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University of Illinois Library JUN 7 195 L161— 0-1096 wet as oo | ee eee ae Gj el Se 3) % PS = ag ~ ; * Fretp CotumBiaNn MusEvuM. PUBLICATION 73. GEOLOGICAL SERIES. Vor lis No: |. NORTH AMERICAN PLESIOSAURS. PAARL TS. BY SamueL W. Wuutston, M.D., Pu.D., Associate Curator, Division of Palzontology ; Professor of Paleontology, University of Chicago. ‘ie Ouiver C. Farrincton, Pu. D., Curator of Geology. ' 8 Cuicaco,4U 5.2A: April, 1903. Fretp CoLuMBIAN MuSEuM. PUBLICATION 73. GEOLOGICAL SERIES. Voz. II, No. NORTH AMERICAN RE ESorOSAU RS: f ghe iP age SRT BY SAMUEL W. Wittiston, M.D., Pu. D., Associate Curator, Division of Palzontology ; Professor of Palzontology, University of Chicago. Oxiver C. Farrinctron, Pu. D., Curator of Geology. Cnuicaco, .U. S. A. April, 1903. Se. a - NORTH AMERICAN PLESIOSAURS. PART FT. BY SAMUEL W. WILLISTON, CONTENTS. - : . PAGE Introduction, ; : : , ; ; ; : : ; ; , 3 Bibliography and catalogue of North American Plesiosaurs, . ; : 7 Dolichorhynchops osborni Williston. Description of skeleton, with restor- ation, ; ; ‘ ; he) : , ; ; 13 Cimoliasaurus snowii Williston. Description of skull and neck, aes 2 Brachauchenius lucasii Williston. Description of skull, vertebree and ribs, 57 Polycotylus latipinnis Cope. Description of paddle, ip ; OSs Polycotylus ischiadicus Williston. Description of pelvis, . ; : 2 Plesiosaurus gouldii Williston. Description of dorsal vertebra, : eal 2 Propodial bones of young Plesiosaurs from the Cretaceous of Kansas, . 73 A peculiar food-habit of the Plesiosaurs, . ; j ; : 7 raters Plates I to XXIX, : i , ; : 3 ‘ "Ate INTRODUCTION. There are few orders of reptiles, so long and so widely known as are the plesiosaurs, of which our knowledge is more unsatisfactory. It has been within the past decade only that a tolerably complete knowledge of any form has been obtained, thanks largely to the researches of Seeley, Dames and Andrews. Especially is our ignor- ance of the American forms yet great. Very few figures or adequate descriptions have been published of our numerous and diverse types. Not only are the specific characters of the descriptions almost wholly undecipherable, but the generic characters even can be satisfactorily made out in but few. Thirty-two species and fifteen genera have been described from the United States, and in not a single one of them has there been even a considerable part of the skeleton made known. The skull is known in but three species, and in only one has there been any description of it. With the exception of a sketch of the incomplete girdles of E/asmosaurus platyurus, and of a few limb bones by Leidy, with an outline figure of a Mega/neusaurus paddle by Knight, nothing of the extremities has been published. And yet, specimens of plesiosaurs are not at all rare in American deposits and collections. Although most of the genera and species of the United States have been founded on such scant material, and even more scanty descriptions, that their identification is almost impossible, except by actual comparison of the type specimens, it is not at all improbable that nearly all the names which have been proposed will eventually be found valid. The group has a wide geological range, from the Jurassic to the uppermost Cretaceous, nearly every epoch being repre- ' sented by one or more species. The writer has for some time given such attention as his duties permitted to the study of the American plesiosaurs, in the hopes eventually of clearing up much of the confusion now existing con- cerning these animals, and the present paper was intended to be pub- lished as a portion of this monographic study. As, however, the publication of so extensive a paper must be deferred for some time, he has thought best to publish that portion now prepared in advance 3 4 Fretp CoLumpian MustumM—GEeEo toecy, VoL. II. of a more final review of the subject. The present paper contains detailed descriptions of Dolichorhynchops osborni Williston and Brach- auchenius lucasi Williston; a revised description of Cimoliasaurus snowit Williston, together with certain descriptions of and remarks upon such other forms from the Kansas Cretaceous as bear more or less directly upon the principal species here discussed. As will be seen from the list given below, no less than nine distinct species of plesiosaurs have been described from the Kansas Cretaceous, all of which, except one or two, are autoptically more or less known to the writer, together with nearly as many more hitherto undescribed. The true generic determination of the most of these species is impos- . sible at present. So little is known of the real generic characters, not only of the American but also of the. European plesiosaurs, that, — unless specimens are very complete, it is impossible to correctly assign them. Furthermore, there is in many respects such wide diversity between the different forms now known that almost every species seems rightfully to belong in a different genus. On the other hand, in our present ignorance of their value, generic differences can, rarely be recognized unless one has a considerable portion of the skel- eton. Generic determination is, therefore, for the most part, at the present time simply guess-work. In the present paper I have, for convenience sake, given names to some of these new forms, but the generic names are always provisional, and the specific names also insome cases. Cvmoliasaurus snowiti | do not believe is congeneric with the type species of the genus; it belongs as well in several other genera proposed by American writers. I do not see, however, much use in giving new generic names to every form until some razson @ étre can be discovered for them. I have departed from this conviction in proposing two new generic names for species herewith described, largely because the specimens upon which the names are based are more than usually complete, and because there seems to be positive characters to sustain the names. The full description and illustration of Dolichorhynchops osborni will, I trust, aid in the solution of many of these generic problems; they will at least furnish a means of comparison for other forms known already or to be discovered in the future. A second part of this work is to follow soon, I trust. It will contain the descriptions and illustrations of two or three other skulls, different in structure from those herewith described and from each other, together with other important material. Iam glad to express my thanks to Prof. Dr. E. Fraas for kind Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON, 5 suggestions, and for the communication of photographs; and to Prof. H. F. Osborn for kind favors. Seeley* has proposed to divide the plesiosaurs into two chief groups, the Dicranopleura, including those forms with double-headed ribs in the cervical region, both long-necked (Dolichodeira) and short- necked (Brachydeira); and of which singularly no certain representa- tives have been discovered in America; and the Cercidopleura, those with single-headed ribs, also including both long-necked and short- necked types. Cope in 1887+ proposed the two sub-families: Pody- cotyline for those with broad epipodial bones; and the /P/estosaurine for those with elongated epipodial bones, of which there are no certain representatives in America. But objections may be urged against both of these classifications. Certain. forms very closely allied to P/osaurus,a dicranopleuran, have single-headed ribs through- out. Polycotylus is a short-necked type, with single-headed cervical ribs, and it seems almost certain that certain long-necked forms that should be widely separated have also broad epipodial bones. Nevertheless, I feel pretty confident that the final classification of the Plesiosauria will include three or four distinct families and twenty or thirty well-defined genera. There is scarcely a group of extinct reptiles, unless it be the Dinosauria, which offers more divergent characters than do the plesiosaurs. The skull may be long and slender or short and broad; the teeth.irregular in size and large, or small and nearly uniform; the prefrontals and postorbitals separated or suturally united; the parietals with a high thin crest, dr without such a crest; the palatines widely separated or broadly contiguous; the supraoccipitals paired or single(?). The neck may include as few as thirteen vertebrae or as many as seventy-two, the vertebre all _very short or the posterior ones elongated; the ribs single or double- headed; the arches anchylosed to the centra or suturally free through- out life: The dorsal vertebra may be no longer than the anterior cervi- cals or much elongated; all the vertebra may have conspicuous vascular foramina below or be without them; the diapophyses may be much elongated and situated low down, or shorter and situated high, up; the vertebral spines elongated or short. In the pectoral girdle there may be a long epicoracoidal process; the clavicles and episternum either present or absent. The epipodial bones are two * Proc. Royal Soc. Lond. 1892, 151. t+ American Naturalist, 1837, 564. 6 Fietp Cotumpian MuseuM—GEOo.ocGy, VoL, II. in number and elongated, or three or four and broad. The ilium may differ in its mode of attachment and the form of both pubis andischium may differ much. Certainly among all these characters, and probably not a few others, there will be no dearth of material for classification. Unfor- tunately there are yet many forms in which we do not know what relations these different characters bear to each other, and until we do, any classification must be provisional. I believe that most herpetological taxonomists will agree with me that the differences between Dolichorhynchops and Brachauchenius are more than generic in . value, and I doubt not that differences of equal value will be discov- ered in yet other species when we shall know more about them than we do at present. The origin of the Plesiosauria I will discuss in a later paper. For the present, I may say that I believe that their nearest affinities among all reptiles, recent or extinct, are with the Dicynodonts. CATALOGUE AND BIBLIOGRAPHY OF THE NORTH AMERICAN PLESIOSAURIA. PLESIOSAURUS. Conybeare, Trans. Geol. Soc. Lond. v, 560, 1821. BREVIFEMUR Cope, Cret. Vertebr. 256, 1875.—Greensand No. 5, New Jersey. Cimoliasaurus magnus (Leidy) Cope, Ext. Batrach. 1869, 43, ff. 13-15. *GuLo Cope, Proc. Acad. Nat. Sci. Phil. 1872, 228; Cret. Vert. 1875, 256.—Fort Pierre Cretaceous, Kansas (evrere, Niobrara). *mupGeEI Cragin, Fifth Pub. Colorado Col. Sci. Soc. 69, ff. 1-3.— Comanche Cretaceous, Kansas. *couLtpu Williston, Kansas Univ. Quart. vi, 57, 1897.—Comanche Cretaceous, Kansas. SHIRLEYENSIS Knight, Amer. Journ. Sci. 1900, p. 115.—Jurassic, ’ Wyoming. All of the foregoing species were based upon fragmentary mate- rial, and it is improbable that any belong in the genus P/eszosaurus. CIMOLIASAURUS. | Leidy, Proc. Acad. Nat..Sci. Phil. 1851, 325 (1852). MAGNUS Leidy, l. c.; ibid. 1854, 72, pl. ii, ff. 4-6; Cretac. Rept. 1865, 25, pl. v, ff. 13-19, pl. vi; Cope, Ext. Batrachia, etc. 186y, 42; Lydekker, Cat. Fos. Rept. Brit. Mus. 11, 211.—Creta- ceous No. 5, New Jersey. PLANIOR Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 22.—Cretaceous, New Jersey (see also Discosaurus). *snowil Williston, Science, xvi, 262; Trans. Kansas Acad. Sci. xii, 174, 1890; Cope, Proc. Amer. Phil. Soc. xxxiii, 109.— Nio- brara Cretaceous, Kansas. LARAMIENSIS Knight, Amer. Jour. Sci. x, 117, 119.—Jurassic, Wyo- ming. ie 8 Fietp Co_umpian MusrtuM—GEo vocy, Vot. II. This genus was based*‘upon vertebral centra alone, from the cervical, dorsal and caudal regions; the author, however, referred them all erroneously to the dorsal and lumbar regions. The type is well figured in Leidy’s work on Cretaceous Reptiles, plates v and vi. The vertebre have infracentral vascular foramina. The ribs are single-headed. The largest centrum measures 110 millimeters in the greatest diameter. This genus has served as a sort of waste basket for the reception of fragments and poorly known forms. C, snow is known froma skull and long neck. It can scarcely belong in C’moliasaurus. DISCOSAURUS. Leidy, Proc. Acad. Nat. Sci. Phil. 1851, 326 (1852). PLANIOR Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 20; 22; Cope, Cretac. . Vert. 1875, 255 (Cimoliasaurus).—Cretaceous, Mississippi. Discosaurus vetustus Leidy, Cretac. Reptilia, 23, pl. 5, ff. ro—r2. verustus Leidy, ‘Cretac. Reptilia, 22, pl. iv, ff. 13-18, pl. v, ff. 1-9; Proc. Acad. Nat. Sci. Phil. 1851, 326; Cope, Ext. Batrachia. etc. 256; Amer. Journ. Sci. 1870, 141; Cretac. Vert. 1875, 255 (Cimoliasaurus).—Cretaceous, Alabama. This-genus was based upon the mutilated bodies of two caudal vertebre from the Cretaceous of Alabama. Leidy associated with these other mutilated vertebre from the Cretaceous of Mississippi, New Jersey and Alabama. Cope suppressed the name, as of a genus insufficiently differentiated from Czmoliasaurus. This is quite true, as it is also true of several of Cope’s own genera of the plesiosaurs, It is not at all improbable, however, that there are different species, and perhaps different genera represented by the specimens Leidy described and figured. oS BRIMOSAURUS. Leidy, Proc. Acad. Nat. Sci. Phil. 1854, 73. GRANDIS Leidy, Proc. Acad. Nat. Sci. Phil. 1854, 73, pl. i, ff. 1-3; ibid. 1870, 10; ibid. 1871, 22 (Déscosaurus); Cope, Ext. Batrachia, etc. 1869, 43,54 (Cimoliasaurus); Proc. Bost. Soc. Nat. Hist. 1869, 266 (¢d¢.); Amer. Journ. Sci. 1870, 269 (¢@.), Rep. Geol. Surv. Terr. 1871, 400 (¢¢.); Cretac. Vert. 1875, 255 (#d¢.)—Cretaceous, Arkansas. This genus and species were founded upon more or less imperfect a Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 9 dorsal vertebre from the Cretaceous,’ probably Benton, of Clark County, Arkansas. Cope suppressed the generic name as of a genus ‘not sufficiently differentiated from Cimoliasaurus. I believe, however, that both genus and species are valid; and that the former will include some of the species from Kansas. Lambe has identified the species from the Belly River Cretaceous of Canada, but it seems to me that the identity must be more or less problematical. | ELASMOSAURUS. Cope, Proc. Acad. Nat. Sci. Phil. 1868, 68. *pLATYURUS Cope, l. c.; Notes on Geology, Leconte, 1868, 68; Proc. Bost. Soc. Nat. Hist. 1869, 266; Amer. Nat. ii, 87; Ext. Batrachia, etc. 1869, 47, ff. 7-12, pl. 11, ff. 1-9, pl. iii; Amer. Jour. Sci. 1870, 140, 268; Amer. Nat. v, 47; Rep. U. S. Geol. Surv. Terr. 1871, 393, 1872, 320, 336; Cretac. Vert. 1875, 44, 79, 256; Bull. U. S. Geol. Surv. Terr. ili, 1877, 578; Amer. Nat. xxii, 724; Leidy, Amer. Jour. Sci. xlix, 1870, 392; Proc. Acad. Nat. Sci. Phil. 1870, 9, 18; Lydekker, Cat. Foss. Rept. Brit. Museum, ii, 181 ( Cimol/iasaurus).—Fort Pierre Cretace- ous, Kansas. INTERMEDIUS Cope, Proc. Amer. Phil. Soc. 1894, 112.—-Fort Pierre Cretaceous, South Dakota. ORIENTALIS Cope, Proc. Acad. Nat. Sci. Phil. 1868, 313; Proc. Bost. . Soc. Nat. Hist 1869, 266; Geological Surv. New Jersey, Cook, Append. (1868), 1869, 733; Amer. Nat. 1869, 87; Ext. Batrachia, etc. 1869, 44, 55, pl. ii, f. 10; Amer. Jour. Sci. 1870, 368; Cretac. Vert. 1875, 255; Bull. U. S. Geol. Surv. Terr. ili, 1877, 567, 578; Am. Nat. xi, 1877, 311; Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 22 (Déscosaurus).—Greensand No. 4, New Jersey. SERPENTINUS Cope, Bull. U. S. Geol. Surv. Terr. iii, 578, 1877; Amer. Nat. xi, 1877, 311.—Niobrara Cretaceous, Nebraska. The genus Z/asmosaurus was founded upon a nearly complete _ series of vertebra obtained near the vicinity of Fort Wallace, Kansas, wrongly ascribed to the Niobrara epoch. The neck was very long. The incomplete girdles are also known. No additional material has been ascribed to the type species since the original description by ‘Cope. . ae) Fretp CoLumMbiAN MusrEuM—GEOLoGy, VoL, II. POLYCOTYLUS. Cope, Proc. Amer. Phil. Soc. xi, 117, 1869. *LATIPINNIS Cope, |. c.; Ext. Batrachia, etc. 36, pl. 1, ff. 1-12; An. Rep. U. S. Geol. Surv. 1871, 388; ibid. 1872, 320, 335; Bull. U. S. Geol. Surv. Terr, 27, 1874; Cretac. Vertebrata, 45, 72, 255, 1, vil, ff. 7, 7a; Leidy, Ext. Vert. Fauna, 279.— Niobrara Cretaceous of Kansas. ; *IscHIADICUS Williston, postea, Niobrara Cretaceous, Kansas. This genus was based upon a portion of a propodial bone and imperfect cervical and dorsal vertebre. The ribs of the neck are single-headed. - PIRATOSAURUS. Leidy, Cretaceous Rept. N. Amer. p. 29, 1865. pLicatus Leidy, |. c. pl. xix, fig. 8.—Cretaceous, Minnesota. Based upon a single tooth. Believed by the author to be Cro- codilian. The horizon is probably Niobrara, judging from the accompanying fossils. If so, it would seem very probable that the tooth belongs to a plesiosaur, though rather sharply conical in shape. NOTHOSAUROPS. Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 74. occipuus Leidy, |. c.; Rep. Geol. Surv. Terr. 1873, i, 345, pl. xv, ff. 11-23; Cope, Bull. U.S. Geol. Surv. Terr. i, 28, 1874 (P/esio- saurus);Cretac. Vert. 1875, 256 (¢d.).—Laramie [| ?] Cretaceous, Dakota. TAPHROSAURUS. Cope, Proc. Amer. Phil. Soc. xi, 274, 1870. : { LOcKwoop1 Cope, Ext. Batrachia, etc. 1869, 40 (Plestosaurus); Proc. Amier. Phil. Soc. xi, 274.—Cretaceous No. 1, New Jersey. OLIGOSIMUS. Leidy, Proc. Acad. Nat. Sci. Phil. 1872, 39 (1873). GRAND&VUS Leidy, 1. c. 40; Extinct Vert. Fauna, 286, 345, pl. xvi, ff. 18, 19.— This genus and species were proposed for a detached caudal vertebra of small size, without definite horizon, from Green River, Apr. 1903. NortrH AMERICAN PLESIOSAURS—WILLISTON. II Wyoming. The processes are attached. The description will apply to caudal vertebre of various genera. URONAUTES. Cope, Proc. Acad. Nat. Sci. Phil. 1876, 345. CETIFORMIS Cope, Il. c. 346.—Fort Pierre (?) Cretaceous, Montana. specIES Cope, Amer. Nat. 1887, 566.—Fox Hills Cretaceous, New Mexico. This genus was based upon cervical, dorsal and caudal vertebre. The cervicals are short, with the prereenes partly attached, and the ribs single-headed. Professor Cope referred the type species to the Fox Hills Cre- taceous with doubt. I suspect, rather, that the horizon is Fort Pierre. OROPHOSAURUS. Cope, Amer. Naturalist, 1887, 564. pauctporus Cope, |. c.—Fox Hills Cretaceous of New Mexico. Based upon parts of three cervical vertebrae. The neural arches are codéssified, the ribs free. Centra short; ribs single-headed. PIPTOMERUS. Cope, Amer. Nat. 1867, 564. MEGALOPORUS Cope, l. c. 564.--Fox Hills Cretaceous, New Mexico. MiCROPORUS Cope, |. c.—Fox Hills Cretaceous, New Mexico. HEXAGONUS Cope, |. c.—Fox Hills Cretaceous, New Mexico. This genus and species are based upon cervical and dorsal verte- bre only. The cervicals are short, the processes free and the ribs single-headed. TRINACROMERUM. . Cragin, Amer. Geologist, Dec. 1888. *RENTONIANUM Cragin, |. c.; ibid, 1891, 171.—Benton Cretaceous, Kansas. A large part of the skeleton was known to the describer, includ-> ing the skull, vertebra, part of the girdles and limbs. 12 FieLp CoLuMBIAN MusgEuM—GEOLOoGY, VoL. II. PANTOSAURUS. Marsh, Report Geological Congress, 1891, 159; Amer. Journ. Sci. xli, 1895, 406; Parasaurus Marsh, Amer. Journ. Sci. xliii, 338, 1891 (preoccupied). srriAtus Marsh, Amer. Journ, Sci. xliii, 338, 1891 (Parasaurus); ibid, i, 406, 1895, ff.—Baptanodon Beds, Wyoming. Based upon a posterior cervical centrum. | ‘‘ Vertebre strongly erqoved. Neck long and slender, the vertebre preserved resemble most in form and size those of Plestosaurus plicatus Phillips.” EMBAPHIAS. Cope, Proc. Amer. Phil. Soc. 1894, 111. CIRCULOSUS Cope, l. c.—Pierre Cretaceous, South Dakota. This genus and species were founded on three vertebra, cervical and dorsal.» The cervicals are short, with persistent sutures. Ribs double-headed(?). MEGALNEUSAURUS. Knight, Amer. Journ. Sci. v, 1898, 375. REX Knight, Science, 1895, 449 (Cimoliasaurus); Amer. Journ. Sci. v, 1898, 379, ff. 1-3.—Jurassic, Wyoming. A large portion of the skeleton of the type species is known; the parts so far described are the vertebra and limbs. * DOLICHORHYNCHOPS. Williston, Kansas Univ. Sci. Bulletin, No. 9, p. 141, Sept. 1902, *osporn1 Williston, l. c.—Niobrara Cretaceous, Kansas. BRACHAUCHENIUS. Williston, postea. *:_ucast Williston, postea.—Benton Cretaceous, Kansas. ~ Apr.1go3. Nortu AMERICAN PLESIOSAURS—WILLISTON. 13 DOLICHORHYNCHOPS OSBORNI. ‘The specimen of Dolichorhynchops osborni herewith described and illustrated was discovered by Mr. George Sternberg in the chalk of Logan County, Kansas, in the summer of 1900, and skilfully collected by his father, Mr. Chas. H. Sternberg, the veteran collector of fossil vertebrates. The specimen was purchased of Mr. Sternberg in the following spring for the University of Kansas, where it has been mounted and where it now is. When received at the museum the skeleton was almost wholly contained in a large slab of soft yellow chalk, with all its bones disassociated and more or less entangled together. The left ischium, lying by thé side of the maxilla, was. protruding from the surface, anda part of it was lost. The bones of the tail and some of the smaller podial bones were removed a little distance from the rest of the skeleton, and were collected separately by Mr. Sternberg. The head was lying partly upon its left side and some of the bones of the right side had been macerated away; the maxilla indeed had disappeared. The task of removing and mounting the bones has required the labor of Mr. H. T. Martin the larger part of a year, and is, as finally mounted, an example of great labor and skill on his part. For the position of the bones in the recreated skeleton and their general arrangement I am of course responsible. There is some little doubt as to the exact position of the pectoral girdle, as respects the ribs and vertebrae. The position as shown in the restoration is that which seemed, upon the whole, most nearly the truth, judging from the _ figured skeletons of P/esiosaurus. There is also some doubt about the proper length of the tail. The relations of the preserved centra seemed to indicate a loss of a few vertebre in this region, and for that reason four plaster models have been intercalated. There are nineteen vertebre preserved in the neck; there may have been one more, or possibly two, but for reasons discussed further on this is doubtful. In the dorsal region there are thirty vertebrae, three of which may be called pectoral. Twenty-five are preserved in the tail. The skull, after its complete removal from the matrix, was found to be so very fragile that it was not thought expedient to mount it. It was also somewhat distorted, as will be seen from the illustrations. A model, therefore, was made under my careful supervision, and mounted in its stead. The skeleton as mounted is just ten feet in 14 Firetp Cotumpian MustEumM—GeEotocy, Vo. II. length. The neck in life must have been thick and heavy at the base, tapering rapidly from the trunk to the head. The'trunk was broad, as is evident from the position of the ribs, with the under side not flat, as might be supposed, but strongly convex from side to side. The abdominal region proper, between the girdles, must have been short, and could not have been very distensible. The short tail was thick atits base, as is conclusively shown by the attachment of the ilia and the elongated ischia. Furthermore, the fore legs, at least, must have. been enclosed for a considerable distance at their attachment by the ~ skin and muscles of the pectoral region; they could not have been pedunculated to the extent that they are usually represented to be in the restorations. The species was named in honor of Prof. H. F. Osborn of Columbia University. The distinguishing characters, both family and generic, may be summed up as follows: Do.icHorHyYNcHops.— Head elongate, the facialregion much attenuated; teeth nearly untform in size, small; prefrontal and postfrontal bones not joined; partetals extending into a high crest; supraoccipital bones separated; tnternal nares small, included between the vomer and patatine only; pala- tines broadly separated throughout; a large vacuity between the pterygoids anteriorly; quadrate process of pterygoids short. Neck but little longer than the head, composed of nineteen or twenty vertebre; all presacral vertebre of nearly equal length, moderately concave, and with vascular foramina below; spines short, uniform in length; diapophyses of the dorsal vertebre situated high up. Coracotds with long epicoracoid process; clavicles and scapule free; episternum with an emargination tn front and behind, the latter forming part of a large interclavicular foramen. Three epipodial bones, all broader than long. Tschium elongated. Length ten feet. Sxutt.—The skull of Dolichorhynchops osborni is of a remarkably elongate and slender form, attenuated in front.of the orbits, and with a thin, high, parietal crest. The region between the eyes is very nar- row, the superior temporal vacuities large, and the teeth numerous and slender. The head is more nearly of the typical aquatic fish-eat- ing type than is perhaps known in any other plesiosaur, and the neck is as short as or shorter than in any other ‘plesiosaur hitherto described. The skull, as received, was lying partly upon its left side, with a part of the right side separated and injured, some of the bones having been macerated away. The specimen was completely removed from the matrix, including even that which was between the bones, and the elements of the brain case were separated out. In conse- Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 15 ‘ quence, the fragility of the skull was such that it was not deemed prudent to mount it with the remainder of the skeleton. A model of it was therefore made, based upon my drawings and studies, and which, I think, represents the skull very nearly as it must have been during life. Its width in all parts may not have been accurately determined, but the discrepancies from the reality can not be great. ‘The premaxillaries are separated from each other distinctly by suture, the long facial processes apparently lying in contact with each other without close union. The suture separating them from the maxilla begins just back of the sixth tooth; it curves upward and backward for a short distance, and then runs parallel with the upper border as far back as the narial opening, whence the margin runs more obliquely to the tip of the processes above the middle of the orbit. Each premaxilla bears six teeth, which are among the largest of the jaws, and are all of nearly uniform size, the first one curved forward. The facial process is slender, flattened on its opposing, sutural sur- face, and with its external, convex surface distinctly striated longi- tudinally. The dentigerous portion is convex, pitted toward the anterior part, and about twenty- five millimeters in height, opposite the last tooth. The relations of the bone on the palatal surface can not be determined. The maxi//e are long and narrow on the facial surface, and very narrow on the palatal surface, at least posteriorly. They bear twenty teeth on each side, the first ten or eleven of which are of nearly equal size, and scarcely smaller than those of the pre- ‘maxilla. The posterior ten teeth are crowded, occupying a space less than one-half that of the preceding ten, and they are smaller. The greatest width of the maxilla on the facial surface —about twenty-five millimeters—is at about seventy millimeters in - front of the orbit, whence the bone narrows to a width of ten milli- meters below the anterior border of the orbit. Below the orbit, the bone extends as a narrow bar, becoming slightly narrower posteriorly, before the beginning of the jugal suture. Beyond this, it flattens posteriorly to near its extremity, which is about midway of the tem- poral bar, and one hundred millimeters beyond the last tooth. There are twenty-five or twenty-six teeth in each jaw. They are inserted by a long fang, the pulp cavity of which occupies more than one-third of the diameter, extending a short distance into the crown. In the largest teeth, the crown is about twenty millimeters in length, with a diameter at the base of six millimeters. The crown is rela- tively slender, strongly convex anteriorly, sharply conical, and with slender, delicate, longitudinal striz, except on the outer, anterior 16 i FieLp CoL_umBian Musteum—Geotocy, Vou. II. part, where the surface is nearly smooth. The posterior teeth are much smaller, as already stated, and are much more closely placed, their length varying from six to twelve millimeters. The united farieta/s form a high, thin, vertical plate of bone, convex in outline, about fifty millimeters in height in the middle, and only three or four in thickness at the margin, and extending nearly as far forward as the pineal foramen. Posteriorly, the sides extend downward and outward into a broad flattened process for union with the upper ramus of the squamosal. The suture, which is clearly apparent, runs downward and outward to the free margin of the parietal on each side, beginning in front of the posterior thickened bar of the squamosal. Anteriorly this free margin of the parietal is continued outward, like the eaves of a roof, to the posterior part of the orbit, where it is somewhat roughened; it turns upward here rather abruptly. About twenty millimeters above this angle, separated by a concave space, is the massive projection for the epipterygoid. This bone has been broken away from its attachment on each side, and separated for a short distance, leaving a jagged fracture, without indications of suture. The upper margin of this thickened epiptery- goid protuberance is continued by sutural union with the postfrontal. A little in front of the parietal foramen, the bone narrows to a width of four or five millimeters, blended with and continued into the frontal, which continues forward to the premaxillary, under which it disap- pears. The sutural union for the postfrontal is well marked on the right side, beginning a little back of the pineal foramen and running downward, outward and backward to the upper margin of the epiptery- goid protuberance. Internally the parietals form a broad roof, to which is attached, rather far forward, by distinct, oval, obliquely placed, V-shaped articular surfaces, the paired supraoccipitals, which | do not reach quite to the lower free margin of the parietals on each side. | Anteriorly, as already stated, the frontal (?) continues, without the slightest indication of a suture with the parietals, forward for forty millimeters or so more, as a narrow, flattened surface above, distinctly divided by a median suture, to the upper end of the facial processes of the premaxillz, which articulate on the outer side of the slender projection, overlapping the upper surface. How much further the bones continue I can not say, but evidently as far forward as the anterior end of the orbits. On the right side, the ‘‘ postprefronto- nasal” has been macerated away, so that its relations are clearly marked. Below these bones are broader, continuous on each side. with the free margin of the roof, as already described. The rostrum Apr. 1903. NorrTH AMERICAN PLESIOSAURS—WILLISTON. 17 formed by the ‘‘frontals”’ is stout and rounded, and is continued at least as far forward as the anterior end of the orbit, clearly separated above and below by the median suture. The anterior ends are lost in front in the broken fragments of bone, between ‘and beyond the anterior end of the orbits. Lying between the orbits, and separated from each other by a narrow interval, are the narrow bones which may represent the conjoined postfrontals and prefrontals and nasals. On the right side, as stated above, the bone had been macerated away, and while some of its processes had been broken off and lost, the sutures for union with the parietal, frontal and prefrontal are beauti- fully preserved, showing the relation to these bones in a way that precludes doubt. The bone shows no trace of division whatever into its supposed elements. It articulates with the ‘ frontal,” parietal, epipterygoid, ‘‘ postorbital,” ‘‘supraorbital,” ‘premaxilla and maxilla. Posteriorly the bone extends downward, outward and backward to the upper margin of the epipterygoid protuberance; externally and posteriorly it sends off a projection for union with the post-orbital ; anteriorly the bone fits into a groove on the outer side of the facial processes of the premaxillaries for a distance of thirty or forty milli- meters, and has a stout process on the outer side for union with the supraorbital, or whatever the element may be here. On the under _ side there is a broad, flattened, vertical plate, continuous from the posterior, inferior angle, and widened in the middle so as to-reach the greater part of the way to the upper surface of the palatal bone, form- ing the inner wall of the orbit in large part. The plate given off for union with the “supraorbital” is separated by a sharp, deep notch from a similar process for union with the ‘‘ postorbital.”” The ‘‘supra- orbital’? bone has been crushed back over this process, so that the distinguishing suture can be perceived in one place only, anteriorly. In front of the orbit, the bone sends out a thin, triangular plate, which curves downward to meet the maxille, separated from its mate by the premaxille. Doubtless this part represents the nasal, and per- haps also the lachrymal, but there are no indications of distinguishing sutures, and I do not believe that the nasal exists as a separate ele- ment in the adult plesiosaur—I can not find that it has ever been described in any plesiosaur. It joins the maxille broadly and the ‘‘supraorbital” behind; in the angle between the three bones is located the small external nares. Below the supraciliar plate, near the anterior part of the orbit, on the side of the prefrontal, there is a well-defined fossa, leading forward into the ethmoidal region, into _ which opens a small foramen from the upper surface between the pre-. frontal and supraorbital. “ a 18 FieLp CoLuMBIAN MusEUM—GEOoLOoGy, VoL. II. The supraorbital forms, as already stated, a horizontal plate extending out over the orbit in front. Its union with the prefrontal posteriorly is obscured by fracture, but indications of a suture are seen anteriorly. Between this bone and the postorbital there is a deep notch, angulated externally. The suture between the prefrontal and supraorbital is clearly seen anteriorly, running from the small foramen already mentioned forward and outward to terminate near the maxilla, at the posterior end of the nares. The connection of the bone with the maxilla can not be made out, as there has been an infolding here; its connecting suture with the ascending process of the maxilla is, however, well defined, running obliquely forward. The descending plate of the supraorbital has, in its orbital margin near the upper part, a small foramen, piercing the bone obliquely. The horizontal portion terminates anteriorly by sinking to the surface of the descending portion. The whole bone reminds one of the pre- frontal of Clidastes. : The fostorbita/ bone is a narrow, elongate and thin bone, united above with the postfrontal, and to a slight extent with the parietal, near the top of the epipterygoid; below to the jugal. On the right. side, this bone, like the postprefrontal and jugal, has been macerated away, and, although somewhat distorted, presents no evidence of being composed of more than one element. In the above description of these frontal elements, I have foie lowed the usual determinations, but I am not satisfied withthem. The ‘‘supraorbital,”” though occupying the position usual for this bone above the orbit, has relations anteriorly that are altogether unusual; the nasal and the lachrymal do not appear to exist as independent elements. It would seem more likely that this supposed ‘‘supra- orbital” is really the lachrymal, if the postfrontal and: prefrontal are fused into one element. Again, such a combination of the postfrontal and prefrontal and their peculiar articulations is remarkable. The very narrow frontal, while showing a distinct suture in the middle, presents no evidence of any connection with the parietal —it seems more to be a very narrow rostrum projecting in front of the parietal and separating the bones, which otherwise would answer very well for frontals. In this latter case, the so-called ‘‘supraorbital” would really be the prefrontal, and the postorbital the postfrontal or post- fronto-orbital. This may seem a violent supposition, but it does not seem at all improbable to me. Nor is the union of the parietal with the premaxilla any more extraordinary than is the union of the supra- occipital with the frontal in many Cetacea. Sclerotic plates are present in the left orbit of this specimen in a Apr. 1903. NORTH AMERICAN PLESIOSAURS*-WILLISTON, 19 nearly undisturbed condition. There are fourteen in the ring with beveled and imbricated contiguous margins, in texture, size and _ position very much like the corresponding bones of the mosasaurs. The pupillary opening measures about thirty millimeters in diameter, and the entire diameter of the ring is about seventy millimeters. The occurrence of sclerotic plates in the plesiosaurs has long been known. I described them in Cimoliasaurus snowiti in 1890, and Owen many years earlier (Fossil Reptilia of the Liassic Formation, p. 10) said: ‘‘In both orbits some of the thin sclerotic plates of the eyeball are preserved ; this is the first specimen in which I have had evidence of their structure.” 3 The juga/ is a small element intercalated between maxilla, post- orbital and squamoso-prosquamosal. The suture separating it from the maxilla runs nearly parallel with the lower border of the bone. _ In its posterior third this suture is very distinct; it seems to be con- - tinued forward to attain the margin of the orbit at its lower posterior part. Above, the bone is distinguished from the postorbital by a nearly parallel suture; behind by a nearly transverse suture from the squamosal. On the right side, the jugal had been separated from the other bones by maceration; its relations, therefore, are positively indicated. The bone terminates about twenty millimeters before the posterior end of the maxilla. On the inner side, just back of the rounded orbital margin, the bone articulates by a flattened surface, about the size of one’s finger-nail, with the ectopterygoid. -The bone is pierced on its outer surface by three or four small zygomatic foramina. ’ The broad, triradiate element, variously considered as being com- posed of, or the homologue of, the squamosal and mastoid by Owen*, the squamosal and supratemporal by Andrewst, the squamosal and prosquamosal by Owen and Baur, the supratemporal and supramas- _toid by Cope}, the squamosal, supratemporal and quadratojugal by Woodward§, differs materially in its structure from that described or figured in other plesiosaurian skulls, in that the element, or elements, whatever they are, articulate proximally with the maxilla, as well as the postfrontal and jugal. Posteriorly, the suture separating the.bone * Trans. Geol. Soc. Load. (2), v, pt. iii, pl. xlv, 1840. + Quart. Journ. Geol. Soc. Lond. lvii, 249, 1896. t Proc. Amer. Phil. Soc. xxxiii, 110, 1894. Cope, in his essay on the posterior cranial arches in he Reptilia (Trans, Amer. Phil. Soc. 1892), reaches the conclusion that the lower temporal bar of he Crocodilia, SAhenodon, etc., corresponds with the zygomatic arch of the mammalia, and there- ore suppresses the term “ squamosal.’’ The squamosal—so-called—in the Reptilia he calls the _ : upramastoid, absent in the lacertilia and other forms. § Vert. Paleont., f. 116 A, 1898, 20 Fretp Co_tumMpran Museum —GEovoey, Vou. II. from the quadrate is situated as in Crmoliasaurus snowit, at the external angle of the quadrate, which it borders to its upper extremity., At the lower extremity there is a very distinct squamate suture, running upward and forward and becoming lost about twenty millimeters from its origin. This suture is clearly apparent on the two sides, and is also seen in the skull of C’moliasaurus snowiti, as it was figured by myself (l.c.) and Cope*. Just what the course of the suture is anteriorly I cannot say, but I believe that it is indicated by a line passing forward to the maxilla, and excluding that bone from union with the squamosal. Whatever be its relations anteriorly, I doubt not that the quadratojugal exists as a distinct ossification in the plesiosaurs. In a separated quadrate of another species of plesiosaur (Z. anonvmum WNill.), from the Benton of Kansas, the sutural sur- faces for union with the quadratojugal and squamosal are clearly dis- tinguished. The quadratojugal does not enter into the formation of the condylar surface of the quadrate, as has been suspected, and as it does in Sphenodon,; this is certain. On the outer side of this quadrate, just above the articular surface, there are two sutural surfaces—one on the posterior and outer border, for the attachment of the squamosal, the other on the anterior border for the attachment of the quadrato- jugal, which, in this case, as also in Dolichorhynchops osbornt, must have been overlapped in part by the squamosal. In Crmoliasaurus snow’, the suture between the squamosal and the quadratojugal is very clearly indicated from the exterior, the squamosal not descend- ing as low as in the other species. The suture shown as separating the quadratojugal from the squamosal anteriorly is conjectural, but I believe, as already stated, that it will be found to extend as. far for- ward as the maxilla. The suture separating the squamosal from the postorbital is short and vertical, joining the border near the anterior extremity of the bone, as seen from the outer side. The suture joining the jugal is a squamous one, extending on the inner side nearly to the margin of the orbit, but leaving a small space for the union of the ectopterygoid with the jugal. The suture with the maxilla is long and oblique, con- cealed.in about half its extent by the jugal. I believe, however, that the squamosal is really separated from the maxilla by the intervention of the quadratojugal, as already described, and for which there seems to be some evidence in the specimen. On the right side the maxilla had been removed by maceration, leaving the sutural surface for the temporal element very clear in its whole extent. Posteriorly, the sutural line of the squamosal passes downward * Proc. Amer. Phil. Soc. 1894. Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 21 by a somewhat zigzag line to reach the inner border of the quadrate a little above the border of the pterygoid process. On the inner side, the sutural line passes nearly directly across, and then upward to the inner border. Fe The connection with the parietal is definite. The suture indi- cated by Cope in his figure of Cimoliasaurus snowitl (1. c.) does not exist in the specimen figured, nor is there any such in the skull of Dolichorhynchops osborni here described. In order to definitely deter- mine this fact I removed the portion supposed by Cope to be the supramastoid from the skull of the Cimodiasaurus specimen and carefully cleaned it, thereby proving beyond peradventure that the supposed suture is in reality a fracture. The squamosal, or as it should be called, the squamoso-prosquamosal, in that form, as will be described hereinafter, reaches to the top of the skull, notwithstanding Baur’s opinion to the contrary... The two squamosals touch each other, or nearly do so, as in the skull of Cryptoc/idus described by Andrews. The temporal bar in the plesiosaurs, it is thug seen, is composed of the jugal, quadratojugal, squamosal and prosquamosal (supratem- poral). This last element is not distinct in either of the skulls here described, nor is it usually apparent in the adult skull, but Owen* describes and figures it as distinct; Andrews also says} that ‘‘ In sev- eral Plesiosaurian skulls in the British Museum the suture between these elements is distinct.” The guvadrate is a short and broad bone, united by a pit-like sutural surface on the inner side with the posterior prolongation of the pterygoid, on the outer side with the squamosal and quadrato- jugal, as already described. Posteriorly the sutural surface for the squamosal begins a little above the pterygoid articulation, runs down- ward and outward for a short distance, then upward and outward to another point, whence it goes downward to appear on the outer sur- face a little below the angle of the bone, which it follows nearly to the lower articulation. The articulation for the paroccipital is imme- diately above and before the pit for the articulation of the pterygoid. A separated quadrate of another species (7. anonymum), already described in part, with its sutures distinct and the bone undistorted, shows an elongated articular surface, broadest upon the inner end, narrowed and turned upward at the outer extremity nearly to the lower end of the squamosal articulation. A non-articular groove on the inner side of the middle behind divides the articular surface; it does not appear to be present in either of the other species. The *Trans. Geol. Soc. (2), v, Pl. xiv (1840). ft Quart. Journ. Geol. Soc. lii, 250, 1896. 22 - Fretp CoL_umpian MusrumM—Geovoey, Vot. II. pterygoid articular surface reaches to within about twenty-five milli- meters of the articular extremity. The inner border of the pit is produced forward for articulation, apparently, with the paroccipital. The two narrow, concave, articular surfaces for the squamosal and quadratojugal are separated by a narrow, non-articular ridge. They both extend very nearly to the cotylar surface of the bone. The fterygords articulate posteriorly by a deep, pit-like suture with the inner side of the distal extremity of the quadrate; the latter does not send out a process to meet the bone. The bar connecting the quadrate with the body of the bone is oval in cross-section, with a rounded inferior border. It is about thirty millimeters in length and is placed obliquely; it does not extend much posteriorly to the coronal plane of the occipital condyle. In front of this quadrate process there is an elongate, flattened or concave plate, with nearly parallel sides, separated from the parasphenoid bya slender, elon- gated vacuity.* At-the posterior extremity of this plate there is a nar- -row bridge connection with the basisphenoid. The connecting suture is not determinable, so that one cannot say whether the two ptery- goids meet here in the middle, as in Pe/oneustes and Pliosaurus, or are separated, as in Plestosaurus. In front of the interpterygoid vacuity the pterygoids unite with the parasphenoid broadly; here also the connecting suture cannot be determined. Opposite this connection exteriorly, the bone sends out a stout process for union with the ecto- pterygoid or transverse bone. Back of both of these, and on the inner side, near. the margin of the vacuities above, there is the attachment of a stout epipferygoid pillar, passing upward, and apparently a little inward to unite with the lower anterior part of the parietals, as already described: both extremities are tumid, and the connecting sutures cannot be determined. The rod is broken on both sides in the specimen near the parietal end, and, as preserved, is curved for- ward. It is oval in cross-section, with the greater diameter of about ten millimeters; the entire length is thirty millimeters. Anteriorly, the pterygoid sends a flattened process to meet the posterior extremity of the vomers; it is flattened and pointed. This process is gently expanded at each extremity, especially the proximal; it has a smooth, thin edge on each side, except at the distal end, where it meets its mate, suturally, in the middle. Between the two processes there is an elongate, oval vacuity, which is not filled by the ossified para- * Andrews calls this opening the posterior palatine vacuity or foramen; but this term is more properly restricted to the opening between the palatine, pterygoids and maxille, corresponding to the posterior palatine foramina of mammals, and is thus used in the Chelonia—the sub- or infra- orbital vacuity of Andrews and other authors. ; eR sea CaM, ce Apr.1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 23 sphenoid in this specimen. There is, however, a slight projection in the middle of the opening behind, which may represent. a more extensive ossification, but it seems very probable that there was a real vacuity here, unlike the condition in Pe/oneustes and Plestosaurus. The union with the vomer is oblique, from without inward and forward. The palatine and ectopterygoid on one side, though retaining Fig. 1. Fig, 2. Palate of Peloneustes. Palate of Plesiosaurus. Px., premaxilla; mx., maxilla; v.,.vomer; é., internal nares; fa., palatine; A7., pterygoid; f#v., posterior palatine vacuity; ¢f., ectopterygoid; 4s., basisphenoid; d0., basioccipital; g., quad- rate; sg.,squamosal, After Andrews. their original positions approximately, were free in the specimen ; they are complete and show their sutural relations very well. On the other side, they are both in position. The palatine is a long, narrow, thin bone, concave from side to side above, and correspondingly con- vex below. The inner, slightly sinuous margin is thin, and overlaps the outer margin of the palatine process of the pterygoid. Near its anterior extremity there is a small emargination for the nares*, where *See description of the palate in Brachauchenius beyond. 24 FieLp CoLumpian MusEuM—GEoL_ocy, VoL. II. the bone comes in contact with the proximal end of the vomer; for a little distance in front of this emargination, and distad to the pointed extremity of the bone, the border is slightly thickened for union with the vomer. Posteriorly, the rounded extremity of the bone is slightly thickened, and with sutural roughening for union with the ectoptery- goid process of the pterygoid. The outer border is slightly concave throughout nearly its whole extent; it is also thin for nearly its whole extent. Anterior to the small narial emargination, the bone forms a long, slender point. On the proximal end, the thin border is under- lapped by the thin anterior prolongation of the ectopterygoid for a distance of about fifty millimeters ; the remainder of the extent comes in contact with the maxilla, but presents no distinct sutural surface, unless it be near the anterior extremity. There is no posterior pala- tine foramen. The ectopterygoid or transverse bone is of a slender, triangular shape. Its slender anterior end extends forward on the outer margin of the palatine. * The posterior inner angle has a well marked sutural surface underlapping the pterygoid process. The outer extremity is thickened, curving somewhat downward to unite with the jugal, and, by a thin border, with the maxilla. The vomer is a very long, narrow bone, uniting with the palatine process of the pterygoids posteriorly by a squamous suture, and, for a short distance on the outer side posteriorly, with the slender pointed extremity of the palatine, the small narial opening intervening. They le closely side by side, apparently without sutural union. They are concave above, and convex below from side to side, and are _ rather stout. The anterior ends are so concealed that they can not be described or figured. Brain-case.—The lateral walls of the brain-case in the reptilian skull are composed of six distinct elements, according to the views of - some comparative anatomists. Two of these may be fused with con- tiguous elements in the adult skull, or one or more of them may be entirely absent. Those elements supposed to contain the otic capsule were called by Huxley, in his lectures on the structure of the verte- brate skull (Elements of Comparative Anatomy, 1864), the epiotic, proétic and opisthotic. The other three are the supraoccipital, - exoccipital and alisphenoid. The epiotic, Huxley homologized with the so-called epiotic of fishes and batrachians, and, although indis- tinguishably united with the supraoccipital in all adult reptilian skulls*, he believed to be a distinct ossificatory element. This has * Parker describes the epiotic as a distinct element in 7yofidonotus natrix. Phil. Trans., 1878, p. 403. ‘Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 25 been denied by Baur*. No indications of such an ossification have been found in adult reptiles, living or extinct, even in those in which the opisthotic remains as a permanently free ossification. The opis- thotic was previously called paroccipital by Owen in 1838, and the name must take precedence. Copet, however, suspected that the opisthotic or paroccipital is really composed of two elements, the outer of which is the true paroccipital, while the inner, that entering into the formation of the otic canals, may be properly called the opis- thotic. Baur denies this, insisting that there is but a single element, persistent in the Testudinata, Ichthyopterygia, the young of Sphenodon, and other Rhynchocephalia, as well as in some of'the Cotylosauria ; firmly and indistinguishably fused with the exoccipital in all other reptiles, so far as is known; free, according to Cope, also, as the so-called squamosal of Baur, the paroccipital of Cope, the supratem- poral of Woodward, in the lacertilia. If there be but one element here, and, so far, the evidence is inconclusive that there are two, then it must be called the paroccipital, a name first given to it by Owen. Andrews describes the element as distinct in the young of Crvpfoclidus§, but there are no indications of it in the present specimen. The prodtic of Huxley, the alisphenoid ot Owen (Comparative * Zool. Anzeiger, No. 296, 1889; Journ. Morphology, 1889, p. é. + The opisthotic in reptiles is generally early fused with the exoccipital, but in the Ichthyop- terygia and Testudinata it is distinct, and takes the place of the petrosal as a support for the quadrate in conjunction with the exoccipital. In the Pythonomorpha a bone which occupies the position of the terminal part of the opisthotic (or paroccipital, which is the older name) issues from between the exoccipital and petrosal, and sifpports the quadrate. Whether this is homologous with part or all of-the paroccipital is an open question. For the present I call it the paroccipital and it is probably a distinct element from the opisthotic.’’ Cope, Syllabus, 2d ed., 1898.