which all the inner whorls are clearly exposed. Volutions somewhat reniform in section, narrowly rounded in the ventral third of the sides, the ventral surface gently concave, the dorsal part of the section nearly semi-circular. Last volution obtusely carinated, with the dorso-ventral diameter increasing toward the aperture more rapidly than is the case with the inner volutions, the hight and width of the whorl just behind the aperture being about equal, while at the smaller end the two dimensions are respectively about as three is to five. Aperture somewhat triangu- lar-ovate, wide below, the expansion taking place chiefly at the lower part of the » < sides In tin- ca-t tin- expansion appears very abrupt )>ut doubtless it is much less -.. in the shell itself. Inner lip slightly reflexed at the side*, thick centrally; outer lip bn»;ully and deeply sinuate. Surface markings unknown; slit long. The best -.[.••.-mien -ecu has the following dimensions: entire hight 46 mm.; hightof aperture •_".' nun.; greatest width of same 33 mm.; width and hight of last volution just U-hiii'l the aperture about 23 mm.; hight and width of inner end of same 5 and 8.5 nun. respectively; greatest diameter of umbilicus about 23 mm.; length of slit about 31 mm. The hight in this species is relatively greater than in R frank fort ensis, which we consider as more closely related than any of the other species. The aperture also is less nearly triangular, the apertural margin, as seen in a side view, less uniformly curved, the umbilicus larger, and the volutions more evenly rounded on the back. The next species, Ji. crassa, is a more closely coiled and heavier shell, having, therefore, also a smaller umbilicus. The form of the mouth and sinus is also different. Casts of If. sinmlatris resemble those of the associated Salpingostoma richmondensis in a remarkable degree. For comparisons see description of that species. Formation and locality.— Richmond croup of the Cincinnati period, Richmond, Indiana. CWfcrtwn.-E. O. Ulrich. l'.lr\XIA CRA88A, W. «/>. I'l.ATK IAVII. KI08. This species, though closely resembling H. fmnkfortensis and ti. nnshv illensis in many respects, will be distinguished almost at a glance by its uniformly convex instead of subangular dorsum. This difference, in conjunction with a greater relative width of the whorls, causes the aperture to be proportionally wider. The lower lip also, though strong, has a longer slope and its surface is less convex. The umbilicus is somewhat smaller and more abrupt than in H. frankfortensis, and the shell more globose. The specimen figured has suffered considerably from maceration, the slit-band and all, excepting the strongest of the surface markings, being quite obliterated. On two other specimens, neither as complete as the one illustrated, there is a low, yet well delined, rounded dorsal ridge, and in one this is accompanied On each side by a faint furrow, while anteriorly it terminates in an open slit about 17 mm. long. Whether this dorsal ridge was originally flat or concave on the summit, and bore lunul;i>. we are unable to say. Still, it is to be expected that such a condition obtained on the perfect shell. As to the surface markings, what remains of them indicates a sculpture similar to that shown in our figures of It. lindsleyi and /;. nashvillensis. (See plate L X V I . » 894 THE PALEONTOLOGY OF MINNESOTA. [Bucania slngularis. The shell in this and the species with which we have compared it is unusually thick for the genus, especially on the ventral side of the volutions, and casts of the interior must look very different from the shells themselves. We have not, how- ever, seen any casts which seemed at all likely to belong to either. Formation and locality. — From the uppermost beds of the Richmond group, near Richmond, Indiana. Collection.— E. O. Ulrich. BUCANIA SINGULARIS, ». Sp. (Ulfick.) PLATE LXVI, FIG. 47. This species is remarkable for the prominence of the transverse lamellae and for the unusual length of the intervals between them. They appear to be especially thick and prominent on the lateral portions of the back. The slit-band is elevated and, like the lamellaB, shows rather distinctly on the cast of the interior. Aside from the lamellae the whorls are rather broadly rounded on the back, and narrowly rounded on the sides, leaving an umbilicus, the greatest width of which equals about one-third of the entire hight of the shell. The mouth is transverse and somewhat elliptical in outline, the inner lip thick, cut out in the middle and with a compara- tively narrow prominence immediately above the excision, the outer lip with a very wide angular sinus and a narrow open slit at least 15 mm. long in a specimen 30 mm. in hight. The surface markings are obscured by a delicate bryozoan which we failed to remove satisfactorily. As near as we can make them out they appear to consist of (1) lines of growth, and (2) of elevated points arranged in decussating series or of lines running rectangularly across the spaces between the elevated edges of the lamella). Similar variations of sculpture have been observed in B, lindsleyi. Though clearly a Bucania, we are in doubt about the specific alliances of this shell. Selecting from the species described in this work, B. crassa and B. lindsleyi (Safford) appear to be the nearest. Still, the differences are so manifest that com- parisons are deemed quite unnecessary. Formation and locality.— Upper beds of Trenton group, Nashville, Tenn. Colkction.— E. O. Ulrich. BUCANIA PUNCTIB'RONS Emmons. PLATE LXVIl, FIGS. 41-44. Bellerophon puncliff,,^ KMMUN-S 1842, Geol. Rept. 2nd Dist. New York, p. 392. liucrtnia pitnctifrons HALL, 1847, Pal. New York, vol. 1, p. 187. Shell rather small, probably not exceeding 20 mm. in hight. Volutions three or three and a half, rounded on the back, subangular on the sides; umbilicus large, • >PODA. 1 -. idth Miinewhat ui-eatcr than half tht> lii^ht of -lit-ll; api-rture -lightly widrr than hitfh. -ubpentagonal. In a transverse section the volutions are semicircular in the n croup, at several localities in New York and Canada. The spori- m->n* u[H.n which \h<- :I|KIV.- r|.-s<-ri|itii>n i- baaed were found in the lower part of the group ("Orthls bed") near Nashville, Tennessee, by Prof. Jas. M. Safford. !'•!• \M.V NANA, n. xp. (l'lricli.) ri.\TK i.\\ : 44. II small, ID mm. or less iii bight, volutions two and a half or three, each embracing more than half of the preceding turn, expanding gradually and with moderate rapidity quite to the aperture, reniform in cross-section, broadly rounded on the dorsum and rather narrowly where the surface descends into the umbilicus; the latter is -mall, equalling only about oin'-fonrth of the greatest diameter of the shell; aperture rounded when perfect, usually appeal -ing more or less reniform, scarcely expanded, its width equalling about four-fifths of the hight of the shell; lips thin. the outer one with a central slit probably less than J nun. in length, the sinus also being unusually shallow, the inner lip prolonged slightly on each side and forming 896 THE PALEONTOLOGY OF MINNESOTA. [Bucania peraouta. a very thin callosity over the back of the preceding whorl. Surface sculpture consisting of sharp, regular, rather closely arranged and but very little curved striee » of growth, and exceedingly fine, obliquely revolving lines, the latter obscure on even the best specimens. Slit-band raised, distinct, narrow, concave, bordered on each side by a sharply elevated thin line; lunulae not very distinct. Out of eleven speci- mens the largest is about 10 mm. high, the smallest about 5 mm. In an average shell the bight is 7.0 mm.; the diameter at right angles to the bight 5.2 mm.; the width of the aperture 5.5 mm.; its bight about 5.0 mm.; greatest width of umbilicus about 2.0 mm. Variety SOBPATULA, n. var. (Ulrich.) PLATE LXVI. FIGS. 45 and 46. Under this subordinate name we propose to classify provisionally three speci- mens found in association with B. nana, but differing in several respects from the typical form of the species. Thus, the aperture is wider, its width fully equalling the greatest diameter of the shell. Then the umbilicus is narrower, being almost closed. On one of the specimens the surface is in good condition, but we failed to notice any evidence of the delicate revolving lines occurring on no better preserved examples of B. nana. If it could be shown that these lines are always absent, then we would favor a removal of the supposed variety to the genus Bellerophon, in which case the varietal name should be promoted to the specified rank. We may add that we have before us three casts of the interior from the lowest beds at Cincinnati, Ohio, that look very much as if they might belong to this variety. We are not satisfied that either the variety or the species is a true Bucania. The umbilicus is too small and the sculpture not what it should be. The markings of B. nana are considerably like those found on Tetranota bidorsata, but the nana is most certainly not a Tetranota. We suspect that the species and variety are close relatives of two Clinton group shells described by Foerste as Bellerophon or Bucania exigua and fiscello-striata. In the surface markings, the last reminds one also of Bucania punctifrons. All five of these forms require further study before their positions can be established. Formation and locality.— Upper part of Trenton group, Mercer county, and Covington, Kentucky. Collection.— E. O. Ulrich. BUCANIA PEKACUTA, n. sp. (Ulrich.) I'I,ATK I. XV I. FHiS. M itml •,',:,. Of this remarkable shell we have seen only a single imperfect specimen which was collected by Prof. J. M. Saflord and kindly sent to one of the authors for ,1 description. When entire it must have looked like a gigantic Cyrtnliffs, and we were at first inclined to place it in that genus. Closer investigation, however, -.bowed that the -mface markings were in reality different and the shell too thick for a Ci/rt"lil>-<. while in both respects it proved to correspond with some of the Bucanin lindsleyi group of species. The curving transverse folds of the flattened dor-al slope- are represented in other species of Hn<-'. nashvillensis, figured on the same plate. A view of the aperture of the specimen therefore agrees rather closely, in its lower part, with figure 37 of the plate. But the umbilicus is larger and much more sharply defined than in that species, the sides of the volutions being compressed into knotted keels. These lateral keels are nearly central on the inner whorls in a side view, but as growth proceeded its position became more ventral, the umbilical slope becoming at the same time more abrupt. For the same reason the transverse section of the whorls changes from rhonil>oidal to triangular. Only a small portion of the slit-band remains. This is slightly elevated and flat. Seven or eight of the revolving lines, which as usual are irregularly wrinkled, occur in 4 mm. Formation and toeott/y.— Upper part of the Trenton group, DcKaltt county, Tennessee. Genus SALPINGOSTOMA, F. Roemer. Salpingotlonut, F. BOBMER, 1876, Lethe* Geognostica. Baeania (pan. M M .1 . 1847, Pal. New York, TO). I. ropHon (part.), KM nw .M.l>. Bueania (t TVemanofiu), WIUTKIKLD, 1882, Geol. of Wls., vol. Iv, p. I This genus will include a number of species that most American paleontologists have considered as typical of the genus Bumnln. However, in discussing the latter genus (see page 8S3) we have given our reasons for restricting its use to species con- forming strictly with the type B. sul<-ntinim/w»/<>w« and Tremanotus, and it at the same time explains the 'Ifvelojmifiit of a row nf small openings in the latter instead of a single long slit In Ti-rintinnfuti, namely, the expanded aperture is a periodic development, a new one being formed at frequent intervals. There is, therefore, no narrow limit to the size of the specimen. The expansion is also always very thin, and the old ones were either broken away or reabsorbed, the latter being in our opinion more likely. As in Suljtini/ost'itH'i. the development of each expansion was preceded or accompanied by the anterior closing of the apertural slit, continued growth at last producing a row of openings instead of a continuous fissure. The number of these openings remaining uncovered varied probably according to their sizes and with the species. The only evidence on this point now available is furnished by casts of the interior. These seemed to show that they remained open for a distance equalling about a third of a volution. In this distance, which slightly exceeds the average length of the slit in Sin>j(ix(r>ni>i, different species of Tremanotus show from four to about ten openings. The surface markings of Tremanotus longitudinalis Lindstrom, the only species of tin- gpmis on which they have been observed in a thoroughly satisfactory manner, are on the whole more like those of Bucania than tialpingostoma, but as they are 1'r.K-tirally of the same type in all three genera, they are of but little assistance in referring a shell to its proper genus.* Finally, we wish to state emphatically our conviction that Buamm, Sa/pinyos- and Trtmanotus stand in close generic relationship to each other. The • K..krn draw* KMM IB* dUtlootloa* between the different «urf »<••• viilpturlnxi of » number of European and OM A»»rlp«n 'peclw belonflnc In tfaU connection. j«v If hi* ot»er*aUoM on UM otben arv HUM which prrtaln «o TiimmuMf. they are certainly of Irule value. But w. art pertaap* more Mvera here than Hoe* !• oar opinion Dr. KokcD ha* (Ire* uanoM pral» worth j »od valuable work. B«-aii*e of Iheceneral minute**** and oorrwtn-*. of his obMrnUtoM. aa error *o palpable u the OM be ha. fallen Into with iMpKt to Tnma* • rT«rrii«d nor* than coodeanwd. Where he (ol tbe Idea Ibat the InMrWd* of the aperture In TrmoMfeu I. radially » awl thai "the told* are rmtrloMd to UM Inner .td« tad In no wUe dependent upon the outer .1 . >nd our coapM- •»Mln». It to (Imply not a fact. 900 THE PALEONTOLOGY OF MINNESOTA. [Salpingostoma. buelll. development was progressive from one to the other in the order named. In the first the aperture is never greatly expanded, in the second it flares abruptly at maturity, while in the third an expanded mouth is developed at more or less frequent intervals. The second type was probably evolved in times preceding the Trenton period, but the evolution of the third seems to have been postponed till after the close of the Lower Silurian. SALPINGOSTOMA BUELLI Whitjield. PLATE LiXVII, FIGS. 34-37 and ?38. Bucania buelli WHITFIELD, 1878, Ann. Kept. Geol. Surv. Wis. for 1877, p. 76. Bucania (Tremanotw?) buelli WHITFIELD, 1882, Geol. of Wis., vol. iv., p. 224. Shell of medium size, consisting of about three and a half volutions. The greatest diameter of the shell, just before the development of the expanded aperture, varies usually between 35 mm. and 36 mm., while the width of the last volution at the same point is about 20.5 ram., and its hight one or two mm. less. Volutions appressed, subreniform in section, the hight of the inner ones just a little more than half the width; dorsum broadly convex, the sides narrowly rounded or subaugular, the ventral surface slightly concave where it is in contact with the preceding whorl. Umbilicus large, exposing all the inner whorls, with the sutural line deep. Aper- ture abruptly expanded, nearly horizontal, slightly raised and gently sinuate in front, broadly ovate or subcircular in outline with the hight and width nearly equal, the latter usually a little the greater; average hight about 35 mm. Transverse surface markings (behind the apertural expansion) consisting of fine sharp lines, three or four in 1 mm., and at intervals increasing with growth from 1 to 2 mm., of a stronger wrinkle-like set; both sets sweep backward with very little curvature between the sides of the volutions and the slit, joining the latter at an angle of about 60°; the transverse striae are crossed by nodular revolving lines, the nodes being arranged in such a manner that by changing the direction of the light a diagonal arrangement will become more prominent than the longitudinal. Toward and on the apertural expansion the revolving lines increase gradually in strength, assuming at the same time a radial disposition, while the interpolation of a smaller set produces a distinct alternation in size at the margin. Inner surface of aperture perfectly smooth or exhibiting a few obscure concentric lines. Dorsal slit about 24 mm. long, its edges raised, represented by a narrow rough ridge on casts. Behind the slit an ordinary band, appearing raised because bordered on each side by a narrow groove. In front of it to the beginning of the expansion a similar band; this continues as a gradually diminishing small ridge to the sinus in the lip. GASTROPODA. 901 !*.1|HOIO.I.....» I ..rill. 1 Tin- lateral \ iew «.f a cast of this species given by Whitfield (op. cit., pi. VI, fig. 1:5 1 does not agree with our specimens, the outer thin! of the last volution being niiirh fuller in the figure, and represented as convex or straight almost to the edge of the aperture in-tead of deeply concave. Still, we cannot for a moment doubt that \vi> have r. ally de«-ril.ed the species intended by Prof. Whitfield, since the inajiinty »f them are from the locality which furnished the original types, and all •are precisely like specimens in the museum of the University of Wisconsin labelled in I'rof. SVhittield's hand as Hiic.inix lutrlli. That the figure objected to may not l>e true to nature is indicated liy the fact thatitdoes not agree with his fig. 12 which ated to be of the same specimen. It may be that the specimen is in part a cast <>f the exterior, which would account also for the presence of the radiating i -ilis. Not a trace of the latter is visible on any specimen seen by us that is truly a of the interior. The Mirface sculpture of S. fxpansn Hall sp., of the Trenton of New York, is not well known. I nit casts of the interior are readily distinguished from those of this -;•••'•;••-. the volutions being less depressed, and subtriangular in section instead of Milirenifonn. We have several fragments of a variety or closely related species from the Black Kiver limestone of Kentucky, differing from the typical form of S. burlli, BQ far as the imperfect material will admit of judgment, in having a thicker shell, coarser surface markings, and smaller inner volutions when compared with the expanded aperture which is fully as large as S. buelli. The aperture also is not so abruptly turned outward dorsally. In the last feature it is more like S. expansa hut the specimens are too small for that species and the volutions rounded on the back ••ad of subangular. Since the form is close to S. buelli we may designate it provisional i nfucl.-ifrnsis. The M"'.-ii!»-n represented by fig. 38 on plate LXV1I is considerably smaller than any other of the species seen. The radiating ribs on the apertural uiMon al-u are stronger than they should be in S. buelli. If these differences pro -ant in other specimens they should be distinguished as a variety at lout Formation and locality. — In Minnesota .S. In* Hi is:i rare foMll and BO far known only from the lime- stone* of the Stones Rh • " -. Cannon Fall* and Old Conr-.r, I In Wisconsin, however. It In nut uncommon and continue* Into th- overlying lime* tones of tin- Hlack River group; Belolt and Janenvllle are the principal localities. In Illinois it ...-.-uni at Rock ton and I)|X»TI. VoUettion*.— Geological and Natural II ' mneoota; University of Wisconsin; Charles Schuchert; E. O. Ulrich; W. H. Soofleld. Mutmrn H'gifter, No*. 7293. 7318. ?&644. 902 THE PALEONTOLOGY OF MINNESOTA. [Salpiugostoma sculptilis. SALPINGOSTOMA SCULPTILIS, n. sp. PLATE LXXXII, FIGS. 16-20. Shell scarcely attaining medium bight, consisting of at least three and one-half volutions, the hight, including apertural expansion, about 40 mm. Inner volutions enlarging very slowly, somewhat rhomboidal in section, obtusely angular on the dorsum and more narrowly angular on the sides, the hight and width respectively as six is to ten. Aperture expanding abruptly till it measures at least 30 mm. in width and 28 mm. in hight; anterior sinus very shallow. Umbilicus large, exposing all the whorls. Surface markings forming a coarse network of alternating hex- agonal meshes; an extra thread passes in an obliquely forward and inward direction through each mesh. In the umbilicus the oblique thread is the most conspicuous. About six rows of meshes occur on the small part of the outer volution on each side between the slit-band and the lateral edges. On the apertural expansion the markings increase in strength, though numerous longitudinal threads are interpo- lated as the space to be covered grows larger. Dorsal fissure about 17 mm. long. This species may be related to S. expansa Hall sp., but it is readily distinguished by its smaller size and by the angularity of the back of its inner volutions, these being more rounded in that species (i. e. elliptical or reniform in section). The dorso-ventral diameter of the aperture also is relatively less in that species. The surface ornamentation of S. expansa being as yet unknown, we cannot say how it compares with that of S. sculptilis. Compared with S. buelli W bitfield, it will be found that S. sculptilis is smaller, has different surface markings, and volutions that are not only narrower but rhomboidal instead of reniform in section. Formation and locality.— Four specimens, all from the Fusispira bed of the Trenton group, three from different localities in Goodhue county, and one from Ollie Hansen's farm near Fountain, Minnesota. Colkrtions.— Geological and Natural History Survey of Minnesota; E. O. Ulrich; W. H. Scolldd. Museum Register, No. 7462. SALPINGOSTOMA IMBUICATA, n. sp. PLATE LXXXII. FIGS. 21 and 22. Of this species we have but a single imperfect cast, the greater part of the expanded aperture being broken away. In the remaining parts it resembles S. sculptilis but the whorls are even narrower, the hight being to the width as five is to six and the section broadly subelliptical. The back of the volutions is broadly convex, the sides narrowly rounded or subangular, and the umbilical or ventral slope slightly flattened. The dorsal slit seems to have been at least 30 mm. in length. The shell is entirely gone except in the umbilicus, where, in the suture lines especially, there are remains of very regularly recurring, salient, thin, trans- verse, imbricating lann-ll.i-. seven or eight in a di-tanco of 5 mm. On the dorsal of the shell these lamella: must be much farther apart. Revolving lines are faintly indicated on the back. There is something so suggestive of Tremnnolus tin- -[..-. •!.•- that it is to be hoped that better specimens may soon be Formation and toea/ity.— Richmond froup of the Cincinnati period, near Spring Valley, Minnesota. (MiMMM.-E. « >. Cln 1V.OSTOMA RICHMONDKN8IH, tl. Sp. (UMch.) PLATE I.XVII. KI08. W and «. Shell .-lightly exceeding medium size, the hight, including apertural expansion, 50 to 55 mm.; known from casts of the interior chiefly. These consist of about three -tr.. n- volutions, the inner ones wide, depressed, sharply rounded on the aides, broadly and evenly convex on the back, less convex and with a very slight central • > on the ventral side, the whole giving a transversely elongate subelliptical cross-section, whose width is a little more than twice the hight. I torso-ventral diameter of last volution increasing very rapidly in the outer half, while the trans- verse diameter enlarges very slowly. Just behind the apertural expansion, where the volution is more or less distinctly compressed laterally, the dimensions in three specimens (casts) are as follows: width 22, 23 and 24 mm.; hight 26, 27 and 27 mm. At the opposite side of the shell the volution is about 15 mm. wide and 7 mm. high in all three specimens. The umbilicus is of the usual size for the inner volutions, I >ut for the entire shell it is comparatively small. This is because the angular or narrowly rounded boundary moves gradually toward the ventral side of the volutions, causing the wall of the umbilicus to become more and more abrupt. •lust behind the aperture it is nearly or quite perpendicular, the ventral surface of the volution being almost flat. Apertural expansion abrupt, apparently not very wiilo, with recurved edges, broadly ovate in outline, .slightly narrower above than below. Dorsal slit about •_'" in in. in length, beginning the same distance or some- what more behind the apertural expansion. The slit is represented by a rough (fractured) ridge on casts. Behind it the cast is smooth, but in front of it there is a more or less distinct broad furrow. The surface markings have been observed only on the back of the second volution. Here they consist of about seven irregular revolving ribs on each side of a very narrow elevated slit-band. At intervals of about !.;"» nun. the rilis are interrupted by transverse lamella'. Where they are shown the volution has a width of 7 mm. 904 THE PALEONTOLOGY OF MINNESOTA. [Couradella. Collectors have heretofore identified this species with Hall's Bucania expansa from the Trenton of New York,* but a comparison proves it quite distinct. In the first place, though of about the same size, there is one volution less. Next, the last volution is relatively narrower and higher just behind the aperture, and the latter very differently outlined. Finally, the last volution is nowhere triangular as is the case in the Trenton species. Compared with S. buelli and S. sculptilis the outer volution will be found much larger especially as regards the dorso-ventral diameter. In practice the most difficult perhaps to separate from this species is the associated Bucania simulatrix. Though of widely different affinities, casts of these two species, especially when, as is usually the case, the aperture is imperfect, are very apt to be confused. Still, after familiarizing one's self with certain differ- ences, they may be distinguished almost at a glance. In the first place the volutions of the Bucania are more slender. This difference is particularly striking in an apertural view, the small end of the outer volution, in specimens of the same hight, being at least a fourth wider in the Salpingostoma. In the Bucania again the width of the last volution continues to increase quite uniformly instead of being almost constricted near the aperture. When the latter is preserved the difficulties have vanished, for this part is readily distinguishable. Formation and locality.— Richmond group of the Cincinnati period, at Richmond, Indiana, where casts of it occur rather abundantly. Good specimens, however, are anything but common. Collection.— E. O. Ulrich. Genus CONRADELLA, n. gen. Phragmoiites, CONUAD, 1838, Ann. Geol. Rep. New York, p. 119. Cyrtolites (part.), HALL, 1847 and 1871. MEEK and WORTHKN, 1868. MEEK, 1873. S. A. MILLER, 1874 and 1892. For generic characters and list of species see pages 851, 852. It is strange that this sharply defined genus of shells has been so uniformly confused with Cyrtolites. Aside from the fact that the whorls are similarly coiled in the two groups, there is not a single character in which they are identical. While the typical forms of Cyrtolites have no slit-band and in some cases not even a sinus in the outer lip, Conradella has not only a sharply defined raised band, but an unusually long apertural slit as well. The form of the volutions also is different, the transverse section in the former being more or less rhomboidal, while in the latter it is ovate or obcordate. Finally, the surface markings are not at all similar, •The erroneous identification of this and :i number of other Trenton fossils In the upper member of Hie thread-like line- arranged in .1 reticulate, manner, while in 'In the surf, overeil !.\ >tn>ngly iinliricabing transverse lamella', the raised edges of \\lii.-h are serrat. i. ('ems to us that f',./i/M. /,//,/ is in reality nearer Hucanin than Cyrtolitts. A •ful comparison brings out what we conceive to be important agreement?. Thus, in HuKinlii there i- a r.tther long apert ural slit, a large umbilicus and the whorls increase somewhat slowly in si/e, while the surface sculpture, though differing in • It-tail, is of tlu> -aim- type. Of cour-e. we do not wish to be understood to say that Bttcani'i aii-l < 'onrmlfHn are closely related, nor that there is any difficulty in keeping the two genera -cparate. the strong dorsal keel, less depressed and more slowly enlarging volutions, ami tin- iressa Conrad the transverse imbrications are but little, if at all. oblique, and the dorso- ventral diameter of the whorls the greater, while for C. si mi Us the opposite is true. formation a»d locality.— Ui>\» r parlnf tli.- Hlac-k River group. In Mercwrand Hoylt ..... unties, Kentucky. .— E. O. Ulricb. CONRADKLLA FIMBRIATA, II. Sp. IM.ATK I. XII. FIO. M: PLATK I.XVII. KIO8. 7-10. Shell n«* Kivrr k'r<>ii|i(\ anux.-im Minnesota, and Dlxnn Illinois. Oollectiott.— Geological and y- XinoesoU (about 22 s i«-n« I. O. Ulrlrh '. -].•••.:!.• M] Mu#vm Reguter, Nos. 063, 5110, 8724. 908 THE PALEONTOLOGY OP MINNESOTA. [Conradella triangularis. CONRADELLA TRIANQULARIS, W. Sp. PLATE LXVII, FIGS. 19-22. Shell usually from 15 to 18 mm. in diameter, compressed discoid, consisting of about three volutions; whorls carinate, slightly higher than wide, triangular- obcordate in section, gently convex on the sides, widest and angular below where the surface sinks abruptly into the umbilicus. Surface very rough, the zigzag or serrated lamella; crossing the whorls almost directly, from 0.5 to 1 mm. apart, each with eight or nine folds between the dorsal keel and the edge of the umbilicus; at the latter the lamellae generally turn somewhat abruptly forward. Usually the folds are arranged so as to present obscurely the appearances of revolving ridges. At other times they may alternate in adjacent series. The angularity of the ventral part of the sides of the volutions varies somewhat, the margin of the umbilicus being in many cases very sharp, while in others it would be more truly described as abruptly rounded. In casts of the interior, of course, the angle is never so distinct as in the shell itself. Most collectors of northwestern fossils have identified this species with the New York Trenton C. compressa Conrad, sp. They are, however, quite distinct, the whorls in the New York shell being wider and more uniformly convex on the sides, the umbilicus not at all sharply defined, and the transverse imbrications more distant. Compared with all the known species of the genus, excepting the next, which see, none seems to us so near as C. dyeri Hall sp., a variety of which occurs in the Trenton of Minnesota. Still, C. triangularis is distinguished readily enough from that species, as well as from all the others, by the more distinctly angular character of the umbilical edge. Besides C. dyeri is a smaller shell, with rounder volutions, and more sharply raised keel, while the transverse imbrications are more crowded and the appearance of revolving ridges much stronger. Formation and locality. — Vanuxemia bed of the Stones River group, Minneapolis, Minnesota, Janes- vllle and Beloit, Wisconsin, and Dixon, Illinois; also at Lebanon, Tennessee. Confections. —Geological and Natural History Survey of Minnesota; E. O. Ulrich. Museum Register, Nos. 7292, 7309. CONRADELLA GRANDIS, n. sp. (Ulrich.) PLATE I.XII. FIG. 67; PLATE LXVII, FIGS. 16-18. This species is closely related to C. triangularis but reaches a much greater size, the greatest diameter of one of the specimens being fully 30 mm. Then the trans- verse section of the whorls, which also increase more rapidly in size, is a little different, the dorsal slopes being more convex, the sides less angular, and the IK'.l-ODA. •'"•' U.nr».l.-lU dycrl.l tian-vcr..c .liaineter relatively greater, the latter exceeding the vertical diameter by one-sixth, whereas the two >limensions are equal, or the hi^ht the greater, in ' . ti-i>in'inliiri<. r'urthermore, the folds of the surface imbrications are fewer in nunil'er. there being only live or six on each of the dorsal slopes to eight or nine in that -| • I li'-n the revolving ridges are more distinct, and the keel is more abrupt. e-|.fruii!\ on interior casts of C. is the usual number for the last whorl, but two extra ones arc -«, mctitnes distinguishable near the aperture of larger examples. Of the transverse lamella- the average number on the back of the last volution in 'J mm. is seven or eight, The keel is prominent, rounded on the summit, and, so far as observed, without a trace of lunula-, although -ome of the specimens before us are in a beautiful state of preservation. The slit has the usual length (i. e., nearly a half volution). 910 THE PALEONTOLOGY OF MINNESOTA. LConradella bellula. We have two specimens of a variety or a closely related species from the Tren- ton of Minnesota which we propose provisionally to designate as Variety CELLULOSA, n. var. PLATE LXVII, FIGS. 27-29. •They are both only about 9 mm. in diameter, and differ from the typical form of the species in having much less of a keel and in the peculiar modification of the surface markings. The lamellae, namely, generally unite with each other in such a manner that a cellular rather than striated surface results. When slightly weathered the connected sides of the successive loops may appear like delicate longitudinal plates. It seems to be a rule that the loops are oblique and joined to each other only on one side, the other being open. Again it may appear that the longitudinal line is independent and runs directly through the loops. The transverse lamellae are unusually crowded, the average on the last volution being from eight to ten in 2 mm. The surface markings of C. dyeri have never been correctly illustrated. On the accompanying plates we show that the " revolving ridges " are as a rule not ridges at all, but only an appearance due to the elevation and longitudinal arrangement of the closely following loops of the transverse lamellae. When continuous revolving lines are formed it is only through coalescence of one or both sides of the loops of succeeding lamellae. Compared with the preceding species C. dyeri is distinguished at once by its smaller size and unusually crowded surface markings. Formation and locality.— The typical form occurs in the Richmond group at Richmond and Versailles, Indiana; Oxford, Clarksville, Freeport and Waynesville, Ohio; near Maysville, Kentucky, and Spring Valley, Minnesota. Variety cellulom was found in the Clitambonites bed of the Trenton group at St. Paul and Cannon Falls, Minnesota. Collection.-*!. O. Ulrlch. CONEADELLA BELLULA, n. Sp. (Ulrich.) PLATE LXVII. FIGS. 23-26. ^ This species in most respects occupies an intermediate position between C. dyeri Hall and C. elegans Miller. From the former it is distinguished by its lesser thickness (compare figures 24 and 31 on plate LXVII) less crowded lamella, and by having numerous well marked lunulae on the slit-band. From C. elegans it differs in having more slender whorls and less coarsely marked surface. Q iffl BO1 '.111 -pfcimen figured seems to be complete. If thi-> i- the case, then we have another feature in which C. bflliil-i 'litler- from both of the species with which we inpare.l it. Namely, ;i slit extending only ;il.«.ut a fourth, instead of half around the circumference of the last turn. format** and locality. -Lower half of the Loralne group, Coving"", K. •ntm-ky. CMbctfM.-K. O. nn.-h. NRADBLLA BLBOANS Miller. i'i MI i AMI. i tat i;-i». CgrtoUla dyeri (pa l"73. Pil. Ohio, vol. I, p. M9, plat.' MM, tigs. 24, 2e. ottw tJrjuiw, MILLER, 1074, Cincinnati Quart. Jour Sol., vol. i, p. 310. This species is closely related to and about of the same size as C. dyeri Hall, I. ut we cannot say that we ever found it difficult to distinguish. In the first place the traii>\er.-e himrll.r are less crowded — sometimes they are more than twice as far apart as in that species; next the undulations or loops of each are not so deep and fewer, there being only five or six to a side as against ten in C. dijtri; then it is only in rare instances that even the most obscure appearance of revolving ridges is observable: finally, the whorls are a trifle higher, while the slit-band bears distinct and closely arranged lunulu1. The last is probably to be regarded as the most important of the ditlerences mentioned. The C. triangularis of the Stones RIMT group, though of a similar type, is readily distinguished by its larger size, rougher MI i face, oftener and more deeply undulated lamella;, and angular umbilical edges. C. ymntlis is perhaps nearer than any other, but it grows so much larger that there is little danger of confusion between them. For comparisons with C. bellula see that description. Formation md IntnHly — As yet ilii* ptvtty shell IK known only from the shaly limestones of the Loralne group, at Cincinnati, Ohio and lo<-;iim> - in the Immediate vicinity of that city. Cb(ieet*m.-X. O. Dlrich. VKAPKM.A IMBKICATA Meek and ll'orthen. I'l.ATK I. XVII. FIO. II. Cyrtoiilt* imbncatiu MEEK and WOIUIIKN, 1W, Geol. Surv. 111., vol. Ill, p. :u<«. pi. iv, tig. u. A good figure of this species has not yet been published, and as it is an interesting form and one that may l>e expected to occur in- Minnesota, we have • li-cided to illustrate a specimen that a careful comparison with the original type proves to belong to the same species. This specimen is from the same locals the type and differs from it only in being smaller. The greatest diameter of the type is about *_'- mm.: in our specimen 15.5 mm. 912 THE PALEONTOLOGY OF MINNESOTA. [Oxydiseus. The chief peculiarity of C. imbricata lies in the fact that the sides of the whorls are the most prominent and somewhat angularly bent just beneath the middle and flattened in the umbilicus, giving a subrhomboidal or Cyrtolites-like transverse section instead of the rounded or cordiform section prevailing among the other species of the genus. In all other respects the species agrees very well with C. triangularis U. & S. and C. elegans Miller. Still, the transverse lamellae are more irregularly undulating and wider apart than in either of those forms. Meek and Worthen make a statement to which we must object. Namely, that the inner volutions are "nearly half embraced by the last turn." This is true of only the anterior part of the last volution of their type, and we are inclined to believe that it is due to oblique pressure to which the specimen has been subjected. On the rest of the type, as in the whole of the specimen now illustrated, the embracing extends only to the base of the carina. Formation and locality.— In strata regarded as belonging to the Trenton group, Alexander county, I Hindis. The same layers contain Hhynchotrema incequivalvis Castelnau (li. increbcscens Hall) and Nemato- pora delicatula Ulrich. Collections.— Illinois State Museum; E O. Ulrich. Genus OXYDISCUS, Koken. Bellerophon, Cyrtolitea, Porcellia and Euomphalus (part.) of authors. Tropidodiscus of MEEK, 1866, and WAAGEN, 1880, not Steininger, 1855. Oxydiscus, KOKEK, 1889, N. Jahrb. f. Mineralogie, etc., Beilageband vi, p. 390. For generic characters see page 852. This group recommends itself to us as not only a convenient but a natural generic division of the Bellerophontacea. Sowerby, Billings and Conrad placed three of the species under Bellerophon, from which they are distinguished by their lenticular form, compressed and sharply carinate volutions, scarcely, if at all, expanded aperture, and by their thin lips and the total absence of any callosity. Lindstrom and Miller placed four of the species with Cyrtolites, a genus that is widely different in all respects excepting the general form. As to Porcellia, Koken has shown, and we can bear evidence for the general correctness of his observations, that that genus represents a totally different type of structure. Finally, the reference of two of the species to Euomphalus rests probably upon nothing more than an error of observation and judgment. Koken excludes all those species from the genus in which even a suspicion of a slit-band occurs. This we think is drawing the line too close and somewhat incon- sequent. He admits into Bellerophon (sens, strict.) species in which the slit-band is represented by a single keel only. And he is probably correct in this, since in not only closely related species but in one and the same species (e. g., B. troosti Safford) a true slit-band may occur occasionally, while the usual form has merely a keel. r,ASTi;<»r<. tu« ) Besides the species list«-.l on page 852 there are three more American. or rather i ana. lian. species that may belong to ' M These were descril.."l l.y Milling jis Helltr»i>h»H ni.icn; II. p.t linn no. ami R e far wrong in placing Ori/disctm in the immediate vicinity of CotirmMln. 'I'll-- only "litlerence of any consequence between these genera are that, while the -nrface of the volutions of the latter are crossed by imbricating, wavy lamella*, wliirh are not turned backward on the dorsum to form an angular sinus where they meet at the keel, the whorls of the former are crossed simply by fine lines of growth, turning backward very strongly in nearing the dorsal keel, their junction here indicating a narrow, V-shaped excision in the outer lip. -THAI-ITUS, ». *p. (Utrich.) I'l.VM I Alt. FIOB. «B-«: PLATE I.XXXII. FIO8.«-«. Shell lenticular; dorsum acutely carinated; greatest diameter from 15 mm. to :> mm.; greatest thickness or width nearly one-half the diameter. Volutions three ami one-half to four ami one-half, thickest near the umbilicus, from which the surface ascends first with a gently convex, then with a concave slope to the sharp • •arli volution embracing between one-third and one-half of the preceding one; umbilicus exposing all the whorls; its width somewhat less than one-third of the diameter of the shell; edge of umbilicus abrupt, subangulai : aperture obcordate. indented below by the sharp dorsum of the preceding whorl; margin of aperture thin, in a side view with a strong backward sweep; slit long, very narrow. Surface marked by fine ami rather indistinct lines of growth. This species agrees perhaps as well as any with the Devonian types of the genus. Of Silurian forms only 0. crwtatus Sallonl ami <>. .llsmfnx Hillings need be -68 914 THE PALEONTOLOGY OF MINNESOTA. lOxydlscus cristatus. compared. The Candian species will be found to be more compressed, and to have the edge of the umbilicus less abrupt. For comparisons with Safford's species see next description. .Formation and locality.— Upper beds of the Trenton group near Danville, Kentucky, where more than twenty specimens were obtained. We have reason to believe that the same species occurs also in Tennessee and in the Fusispira bed in Minnesota. Collection.— E. O. Ulrich. OXYDISOUS ORISTATUS Safford. PLATE LXXXII, PIGS. 26-28. Cyrtolites cristatus SAFFORD, 1869, Geol. of Tenn., p. 289. Through the kindness of Prof. J. M. Safford we have before us the types of his Cyrtolites cristatus. These show conclusively that the species is an Oxydiscus, closely related to 0. subacutus Ulrich, yet not strictly identical. The Tennessee species is uniformly larger, the greatest diameter in four specimens varying between 30 and 38 mm. More important differences are (1) that the whorls are one less in number in mature examples, (2) that they increase more rapidly in size, (3) that they embrace each other in a lesser degree, the amount being in no case more than a sixth of the hight of a whorl, while the last may become entirely free, without, however, any appreciable diminution in the depth of the sharp furrow, which, farther inward, receives the keel of the preceding whorl. In consequence of the peculiarities mentioned, the umbilicus is relatively somewhat larger. Finally, the shell substance is comparatively thicker on the ventral side, and the keel more distinct than in the Kentucky species. Taken all in all, we do not see how we can do otherwise than regard 0. subacutus as distinct from 0. cristatus. Formation and locality.— From Safford's "Middle Nashville," which we regard as representing an upper member of the Trenton group, at Nashville and in Jackson county, Tennessee. Collections.— J. M. Safford; E. O. Ulrich. Genus BELLEROPHON, Montfort. Bellerophon, MONTFORT, 1808, ConchiliologieSystematique, vol. i,p. 51. WAAGEN, 1880, Pal. Indica, ser. 13, pt. 2, pp. 130 and 133. Bellerophon (part.), HALL, LINDSTROM, and most authors prior to 1880. Waagenia, de Koninck, 1882, Ann. Soc. Geol. de Belgique, p. 14. Waageniella, BAYLE, 1883. Proposed instead of WAAGENIA which was preoccupied. For generic characters and list of species see page 853. Adopting this genus in the restricted sense proposed by Waagen, we have an easily recognized and still large group of Paleozoic shells. The numerous species are of a remarkably uniform type, distinguished at once from Protowarthia by its slit-band and different apertural emargination; from Bucania and allied genera by OASTROPOI'A in- the total absence of revolving -urface lines. Within its own family, the lieller-'plifiHt > ."Aon has not the revoh ing sculpture of hn,-,, n^/mis, nor the i« \tremely expanded aperture of PofottMfNMM, nor the revolving folds of the inner lip which characterize Kuphttnus, while neither Moyulin nor Wnrthiit have a distinct The principal distinctive features of the genus are: (1) the absence of all kinds of sculpture save the more or less strongly developed lines of growth, (2) the small or entirely closed umbilicus, (3) the moderate expansion of the aperture, (4) a more or le— >trong callosity on the inner lip, and (5) a well developed, generally raised, si it -hand terminating anteriorly in a short median emarginatioo or slit in the outer 1'P. The genus might he divided into several subordinate groups none of them, however, seeming of more than doubtful utility. One, Waagenella, including a few Carboniferous species, is distinguished by a definite callosity in the umbilical region. Regarding the Bellerophon cuntortus group of Koken, we have already distinguished it as a separate genus under the new name .U«y/.i/«»w/*//»//« (see p. 850), this type belonging in our opinion to the liuranin/n rather than the IMIer»]tliontiiconcave ridge with a rounded central prominence; the latter constricted within the mouth and continuing inwardly as a di-tinct ridge; latero-ventral angles turned backward. 916 TEE PALEONTOLOGY OF MINNESOTA. (Bellerophon cluusus. in some cases partly overhanging the umbilicus. Surface marked by growth lines only. They are more or less distinct, though on the whole fine. They are also some- what irregular, being generally arranged in bundles, which, especially near the aper- ture of adult shells, may produce obscure undulations of the surface. The course of the striae from the umbilicus to the dorsal carina is very little curved and nearly at right angles with the carina. However, just before joining the latter, they bend sharply backward. Hight of one of the largest of the Kentucky specimens 16 mm.; greatest width of the aperture 19 mm.; width of whorl just in front of edge of inner lip 7 mm. In Tennessee the species often attains a hight of 20 mm. We have before us an excellent series of silicified shells of this species and can testify to the unusual constancy of its specific characters. Considering this persist- ence we might be justified in separating the following form as a distinct species, but after considerable reflection we have concluded that such a course would not now be warranted. We propose th'en that it be known as Variety BURGINENSIS, n. var. (Ulrich.) PLATE LXIV, FIG. 6. This variety grew to be a litttle larger than the typical form (22 mm. in hight), has a proportionally less expanded mouth (the greatest diameter of the shell is about the same as the width of the aperture), more slowly enlarging volutions, and a larger umbilicus. On the best specimen the dorsal carina besides has the characters of a true slit-band and near the aperture it exhibits distinct lunulae. B. troosti is one of a number of closely related Lower Silurian species. The group is well represented in the Trenton of Minnesota, but that B. troosti itself occurs here is as yet very doubtful. B. similis is very much like it, and before we found specimens showing the mouth and lines of growth, we unhesitatingly referred the casts of the interior to this species. Still, it is possible that B. troosti is really represented among the casts now assigned to B. similis. Formation and locality.— The typical form is not uncommon in the Trenton group at Nashville and Hartsville, Tennessee, and Danville, Frankfort and other localities in central Kentucky. Var. buryinensis occurs with the typical form near liurgin and Danville, Kentucky. The species is limited to a vertical range ot a few feet in the upper half of the group. Collections.— Prof. J. M. Safford; E. O. Ulrich. BKI.LEROPHON CLAUSUS, n. sp. (Ulrich.) PLATE LXIV, FIGS. 7-10. In the general form of the shell and the course of the lines of growth, this species resembles B. troosti very closely. Carefully compared we find that the new species differs in several important respects. First the umbilicus is entirely closed, OPODA 'I I 7 i next tin' lines of growth are more regular ami -harper, then tin- -lit -liand. and locality.— Tr. ;p Krunkr..rt, K.-nturky, and noar Na»h»llle, TYn CMtettm.-E. O. ririch. P.KI.I.KI: .ii-iios- HII.INKATI s. n. sp. (Ulric/t.) n.ATK i. xiv. noa. »-si. Very much lik. -//'. only smaller, narrower across the aperture, with fine an. I sharper, as well as more regular, lines of growth, and much less prominent slit-1'aml. The latter is concave, lies between two sharp lines and is crossed by rat her «li-tinct lnnuhr. The posterior curve of the lines of growth on the dorsum also is broader, while the inner portion of the lower lip is much less thickened. The last difference is even more conspicuous when we compare the species with II. claustw, and this, coupled with the fact that the umbilicus is closed in that species and rather large in li. l>ilinffitiu, renders confusion with that form quite improbable. FtrrmalioH and locality.— Upper portloa of the Trenton group, near Danville, Kentucky. CMtetfo*.— E. O. Ulri.-h. HRLLRROPHON SUBOLOBOLUS, n. sp. (Ulrich.) I'l.VTh IAIV. I li,<. 17 and !«. This also reseml'li'- /•'. trn,,tinKtii-ln"l without much troiiMe. The surface striae, though their direction with respect to the dorsal keel is nearly the same us in li. trooxti (the retral curve on the back is somewhat wiy similar • litterences. while the presence of a small umbilicus adds another, the umliilicu- being closed in that species. In H. liil< iie uml.ilicu- i- larger and the slit concave instead of rounded. 9 IS THE PALEONTOLOGY OF MINNESOTA. tBellerophon platystoma,. Formation and locality.— Black River limestone, Mercer county, Kentucky. Collection.— E. O. Ulrich. BELLEROPHON PLATYSTOMA Meek and Worthen. PLATE LX1V, FIGS. 22-30. Bellerophon (Bucania?) platystomi M. & W., 1868, Geol. Surv. 111., vol. iii, p. 312, pi. in, figs. 8a, 6. Shell exceeding medium size for the genus, composed of about three volutions, which increase rather slowly in size until near the aperture where the last one is suddenly and greatly expanded laterally; whorls embracing very little, subtri- angular in cross-section, with the dorsum strongly carinate; surface descending on each side from the keel, first with a concave then a nearly flat slope, toward the edge of the umbilicus into which it turns very abruptly; umbilicus open, rather large, about one-fourth as wide as the greatest diameter of the shell; aperture somewhat triangular-reniform, the hight a little greater than half the width, the width exceeding by nearly a fifth the greatest diameter of the shell; outer lip thin, broadly sinuate, the center of bottom of sinus prolonged into a narrow slit; inner lip apparently with but a very little developed callosity. Lines of growth sharp, rather regular, curving backward gently between the umbilicus and carina. The latter, on which we have not observed any well defined slit-band, is very prominent and almost sharp on casts of the exterior, but on casts of the interior it is not distinguishable from the general regularity of the dorsum. We are quite confident of the specific identity of the Minnesota shells above described and the original types of B. platystoma, the latter having been examined by us. In Minnesota we have two varieties of the species, one, agreeing exactly with Meek and Worthen types, occurring in the Fusispira bed, the other, which is much smaller, its greatest diameter but rarely exceeding 20 mm., being a common fossil of the Clitambonites bed. B. platystoma is closely related to B. similis, but may be distinguished readily enough by the different transverse section of its volutions, this being subtriangular while in the new species it is semicircular rather than triangular. When, as is often the case, the expanded aperture is broken away, the remaining whorls of B. platystoma remind one greatly of Crytolites. Similarly imperfect examples of B. similis, however, are scarcely distinguishable from B. troosti. None of the other species known are closely related, nor have we experienced any difficulty in separating B. platystoma from them. Formation and locality.— The original types are from the Trenton (Galena) group at Galena and IMxnti, Illinois. In Minnesota the small form is common in the Clitarnbonitos bed at localities in Good- hue county, while the larger or typical form is not rare in the Fusispira bed at Kenyon, Holden P. O., Wykoff, Weistiachs' dam, and other localites. -TKOl'OKA '.'!'.» f..ptKH> .In, III. I CMbeffeM.— Geological and Natural Id-tor - >t.i. \\ II. Scofleld; E. O. t'lrirh; l>r. * ll. Mtueum Remitter, New. «76&, 7390, 7440, 74«3. HKLLKKOPHON HIMILIS, ». «p • 1 1 ATE LXIV. FIOB. n-m. This species is represented by about thirty casts of the interior and exterior, showing a decided constancy in its specific peculiarities. The form of the carinated volutions, indeed the general aspect of the whole shell in its usual state of preservation. is so murli ;is in If. troosti that at first sight it may peem to be identical witli that Kentucky and Tennessee species. A closer examination and better specimens, however, will soon prove them to be quite distinct. In the first place, the surface striations, instead of passing from each side almost straight across the back of the volutions to the carina, curve strongly backward, thereby forming a deep though wide-angled sinus in the outer lip. Next the striae are coarser, sublamellose, more regular and not arranged in bundles as in B. troosti. Further, the keel grows more prominent toward the aperture and the umbilicus is larger, though this is probably due entirely to the lesser thickness of the test. Finally, the aperture is of a different shape, less expanded laterally and less contracted by the callosity of the inner lip. The callosity is much less and forms no transverse ridge at the inner part of the lip. B. similis occupies an intermediate position between B. troosti and B. platystoma Meek and Worthen, the section of the volutions being as in the former, while all the other characters are more nearly like those of the latter. With ordinary care good specimen- of H.ximilis and li. pll'ity.it<»nn the slope on each side of the prominent keel is decidedly flattened. This difference in the transverse sections of the whorls we have found to be very reliable and of itself sufficient for the separation of the two forms excepting in a few cases in which the specimens were either poorly preserved or badly crushed. It remains to be mentioned that several specimens show very faintly a number of wide revolving banmi»A. -'-I expand. .linK' below almo-t to the periphery of the outer volutinn; concave on each side of the latter, the inner ed^e thick and with a rounded central swelling which continues inwardly as a rounded ridge; inner aperture subtriangular, the inner or lateral angles rather sharp, the outer more obtuse. Surface marked by -tn.n^r. regular, tliread-like lines of growth, of which, on an average specimen, \e to fourteen occur in "• inin. The course of the stria- from the umbilicus to the slit-band is gently curved in the central half, but more strongly at each end. Slit-hand very rarely preserved; when perfect it surmounts a low ridge, is of ni< .derate width, concave, bordered on each side by a thin sharp line, and covered !>y more or less unequal lunula*. In casts of the interior the umbilicus is much r. sharply defined and very abrupt, the ventral side of the volutions appearing to he almost Hat and the section of the outer one triangular. This fine species is related to B. plafyxdnnn and H. similis, but has a thicker shell than either of the Trenton species. This shows itself especially in the much stronger development of the inner lip, and in the smaller umbilicus. As casts of the interior, in which condition all three of these species are most commonly met with, />'. Hi'thri may l>e distinguished from the others by the impression of the callosity of the inner lip which causes the umbilical cavity to appear as drawn out narrowly above. The volutions besides enlarge more rapidly, and the umbilicus, especially when compared with H. similis, is deeper and much more sharply defined. Good testiferous specimens are very rare, many being distorted by pressure, and in most of them the greater part of the aperture is broken away, and the surface markings obscured by weathering or maceration. The majority, however, preserve a large part of the expanded inner lip. F<>rm»tin* and locality.- Not iin<-<>iiiiiinii in the upper part of th<> Kirlmioml tfrnupnf tin- Cincinnati perlul at Ki<-)i!ii»iul. Indiana. We have It also fn>in Lincoln enmity. Ki-nlu CMtetimt.-E. O. Ulrlch. liK.M.Kllol-IION CAPAX, ft. Sp. (Ulrirll.) PLA1K I. Mil. Hi.S. 50 an.l 51: PLATK LXIV. FIGS. «-«. This species agrees closely with />'. m«hri. l>ut on comparison proves to differ in a greater or lesser degree in nearly every feature. First, the volutions enlarge more rapidly, second, they are more ventricose, third, the umbilicus in casts is a trifle smaller and more rounded at the edge, fourth, the outline of the aperture is less narrowly rounded on the sides, and fifth, the cross-section of the outer volution of casts is nearer semicircular than triangular. The shell is larger, the volutions increase in size much faster, the umbilicus is smaller, and the inner lip much heavier than in B. platystotna and H. similis. When the aperture is imperfect, specimens of 922 THE PALEONTOLOGY OF MINNESOTA. [Bucanopsls, this species sometimes look very much as though they might be a larger variety of Protowarthia granostriata. Yet this is most certainly not the case, since the species possesses a slit-band and the aperture of a true Bellerophon. When neither of these features is preserved, then it is distinguished from the Protowarthia by its open umbilicus and larger size. .Formation and locality.— Lower part of the Loraine group and upper part of the Utica group at several localities in the vicinity of Cincinnati, Ohio. Collection.— E. O. Ulrich (7 specimens). Genus BUCANOPSIS, n. gen. Bellerophon (part.), HAI..L, MEEK, DE KONINCK, McCoy, D'ORBIQNY, and other authors prior to 1880. LINDSTROM, 1884, Silurian Gastropoda of Gotland. Bucania (part.), WAAOEN, 1880, Palasontologica Indica, ser. 13, pt. 2, pp. 130 and 150. KOKEN, 1889, N. Jahrbuch f. Mineralogie, etc., Beilagehand vi, p. 379. ?Euphemus (part.), McCoy, 1844, Synopsis Carb. Foss. Ireland, p. 25. For generic characters see page 853. The greater part of the species which we propose to classify under this generic name were originally described as of Bellerophon, an arrangement that was quite satisfactory to paleontologists till 1880 when Waagen proposed to separate them on account of their spiral surface sculpture. In this we think he was fully justified, because extensive studies of the Bellerophontacea prove conclusively that the surface markings deserve a high rank among the characters that are available to the systematist who seeks to subdivide the group into natural and convenient generic sections. But, as we shall show in discussing that genus, both he and Koken, who adopts Waagen's proposition, are wrong in extending the application of Hall's Bucania to all the spirally striated bellerophontids. Bucania must be restricted to species of the type of B. sulcatina, which is quite different in other respects from the Devonian and later Paleozoic shells that make up the bulk of the species referred by them to Hall's genus. The surface markings even are not exactly the same in the two groups, they being straight and parallel with the direction of the whorls in Bucanopsis while in true Bucania they are wrinkled, interrupted and more or less oblique in direction. It seems very clear to us that Bucanopsis was developed from Bellerophon and not from Bucania. Every character of the genus, excepting the revolving lines, corres- ponds with the former and is more or less different from the latter. A comparison of the figures of species described in this work alone can scarcely fail to convince students that this is really a fact, and the same must continue to grow more obvious when they extend their comparisons to Upper Silurian, Devonian and Carboniferous Bellerophontidce . • •TO i, \ i;i../.siX if we include in it, as we must provisionally do, all the Paleozoic spirally striated shells which agree in other respects with nhon, may not be an entirely natural -jonus. I'.y this we mean that many of the later forms are probably not .les.-en.le.l from the Trenton type of the genus. We think it possible that Bucanop- >••'.>•- like species were evolved from ll?U,roj>h,m not only in Lower Silurian times but at later periods as well. Again it is not unreasonable to suppose that certain developmental lines, originating in some period preceding the Trenton, may have resulted in forms that we cannot now separate satisfactorily from Bucanopsia. The last possibility is suggested by Koken's remarks on the development of the shells which he erroneously places into Meek's genus Bucnnella (see this work pages 849, 876 and 882). If he is correct in regarding Bellerophon tubstriutus Krause, and several I ifvonian >pecies mentioned by him, as having descended from his I/ower Silu- rian l>. fxi/ionii. then the possibility is strengthened into probability; for B. esthona most certainly came from quite a different stock than that which produced Bucanopsis \ hile the supposed Devonian descendants are scarcely distinguishable from •itopitis, and only by the slightly greater width of their slit-bands. However, we are strongly inclined to doubt that Koken's views on the question under considera- tion are ju-t Mi-->l \urfare markings and place the species with little or no hesitation under Tetranota. Hut to show the difficulty of correctly estimating the generic affinities of many of the bellerophonti'is from figures ami descriptions above, we may say that so far nothing has been published of B. substring that might be considered as thoroughly antagonistic to the view that would consider it as a modification of the Lower Silurian Protoicarthin. in which delicate revolving lines are also often present. The broad apertural sinus reminds one strongly of Protoir«rfhin, and when it com- the tripartite character of the shell, which character in connection with another about to be considered led Koken to place these species with Bucnnflln, If. snlistr!o««l tbmt kokrn »«rjr properly place* B. wttona In Uie InuMdlkta vIclDlly ul Uueaina or. u • •• call It, 924 THE PALEONTOLOGY OF MINNESOTA. [Buoanoptls. resembles Protowarthia granistriata more closely in this respect than either Biicanella trilobata Conrad sp., or Kokenia esthona. The longitudinal striation, unusual width and elevation of the slit-band, the last feature producing an obscure tripartite character to the shell, seem to be the principal characters upon which Koken bases his conception of Bucanella as distinct from Bucania, which with him included Bucanopsis. These features he finds in his B, esthona, Krause's B. substriatus and in several other Silurian and Devonian shells which he assumes to be related to species upon which Meek founded Bucanella. This assumption, however, is totally unwarranted, and in the absence of sufficient evidence to prove his point Koken should not have charged Meek with an incorrect description. The elevation of the slit-band in the group of species under consideration is probably not of much consequence, though usually present. Its unusual width, however, may be of importance but we see no way of utilizing it at present. The extension of the revolving lines over the slit-band also seems to us to be of little value. We came to this conclusion because they may be present in one and absent in the other of two closely related species. For instance, in Bucanopsis textilis Hall (not De Koninck sp.), of the Warsaw or St. Louis group, the slit-band seems always to be without revolving lines, but in an undescribed form recurring in the Chester group of Kentucky, and which can scarcely be distinguished, such lines are clearly present. We find them also in B. leda Hall, while they are absent in the closely related B. lyra Hall. Then they are developed again in some of the Carboniferous species, notably B. marcouiana Geinitz, B. ellipticus McChesney, and B. montfortianus Norwood and Pratten, the last belonging to the Bellerophon patulus group of species. It seems to us, therefore, unreasonable to accord any more than specific importance to the presence or absence of these lines. There is another assertion made by Koken to which we must take exception. He says that B. esthona is "obviously a combination of the characters of the so-called Euphemus and Bucania." This observation is so totally at variance with our own opinion that we are almost at a loss to answer it except with a simple contradiction. He is most assuredly far from the truth if he means to imply that the revolving ridges of Euphemus, which we cannot for a moment doubt are really folds of an extension of the inner lip, are in any way comparable with the spirally ribbed external surface sculpture of Bucania and Bucanopsis. •'-•"' III . V. >/. Sfi. I t'lricll.) \\t I Ml. I HiS. M-tl. Shell less than medium si/e, the bight varying in thirty-five specimens between 7 iniu. and 1"> mm.; width of aperture nearly or quite equal to the bight. Volutions two or two and one-half, rather closely coiled, embracing to a little more than one- half, with a -trong. prominent, flat-topped dorsal keel, from which the surface descends in a wide concave slope; sidas rounding somewhat narrowly into the small open umbilicus; section of volutions broadly cordate. Aperture broad, somewhat igular-ovate in outline; outer lip thin, with a moderately deep V-shaped central emargi nation; inner lip thick, vory wide, reflected laterally, extending downward i>\er the preceding volution whose keel shows through very distinctly. Surface with tine straight revolving stri.e, alternating somewhat in strength; transverse or growth lines, excepting an occasional wrinkle, usually very faint, but on the larger specimens they become much stronger and incline to be irregular. Slit-band flat, smooth so far a- known. This, the type an. I only known Lower Silurian representative of the praised genu- ftm-'inopsis, reminds one somewhat of the European li. xubxtrintu* Krauss, but the dorsal carina is much more prominent and the slit-band narrower than in that rather doubtful Upper Silurian species. None of the Gotland -penes of the gemi- • the dorsum carinated. Of Lower Silurian />'.//./,////////-/./, li,-ll, /-.)/'/""' t roost i and />. pl'itystoma are somewhat similar, but as the former has more rounded volutions and the latter quite a differently shaped aperture, there is little likelihood <>f confusion between them even as casts. Being true bellerophons they have of course no revolving lines, while the carina is never so prominent as in Bucanopsis rii. We have about fifty specimens of what we take to be the same species from the line group at Cincinnati, Ohio. They are, however, smaller than the Trenton form, the hight being in most cases less than 7 mm. and in only one as much as 10 mm. Not one of them exhibits even a trace of surface markings although preserv- ing the shell, or rather a replacement of the same in crystalline calcite. But the absence of surface markings on these specimens should not be considered as proof that they were originally without them, since they are wanting also on all the other Gastropoda occurring in association with them. Among these other forms are well known species of Isophospira and ( 'i/rtoliti t he surfaces of which under more favorable conditions are always distinctly sculptured. Formation and locality.- Upper p»rt of T; up, near Dmnvlllo, Krnturky: Loral n«- uroiip .,f th<- Cincinnati period, Cincinnati. Ohl«. CWtoe«ion.-E. O. Ulrich. 926 THE PALEONTOLOGY OF MINNESOTA. [Oarlnaropsls. Genus CARINAROPSIS, Hall. Carinaropsis, HALL, 1847, Pal. New York. vol. i, p. 183. Phmgmostoma, HALL, 1861, Fourteenth Kept. N. Y. St. Cab. Nat. Hist., p. 94; not Waagen, 1880, Pal. Indica, ser. 13, pt. 2, p. 131. For generic characters see page 857. This is a well-marked genus, and one that we find it difficult to place satisfac- torily in our scheme of classification. Taking the small inner volution alone, we are reminded sometimes of Cyrtolites, at other times of Oxydicus, but the whole shell with its greatly expanded and peculiarly constructed aperture, is so widely different from these genera that, with our present knowledge, we cannot think even for a moment of seriously comparing them. There are perhaps better reasons for bringing the genus into connection with Bellerophon, there being in reality scarcely a single — if indeed any — feature of Carinaropsis that is not also present in some form or other in species of that geuus. Thus, picking out the more essential characters of Carinaropsis, an expanded aperture is frequently present in Bellerophon, though the inner volution or volutions are never minute as in Carinaropsis, the inner lip is often thickened within into a blunt ridge (e. g. B. troosti) but the ridge is never developed into a projecting wide plate; then the volutions are often carinated, though but rarely, if ever, so distinctly as the smaller volution of Carin- aropsis. Finally, the shells of both genera have a slit-band and a sinus in the outer lip. Though their features on the whole are the same in kind, they still differ so greatly in development that, especially when resemblances in very different directions are considered, we are more than satisfied that Carinaropsis represents a distinct family. We have already alluded (see page 857) to certain striking agreements in structure existing between Carinaropsis and Pterotheca, a genus of Silurian shells that all authorities now place with the Pteropoda. In both of these genera the aperture is broadly expanded, a septum is developed, and the back is carinated, in each case more strongly in Pterotheca than in Carinaropsis. But while in the latter the shell forms as much as two volutions, in the former it is merely arcuate, the curvature in no case amounting to a single volution. Though the differences between the two genera are doubtless important, are we not so far justified in claiming that Pterotheca is not farther removed from Carinaropsis than this genus is from Bellerophon? We say "so far" because Pterotheca possesses one character that is not represented in Carinaropsis nor in any true member of the Bellerophontacea. Namely the apical extremity of Pterotheca is divided by two small vertical septa into three portions of which the central one is longer and somewhat wider than the lateral ones. OASTROP01>\ C»rlntrop>i« runulr ) :itin^ for the present that I'tfrotheca is a pteropod, we look in vain among the other types of that suit-class of shells for anything corresponding to the triti'l apex of rttmtlicca. We conclude, therefore, that the peculiarity is of generic importance only, and consequently not a serious objection to an arrangement whii-h. in following the suggestion of the other characters, would bring Carinaropsi* atnl rtrrnthfru within the limits of the same order and family. According to our opinion this family will prove to belong to the Docoglossa and not to the Pttropoda. CARINAROPSIS OCNUUB Hall. PLATE I.XII. FIGS. 10-11. OarhiawjHfa (PK>*gmo+mn) cunulit HALL, 1M1, Fourteenth Kept. N. Y. St. Cab. Nat. Hist., p. 94. Shell 20 mm. to 25 mm. in width, the length of the largest specimens about 20 mm., the bight of the same about 10 mm.; consisting of two or two and one-half volutions, the la-t abruptly expanded. Dorsum angular, or slightly carinated on the .-mall volution, the angle becoming gradually more and more obtuse toward the deeply emarginated anterior edge, where it may be quite obsolete and in some specimens replaced l-y a liroaut the best difference lies in the septum whose outer surface is much less excavated in this species. formation and locality.— Vpp?r part of Trenton jtroup, NaahTllle, Tennewee, and Boyle county, Kentucky. — B.OlUMeh. CARINAROPSIS CYMBULA flu/I. PLATK I.XII. ill.- I I (Pkraymortoma,) cymbtJa HALL, 1861. FmirU-. -nth It-pt. N. V. St. Cab. Nat. IINl.. p. W. (\n error for eymbtOn) HALL, 1862, Fifteenth Kept. H-m., pi. vi. tig*. 12-14. Volutions one and a half or two, the first very minute; posterior margin of 928 THE PALEONTOLOGY OF MINNESOTA. lOurlnaropsIs phalora. aperture not reflected, causing an unusual depth between the lip and the edge of the septum; edge of septum scarcely thickened, the whole outer surface of septum nearly smooth. In other respects like C. cunulce. The great excavation of the septum is the principal peculiarity of the species. Formation and locality.— Top of the Trenton group, near Danville, Kentucky. The original types of the species are said to have come from the Hudson Eiver group, but this is probably an error. Collection.— E. O. Ulrich. CARINABOPSIS PHALERA Sardeson. PLATE LXII, FIGS. 14-18. Carinaropsis (or Bellerophon) phalera SARDESON, 1892, Bull. Minn. Acad. Nat. Sci., vol. iii, no. 3, p. 336. This form is very near C. cunulw Hall, the only differences that we can now see being the apertural margin which is less reflected and scarcely truncated posteriorly, giving a more nearly circular outline and greater depth to the concavity of the septum. Mr. Sardeson mentions " indistinct radiating folds on the dorsal surface " of one of his specimens (a cast), but we have failed to notice anything of the kind. Formation and locality.— Black River group, Rhinidictyaand Ctenodonta beds, St. Paul, Minneapolis Chatfleld, Minnesota. Colkctions.— E. O. Ulrich; original types in the cabinet of the geological department of the Uni- versity of Minnesota. CARINAROPSIS ACUTA, n. sp. PLATE LXII, FIGS. 8-9. Shell very delicate, the largest about 27 mm. in length, but the majority of the specimens before us, perhaps because of imperfection, are only from 3 to 11 mm. in length. Volutions about three, the inner ones very small, greatly compressed, and very sharp on the dorsum, the last expanding very rapidly. As the dorsal angle becomes gradually less acute and the rate of expansion of the volutions increases, the aperture changes from triangular to subcircular. Septum comparatively short, the edge much within the plane of the apertural margins. Posterior lip not reflected. Surface, so far as observed, quite smooth. This differs from the preceding species in the greater compression and much sharper dorsal augulation of the inner whorls, and in the much shorter septum. Formation and locality.— Black River shales, Rhinidictya and Ctenodonta beds, Cannon Falls, and near Fountain, Minnesota. Collections.— Geological and Natural History Survey of Minnesota; E. O. Ulrich. Muxeum Register, No. 7".:t4. iSTBOPO •'-"•l n.lnlm. 1 <'\I:IN\ MIVIMK. ii. PI. Ml I \ I I Shell very small for the genus, the width of the aperture about 8 mm. in a specimen having a length of r, mm. and a concavity of about 4. :t mm. Dorsumonly moderately acute at tii-st and In-coming gradually quite obtuse. Surface with several com ,\ strong lines or wrinkles of growth. of this species we have seen only the small specimen figured on plate IAII. At tii-st we thought it might be an immature example of C. phnlrru, but a more careful comparison proved conclusively that so great an expansion of the aperture could not have occurred in the young of that species. Indeed, the expansion of the aperture iM.-E. O. rirlch. 980 THE PALEONTOLOGY OP MINNESOTA. LKiipbistninlclif. Subclass PROSOBRANCHIATA. Order PECTINIBRANCHIATA. Suborder EOTOMACEA. This proposed suborder is made up chiefly of four families of shells that are perhaps the most important of all to the paleontologist, namely, the Rapliistomidce, Pleurotomariidce, Euomphalidce and Trochidce. Besides these it should include other families, as for instance the Fissurellidce and Haliotidce, which were most probably derived from the Pleurotomariidce, provisionally also the Maclureidce because of their evident relations to the Euomphalidce. Then we include also the Turbinidce because their early Paleozoic prototypes can be shown to have very close relations with unquestionable members of the group, while of their recent representatives it is well known that they are not greatly different from the Trochidce. We find it most difficult to designate the characters of the shell which may fairly be said to be peculiarly characteristic of the group. Perhaps such characters do not exist, — at any rate we shall not now attempt to point them out. For the present it must suffice to say that the suborder rests principally upon observations which we regard as proving the common origin of the four families first mentioned. These observations will appear in the course of our remarks on the families known to have representatives in the Lower Silurian rocks of Minnesota. Family RAPHISTOMIDJ], n. fam. This family includes shells which we regard as the best known representatives of the original stock from which the Euompholidce, Pleuroiomariidw and Trochida: were almost simultaneously evolved. The position of the majority of the forms is intermediate between the first two families, leaning toward the second rather than the first, while the rest compare better with types that we place as early representa- tives of the last family, particularly with certain of the Upper Silurian shells which Lindstrom refers to the recent genus Trochus. The most persistent character of the Raphistomidw is one that at first may seem almost trivial, but because of its persistency it is justly entitled to rank as important. Namely, the lines of growth on the upper side of the whorls, which of course correspond in direction with the outline of the upper lip of the aperture, though directed on the whole backward, are curved sigmoidally, thus causing a usually very slight sinus in the outer part. The curvature is never strong and is perhaps best developed in Raphistoma in which the point at which the change in GASTK"!'. >l>\ direction of the curve occur- is usually marked by a Alight seam-like line or interrupt ion. In /,'<»/.// I.V/»WM mi ;nnl Knnmpli >lit-kmd does not occur in any of the Ripkutomida, yet it would be quite reasonable to consider the angular or lamellar periphery of the whorls as its representative. Or it may be that the slightly sinuate outer parts of the lines of growth on the upper side of the whorls are homologous with the lunulte crossing the band of true /'/--I, >•<>(,, mm -H-ln . Still, the evidence at hand is insufficient to establish oit her view. Kor the present then we have two well marked differences between the shells of the two families that may be utilized even should the suggested limnologies admit of demonstration. The first of these differences lies in the absence of an apertural -lit ami the resulting slit-band, while the second may be expressed by saying that the retral sweep of the lines of growth in the Plturotoinariitio is never diminished but, on the contrary, is nearly always im-MM-fl just before reaching the band, while in the Raphistomidtr it is decreased and often overcome entirely on the peripheral carina. In cases like StMMptefopfenM -//•;/(/-. in which the carina is extremely developed, the second curve is again overcome by a third which is strongly retral. The last, it seems to us, has no further significance than the preservation from injury of the anterior outer angle of the carina which would have been exceedingly liable to breakage if the second curve had continued. We place here in all five genera. The position of the first three we regard as unquestionable, the fourth, Omospira, differs very decidedly from the rest in the rounded form of its volutions and relatively high spire, while the fifth, Sen lit- doubtful because there is yet much to learn respecting its most important charac- teristics. If the last should prove to have the really essential features of the family then its systematic position would most likely be between Kaphistoma and 0mo. -;p|.-r whorls In section and the uuiblllcal legion and •ly twisted columellar lip. Received from }'r«t. H. M. Sn-l.-y and now In the collection of E. O. •h. The accompanying figure shows nearly all we could learn of this genus and specif-. The general form reminds one of certain species of Ijophospira, but we are certain that the angular periphery of the whorls does not carry a band as in that genus. Unfortunately, neither the original types nor, so far as known, any of the specimens discovered since, afford any positive knowledge concerning the form of the outer lip and surface markings. Although we believe that these characters will prove to be essentially as in the preceding genera of this family, we must admit that the question i- complicated by the marked resemblance which S. anyululus\)ea.n to '•'ifi/'inn. For the present then the name Scalitcs should be restricted to the species to which it was originally applied. Of these five genera Euomphnlnpt'-ru* is the most recent, being perhaps entirely an I pper Silurian type. The others with a few doubtful exceptions, are confined to Ixjwer Silurian deposits. Hnjilii-tinna begins with several species in the Chazy and continues to the top of the Cincinnati period; Ifapliistntiiiint is known in the Trenton, Hlack River and Calciferous formations, and we have reason to believe that the type reaches as far back as the Cambrian: while 0m'» comprises Hlack River and Trenton species and perhaps a single Cpper Silurian form. i:liistliixfi to l>e replaced by a notch in the upper side of the outer angle of the aperture. Btiomphalopt differs chiefly in its more rounded volutions, and c "ly develop! carina. The 934 THE PALEONTOLOGY OF MINNESOTA. [Kaph Is torn Idle. lower lip also has become more strongly and constantly sinuate, causing a more oblique aperture. The evolutional modifications, it will be noticed, are almost exactly opposite in the two cases. As to Omospira, it was most probably derived from Raphistoma, or from some unknown allied type. The relations and differences existing between Raphistoma, Raphistomina and Euomphalopterus are clearly shown by the figures in the accompanying cut: FIG. 5.— Sketches illustrating the character of Raphistomina, Raphistoma and Euomphalopterus. a, b, c, three views of Raphistomina lapicida Salter sp.; d, e, f, similar views, x 2, of Raphistoma peracutum, a depressed but otherwise very typical species of the genus; g, h, i, similar views of Euomphalopterus alatus var. obsoletus, n. var. The last is from the Niagara group near Waldron, Indiana, and is the only American representative of this peculiar genus known. It differs from the European varieties of the species chiefly in wanting the ridge which surrounds the umbilical cavity in those forms. The umbilicus in our variety is also a trifle narrower than usual. Raphistoma, Hall, that long misunderstood and much debated genus, is now for the first time since 1847 correctly interpreted, limited and placed. Justice demands that Prof. James Hall, the author of the name, should be credited with having given a diagnosis that is strictly correct and sufficiently detailed to satisfy even the pres- ent requirements. He noticed and says distinctly that his Raphistoma has no band, and this fact of itself should have been accepted as fully justifying a separation from Pleurotomaria. Instead we find that authors have generally regarded his genus as indistingishable from Scalites Conrad, and both as synonyms of Pleuroto- maria. Salter,* it is true, gives Raphistoma, together with his Helicotoma and Vanuxem's Ophileta, the rank of subgenera under Scalites (which he refers to the lanthinidd), and distinguished them from Pleurotomaria because of the absence of the spiral band. However, as we will show later on, Helicotoma and Ophileta are •Canadian Organic Remains, doc. 1. p 10, 1850. II:»|TI»A. MB euomphaloids ami therefore quite different genetically from /U/////I.S/OH*'/. while ithViently known to l>e placed satisfactorily. It i-i not worth while to review the literature of the genus that appeared during tin- time included l*?tween the years 1H5'.» ami 1VH>. It will suffice to say that the naim> gradually attained a somewhat precarious standing among American paleon- tologists as a convenient designation for lenticuliar shells which in other respects were supposed to be of the type of l'lntri.' Taking Miller's list of species referred to Raphistoma* as a fair example of the use to which the genus had attained in recent years, it is evident that it is truly an incongruous assemblage. Of the nineteen specie* prokiMy only the three originally referred to the genus really belong t here. The others belong mostly to our new pleurotomarian genera Eotoman'n ami Lioxftii-'t. ami to L'>ij>histominti, while several are too ill known to justify a definite arrangement under any genus. In 1 viol Koken endeavored to establish #i>tertis ami EccyliompkaltU on the one hand and I/i-lirtoma on the other. Still, we are inclined to believe that Koken has overestimated the closeness of the line of the development which he seeks to establish between li'ijihisioma and /•><•// h'o/tfTiw. Koken's observations are based chiefly upon European specimens which he has identified with A'.//. //)>//»/<; in accordance, as he believes, with Hall's description of the genus in the tir-t paleontological volume of the New York Survey. He starts with Schlotheim's /-.'/MMI/I/I^/MX idering the great variety of shells that have been referred to the species n>u«l.t out on Uw plat*. 936 THE PALEONTOLOGY OF MINNESOTA. [Raphlstomidte publish good figures of the form that alone is entitled to bear the name. Under the circumstances we are unable to decide whether it is a true Raphistoma. But we will concede for the present that it is. The second species is a new one which he calls E. schmidti and compares with the American R. striatum. This strikes us as not a true Raphistoma, the striae upon the upper sides of the whorls curving back- ward too strongly and being neither interrupted nor sigmoidally curved. The figure (op. cit., pi. XI, fig. 7) represents the shell as preserved on the inner volutions only, but a small peripheral rim or "collar" is rather distinctly indicated so that the species may be an undeveloped and closely coiled Eccyliopterus or an unusual type of Helicotoma. The remaining species constituting the supposed phylum (Euomphalus marginale Eichwald, Raphistoma spirillum Koken, Pleurotomaria replicata Lindstrom, and Eccyliopterus alatus Roemer, sp.) are doubtless all good species of Eccyliopterus and not Raphistoma at all. In constructing the line Koken seems to assume that the other characters are equal, and then to depend upon the gradual sinking of the spire and on the increas- ing freedom of the whorls. Neither of these conditions, however, appears to us of material consequence in the case, both pertaining strictly to the Eccyliopterus end of the line and neither occurring ever in any true Raphistoma. Further, we doubt very much that Raphistoma and Eccyliopterus represent different stages of one and the same line of development, nor have we met with any evidence that might cause us to believe that the distinction between the two is ever likely to become arbitrary or artificial ("eine kunstliche"). Finally, according to our opinion, the validity of Eccyliopterus will be determined not so much by its relations to Raphistoma as by its connection with Ophileta and Helicotoma and possibly Eccyliomphalus* We find that Eccyliopterus is very closely related to the latter genera, only one so far constant peculiarity separating it in either case. The feature alluded to is the prominent thin plate into which the notch-keel is produced and which surmounts the top of the whorls like a high "collar." On seeing a shell like the Calciferous Eccyliomphalus volutatus Whitfield, which, from a careful study of a series of specimens recently sent us by Prof. H. M. Seely, we have determined to be a true Eccyliopterus, the first impression would naturally be that the genus is a very near relation to Eccyliomphalux. And so it may be, yet, if for a moment we leave out of sight the fact that its whorls are widely disconnected, and consider only the other characters, it will soon become obvious that the balance of agreements lies on the side of Ophileta rather than Eccyliomphalus. The whorls of E. volutatus are flattened on the lower side, although casts of the interior are rounded here, the shell •When we say Krrnli»tniiliiiliu we are to be underwood as referring to shells of the type K. in/wliix ami nnuulciuitiol Hillings anil /•.'. iin' to separate them. [.A i . i- •• •»•••• thickened at the outer and inner corner-. Tins agrees with Ophibta, as does :I!MI the form «.f th«> aperture, and tlie course of the lines of growth. Finally, the position and character of the "collar " i- certainly much more like the notch-keel of Ophilet-i than the more obtuse keel or undulation which murks the position of the rather broad ami more shallow upper sinus in Eccyttompkaku. Loosely coiled or disconnected whorls we do not consider as an essential charact. ' n.<. All the species may perhaps exhibit a proneuess to assume such a condition l>ut it is certainly not very apparent in any of the American species. Of the latter, /.'. mhtinttts Whitfield .-p.. (see plate LXXIV) is the only one known to u* having all the whorls separate, and it is doubtless closely related to the KurojH'an /.'. n/atus Roemer sp., the type of the genus. Then we have l-'-.tri-inijtiltta Whit- tield sp., also from the Calciferoii- at 1'iovidence island and Fort Cassin, Vermont, which is exceedingly like the SwedMi /.'. ri'i>lirala Lindstromsp., especially when it has the inner whorls in contact. The next species, our E. beloitensis, is from the Stones i jrrmip. It, like the preceding, hasa representative in Kurope, being apparently very similar to /.'. hwald sp. All the whorls are in contact in this species excepting occasionally the apertural portion in old examples. The fourth American species is the Oplnlf 'fnsis of Billings, from the Trenton of Canada, while the fifth ami. so far as known, the last is the Ophilrhi mrenana of Meek and \\ orthen. c;ists of which are not uncommon in the Trenton group of Minnesota and Illinois. In )>oth the whorls are always in contact. From the foregoing statements it is e\ident that, in the development of the genus from the Calciferous on, the it.- or free character of the whorls became gradually less ami finally was lo-t entirely. All the other characters, however, ure maintained with rare persistency. If Kr>-i/lii>i>tmi* ami linjittixtnma are sections of the same line of development, then the evidence of their geological distribution indicates the former as the parent stock and not the la mv ll'ijthitloma occurs so far as known first in the Chazy when /•>, -i/Hnfitem*. which enjoyed its greatest development in the Calciferous formation, had already begun it- decline. We do not wish to deny that much may he said in favor of -iich a derivation of Ituphistonin, still we are confident that the modifications required are more difficult to prove and altogether less rational than in the view which derives the genus from /»'•//)/(/'.>•/•»//»/';»./. l!illinur- ha- de-cribed a number of low-spired <'alcift>rous ;lnd (jup.bec -| j,., amoii^ which we expect to find links connect MIL' tin- l.i-t ^emis with the t'lia/.y /,'•;//M«/owi«a on the one hami. and the " collar" of !•:••>• til i»i>tenu on the other. On later pages of his valuable work (488, ! Koken compares the genus BNMyAoJppfcnM with l>'l/iliinuln and particularly with the so-callo'l >V./n'n»i rtock. According to the second explanation the groups of species mentioned in the pn-ci»iing paragraph are actual descendants respective! '../i. <»./. \\ hich, because they lived under the sanx- ciinors, the gradual convergence of characteristics re- sulting inaseriesof f"im- that to many may seem almost inseparable. liothof these explanations are theoretically correct, ami although we are inclined to accept the second as the most rational, it is not at all improbable that the truth lies l..-t ween them. 940 THE PALEONTOLOGY OF MINNESOTA. [.Raphistoma. RAPHISTOMA, Hall. Raphistoma, HALL, 1847, Pal. New York, vol. i, p. 28. RapJiistoma (part.) and Pleurotomaria (part.), of many authors. For the generic characters and a full discussion of the relations of this genus the reader is referred to the preceding remarks on the family. (See pages 931, 934.) Of the nineteen species referred to this genus in the last edition of Miller's catalogue, perhaps only R. stamineum and R. planistria, with its variety parvum, really belong here. The majority of the remainder must be classed as doubtful, since we do not know whether they have a slit-band or not. Some may belong to Raphistomina, as does R. lapicida Salter, or to Liospira, as do R. a'mericanam Billings sp. (= Unticulare Emmons) and R. subtilistriatum Hall sp. R. niagarense Whitfield certainly is not a Raphistoma. It seems to be congeneric with Meek and Worthen's Platyostoma trigonostoma. Two good species of the genus were described by Billings as Pleurotomaria calyx and PI. crevieri, both from the Canadian Chazy. To these we add the two following new species. RAPHISTOMA PERACUTUM, n. sp. PLATE LXVIII, FIGS. 1-6. Shell small, not known to exceed 12 mm. in diameter, consisting of three or three and one-half whorls, flat above, rounded below; periphery very sharp and thin; umbilicus equalling a little more than a fourth of the greatest diameter, its edge narrowly rounded; hight of shell very slightly exceeding a fourth of the width. Surface marked on the flat upper side with very fine subequal striae sweeping on the whole rather strongly backward from the suture. About a third of the width of a whorl from the suture the striae are interrupted by a delicate revolving line. Between the latter and the extreme edge of the peripheral carina the striae make a distinct sigmoid curve. Below the periphery the surface is marked with similar striae, which, in descending, curve first forward and then almost directly toward the center of the umbilicus. In this species the hight is relatively less, and the peripheral edge consequently thinner, than in any previously described species of this genus. It is the only j^istropod known to us as occurring in the Lower Silurian rocks of Minnesota having a perfectly flat spire. Formation and locality.— Black Uiver group, Ctenodonta bed, Goodhue county, Minnesota. Rather rare. Collections.— E. O. Ulrich: W. H. Scofleld. (SASTHOPODA. KM III-I..M v 1:1. HVMNI.K.V- •/'. (I'lricli. 1-1 v 1 1 i \\ in. nos. 7-«. Shell 1') to 20 nun. in diameter, the spire almost flat, the hight between one- thinl aii.l two-seventh- of the width; volutions four, very slightly convex on the upper side, /. ••. within the outer edge which forms a thin elevated rim; umbilicus very small in casts, apparently dosed in shells. Surface striie fine and subequal on uppe making the usual sigmoid curve, the change incurves occurring near tin* mi.l.lU' of the whorU. -hist before reaching the peripheral rim the stria> make another short backward turn. Beneath the periphery the stria* are more unequal. At fir-t they turn forward then more directly inward. This species resembles the Chazy If. ralyr Millings, but is smaller and relatively wider. In / of the same author and formation, the edge is blunter, and the lines of growth curve more strongly forward beneath it. R. peracutum has an uml.ilicus and diU'ere in several other respects. A very similar species, differing only in that it has a small umbilicus, occurs in the Stones River group in Tennessee. Forwuitio* and totality.— Hli-hnmml nr. -.Ji>. Kn •humml, Indiana. Good speclmena ru CMlM*M.-E.O. Genus K.M'HISTOMINA, n. gen. (part.) and Plturotomana (part.), of author*. Tor generic characters and general remarks see pages 932 and 934 to 939. As species of this genus are generally confounded with Raphixtomn, it may be well to repeat the peculiarities upon which we base our separation. In Rdphistniifi the lines of growth on the lower side, which of course correspond with the outline of the lower lip. curve forward more or less strongly from from the peripheral edge. The outer half ami more of the under lip therefore is convex, whereas in i;>ij>/iist<»ninhixt<>inin. together with the forward nine immediately beneath the edge, produces'a small notch in the outer angle of the aperture. In l{>iphi*t»niin>it on the contrary, there is no notch, tin- angle being either rectangular or turned slightly forward, in some cases forming a beak-like projection. Comparing the upper and lower lips we find that in A'- ////i />/«;«,/ their outlines do not correspond, the lower being more prominent and -imply convex in the outer two-thirds where the upper forms a sigmoid curve. In J;inn, however, the anterior outlines of the two lips are either equal. y the ranch deeper and wider -inn- in the outline of it- lower lip. Fbrrnatvm and locality.— The orlglnml type* an- from th<- Ulack Kivcr lime* tone at Allumotte Inland, In th.- < Htawa rlvi-r. Canada. :ioeMee •(•• "iin- inun an niulvalfnl horl/oii near Lebanon. If the >peclM occurs In MlnneeoU It will probably U- found In ih>- Ct>-tKHlonta • If \riu-i.-MiN \ nK.NTirci.ATA, M. »/> (Ulrirh.) I'l Ml I. XVIII. FI08. JI-0. This species is very closely allied to ft. //. (t'/n'r/i.) I'l \TI I. XVIII. H'.S It IT. Differs from /.'. /•//•/••/•//i. which it resembles more closely than any other known, in )>eing smaller (12 to 15 mm. in diameter), in having a proportionally smaller umbilicus, and in its surface markings. DM the upper -i-le. which is also a little more depressed, the lines of growth are very faint, while the peripheral edge turn- rather di-tiiictly upward. «»n the lower side the lines of growth are likewise obscure except in the peripheral half of the la-t whorl, where they appear as rather coarse undulations of which the I.e-t -p.-cimen has about seven in 5 mm. The course of the lines on this side, which of course corre-pond- with the outline of the lower lip, is more convex anteriorly than in /,'. /,//,iV/'//,/. (Compare tig-. 1C, and 18 on plate I.XVIUi. /.' '/••ntirii/nf,i is a larger shell, has a higher spire and deeper 944 THE PALEONTOLOGY OF MINNESOTA. [Raphistomina rugata. Formation and locality.— Lower division of the Stones River group (Safford's Central limestone), near Murfreesboro, Tennessee. It is here associated with a broadly umbilicated and much larger species, apparently of this genus, of which, unfortunately, we have so far failed to secure satisfactory examples. Several other discoidal shells occur at this locality rendering great caution a necessity in discriminating between them. Collection.— E. O. Ulrich. RAPHISTOMINA RUGATA, n. sp. PLATE LXVIII, FIGS. 10-13. This pretty species differs in at least two respects from all of the foregoing species. First, the surface markings are relatively stronger, second, the umbilicus is more sharply outlined. As usual the surface markings are faint in the umbilicus and near the suture line, and much stronger in the peripheral portion of the shell. The umbilicus is rather larger than the average, its diameter equalling about a fourth of the entire width of the shell. Another peculiarity is that the upper surface of the whorls is almost flat from the but slightly impressed suture line to the edge; nor is there more than a barely perceptible concavity beneath the edge. Often the whole upper surface of the shell is perfectly flat, giving it more of the usual appearance of a Raphistoma than a Baphistomina. The spire is always lower than in any of its congeners, and in no observed case higher than in fig. 12. Formation and locality.— Clitambonites bed of the Trenton group at various localities in Goodhue county, Minnesota. Colkctions.— E. O. Ulrich; W. H. Scofleld. Genus OMOSP1RA, n. gen. (Ulrich.) Murchisonia (part.), HALL, SALTEK and BILLINGS. For generic characters see page 932. We are anything but satisfied respecting the systematic position of this genus. If Scalites, Emmons, could be proved to possess the essential characteristics of the Raphistomidce, th,en we would have an undeniable link between Omospira and Raphistoma. In the absence of such a link, the general resemblance which Omospira bears to certain Pleurotomariidw, like Hormotoma bellicinda and Eotomaria elevata, gives us not a little trouble to explain away in a convincing manner. Still, there are two features about the sinus in the upper lip and the band-like space resulting from it in the growth of the shell that are anything but indicative of pleurotomarian affinities. First, the great width of the band, and second, the oblique, — perhaps it would be better to say the outwardly increasing, — curvature of the lines crossing it. In all true Pleurotomariidcc the lunulae or lines crossing the slit-band, providing the latter does not lie, as in Liospira micula, partly over the peripheral edge, form a uniform curve in passing from one to the opposite border of the band. (See fig. 13, -iTROPODA. -»••". Ommplr. l.iMi plate I \l\ As may be seen in fig. 65 on plate l.\\. tin- is not the case in Omosi'i>-'t, tin- line- in this case cro—in^ obliquely and increasing in curvature downward. The lines on the hand. furthermore, are of the same character as those above tin- band, only curved in the opposite direction, the two portions united forming a sigmoid curve as in /i'u/i/ji «,•'••»» ;';n;t- and their rout inuity is interrupted when tlic change in direction occurs l>y ;i raised line, a- i- frequently the case in I- it fair to explain tho conditions observed in Omospira by supposing that they have resulted, first, through the elevation of the spire and the consequent reduction of peripheral carina ami lightening of the volutions, and second, either by a mere approximation toward the prevailing character of the Gastropoda with which they are chiefly associated, or by following the more prevalent tendency which they, as Raphisdnniilir, inherited, like the Plfurotomuriiiln, from their common ancestor? For the pre-ent we must confess that we have allowed such theoretical reasons as the foregoing to dominate our placement of the genus. whatever position Omospira may be ultimately assigned, the validity of the H is not likely to be seriously affected. If it really belongs to the Raphistoin then it will >tand as a type obviously distinct from the other genera of the family, because of it- high spire and comparatively rounded volutions. If, on the contrary, it proves to be one of the PlturntniiKiriiilie, then it will be readily distinguished by the peculiarities of the band mentioned in the preceding paragraph. The high po-ition of the band would also serve in the latter association. As to the specific representation of the genus, we know of only two species that can be referred here positively, namely, the type 0. luticinrtn and Murrhisonia •n'lr-i Hillings tlter. not Hall). Possibly Hall's M. rmtricosa also Belongs here, but W bitfield says it is a OMOSPIRA LATICINCTA, n. sp. (Ulrich.) PLAT) 1 \\ FIGS. M *nd « i '•" i '.", .the angle formed by the h'r-t three or four wliorU n-nally about live degrees more. Volution* a bout seven in number, obliquely flattened above, ventricose below, their -ides ahno-t vertical, the upper turns more rounded than the last three. Sometimes the flattened upper portion is more nearly horizontal than in the specimen illu>trated. Aperture -nbtriangular, somewhat higher than wide, the outer lip thin and curving gradually inward from the shoulder- like upper angle to the narrowly rounded base; inner lip only moderately thick. nearly straight, and generally reflexed in its upper part over a minute umbilicu-. -60 946 THE PALEONTOLOGY OF MINNESOTA. [Omosplra alexandra more or less completely closing the latter in all save one of the specimens before us. Surface marked with fine, regular, equal, raised lines of growth. These curve rather strongly backward on the flattened upper portion of the whorls until they approach the shoulder-like angulation, when they turn sharply forward. About midway between the suture line and the outer angle, the growth lines are interrupted by a sharply elevated revolving line, causing the outer half of the upper slope to resemble an unusually wide slit-band. Beneath the angle the lines descend with a gentle forward curve to the base of the whorl. This fine species is readily distinguished from 0. alexandra Billings sp., by its higher and more angular whorls. Formation and locality.— fop of Stones River group or base of the Black River group, near Leb- anon, Tennessee. Collections.— Plot. J. M. Safford; E. O. Ulrich. OMOSPIRA ALEXANDRA Billings. PLATE LXX, FIGS. 66 and 67. Murchisonia ventricosa SALTER, 1859, Can. Org. Rem., Decade 1, p. 23. (Not Murchisonia ventricosa Hall, 1847. Murchisonia alexandra BILLINGS, 1865, Pal. Foss., vol. i, p. 172. • This species has the same general characteristics as the preceding, yet may be distinguished at once by its more depressed and more rounded volutions. Its apical angle also is narrower, being between 40° and 45°, while the aperture is more rounded. There is not a sign of an umbilical perforation. The cast of the interior figured as possibly of this species may in reality belong to something quite different. At any rate, it is the only fossil from the north- western states which we could say probably represents this species. Formation and locality.— Base of the Trenton group or at the top of the Black River group, in Mercer county, Kentucky. The types are from the latter horizon at Allumette island in the Ottawa river. Canada. Collection.— E. O. Ulrich. Family PLEUROTOMARII1LE, d'Orbigny. This large and most important family of fossil shells has given systematists not a little trouble to classify. The great number and variety of the species has occasioned many attempts to arrange them in convenient generic and subgeneric groups, sometimes happily, but in most cases the result proved neither convenient nor successfully defensible when subjected to the test of genetic relationship. As usual many of the subdivisions as drawn by authors were necessarily wrecked through the prevailing ignorance concerning the structural peculiarities and lines of development exhibited by the Paleozoic types, the early Paleozoic especially. ifODi •' 1 7 PUuroUMMtrlld* ) h year the absolute necessity of extending our systematic paleontologies! studies backward as far us possible becomes more and more obvious. The rapid changes which took place among the early representatives of all olaMOB of animals and the con-.-. (in-lit relati\e ea-e \\itli \vliirli the lines of evolution may In- traced. j_'i\e- them an importance in Biology that is scarcely to be overestimated. For the ' he Lower Silurian species, because the class is but sparingly represented in the <'aml>iiaii, are the most likely to throw light upon the genetic relations of the succeeding forms, and are therefore deserving of the most careful investigation. Concerning the Heurotomnriidn; the facts brought out in an extended study, of the 1'aleo/oic -pecies chiefly, have led us to conclusions that, while not greatly different from those publish^! i>\ Koken, who has adopted methods more nearly in accordance with our own than any previous observer, are still sufficiently original to cause great changes in the views and nomenclature heretofore in vogue. We have gone into the subject more extensively than the present work demanded or perhaps even ju-titied. hut the knowledge gained, if it cannot all bear fruit immediately, is -till not in vain, -ince it will doubtless prove of use in our future work. We have most carefully considered the published papers of authors who have dealt with Paleozoic -M< ;•<•///lit. The Ion- parallel-edged slit occurs, as far a- known to us, in but two Lower Silurian species (.sV/M.-o/oy,/,,; of tin- work), and is comparatively rare among the I pper Silurian and Devonian form*, l.ut with t lie Carboniferous species it is common, while among the more recent form- it i- nearly always present. Of all the char. f the family, the peculiarities of the lit or a series of openings. These groups are again divisible, according to the character of 948 THE PALEONTOLOGY OF MINNESOTA. [PleurotomariidtB . the slit-band, each into two similar groups, one having the band convex, the other concave. Such an arrangement might at first appear convenient, yet a careful study will soon reveal that it would be quite arbitrary, therefore unnatural, and in the end not even convenient. This is so obvious that it is quite unnecessary to cite proving instances. Still, there is an element of truth in the first of these suggested divisions, for it would separate what we may call the archaic from the more recent stages in the development of the family. We have already referred to the almost total absence in the Lower Silurian Pleurotomariidce of the long parallel-edged slit which occurs so generally among the more recent types of the family. This difference has not received the attention from paleontologists that it deserves, for surely it must indicate a structural difference in the animals. Lindstrom barely alludes to it, while Koken, much to our surprise, takes no notice of it whatever. Unfortunately, the presence or absence of the slit is not positively determinable except when the aperture is entirely preserved, the band behind the slit presenting, so far as we can say, no evidence that might lead the observer to suspect either the one or the other condition. The slit which should be carefully distinguished from the apertural notch, which is more or less widely V-shaped and does not extend backward any farther than the bottom of the sinus formed by the lines of growth, seems to be a later phase in the evolution of the majority of the lines of development that can be traced from the Lower Silurian into subsequent periods. Its development appears to be the result of a tendency to which the whole family, rather than any particular generic line, is subject. As we have already said it is almost entirely absent in the Lower Silurian Pleurotomariidce, in the majority of which the lines of growth, and, therefore, the outer edges of the lip, sweep backward toward the band more strongly than in the prevailing types of subsequent ages. We might then assume that the slit was represented in those ancient times by a deep notch, and that the presence of the latter in many Devonian and Carboniferous forms is merely a retention of a primor- dial character after its real cause or purpose had been removed or satisfied by the development of a long slit. However, before such a view can be accepted we must account for the extreme shallowness of the apertural sinus in such slit-less species as are comprised in the Bicinda section of Lophospira, which, as far as our present knowledge goes, existed in numerous species from the Chazy to the close of the Upper Silurian. Now, Shizolopha textilis, which has a long slit, was almost certainly developed from some member of the Bicinda section, so that the suggested explanation of the development of the slit cannot apply here and is rendered highly improbable in any case. '.M'.t •••1 In f I'/, nr«tniHitriilit varies greatly in different members of the family. On the whole the length is considerably greater in Mezozoic than in Paleozoic species. In the latter the length has not been observed to exceed three-eighths of the circum- ference of the last whorl. In the Devonian PI. sul<-omt<»nari(i and Chelolin. the length often exceeds one-half and may reach fully two-thirds <>f the last whorl. It is interesting to note that, as far as we now know, the slit which furthermore seems to have been developed almost suddenly, is longer in the earliest species known to possess one than in any of the later Paleozoic forms. Th»- land which i- left behind by the gradual closing of the slit presents considerable variety in position and structure. As a rale, especially among Paleozoic species, it lies on the peripheral part of the whorls. When the volution- are angular it commonly forms the summit of the principal angle, a- in Lnphospira and \\'<>rthenia. In conical shells, like those of the group of PI. turbhil/nniii*. it forms a narrow vertical band at the extreme periphery of the whorls. In other conical shells, like / Killing, it lies at the base of the flat slope, the lower edge of the band in -m-h ca-es funning the periphery. In certain Mesozoic ami recent types (Pyr :' .UP! /..,'. -..I '/.<',/- (.; Fitther) in which the shell is similarly conical, the b.ind lies considerably above the angular periphery, but it never occupies such a position in any of the angulati-1 1'aleozoic t\pe-. l.eing in these placed al\\.r. - very near or entirely upon the angle. Occasionally, as in the oniferous group of PI. Lrnzoensis, it lies in a broad peripheral concavity, beneath the principal carina. 950 THE PALEONTOLOGY OF MINNESOTA. [Pluerotomarildm . What we conceive to be the most primitive type of slit-band occurs in the Lower Silurian Lophospira. In this genus it occupies, or rather forms, the summit of a more or less prominent peripheral ridge, above and beneath which the lines of growth curve backward in directions corresponding to the outline of the apertural notch. The band itself may be simply a blunt edge, upon which the growth lines make their turn; but more commonly it is defined on each side by a delicate raised line, which separates the lunulae of the band from the surface striations. The markings of the band are always different from that of the rest of the surface, being as a rule more regular, while the arched transverse lines or lunulse may be stronger or weaker, and farther apart or closer than the lines of growth either above or beneath the band. Occasionally, as in Lophospira tubulosa and L. imbricata Lindstrom sp., and our L. notabilis, the lunulae are widely separated and strongly imbricating; sometimes, as in L. bicincta, they are much finer and very closely arranged; frequently they consist of simple elevated lines; in other cases they have a median excision (Pleurotomaria limata Lindstrom), or they are crossed by one (PL ohioensis James) or two (PL scutulata Lindstrom) median lines; or the central line may be developed into a thin undulating plate (Lophospira sermlata Salter sp.) or into a row of nodes (PL [Worthenia] tabulata Conrad). In short, the marking of the band in the members of the family is of great variety, but as a rule we cannot say that the various types are of much assistance in determining the generic or subgeneric position of the species. Although we can already see some possible exceptions, we think that provis- ionally it is advisable to regard species having a concave band as generically distinct from those in which the band is convex. We have very carefully examined a large number of species, and so far the separation on this difference has resulted in a very much more satisfactory classification than any we have yet had. Consid- ering the form of the band, as far as its being concave or flat on the one hand and more or less convex on the other is concerned, as a leading test of relationship, we bring together many forms that have hitherto been separated, while many others that had been associated are widely separated. As generally understood heretofore, particularly among American and Canadian paleontologists, the two principal Paleozoic genera of the family are Pleurotomaria, De France, and Murchisonia, d'Archiac and Verneuil, the former embracing the species with a low spire and relatively few volutions, the latter those forming a high shell of numerous whorls. As viewed by us this broad separation or arrange- ment of the species according to the hight of the spire results in a most artificial classification, since it causes the separation of shells that comparative studies prove to be closely related genetically, while others are associated that have only very 951 Sjr»op*to of remote allinities for each other.* Beside- it leaves a large number of intermediate forms which may be placed with equal propriety into either genus Hut this is not all. for w«» believe with other author- that, as now constituted, these genera embrace material more than -ulh'ciently various t«» admit of defining a comparatively large number of vali'l generic group-, valid in the sense that they are relatively as important group- ot -pecies as are ordinarily considered to be of generic value. Now. what are the characters upon which we propose to base these genera? *. upon the presence or absence and relative length of a true slit, as distinguished from a mere apertural notch; second, the characters of the slit-band, among which its outline, as exhibited in transverse section, is the most important; third, the width of. and the position of the band and slit or notch with respect to the hight of the volution*: fourth, the form of the volutions, with respect to angularity and roundne--; fifth, the form of the entire shell; sixth, the character and depth of the *uture; seventh, the form and outline of the aperture as shown by the lines of growth, and eighth, the changes in the character of the volutions from the embry- onic to the mature stages. Corroborative and subordinate characters are furnished by surface markings, the apical angle, the relative size of the last volution, the presence or absence of an umbilicus, and minor peculiarities of the aperture, the notch, the slit and the band. The relative importance of these characters is not always the same, but they are sufficiently reliable for present requirements. SYNOPSIS Or OBHERIC AND SUBORDINATE GROUPS OP PALEOZOIC PLKUROTOM ARIIDJt.f I. IX>PHOSPIRA, Whitfield, 18864 Shells with more or less elevated spires; whorls closely coiled throughout or only in the upper part, the last often exhibiting a tendency to become disconnected; whorls angular on the periphery and bearing from one to five distinct carin.i-; central or peripheral keel strongest and most prominent, carrying the band, which is obtusely rounded, or more or less distinctly trilineate, with the median line heavier and more prominent than the other two; rarely, if ever, solid; an umbilicus n-ually of very small size, nearly always present Inner lip generally thickened, often slightly twisted, turning around the umbilicus so as to form a kind of hollow pillar. Outer lip more or less deeply notched, but the center of the notch, which lies at the peripheral angle, is never prolonged into a -lit. Surface markings parallel with the apertural edge; occasion- ally cancellated l>y linespir.il lines. Typ—. M'ir. -1,1,1- mln ///>/'/! • • • 3i tor M helicUm Whitii.-ld. n..t Salt.-r.i •To appreciate the «ubordlnat*ne*> of lite ralm- of dlferrnCM In the hl«bu of Uw iplre within moderate llBlU. » oomparteoaof U>« >curM of *pMta* of t*f*wp*v deeerlbcd In thl- wurk We pe«* by almoat Imperceptible tmdatloaa from •perlr* Ilk* L. ••pin and L. MloMib. In wlili-h the apical angle t« » and «0 decree*. to other*, like L. titmtnt teford .p.. In «hlrh the aaclc I. of MmeUmea ICM than » decree*. And. to far w we out tee, there I* not the otcct rfaaoee for a i»«4rte •eparaUon between the Int and the la.t of the ipecta* mentioned. •Remarkiuo (earraof whtchcpedeeandewrlbMl In t I ,1 \~ fuund oa »occeedla( pace*. t Bull. Aner. Ma*. Nat. HIM, roLI. p. III. 952 THE PALEONTOLOGY OF MINNESOTA. [Synopsis of PleurotomaritdaB. II. SCHIZOLOPHA, n. gen. (Ulrich.) In every respect like Lophospira excepting _ that the apertural notch is prolonged into a long parallel-edged slit. Type, S. textilis, n. sp. (Ulrich.) III. PHANEROTREMA, Fischer, 1885.* Shell turbinate, whorls few in number, flattened above, the last large and high, the others rising step-like; spire short; slit long, region of band salient; aperture subquadrate, inner lip thick; lines of growth nearly vertical beneath the band, above it turning more decidedly forward; strong revolving lines occur especially on the lower and outer parts of the whorls. Type, P. labrosa Hall. This Upper Silurian genus seems to have been derived from the Trochonemoides section of Lophospira, our L. trochonemoides and L. knoxvillensis being very similar in general form and having almost exactly the same kind of aperture. The band, though salient also in those species, is somewhat different, the central line being, as it should be in Lophospira, considerably stronger and more prominent than the bordering lines. Still, in our opinion, the peculiarities of the labrosa type of band were produced by an extreme development of the bordering lines, the space between the elevated edges being gently convex. Aside from the band, Phanerotrema is distinguished from all the Lower Silurian Pleurotomariidce, except Schizolopha, by its long slit, and from the excepted genus by its relatively smaller spire, much larger last volution, peculiar band, and strong revolving lines. Further, it seems very clear that, although both types originated in Lophospira and deviated from the general character of that type in similar directions, their immediate ancestors represent widely different sections of that genus, and constitute distinct lines of development. Of the two species of Schizolopha, S. textilis evidently came from the Bicinda section, while S. mooresi accords more nearly with the Perangulata section. As to Phanerotrema, we have already said that it was most probably derived from the Trochonemoides section. Phanerotrema includes besides the type species, PI. occidens Hall, and a Goth- landic shell which Lindstrom erroneously identified with Hall's labrosa. The genus appears to be sparingly represented in the Devonian of Europe, but we know of none in American deposits of that age. Two of our Carboniferous species, however, PI. grayvillensis Norwood and Pratten, and PL marcouiana Geinitz, appear to have all the essential characters of Phanerotrema, and we expect to find that they are actual continuations of the same generic type. IV. WORTHENIA, De Koninck, 1883. Shell conical, tabulate, the general aspect much as in Lophospira; whorls angular on the periphery, the latter carrying the band; slit extending backward from the mouth between one-fourth and one-third of •Muuual lie Concbyliologie. p. 651. ..i-oiiA. at Plror»U,»«rllJ^ 1 the c i iv n inference of the last whorl; band narrow, convex, the lunulip not much cur\' -tronj; aii-1 prominent at regular intervals, giving the band a crenulated ..i toothed appearance; columellar lip scarcely callous, reflected and forming a sort of false umbilicus; Mirfaco ornamented with -piral ridges; lines of growth moderately curved backward on the upper side of the whorls, nearly vertical beneath the band. Typo, /'/. munsteriana I 'e Kmiinck. This tfenus i- represented by three good species in the Carboniferous deposits of America, vi/ : /'/. taljulti/,1 Conrad, /'/. subscalari* Meek and Worthen, and PI. sptciosa M. and W. We have before us a small undescribed species from the • man of Ohio that probably belongs here. The Worthenias remind one greatly of certain Lower Silurian types of Lophospira, particularly of the Bicincla section and L. knoxtillensis, and it is highly probable that they will be traced back to some member of that genus. We think further that they will be brought into connection with the I'pper Silurian 1'hanerotremas. For the present they are readily • li-tiMjiiUhfl from the latter by their higher spire, more gradually increasing volutions, and different band. From Isophospira they are separated by the denticu- late band, strong spiral ornamentation and in having a true slit V. LIOSPIRA, n. gen. Shell sublenticular, the spire low, depressed conical, almost smooth, the sutures very close, scarcely distinguishable; volutions aubrhom- boidal in section, flat, gently convex or slightly concave above, sharply rounded at the periphery, convex below, and not infrequently angular at the edge of the umbilicus. The latter is usually present but may be filled entirely by an extension from the inner lip, in other cases it may be open during the younger stages only. Aperture deeply notched; band scarcely distinguishable as such, wide, situated on the narrow outer edge of the whorls though chiefly upon the upper side. Surface markings very delicate, rarely preserved, consisting generally of exceedingly fine transverse lines bending strongly backward on the apical side to the peripheral hand over which they continue with little interruption to sweep sharply forward again on the lower side. Faint revolving lines occasionally observed. Types, •'"•«/./ Hall. /'/. . nn Billings. VI tu, n. gen. (Ulrich.) Shell subtrochiform, regularly conical, base nearly Hat. -uture >hallow; umbilicus usually of largo size; mouth subqnadrate, the inner lip but little reflected and scarcely thickened, the outer with a wide notch but no slit, the upper projecting l>eyond the lower: whorls numerous, enlarging very gradually, sharply angular at the lower edge; band not sharply defined, of moderate width, lying entirely upon the upper side of the peripheral edge; on the upper side of the whorls the lines of growth are fine and strongly curved backward from the ;re to the band; on the lower side, where they are usually somewhat stronger, 954 THE PALEONTOLOGY OF MINNESOTA. [Synopsis of Pleurotomariidoe. they pass almost directly across the whorl, a short backward curve occurring only just before they reach the periphery. Types, PI. etna and ramsayi Billings. At least two other species, the PI. amphitrite Billings and PI. beekmanensis Whitfield, are known to belong to this generic type. A possible fifth species (it may be the same as Billings' etna) occurs at Ft. Cassin, Vermont. With the exception of the species amphitrite, which may be a Chazy fossil, all these forms occur in the Calciferous formation, so that the genus represents one of the earliest fixed types of the family. Though fixed, in the sense that the known species adhere very strictly to the characters mentioned in the generic diagnosis, the type was evidently of vShort duration. We have very carefully examined the Pleurotomariidce found in succeeding geological divisions but have failed entirely to discover any that might reasonably be viewed as descendants of Euconia; nor do we know anything positive about their ancestors. We are therefore obliged to consider the genus as a rapidly evolved, short and abruptly terminated branch from the stock which produced also Liospira on the one side and Eotomaria on the other. Euconia is distinguished from all of the Lower Silurian Pleurotomariidce by the regularly conical spire and flat base, and the very slight curvature of the lines of growth on the under side of the whorls. These features are all reproduced in the Carboniferous group of shells which we propose to distinguish as Euconospira, but they have another character, namely, a long open slit, which is absent in Euconia and of itselt demands a separation. The surface of the Carboniferous shells differs also in being spirally lined. VII. EOTOMARIA, n. gen. Shell depressed-conical, sometimes sublenticular; base more or less convex, its bulk usually neai'ly equal to the apical part; umbilicus very small or wanting; volutions not very numerous, sometimes slightly turriculate or strongly angular near the mid-hight; aperture oblique, subquadrate, the inner lip slightly reflected or merely thickened, the outer deeply notched at the peripheral angle; no slit; band of moderate width, concave, sharply defined, oblique or horizontal, lying upon the apical side of the periphery. The surface markings consist of fine lines of growth only. These curve backward more or less strongly toward the band on both the upper and lower sides of the whorls. Type, E. sublcevis, n. sp. (Ulrich.) VIII. CLATHROSPIRA, n. gen. Shell in all respects like Eotomaria except that the band is nearly vertical and situated upon the periphery of the whorls, and the surface beautifully cancellated. Type, PI. subconica Hall. IX. BEMBEXIA, (Ehlert, 1887.* Shell depressed subconical, imperforate, volu- tions angular; band distinct, concave, vertical or oblique, situated on the periphery, EXIT. Bull. Soc. d'Etu. Sclentlf. d' Angers.p.'St. Syw.p.1. of Pl.urw«om«rtld«-.) ~ul. MI. ''11.111 on the last whorl; -lit about one-fourth volution in length; aperture moderately ol.lique. the edge of the upper lip sweeping backward rather strongly, the lower broadly concave in the middle, the inner lip generally somewhat thickened and reflected. Surface with rather strong lines of growth; on one or both sides of the band often a more or less well-defined smooth space. Type, Bembexia lartcli Munier-Chalmu- -p. We lia\e adoptod this name for the group which in America is typified by the well-known Hamilton species, Pl.8ulcomar>jin>it-ll'• < VxiV/, as here defined, corresponds very nearly with Koken's " Plfurotomarii int> mipin ." The group, whether viewed as a genus or a snli^enu- i- immaterial, seems to be a perfectly natural one. Provisionally we would give it an intermediate position between the Silurian Eolomaria and the r.irboniferous /•;//,-,,»,,^,/;-,i, the tendency of variation exhibited by the species being toward the latter, while their general expression reminds one of the former. \. i, De Koninck, 1888. Shell conical or somewhat discoidal, umbilicated. Band forming the periphery of the whorls, extremely prominent, thin, flange-like. On the upper side of whorls lines of growth curve backward without interruption from the suture line to the extreme outer edge; on the lower side first forward, then in a broad curve backward, and finally forward again as they turn into the umbilicus. Surface with revolving lines or not Type, PI. limata Lind-tr»m (/'/. r,,rinntn Sowerby). This type of shell is represented in American deposits by Miin-hi^min tcorfhenana, a rather high species described by Miller from the Niagara limestone at Chicago. As now understood the principal peculiarity of Monrlonia, when compared with true PltuntomariUm, lies in the excessive development of the bounding plates of the slit-band. Thi< particular feature reminds one of S^omfkotofttrut, Koemer, and it i- possible that Mourlunin is really allied to that remarkable genus. Still, they are readily distinguished by the sigmoid instead of uniform curve of the lines of growth on the upper side of the whorl- in Enomfkalopttnu. Despite the resemblances we are firmly convinced that the genesis of the two types is quite different. \1. K; . "Nu-i -IRA. n. gen. (Ulrich.) Shell almost regularly conical, the base nearly flat, sometimes a little convex but oftener slightly concave; not perforated, though a small umbilical depression is always present; whorls rather numerous, the rir-t three or four, so far as observed, leas flattened on the upper or visible slope than 956 THE PALEONTOLOGY OF MINNESOTA. [Synopsis of Pleurotomarildfe. the following turns; aperture oblique, the width much greater than the hight, the inner lip scarcely thickened, the lower border, beginning at the inner extremity, first convex then broadly concave and finally convex again when the edge turns rather sharply backward to the slit which lies in the peripheral angle; upper margin sweeping backward very strongly from the suture; length of slit equalling between a third and a fourth of the last volution; band narrow, slightly truncating the pheriphery, visible on all the volutions, concave, lying between sharply elevated lines. Excepting the first three or four whorls, the surface is cancellated by fine spiral lines crossing the lines of growth. Types, PI. turbiniformis Meek and Worthen, and PI. missouriensis Swallow. 'V>i>/iWu4 a£tfaw <*_ ptAfad The deriviation of this genus is doubtful. There are two widely distinct Devonian groups of species from either of which it may have been evolved. With the evidence at hand, one derivation seems as plausible as the other, so we find ourselves unable to decide for either. The first brings the Ewsonoapirce from the PI. lucina group, in which the slit-band and surface markings are similar while the form of the shell and of the volutions is very different. If this is the stock from which the genus under consideration sprang, the first change consisted probably in the gradual flattening of the dorsal surface of the whorls. In PI. filitexta, PI. ella and PI. hebe, all species of the Hamilton group described by Hall, the necessary conditions are supplied in increasing ratio. The next step is furnished by Meek's Waverly species, PI. textiligera, in which the apical side of the shell agrees exactly with the Euconospirce. The basal portion, however, is very different, being ventricose instead of flat. Now, if we could find a shell having the convexity of the base considerably reduced, we might say that the chain connecting PI. lucina and Euconospira turbiniformis is reasonably complete. The second line of development would begin in, say PL sulcomarginata Conrad of the Hamilton, and include PI. nitella Hall, of the same formation, PI. shumardi Meek and Worthen, of the Keokuk, and PI. elegantula Hall, of the St. Louis. The last species, though still too full at the base, nevertheless approaches very nearly to the form pertaining to the Euconospirce. The principal feature lacking is the spiral sculpture, which is wanting in all of the sulcomarginata or Bembexia group. This difficulty, however, is lessened by the fact that the spiral lines are wanting also on the first volutions of at least two species of Euconospira. These early turns, furthermore, are slightly rounded on the dorsal surface, thus strongly indicating that the type was evolved from another in which the whorls were more rounded and without spiral markings. Taking all these points into consideration, the balance of agreement seems to be in favor of the second rather than the first line of development. "I-ODA. of n»>i>im i- ino-t probably related to the Mesozoic group of species which ha- distinguished by the name /' '/"-. with /'/. Intonjuitta Deslong- champs, as the type. The latter differs from our genus principally in having the band ii«>ar the middle of the dorsal side of the whorl- instead of at the basal edge. The presence of a long slit distinguished the genus from Euconia, Eotomaria and Clathriispirii. XII. TRKI-OSHKA, n. gen. Shell sublenticular to depressed conical; base convex; without umbilicus; whorls, six or seven, the first two or three very small, rounded. |irominent au-1 -month. the next two flat and coiled more or less nearly in tin- same plane, the rest sloping according to the apical angle of the shell; aperture -verse, subrhomboidal, the upper lip projecting beyond the lower, the outline rurving strongly backward to the slit; edge of lower lip strongly convex in the middle; inner lip rather thin but cunt inning into a concave callosity which is spread the umbilical region; slit very short, scarcely extending beyond the notch formed by the converging lip-: band rather wide, slightly concave, smooth, visible on tin- la-t svhurl only, so situated that its lower edge forms the peripheral angle of the volution: l.epnnin^ with the fourth turn the sutural edge bears a row of nodes covering the banf fapt In its most essential characters— form of shell, nearly smooth surface, short slit, and direction of lines of growth on the lower side — this genus resembles the Lower Silurian Lio»f>ir