pe Lnftnttiactha tne tbe tno nfo Minto ant ohn teen beri tacecih ened tafe tectha ie fe toateiny che Garepavniconaieemen tt 1 ayer mn Ay He SpdlpesiptantinceLicetinateubeeeae eaten Ey eaebetb ane et ty a A eat Pain hai Snap teita’ etait eR aleemnke eae t THE GEOLOGICAL MAGAZINE. NEW SERIES. DECADE IV. VOL. X. JANUARY—DECEMBER, 1903. att 24 Peay Wee °s AS a Hives 7) SUA GEOLOGICAL MAGAZINE Monthly Jounal of Geologn: WITH WHICH IS INCORPORATED “THE GEOLOGIST.” NOS. CCCCLXIII TO CCCCLXXIV. EDITED BY HENRY WOODWARD, LL.D., F.R.S., Pres. R.M.S., F.G.S., LATE OF THE BRITISH MUSEUM OF NATURAL HISTORY 5 PRESIDENT OF THE PALHONTOGRAPHICAL SOCIETY, VICE-PRESIDENT OF THE ZOOLOGICAL AND MALACOLOGICAL SOCIETIES ; MEMBER OF THE LYCEUM OF NATURAL HISTORY, NEW YORK; AND OF THE AMERICAN PHILOSOPHICAL SOCIETY, PHILADELPHIA; HONORARY MEMBER OF THE YORKSAIRE PHILOSOPHICAL SOCIETY; OF THE GEOLOGISTS’ ASSOCIATION, LONDON; OF THE INSTITUTION OF MINING AND * METALLURGY, LONDON; OF THE GEOLOGICAL SOCIETIES OF EDINBURGH, GLASGOW, HALIFAX, LIVERPOOL, AND SOUTH AFRICA; CORRESPONDING MEMBER OF THE GEOLOGICAL SOCIETY OF BELGIUM; OF THE IMPERIAL SOCIETY OF NATURAL HISTORY OF MOSCOW; OF THE NATURAL HISTORY SOCIETY OF MONTREAL; AND OF THE MALACOLOGICAL SOCIETY OF BELGIUM. ASSISTED BY ROBERT ETHERIDGE, F.R.S. L.&E., F.GS., F.C.S8., &e. WILFRID H. HUDLESTON, M.A., F.R.S., F.G.S., F.LS., F.C.8. GEORGE J. HINDE, Px.D., F.BS., F.G.S., &e. AND HORACE BOLINGBROKE WOODWARD, F.R.S., F.G.S., &c. NEW SERIES. DECADE IV. VOL. X. JANUARY—DECEMBER, 19038. LONDON: MESSRS. DULAU & CO., 37, SOHO SQUARE, W. 1903. SATIN Ree Gi oe ea LER REORD Cian uit g i | PRINTED BY STEPHEN AUSTIN AND SONS. SOM EATEN AN eT Tei eo See OLS OL ee EAM HEN pate LIST OF PLATES. Some Wenlock Species of Lichas Professor Albert Gaudry Flint Implements from the Fayim, Egypt Flint Implements from the Fayim, Egypt Fossil Prawns, etc., from the Isle of Wight Eoliths from South-West Hants Koliths from South-West Hants Map showing the course of the Avon below Downton A giant Cirripede from New Zealand A giant Cirripede from New Zealand Shells and Concretions from Creechbarrow Barranca de las Calaveras, Concud, Spain . Sections at Strathy Point and Kinbrace Royal Bohemian Museum, Prague Beer Head, from the West .. . Under Hooken and Hooken Cliff Markings on Quartzite Slabs from Canada . Photograph of the newly discovered Mammoth River Curves . Carboniferous Sandstone at Muckros Head Memorial Tablet to Professor H. A. Nicholson Palxozoic Nautiloidea from North China Profile of Skull of Arsinditherium Zitteli, Beadn. Front view of Skull of Arsinditheriwm Zitteli, Beadn. . FACING PAGE 12 49 LIST OF ILLUSTRATIONS IN THE TEXT. Section of Deposit of large Detritus at a River’s Mouth Distribution on Sea-bottom of Vertical Sheet of Sediment . Homalonotus Barratti, H. Woodw., sp. nov. . Map of the Northern part of the Fayim Submarine Contour-lines from Ireland to Portugal Section showing the succession of the Osborne Series . River Meanders Creechbarrow from the north-east Manganese nodule from Creechbarrow Part of a calcareous nodule Brachymetopus Strzeleckii, McCoy Pisolitic limestone showing two faces Triangular Flint Implement from Herne Bay . Shoe-shaped implement from Northfleet Chert implement with curved edges Chopping tool, province of Poitou Axe-head with hollowed edge, Denmark Flint chisel, Denmark Chipped knife of chert, Egypt Flint knife, Denmark 3 Unground axe-head, Hitcham, Bucks Flint javelin-head from long barrow, Wilts Anthracosiro woodwardi, R. I. Pocock, gen. et sp. nov. Section at Wockley Burrows on quartzite slab Olenellus *Thompsoni, Hall Isochiline at ea Post-Glacial Section at Dundee Upper Dentition of Megalohyraaz eocenus, Andrews, gen. et sp. nov. Right ramus of Mandible of Pterodon africanus, Andrews, sp. nov. Restoration of Palate of Scylacosaurus Sclateri, Broom, gen. et sp. nov. Lower Jaw of Karoomys Browni, Broom, gen. et sp. nov. Palatal view of Skull of Hyperodapedon Gordoni, Huxley 146, 147 Vill List of Illustrations in the Text. Dorsal aspect of Skull of Stenometopon Taylori, Boulenger, gen. et sp. noy. Matheria brevis, Whiteaves, sp.nov. . . . ... - Section of Cutting at Charmouth. . .....2.. =. Anthracosiro fritschit, Pocock, sp. nov. G6 Section of the Alluvium of the River Thames, Bermondsey Longitudinal section of Actinoceras docens, Barr., sp. nov. . Actinoceras imbricatum, Hisinger, sp. . - . . - « « Goniocenasvancep stl all Si essr- sew iNoutcu-noin a= nnnrnr Listraeanthus Wardi and Petrodus acutus, A. 8S. Woodw. . ivpostomayot Bronteus 2). 9. Skull of Batrachosuchus Browni, Broom, sp.nov. . PAGE 356 358 390 406 456 482 483 484 487 490 500 THE GHOLOGICAL MAGAZINE. NEW SERIES. \IDIEGAIDE MIN. > WOES XG No. I.—JANUARY, 1903. QR IFES PEIN( AGI, RASS aD IO sa. —— I.—Somz SuecEstions on Exrinorion. By C. W. Anprews, D.Sc., F.G.S., British Museum (Natural History). ee sudden disappearance of groups of animals, which have existed through long periods of time and have attained a high degree of specialization, is a phenomenon of which many instances will occur to every student of Palzozoology. For instance, to mention only two cases in illustration, we may refer to the disap- pearance of the Dinosaurs at the end of the Secondary period, and that of the North American Titanotheres in the Miocene. Of the proximate causes of this extinction little is known: they must have been either inherent in the organisms themselves, or have been connected with the relations of the organisms with their environ- ment; probably in every case several factors co-operated to bring about the observed result. In a recent paper by Mr. C. B. Crampton (Proc. Roy. Phys. Soc. Edinburgh, vol. xiv, p. 461) a possible inherent cause of extinction is suggested. It is impossible to do justice to this interesting paper in a short note, but the gist of the argument seems to be as follows:—In the original unicellular organism the possibilities of variation are almost infinite, but as soon as evolution along any line begins, these possibilities are restricted, and become more and more so the more highly specialized the animal is; in short, the potential variation of an organism becomes less and less as specialization advances. Furthermore, under the influence of natural selection, in each generation the individuals which tend to vary in the same direction will survive, while at the same time, as already pointed out, their capacity for variation becomes more and more restricted. The consequence of this will be that the more highly specialized any stock becomes, the more the individuals composing it will come to resemble one another, until at length the same results as arise from close inter- breeding, viz., weakening of the stock and, finally, extinction, may follow. In a paper recently read before the Zoological Society, the present writer, in speaking of the evolution of the Proboscidea, took the DECADE IV.—VOL. X.—NO. I. 1 2 F. R. Cowper Reed—Some Wenlock Species of Lichas. opportunity of pointing out another possible cause of extinction of some groups of animals. It will be observed that in many cases the evolution of a group of animals is accompanied by a simultaneous increase in the bulk of the individuals composing it. The Proboscidea themselves offer a fairly good instance of this tendency, but a better known case is that of the horses. An almost necessary corollary of this increase in bulk is the lengthening of the individual life, or at least what, for our argument, amounts to much the same thing, the lengthening of the time taken to attain sexual maturity. In many Ungulates this increased longevity is indicated by various modi- fications of the teeth, tending to give them a longer period of wear: generally this end is attained by the increasing hypselodonty of the cheek-teeth. A necessary consequence of the longer individual life will be that in a given period fewer generations will succeed one another, and the rate of evolution of the stock will therefore be lowered in the same proportion. If now the conditions of life undergo change, the question whether a given group of animals wiil survive or become extinct will depend upon whether it can undergo sufficiently rapid variation to enable it to avoid getting so far out of harmony with its surroundings that further existence becomes impossible. It seems to follow then that the smaller animals, in which the generations succeed one another rapidly, will have a better chance of surviving than the larger and more slowly breeding forms, which at the same time will be still further handicapped if, as is usually the case, they are more highly specialized than the smaller forms, and therefore have a more restricted range of possible variation. Another result of the increased length of the individual life would be that, during the earlier history of a stock the modification under- gone by its members would be more rapid than among the later forms, a phenomenon of which actual instances might be cited, e.g. in the Proboscidea. On the same principle it may perhaps also be explained why certain groups have remained comparatively unchanged through long periods of time. The Sirenia may be a case in point, though no doubt in this case, among other factors, the comparative stability of the conditions of life has had much to do with the conservative character of the group. JI.—Woopwarpian Musrum Norres: On some Wentock SPECIES oF LIcHAs. By F. R. Cowrrer Rezep, M.A., F.G.S. (PLATE I.) ({\HE entire collection of Wenlock fossils made by T. W. Fletcher, Hsq., which is now in the Woodwardian Museum, affords unsurpassed facilities for studying the material on which a large number of species of trilobites were founded. Particularly is this the case with those of the genus Lichas, and a recent examination of the types and other specimens which Fletcher used in writing his paper ‘Observations on Dudley Trilobites” (Q.J.G.S., 1850, F. R. Cowper Reed—Some Wenlock Species of Lichas. 3 vol. vi, pp. 235-239, pls. xxvii and xxvii bis) has led me to make the following notes upon them. I have also had the privilege, through the kindness of Dr. Arthur Smith Woodward, F.R.S., of examining the specimens in the British Museum (Nat. Hist.), Cromwell Road. Licuas (CorypocEePHaLus) ANGLIcUS (Beyrich). (Pl, I, Figs. 1, 2.) Lichas Bucklandi, Fletcher (pars): Q.J.G.S., 1850, vol. vi, p. 235, pl. xxvii, figs. 2, 3, 4, ?5, 5a (non figs. 1, 1a); pl. xxvii dis, figs. 1, la, 10. There is considerable variation in the degree of development of the spines on the pygidial margin of this species. A similar variation is noticeable in Cheirurus bimucronatus and the species of Acidaspis from the same beds. The relative length of the axis of the pygidium also shows marked individual differences. Fletcher figured one specimen (op. cit., pl. xxvii, figs. 5, 5a) which he described as a young individual, and probably it should be regarded as such. But there are two well-marked and constant varieties which show definite features separating them from the type-form, and in fact are more abundant than the latter. (i) The first variety, which may be called wenlockensis (Pl. 1, Fig. 1), has a pygidium which is subquadrate in outline, and has almost a straight posterior border. ‘The nine marginal spines are unequally developed ; the first two pairs are strong and of equal size, but the third pair, situated at the lateral corners of the posterior margin, are much stouter and larger, projecting nearly straight backwards behind the pygidium. Between them lie three equidistant smaller spines, the median one of which is generally the largest. Minute prickles are in some specimens noticeable along the margin between the spines. A shallow groove parallel to the posterior edge of the pygidium and marking off a distinct border, but not crossing the post-axial median piece, is present on the lateral lobes behind the second pair of pleure. A similar though fainter groove is distinguishable on the pygidium of the type-specimen and type-form fioured by Fletcher (op. cit., pl. xxvii bis, figs. 1, 1a), and in the other specimen regarded by him as a young individual (pl. xxvii, figs. 5, 5a), but no mention of it is made in his description. The posterior half of each of the two pairs of pleurz behind the pleural furrow in the variety wenlockensis is also remarkably narrow in comparison with the anterior portion. In Fletcher’s figure of the type-form the posterior portion is made broader than it is in reality in the specimen. From the above remarks it will be seen that the distinguishing features of this variety are the general shape of the pygidium and the development of the lateral spines. The thorax and head-shield in complete specimens show no points of difference from the type- form which can be established as constant. (ii) The second variety (Pl. I, Fig. 2), of which there are also complete specimens in the Woodwardian Museum, likewise exhibits its distinctive features only in the pygidium. In this form there are only eight marginal spines, the posterior median one being absent or merely represented by a small prickle. The shape of the pygidium 4 F. R. Cowper Reed—Some Wenlock Species of Lichas. is subquadrate rather than semicircular ; the first two pairs of lateral spines (i.e. the pleural points) are moderately developed, and equal or subequal in size; the third pair of spines is developed as in the variety wenlockensis, being stronger and stouter than the others; the fourth pair of spines is reduced in size, and slender, and usually rather closely placed to the third pair, leaving the median portion of the posterior margin free of spines and only armed with small prickles. In other respects this variety resembles that above described. Both differ from the type-form by the subquadrate rather than semicircular shape of the pygidium, and by the specially strong development of the third pair of marginal spines. This second variety may be termed obtusicaudatus. Salter attributed both these varieties of Z. anglicus to L. hirsutus, as his labels and Catalogue show (Cat. Camb. Sil. Foss. Woodw. Mus., p- 130, a 961, a 968, a 964), but they differ completely from it, as a reference to Fletcher’s figured specimens and the descriptions of that species at once proves. ' The ‘angularity ’ of the head-shield upon which Fletcher remarks in one specimen (figs. 3, 3a, pl. xxvii) is caused by the sudden bend in the front margin of the free cheek, just outside the point where the facial suture cuts the border. This projection of the middle portion of the head-shield is very well marked in some specimens of the type-form and in the variety wenlockensis, and is indicated in the restoration of the front border by Fletcher (op. cié., pl. xxvii bis, fig. la). It appears to be a characteristic and constant feature, being noticeable wherever that portion of the head-shield is preserved. Licuas (CoRYDOCEPHALUS) HirsuTUS (Fletcher). (Pl. I, Figs. 3, 4, 5.) L. hirsutus, Fletcher (pars): Q.J.G.S., 1850, vol. vi, p. 236, pl. xxvii, figs. 6, 6a ; pl. xxvii dzs, figs. 2, 2a (mon pl. xxvui, figs. 7, 7a). L. Bucklandi, Fletcher (pars): ibid., pl. xxvii, figs. 1, la, 1b (mon cet.). There are three specimens ascribed to this species by Fletcher and figured by him, all of which are in the Woodwardian Museum. Excluding the remarks on the specimen figured on pl. xxvii, figs. 7, Ta, the description of the species given by Fletcher is fairly accurate and complete so far as it goes, but the figures (pl. xxvii, figs. 6, 6a; pl. xxvii bis, figs. 2, 2a) show such differences that they might be thought to represent distinct species. The specimens, however, from which these figures were drawn are in reality closely similar, and do not exhibit more than the customary amount of variation- The specimen on which figs. 6, 6a, pl. xxvii were founded is so imperfect that it shows Fletcher used other specimens together with it in order to draw up his description of the species. There is no distinctly raised border round the pygidium, the appearance in Fletcher’s figured specimen (pl. xxvii, fig. 6a) being due to unequal crushing. Other specimens show that the relative length of the axis slightly varies, and also the number of tubercular rings upon it. A well-preserved complete specimen in the Woodwardian Museum showing head, thorax, and pygidium attached, and several other less F. R. Cowper Reed—Some Wenlock Species of Lichas. 9) perfect specimens, enable me to give a complete description of the species, and render possible the identification of isolated head-shields, previously of doubtful specific position. Draenosis.—Head-shield broadly parabolic, more than twice as broad as long, swollen centrally, bent down at sides and strongly in front. Glabella elevated, convex, large, broader than long; greatest width across middle third. Central lobe long, subcylindrical with parallel sides between anterior bicomposite lateral lobes, slightly expanded in front, embracing front end of these lobes; defined pos- teriorly by strong curved transverse furrow at level of second lateral furrow. Anterior lateral lobes rather swollen, oval but slightly pointed behind ; each as broad as central lobe; extend three-fourths the length of the glabella; are defined externally by strong furrow. Middle and basal lobes obsolete, their place being occupied by a sub- triangular, uniformly swollen surface, not differentiated or marked off from the fixed cheek, except behind the eye, where the posterior portion of the axal furrow is faintly developed. Between the central lobe and neck-ring is a narrow post-central lobe depressed below the level of the central and lateral lobes, and defined laterally by the weak backward continuation of the first lateral furrows to the neck-ring; three conspicuous large isolated tubercles usually ornament it. First lateral furrows curve inwards strongly from anterior point of origin, sweeping round front end of anterior lateral lobes ; then run backwards to transverse furrow with increasing strength and almost parallel to each other, behind which they diverge and are feebly continued to neck-ring. Axal furrows strong, curved outwards, defining outer border of anterior lateral lobes; not continued behind second lateral furrows, which at level of eyes pass imperceptibly into them. Close to the neck-ring a faint furrow on each side represents the posterior portion of the axal furrows. Second lateral furrows form a continuation inwards of the axal furrows round the base of the anterior lateral lobes, joining first lateral furrows at angle of 75°-90°. Transverse central furrow runs across middle of glabella as continuation of second lateral furrows with equal strength, but with independent backward curva- ture. Occipital ring arched forwards, swollen, broadest in middle, generally with median tubercle. Fixed cheeks triangular, swollen towards inner portion, not marked off in middle from glabella; posterior edge straight, hori- zontal at right angles to axis of glabella, but bending sharply forward at outer angle at about 130°. LHye-lobe moderate, prominent, horizontal, at level of second lateral furrow. Neck-ring on posterior margin elevated, narrow, ornamented with single row of large tubercles. Facial suture makes a sharp bend outwards behind eye, curving thence backwards to cut lateral margin behind spine. Free cheek narrow, elongated, triangular, inner portion swollen, bearing prominent elevated eye of moderate size. Middle of lateral 6 fF. R. Cowper Reed—Some Wenlock Species of Lichas. margin furnished with strong short outwardly projecting spine, curving slightly backwards. Head-shield in all parts (including spines) ornamented with large tubercles, not closely set, with smaller ones interspersed. Thorax composed of eleven segments. Axis moderately convex, nearly as wide as pleural portions, cylindrical for first six or seven rings, then tapering gradually backwards to pygidium. Axal furrows well-marked. Axial rings narrow, rounded, with narrow articulating band. Pleuree narrow, rounded, cylindrical, with free pointed extremities ;. horizontally extended to fulcrum, which is situated at about half their length, then bent downwards and slightly backwards. Narrow flattened band on front edge. Hach thoracic segment bears a single row of a few large equally-spaced tubercles. Pygidium broadly parabolic, usually slightly broader than long. Axis convex, subcylindrical or slightly tapering, bluntly rounded at posterior end; extends about two-thirds the length of pygidium, and occupies about the middle third of width. One strong complete axial ring at front end with narrow articulating band on front edge, followed by 8-5 narrow transverse rows of tubercles in middle portion of axis; the first one or two rows are separated by more or less distinct furrows. Posterior end of axis abrupt, blunt, not circumscribed by furrow, but continued posteriorly by narrow, depressed, tapering post-axial median piece, which becomes parallel- sided and extends to posterior border between third pair of marginal spines. Lateral lobes flattened, slightly bent down, with three pairs of large spines projecting beyond the margin and numerous minute spinules or prickles. ‘Two pairs of well-defined pleure curving backwards; each pleura marked by median furrow dividing it into two unequal portions, of which the posterior is the narrower and more elevated. Hach pleura is produced beyond pygidial margin into short free point, forming thus the two anterior pairs of marginal spines, which also bear small lateral prickles (only occasionally preserved). Pleurze separated by well-marked interpleural furrows curving backwards, of which the first makes an angle of about 30° with the front margin, and the second makes an angle of about 60°-70° with the same. Between the second pleurz and the post-axial piece is a triangular, irregularly tuberculated area on each side with no furrow upon it. The posterior pair of spines are approximate and directed straight backwards, and are generally about equal in length to the second pair, from which they are removed by about twice the distance that they are from each other. MEASUREMENTS. mm. Length of trilobite ... a0¢ aye see cis cole SO Length of head-shield si Sas a 6°5 Width of head-shield (from tips of genal spines). ee ls 30 Length of thorax ... ane bb ae ese 75 Length of pygidium... 7-0 Width of pygidium ... 9°0 F. R. Cowper Reed—Some Wenlock Species of Lichas. if Remarks.—The head-shield shows considerable resemblance to that of L. anglicus (Beyr.); but the latter may be distinguished by (1) the more quadrato-oval shape of the anterior lateral bicomposite lobes of the glabella, owing to the second lateral furrow meeting the first lateral furrow at a right angle, (2) the greater size of the post-central lobe of the glabella, (3) the small outward bend in the first lateral furrows in the middle of the central lobe, (4) the absence of the basal portion of the axal furrow, (5) the smaller lateral expansion of the anterior end of the central lobe of the glabella, (6) the different shape of the free cheek, and (7) the regular curve described by the posterior margin of the head-shield. A comparison of Fletcher’s figure (pl. xxvii bis, fig. la) of L. anglicus plainly shows the points of difference. The glabella in LZ. anglicus is also generally of rather less width, but is somewhat longer ; and the head-shield is not so bent down in front, nor so swollen centrally. In the pygidium we see in L. hirsutus much resemblance to ZL. Haueri (Barr.),! and the head-shield, with the exception of the transverse post-central furrow, is likewise somewhat similar. The peculiar laterally angulated outline of the posterior margin of the head-shield and position of the spine on the free cheek is likewise met with in Z. Haueri and in other Bohemian species. The head-shield referred by Fletcher to Z. anglicus (pl. xxvii, figs. 1, la, 1b), but mentioned as being of a slightly unusual form (p. 236), should be attributed to Z. hirsutus, with which it agrees in all essential features. Barrande (op. cit., p. 602) considered that Z. hirsutus, Fletcher, was identical with his L. palmata (Barrande, op. cit., p. 599, pl. xxix, figs. 1-13), but remarks that one of Fletcher’s specimens (shown in fig. 5, pl. xxvii, Q.J.G.S., 1850, vol. vi) represents a different form to which the specific name L. hirsutus must be restricted. Probably Barrande meant fig. 7 instead of fig. 5, for the latter is attributed by Fletcher to LZ. Bucklandi in his explanation of plate xxvii. L. hirsutus, Fletcher (excluding fig. 7, pl. xxvii), however, differs from L. palmata in numerous points, the most important of which are the absence of the well-defined middle glabellar and occipital lobes, and in the pygidium the presence of only one strong axial ring followed by several incomplete rows of tubercles. These features are amply sufficient to separate it specifically. Licuas (CoRYDOCEPHALUS) HIRSUTUS, var. TUBERCULATUS (var. nOV.). (Pl. I, Fig. 6.) Several specimens of a Lichas from the Wenlock Limestone or Shale of Dudley show points of difference from the type-form of L. hirsutus almost sufficient to constitute a distinct species. In the head-shield the basal portion of the axal furrows is wanting, and the fixed cheeks are completely confluent with the middle lateral portions of the glabella; there is one conspicuously large tubercle on the middle of the fixed cheek, and the eye-lobe projects laterally in a very prominent manner; the occipital ring also bears a large 1 Barrande: Syst. Sil. Bohem., vol. i, p. 604, pl. xxviii, figs. 38-44. 8 F.. R. Cowper Reed—Some Wenlock Species of Lichas. median tubercle. There are only ten segments recognizable in the thorax in the one complete specimen which I have examined, but this probably only indicates immaturity. The pygidium has a large prominent central tubercle near its posterior end; the transverse rows of tubercles on the axis behind the first ring are very indistinct; the post-axial piece is very short and ill-defined. The two pairs of pleure have their free ends more elongated than is usual, the second pair indeed projecting back behind the posterior end of the pygidium and behind the third pair of spines, which are very short and blunt. Fletcher labelled one of these specimens LZ. Bucklandi (= L. anglicus), but Salter labelled another (2963) Z. hirsutus. From the presence of several specially large tubercles this variety may be termed tuberculatus. Licuas (CoRYDOCEPHALUS), sp. L. hirsutus (Fletcher), ‘‘young’’: Q.J.G.S., 1850, vol. vi, pl. xxvii, figs. 7, 7a. The pygidium figured by Fletcher as belonging to a young individual of Z. hirsutus, “from the great similarity in the arrange- ment of the tubercles on the axis and sides,’ shows such important differences that it does not seem possible to regard them as merely marking a stage of growth in an individual of this species. The pygidium is semicircular, with three pairs of marginal spines of sub- equal size. The axis is very broad, blunt, and subconical, reaching fully three-fourths the entire length of the pygidium, and occupying considerably more than its middle third. There is one strong ring at the front end of the axis, followed by two or three much narrower and fainter rings marked by tubercles. There is no distinct post-axial piece. The axal furrows are strong and deep. There are two pairs of pleuree on each side (not three ‘ribs’ as Fletcher states), curved backwards, and ending in short stout, backwardly directed free points on the margin. The surface of each pleura is divided down the centre by a strong median furrow, equal in strength to the inter- pleural furrows; the anterior and posterior parts of each pleura are of equal size and elevation, and each is ornamented by a single row of large tubercles. The posterior pair of spines is rather shorter than the first and second pairs, and its members are twice as closely approximated to each other as they are to the second pair of spines. A few large tubercles are somewhat regularly disposed on the axis and the portions of the lateral lobes behind the second pleure. The margin is strongly and sharply incurved below, and is marked by concentric raised striz, which also cross the under-surface of the spines. MEASUREMENTS. mm. Length of pygidium Width of pygidium Width of axis ... 586 sa Me ae Remarxks.—It is possible that the specimen above described belongs to an immature individual of some species, though probably not to I. hirsutus. It is advisable, therefore, in the absence of further evidence to leave it unassociated with any of the described species, and to refrain from considering it a new species. Co aT F. R. Cowper Reed—Some Wenlock Species of Lichas. 3g Licuas (Dicranopetris) Woopwarpt, sp. nov.’ (Pl. I, Figs. 7, 8.) L. Barrandii, Fletcher (pars): Q.J.G.8., 1850, vol. vi, p. 238, pl. xxvu, fig. 10 (non pl. xxvii bis, fig. 5). The description which Fletcher gave of the species which he called LZ. Barrandii corresponds exactly with his fig. 5, pl. xxvii bis, and with the two specimens on which this was founded, but it does not at all agree with the figure on the preceding plate (fig. 10, pl. xxvii), nor with the specimen which it represents, and the only point in the description which is borrowed from it refers to the con- centric striation of the under side, which is not seen on the other specimens. A suspicion that two species have been confounded at once arises, and an examination of the type-specimens which are in the Woodwardian Museum confirms it. . Moreover, the type-specimen represented in fig. 10, pl. xxvii shows only the inner surface of the shell, but another showing the actual outer surface in relief has come into our possession with the remainder of Fletcher’s collection presented in 1897, and it was labelled by Fletcher himself L. Barrandii. From this material a fairly complete description of this new species can be given, so far as the pygidial characters are concerned. Pygidium broadly parabolic; ratio of length to width as 3: 4. Axis rounded, convex, slightly elevated above side-lobes; nearly one-third the width of the pygidium at front end; short, broad, not as long as broad; sides converge posteriorly at angle of about 00°; abruptly truncated at posterior end by straight transverse furrow; bears two well-marked continuous rings at anterior end. Axal furrows well-marked, nearly straight. Transverse furrow defining termination of axis weak in centre, strongly impressed at sides. Lateral lobes flattened, nearly horizontally extended, furnished with six pairs of furrows of equal strength; each lobe consisting of three broad foliaceous pleure with free falcate, backwardly directed ends. First two pleure on each side complete, and well-defined by ‘strong interpleural furrows of equal depth, the first furrow making an angle of about 30° with the front edge of the pygidium, and the second an angle of about 60°. First pleura marked by diagonal furrow which runs parallel to the first interpleural furrow, but dies out before reaching the free point of the pleura. Second pleura marked by similar furrow starting from axal furrow at the point of origin of first interpleural furrow, and running thence parallel to second interpleural furrow, but dying out before reaching free point. Axal furrows continued backwards behind axis, at first with same angle of convergence and then almost parallel to each other, but disappearing at some distance from the posterior margin of pygidium. The post-axial median piece enclosed between them is narrow, and slopes down rapidly to level of side-lobes. Third pair of pleure 1 This species is mentioned by the author in his paper on the genus Lichas: Q.J.G.S., 1902, vol. lviii, pp. 72 and 82. 10 F. R. Cowper Reed—Some Wenlock Species of Lichas. between second pair of pleure and post-axial median piece; each third pleura ends in backwardly directed free point, and is crossed by diagonal furrow making an angle of about 80°-90° with front edge of pygidium. Free points of third pair of pleurze approximate- (not well preserved) ; margin of pygidium incurved, and shows on under-surface concentric equidistant raised thread-like lines. Ornamentation consists of large round tubercles of two or three graduated sizes, not very closely set. Owing to the breaking off of the heads of the larger tubercles (which are hollow), circular pits with a raised margin are left as cicatrices. MEASUREMENTS. IL (Fletcher’s figured specimen). II. Length of pygidium a an Boe B se c. 31 mm. Width of pygidium oe ae Ba 46 mm. sls LO. Width of axis at front end te son 1B 35 ie UBB 96 Length of axis... hen $50 sae Te ad na OO 56 Remarks.—This species differs from L. Barrandii (Q.J.G.S., 1850,. vol. vi, pl. xxvii bis, fig. 5) by the following features: (1) greater relative length of pygidium, (2) narrower and shorter axis, (3) only two ‘axial rings, (4) no axial tubercle, (5) straight transverse posterior furrow defining end of axis, (6) longer post-axial median. piece, (7) less backwardly curved pleura, (8) course of furrows on lateral lobes, (9) coarser tuberculation. The pygidium of L. scaber (Beyr.) bears a considerable resemblance to that of L. Woodwardi. It may also be mentioned that the ornamentation of L. Grayi, of which only the head-shield is known from the Wenlock Limestone, is somewhat similar. Licnas (Dicranopextis) Barranpet, Fletcher (emend.). Lichas Barrandii, Fletcher (pars): Q.J.G.S., 1850, vol. vi, p. 238, pl. xxvii dis, fig. 5 (non pl. xxvu, fig. 10). Fletcher’s diagnosis of this species, with the exception of the statement that “the incurved under-portion is concentrically striated,” which cannot be verified with our present material, applies to fig. 5, pl. xxvii bis, and does not need any amplification. It may, however, be remarked that the figure is partly a restoration based on two nearly complete specimens (b 28, 6 29 in Salter’s Catalogue), the measurements of which are as follows :— I (029). II (6 28). Length of pygidium ... wns 20 mm. mh 18 mm. Width (at front end) of pyg eidium ae ® as 24s. Width of axis Cy front end) ... See 1B 5. oan iLL Length of axis.. ane ae wes 10 sae ? be) It is unfortunate that of this species only the pygidium is known at present. In one of the specimens (I) a faint transverse furrow, incomplete in the middle, defines the posterior end of the axis, recalling the much stronger furrow seen in L. Woodwardi. Fletcher does not mention it, and it appears to be obsolete in the better F. R. Cowper Reed—Some Wenlock Species of Lichas. 11 preserved specimen (II), which he used chiefly in drawing fig. 5,. pl. xxvii bis. Licuas (Dicranorettis ?) Saurert, Fletcher. L. Salteri, Fletcher: Q.J.G.S., 1850, vol. vi, p. 237, pl. xxvii, figs. 9594; pl. xxvii dis, fig. 4. Lindstrém? records this species from Gotland, and believes that L. laticeps, Angelin (Pal. Scan., 1854, pp. 70, 72, t. xxxvii, figs. 8, 8a, non t. xxxviili, fig. 5), and L. gibbus, Angelin (Pal. Scan., p. 71, t. xxxvii, fig. 1, pygidium only), are synonyms. The rows of large: tubercles on the glabella and side-lobes are held by Lindstrém to. be the particular characteristic of the species; and unfortunately no part but the head-shield, and that incomplete, is known from the Wenlock Limestone. It is impossible to feel on safe ground in assigning any of the isolated pygidia of this horizon to L. Salteri, but Lindstrém * considers the pygidium figured by Angelin (op. cit. sup.) as L. gibbus as probably belonging to this species, and describes it as possessing a linear axis narrowing posteriorly, furnished with about eleven segments, of which the posterior ones are inconspicuous ; anarrow prolongation extends behind it towards the margin. Three small pleura-like ribs are given off on each side from rather in front of the middle of the axis. There is a raised border round the pygidium, and from it short, backwardly directed spines project near the terminations of the ribs. Between the two posterior ones are three pairs of small spines, one of which projects from the axis. It is to be regretted that Lindstrém did not give a figure of this specimen, as Angelin’s figure leaves much to be desired, and it is difficult to form an adequate idea of the pygidial characters from the description. The old generic designation Trochurus is revived by Lindstrém for this species, and applied also to J. pusillus, Angelin, and T. Bucklandi, Milne Edwards (= L. anglicus, Beyrich). Beyrich, however, in 1846 (Untersuch. tiber Trilob.) declared that this name,. which he had instituted in 1845 (Ueber Boh. Trilob., p. 31, fig. 14), should be allowed to drop, as the genus had been founded on a specimen consisting of portions of two distinct trilobites (i.e. a head of Staurocephalus Murchisoni combined with a pygidium of L. speciosus, Beyr. [= L. palmata, Barrande]). Barrande (Syst. Sil. Boh., vol. i, p- 603) points out this fact, and also rejects for this reason the specific name ZL. speciosus, which Beyrich had given in 1845 to the composite form. It accordingly appears inadvisable to revive the name Trochurus under any form. Beyrich himself employed in 1846 Goldfuss’ earlier name Arges (1839) for his species L. speciosus (= L. palmata, Barr.), but, as previously pointed out by the present writer,® this name is preoccupied. 1 Lindstrém: Gotl. Silur. Crust. Ofv. K. Vet. Akad. Forhandl., 1885, No. 6, p- 60 (Lrochurus Salteri) ; List of the Fossils of the Upper Silurian Formation of Gotland, Stockholm, 1885, p. 3 (Zrochurus Salteri). 2 Gotl. Silur. Crust. Ofv. K. Vet. Akad. Forhandl., 1885, p. 60. 3 Q.J.G.S., 1902, vol. lviii, p. 60. 12 Rev. J. F. Blake—Form of Sedimentary Deposits. EXPLANATION. OF PLATE I. Fic. 1.—Lichas (Corydocephalus) anglicus, var. wenlockensis. Outline restoration of pygidium. x 3. 99 ot be ee: ) anglicus, var. obtusicaudatus. Outline restoration of pygidium. 9 OL. "(Cor ydo.) hirsutus. Specimen with eleven thoracic segments. x 23 (partly restored). Woodw. Mus. », 4.—Ditto. Specimen with eleven thoracic segments. x 22 (partly restored). Brit. Mus. _ 5, 0.—Ditto. Outline restoration of pygidium from Fletcher’s type. x 3. », 6.—Ditto. Var. tuberculatus. x 3. Woodw. Mus. >, @.—L. (Dicranopeltis) Woodwardi. x 14. Woodw. Mus. » 8.—Ditto. Nat.size. Figured by Fletcher as Z. Barrandii (Q.J.G.S., vol. v1, pl. xxvii, fig. 10). Woodw. Mus. IIJ.—On tHe Oriainat Form or Sepimentary Deposits.! By the Rev. J. F. Buaxr, M.A., F.G.S. HE form of the deposits that are taking place on the sea-bottom at the present day is one of the essential elements required to be known when we wish to interpret the submarine contours, as throwing light on the submergence or elevation of the land in late geological times, or when we propose to use the variation of thickness of the strata deposited during any epoch as an indication of the position of the shore-lines at that time. In the case of deposits in small or temporary masses of water, their form and arrangement may sometimes be observed directly ; but in the case of the deposits in the sea, where we can neither remove the water nor make borings beneath it, we can only avail ourselves of theoretical considerations. It might have been expected that the original form of various sedimentary deposits would have been considered in detail long ago, but as a matter of fact the few writers who have touched upon the question have mostly been content with the assumption that deposits taken as a whole are thickest near the source of supply, and the figures given in illustration of the arrangement of various kinds, and thereby the shape of each, are remarkable for their variety.” As the theoretical results at which I have arrived differ funda- mentally from the ordinary assumptions, it is to be hoped that some one will be able to point out the fallacy, if any, which has led me astray, and to explain more satisfactorily the observed features which appear to confirm the theory. It will be seen, however, that it is just those writers who have paid most attention to the matter who approach most nearly to agreement with my results. The actual form of any deposit on the sea-bottom, supposed, for the sake of argument, to be flat, will depend first upon the forces to which the material is subject, and secondly upon the nature of the 1 A paper read at the Meeting of the British Association, Belfast, September, 1902. 2 See Godwin-Austen, Q.J.G.S., vol. vi, p. 82, fig. 2 2 (1850); Hull, Ou G.S., vol. xviii, p. 135, fig. 4 (1862) ; Green, Lectures on Coal, p- 9 (1878), and Geology, p. 211 (1882) ; Page & Lapworth, Introductory Textbook, p. 59, fig. 22 (1888); Marr, Principles of Stratigrapl hical Geology, p. 117, fig. 13 (1898) ; Watts, Geology for Beginners, p. 78, fig. 47 (1898). Geol Mag.1903. Decade IV. Vol.X PL.1. “y oy Pst he PE Ab