: CRM MEE ER, RAE (eee “SES = Mie a Ga ee OE ee 4 CE COR - & : Ke Ce KE < Qa ¢ VC ERS < Pe << S Se CEN COM OER EE KR, CES ee Y o J 5 i oa ‘ x wh ’ ‘ \ A i 2 * ie N ¢ _ h f pp p : € » ay 4 - ‘ c i ae ag AL ‘ Me wat aie ‘ M % . vethe ? . = y é ‘ fe ere Neale bP aa ah ean ‘oY hier sh en ee Bit NS tek me YS" ISN oii MEMOIRS me e712 NH GEOLOGICAL SURVEY oF OF THE THE UNITED KINGDOM. Figures ant Descriptions ILLUSTRATIVE OF BRITISH ORGANIC REMAINS. DECADE VIL. {i PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY’S TREASURY. LONDON: PRINTED FOR HER MAJESTY’S STATIONERY OFFICE: PUBLISHED BY LONGMAN, BROWN, GREEN, AND LONGMANS. 1853. phe BRITISH FOSSILS. DECADE THE SEVENTH. Tats Decade is devoted to figures and descriptions of Trilobites, a group of extinct Crustacea of the highest geological interest. These remarkable fossils are wholly restricted to Palzeozoic formations. The progress of research has shown that the various genera and species of Trilobites are remarkably characteristic of well-defined geological horizons ; consequently, the study and exact definition of them is laid much stress upon by the geologist whose labours are directed to the investigation of the more ancient rocks. ' The recent publication of a beautiful work by M. Barrande, on the Trilobites of Bohemia, in which the species are fully illustrated and described, affords means of comparison with the specimens of British Trilobites (usually less perfectly preserved), such as we did not before possess. It will be seen from the following descriptions that but few of our species are identical with those of Bohemia, and thus we get at an interesting indication of a geographical distribu- tion of these primeeval animals. Of forty-five species here described, but one, a Phacops,—-a member of a different section from that previously illustrated, belongs to any genus as yet selected for these Decades. Cheirurus is exemplified by a species heretofore known only in a fragmentary state. Spherexochus mirus is a cosmopolitan fossil, of which excellent - specimens have been lent to us for illustration. Encrinurus and Acidaspis are typified by new species from the lowest fossiliferous deposits. : [ vil. | a 2 BRITISH FOSSILS. Cyphaspis and Aglina are for the first time published in England; and a new genus, Cyphoniscus, is i cas for some minute and hitherto undescribed forms. Remopleurides is republished, with some additional data for the correct account of its structure. It is proposed, for what appear to be cogent reasons, to refer some curious variations in closely allied forms to sexual differences. Under the ten genera here illustrated, the descriptions of all known British species are given. They have in every instance been drawn up by Mr. Salter. EDWARD FORBES. August 1, 1853. Bae DECADE 7. Pht. Ovolog cal Surbep at th r Varted Rar OM . PIBUNCOIPS Z t - (Silurian. ) WLI EDANN): Murchison. Gg eee ee Oe PHACOPS DOWNINGIA BRITISH FOSSILS. DercaDE VII. Puate I. PHACOPS DOWNINGIA. {Genus PHACOPS. Emmricu. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca.. Tribe Trilobite or Paleade.). Head. strongly trilobed; glabella lobed, and broadest in front; facial suture ending on the external margin; eyes largely facetted ; hypostome oblong, rounded at the end; thorax of 11 segments, the pleure grooved and facetted for rolling up; tail strongly ribbed, of several segments, the margin entire or toothed. | _ [Sub-genus Acaste. Gotpruss. Form convex, and contractile into a ball. Glabella not much inflated, all the lobes distinct; facial suture within the edge or marginal in front; head angles rounded or with short spies; hypostome obtuse, entire; body segments rounded at the ends; tail of a moderate number of distinct segments (11 or less), its edge without lateral spines. ] Driaenosis. P. alutaceus ; capite transverso, margin frontali angulato ; glabella depressa oblonga subparallella, sulcis utrinque tribus distinctis, lobo basali lineari, secundo ovali, superiori transverso—sed margine superiore ascendente sinuato—lobis omnibus planis et fere ad medium glabelle extensis, spatio angusto interjecto : lobo cervicali elevato; oculis magnis nec eminenti- bus: cauda subtrigona, axi convexo costis quinque distinctis tribusque obscuris predito,—tlateribus quinque-costatis, costis duplicatis ; margine distincto, apice angulato. Synonyms. Calymene macrophthalma (Bronen.), Buckianp (1836), Bridgw. Treatise, pl. 46. fig.5 (not 4.) Calym.? Downingie, Murcuison, Silur. Syst. (1839), pl. 14. fig. 3. Mine Epwarps (1840), Crust., 3. 324. Acaste Downingie, Goitpruss, Syst. Uebersicht der Tril., Neues Jahrb. (1843), 563. Phacops macrophthalmus, Burmeist. (1843), Org. der Tril., 1389, 140, and in ed. 2. (1846), p.92. Phacops Downingie, Emmricn, Neues Jahrb. (1845), 40. pl. 1. fig. 2. [icon mala]; Transl. in Taylor’s Scient. Memoirs (1845), vol.iv. pl. 4. fig.2. Pamiies and Satter, Memoirs. Geol. Surv. (June 1848), vol. ii. pl. 1. p. 239, 386. pl. 5. fig. 2. 3. 4. M‘Coy (1851), Synopsis Pal. Foss. Woodw. Mus. 160. Junior.— Asaphus subcaudatus, and A. Cawdori, Murcuison, Sil. Syst. pl. 7. fig.9,10. Phacops subcaudatus, SALTER and Puitiirg, |. c. 239. One of the most common, and certainly one of the most elegant trilobites in the Silurian System—occurring in abundance wherever Upper Silurian strata are found. It is a very characteristic fossil of [vir.1.] 7A 2 BRITISH FOSSILS. the Dudley limestone. And yet, perhaps, there is no species of trilobite which has been so much misunderstood; the confusion apparently arising from this circumstance—that it is rarely, if ever, found out of Britain ; although somewhat similar species have been identified with it, both British and foreign. It was named in com- pliment to Mrs. Downing, of Dudley, from whose cabinet the figures in the “Silurian System” were drawn. Description.—Length from an inch and a half to two inches. The general form long-ovate, the anterior end being considerably broader, and with the axis following the same lines, and regularly tapering from head to tail. The surface is moderately convex, the axis raised above the sides, not separated by deep furrows except in the head, and more convex in the thorax than in the head or tail. The head is somewhat less than a semi-circle, though just twice as long as broad, the general outline being rather triangular, from an indentation in the curved outer margin on each side of the wide glabella ; the front is not produced, but angular. The glabella occupies more than one third the width of the head in front, and tapers but little backwards, having nearly straight and parallel sides ; it rises considerably above the cheeks, but is rather depressed than convex, especially the forehead lobe, which is not at all inflated, but slopes gradually to the narrow front margin, from which it is separated by a shallow furrow. Neck lobe strong, broader than the first basal lobes, which are transverse and linear; the middle pair are broader than these, and oval, the direction of the first and second rrows determining their shape—the lower furrow curves downwards, and reaches the side of the glabella; the upper one, which is abbreviated, curves the reverse way ; the upper lateral lobe is transverse, scarcely triangular, and bounded above by a sigmoid furrow, which runs very obliquely out above the eye. All the furrows stretch equally towards the middle of the glabella, leaving but a narrow space between their ends; between the upper pair a short longitudinal depression occurs. The lobes are not swelled between the furrows, but the surface is even and the furrows shallow (they are, however, sharply defined on the internal cast) ; the neck furrow and basal furrows are strong—the two upper ones very faint.* The cheeks are steeply bent down, their outer margin not distinguished by any furrow, and they slope gradually from the eye, without any ridge or groove beneath the latter ; the neck furrow is continued almost to the posterior angle, which is rounded off and only shows a slight projection (fig. 10, ¢) in the place of a spine. The facial * Memoirs Geol. Survey, vol. ii. p. 1. pl. 5. fig, 2. BRITISH FOSSILS. 3 suture cuts the outer margin in a curved line in front of the pos- terior angles, and opposite the base of the eye; on the under surface of the head (fig. 5) the suture cuts the margin further back- ward (bb). Above the eye it continues along the axal furrow and round the front of the glabella just outside the marginal furrow. Hyes rather large, conical, rising in some specimens nearly to the level of the glabella, placed about half-way up the cheek, near to the two upper glabella lobes, and occupying their length: eye lobe with a raised outer margin ; lentiferous surface broad, with about 155 lenses in each eye, each vertical row containing eight. The cornea is convex over the lenses, and the intermediate flattened spaces are finely granular, the granules forming a roagh hexagonal network toward the base of the eye ; the lenses are nearly their own diameter apart, but this varies much in different individuals, the ‘space being often much less (figs. 7, 8). On the under side of the head, the incurved front portion (which, as in all the genus, is continuous across,) is broad (fig. 5, a), and granular, like the upper surface ; it supports the broad base of the hypostome, which is also granulated. This organ is subquadrate but broadest at its base, and very regularly convex, almost tumid ; a faint concentric furrow running round the sides and tip just indi- cates a narrow margin, more flattened than the other parts ; there are no lateral furrows, but high up on each side is a small tubercle. The tip is straight and somewhat truncate, and the exterior angles are cut off so as to render the end somewhat polygonal; but there are no traces of projecting teeth, and the appearance of the apex is obtuse. The entire organ is much narrower than the glabella, and not above half its length, but from the position of its base it reaches as far backward as the middle pair of glabellar furrows. And these glabellar furrows, as Burmeister has shown, doubtless indicating the position of the jaws and accessory parts of the mouth, the hypostome must have served the office of labrum or upper lip. Thorax considerably longer than the head, of 11 not very highly arched rings—the axis moderately convex, of nearly equal breadth with the pleure. These, which are traversed bya straight deep groove, (fig. 10, d), are curved rather abruptly downwards at the fulcrum (fig. 10, e), which anteriorly occurs at the inner third of their length, and in the posterior ring does not reach further than one fourth. The anterior edge of each pleura is sharpened or facetted* to pass under the preceding one, and the posterior edge is thickened. Each pleura is much bent forward at its end, which is deeply notched * M‘Coy, Annals Nat. Hist. (Dec. 1849.) be 4 BRITISH FOSSILS. (figs. 12, 13), and on the under side of each, in front of this notch, is placed a tubercle (fig. 13,a). When the animal was in the act of rolling up, the tubercle prevented the next ring from being pushed too far forward ; the tail, too, has them on its anterior edge. Some such contrivance as this, for giving compactness to the rolled up form, is probably general in trilobites, and Mr. John Gray, of Dudley, who first drew my attention to it, has succeeded in developing nearly the whole of the under surface of this species. The tubercles just mentioned occur on the incurved crustaceous porticn (fig. 13, 6) of the pleuree, which, in this species is but narrow, while in P. caudatus, Decade II. Pl. 1., it extends some distance inwards. The tail is sub-triangular and rather poimted, nearly twice as wide as long, and moderately convex ; the axis is more convex, but does not rise abruptly from the general surface, nor is it separated from the sides by any distinct axal furrows. It is conical, not so wide as the sides, extending to about four fifths of the length of the tail, with an obtuse scarcely prominent end; it is crossed by five distinct and two or three obscure rings. The sides have five or six rather deep and curved furrows, which end abruptly at the thickened margin; smaller and shallower furrows occur between each of the principal ones for the whole length. The incurved under margin is narrow but thick. The whole of the upper surface, and the incurved margins of the head and tail, are covered with fine, close, equal granulations ; the hypostome is also equally rough—none of the grains become tubercles, but all remain of equal size. Variations. Among the specimens in the cabinets of Messrs. Fletcher and Gray, occur one or two with the eyes (fig. 3) very considerably larger than usual, so as almost to equal those of P. Stokesw ; the specimens, however, clearly belong to the species we are describing. The following measurements in lines will give an idea of this difference, which is represented in our figure 3: Ordinary specimen :— Large-eyed variety :— Length of head - ~ 5 lines. Length of head - - dt lines. Length of the eye - ase Bs Length of the eye - 220 Height of eye - Be) tis Height ofeye = - Le bs The surface, therefore, in one case is nearly double that of the other, and the number of lenses is increased to about 180, the lenses themselves being each a little larger and not distant from one another more than half their diameter. Another specimen, m BRITISH FOSSILS. 5 Mr. Gray’s cabinet (fig. 8.) has the lenses decidedly small, distant their full diameter from each other, and the intermediate granula- tions more elevated and connected into zigzag lines. Fig.7* shows the ordinary surface of the eye. Some specimens have the axis of the body more prominent than others, and the tail is more pointed in some than in others. The glabella varies in width, and divergence of the axal furrows; many specimens having the sides nearly parallel, as in fig. 4, others, as fig. 10, somewhat more clavate. And in a dwarf variety from the Caradoc sandstone, found by Pro- fessor Sedgewick at Llanrwst, in North Wales, the clavate form is very marked. Occasionally (fig. 4) the two front furrows become quite obscure ; but this is a rare variation. These two upper furrows are always shallower than the lower one and neck furrow, and they show but little in the internal cast ; but they are never quite lost. Fig. 14 is from a fine large head from Ledbury, in Mr. C. Stokes’s cabinet ; the glabella furrows are remarkably deep, considering it is an. internal cast, and the lobes somewhat more tumid than usual. A ffinities.—The variation just noticed gives the specimen a great resemblance to a nearly allied species, which, however, belongs to the section Phacops, viz.—P. Stokes, M. Edwards, (P. macrophthalma, Brongn., t. 1. f. 5., figured in Mem. Geol. Surv., vol. ii. pt. 1. pl. 5. fig. 1). This, which is abundant at Walsall and Dudley, and fre- quently met with in the Wenlock limestones of the Malverns, is easily distinguished from all the varieties of P. Downingic by the shape of the lowest glabella lobe, which in this is narrow, very strongly marked off from the rest of the glabella by a nearly continuous transverse furrow, and its extremities are terminated by two rather small but strongly marked tubercles, while in P. Downingic this lobe is always linear and destitute of tubercles. The uppermost glabellar furrow is bent as if broken, while in P. Downingie it is a simple sigmoid curve. The tail of P. Stokesii has only two or three of the upper furrows of the axis and sides distinct; P. Downingie has them all marked, and the side furrows interlined by finer ones. But there is a Lower Silurian species, hereafter noticed, still more nearly resembling ours in all its parts—the P. apiculatus, Salter. In this the general shape of the head, and of the glabella and its lobes, have just the same appearance as those of our species, but a careful comparison will show marks of decided difference in all these parts. In the P. apiculatus, which is as common in the Lower as the P. Downingie in the Upper Silurian, the head is _ longer, and the glabella more elongate and narrower, and more con- 6 BRITISH FOSSILS. vex anteriorly ; from its greater length, too, the lobes do not appear so crowded ; they differ also in shape. The lower or basal pair are not linear and transverse, but subtriangular, and are cut off by a shallow depression from the body of the glabella (as in the sub-genus Pha- cops), and the neck lobe rises in the middle between them. The second or middle furrow extends to the glabella edge, and is bent down there ; and the upper one is more deeply impressed, and ends in a decided notch at the glabella margin, (even of this there is some trace in our species, but not nearly so distinct). There is an impor- tant difference, too, in the presence of a small spine at each of the head angles. The tail in P. apiculatus is decidedly triangular, and at the apex pinched up and drawn out into a recurved spine. With P. macrophthalma, Brongn., t. 1. fig. 4, it really has little in common. The head of that species* is far too long in propor- tion to the breadth for P. Downingic ; the forehead lobe is too clavate, and the head long, not transverse, and with a strongly pointed front, as represented in the original figure. The eyes, cheek angles, glabellar furrows, and tail all differ widely from those of the species before us. From P. Brongniarti, considered the same with it by Col. Portlock, it differs considerably. In that species, independently of the great length of the head, the glabella is widely clavate, with its basal pair of lobes obsolete, and the eyes enormous ; the furrows also of the tail are almost twice as numerous. It appears to be the pointed form of the head, not, however, very con- spicuous in P. Downingice, which has suggested the reference of this and of other trilobites to our species. P. microps (Green), as far as can be ascertained from his cast, No. 6, much resembles P. Downingice, but it cannot be identified. P. Phillipsi, Barrande, is very like our species, but the glabella furrows do not converge, and the upper ones are nearly obsolete. History.—Had Brongniart not figured two trilobites with large facetted eyes under one common name, thereby implying that they were at least closely related, it is not probable that any succeeding author would have identified the species we are describing with either of his figures. But as one of these was from an original drawing, made for Mr. Stokes from a Dudley specimen, it was * M. Ad. Brongniart’s kindness permitted us to examine the original figured specimen at the Jardin des Plantes in 1849. Of four specimens arranged as P. macrophthalma in this collection, the figured specimen is the only one without the name attached. One, par- ticularly labelled by Alex. Brongniart as P. macrophthalma, has a more clavate glabella than the true species, and is a decided Crypheus, from the United States. BRITISH FOSSILS. 7 likely that both British and foreign naturalists should conceive the common Dudley species, with a pointed front, to represent the more pointed variety of Brongniart. Green, in his description of the C. macrophthalma, 1832, noticed the great difference between the two figures: and, referring to a fine slab of Dudley trilobites, noted that these agreed exactly with the description given by M. Brong- niart of the head of his species; and one of Green’s published casts is from a British specimen. Professor Buckland, who in 1836 published a drawing of this species in the Bridgwater Treatise, conceived it to be represented by the more pointed form of P. macrophthalma, (Brongniart, fig. 4), and named it accordingly ; and Sir R. I. Murchison followed this view, at the same time rightly distinguishing it from the obtuse headed species (fig. 5 of Brongniart), which occurs, though rarely, in com- - pany with it at Dudley. He considered the latter fossil, which has enormous eyes, to be more properly the type of Brongniart’s species ; and gave the new name to that one which was conceived to repre- sent his figure 4. Milne Edwards in 1840 recorded it as distinct from either of Brongniart’s species ; and as the French fossil with a pointed front evidently furnished Brongniart with his description, retained his name, Calym. macrophthalma, for that species, and gave that of C. Downingie to the present one. He also applied a new name, C’. Stokesvi, to the rarer British fossil represented by Brong- niart’s fig. 5. In this view all naturalists are now agreed. In the meantime, and immediately after the publication of the Silurian System, Professor Emmrich had established the very natural genus Phacops for all those trilobites with largely facetted eyes and 11 segments to the thorax ; and he of course quoted the present species under the genus, but supposed it might probably be a variety of his Bohemian species, P. prowvus. He afterwards, 1845, admitted it under the present name. Professor Goldfuss, too, in the general sys- tematic Review of Trilobites, published in the Neues Jahrbuch for 1843, had admitted the species; and perceiving the great distinction that existed between those forms with all the glabella furrows distinct and strong, and those in which the anterior ones were obsolete, he separated the group which includes the present species under the term Acaste, reserving Phacops for those species with inflated heads and obscure glabella furrows, which Dr. Emmrich had already pointed out in his Dissertation as the type of his genus. The latter, in his systematic table of the genera, published in the Neues Jahrbuch for 1845, objected to this arrangement, and grouped together the two sections just adverted to as constituting 3 BRITISH FOSSILS. a sub-genus Phacops, while he formed the section Dalmannia for the more expanded forms, such as P. caudatus, P. Hausmanm, &c.* Professor Burmeister had already, 1843, regarded our species as a synonym of P. macrophthalma, Brongn., and has repeated this reference in his second edition, 1846. And Lieut.-Col. Portlock, in his admirable work on the Geology of Tyrone, endeavoured to escape from the difficulty by proposing a fresh name, P. Brongniarti, to include Brongniart’s and Murchison’s species, as well as a new and perfectly distinct form, discovered by himself; thus adding mno- cently to the confusion. In the Mem. Geol. Survey, 1848, I returned to Milne Edwards’ correct classification of these species, and de- scribed both the English forms. Professor M‘Coy has since confirmed their distinctness, and we may now consider P. Downingice as having established its claim to rank as a distinct British species, highly characteristic of the Upper Silurian rocks, and unknown, so far as we are able to learn, in other countries. British Localities and Geological Position.—CAaRADOC SANDSTONE to LupLow Rock.—Caradoc Sandstone; Moel Seisiog, and other places near Conway and Llanrwst, North Wales (dwarf specimens). Wenlock Shale ; Bryn Craig, &c., Usk; and Slate Mill, Hasguard, in South Wales. Wenlock Limestone ; west of Hereford Beacon ; — Ledbury ; Malvern Hills; Dudley and Walsall, abundant. Lower Ludlow and Upper Ludlow Rocks of the Abberley Hills. Upper Ludlow ; Underbarrow and Benson Knot, Kendal; Pont-ar-y- Llechau, near Llangadoc, South Wales; Ludlow Rocks, Golden Grove, and other places south of Llandeilo. | EXPLANATION OF PLATE I. Fig. 1. Phacops Downingia, of ordinary size ; Dudley limestone. (Collection of John Gray, Esq.) At 5, the outer termination of the facial suture is seen. Fig. 2. Do.; a rolled-up specimen, same locality. (Collection of T. W. Fletcher, Esq.) Fig. 3. Do.; variety with very large eyes, each with about 180 lenses. Same locality and collection. * As we think, however, that there are three distinct groups, we have adopted the term Acaste for the present sub-genus, and left the species with inflated and lobeless glabella in the section Phacops. In this latter view we have the sanction of the greatest authority on trilobites, M. de Barrande, whose great work, just received from the publisher, will long be the standard for reference. Otherwise we should have been unwilling to disturb the nomenclature adopted by Professor M‘Coy, who has given to the latter group the new name Portlockia, reserving Phacops for those species which have the glabella lobes distinct, but have not the expanded form or numerous tail segments of Dalmannia, BRITISH FOSSILS. 9 Fig. 4. Glabella of a specimen from the Wenlock limestones of the Malverns, with the two upper furrows nearly obselete ; the lower ones are stonger than usual; a rare variation. (Coll. Mus. Pract. Geol.) Fig. 5. Under side of the head, showing the entire rostral portion a, the termination of the facial suture on each outer side at 66, much further backward than on the upper surface (see fig. 1, 6); c, the obtuse hypostome or labrum. (Coll. Mr. John Gray, Dudley.) ‘Fig.6. Hypostome of last specimen, magnified. ‘The basal processes (a) extend even further outwards in some specimens, and are probably attached beneath to the ends of the upper glabella furrows. Fig. 7. Eye of an ordinary specimen, natural size. Dudley. Fig.7*. Portion of do., highly magnified, showing the separate convex portions of the cornea over each lens, with granules on the interspaces. Fig. 8. Portion of the eye of another variety, with the lenses proportionally smaller and more distant, and the granules collected into an hexagonal network between them. Dudley. Fig. 9. Highly magnified cast, in fine silty mud, of the interior of the eye, showing the cups from which the lenses have fallen out. These cups therefore occupy the place of the depressed tip of the crystalline or vitreous body. (Burmeister.) Fig. 10. Enlarged specimen, the head divided at the facial suture, showing the first segment, a, as an entire ring or segment which bears the eyes. On the second ring, 6 is the upper eye lobe; c, the tubercle or rudimentary spine; at d, the pleural furrow is shown, and at e, the fulcral poimt of a middle thorax joint; ff, the notched tips of the pleure ; g, the tail. Fig. 11. Part of the front of the head and glabella, to show the equal granulation of the surface. Fig. 12. Magnified notched ends of the pleure (upper side), showing their surface to be granulated even over the facetted portion, 6; at a the tubercle is shown, which is better seen in the next figure. Fig. 13. Magnified under side of three pleure, showing the narrow incurved under portion 5, and the tubercles which serve as buttresses in rolling up, a. Fig. 14. Internal cast of a large head, from Ledbury, Wenlock limestone (Mr. C. Stokes’s cabinet) ; the furrows are much broader and deeper than usual. Fig.15. Tail, natural size, from Dudley, to show the sub-triangular pointed form usual in the species. Other British Species of Phacops, of the Section Acastn. 1. P. apiculatus, Salter (1852), in Prof. Sedgwick’s Synops. Classific. Paleozoic Rocks, fase. 2, Appendix, iii, pl.1 G. f.17-19. Portlockia? apic. M‘Coy (1851), ib. fase. 1, p. 162. P. omnino P. Downingie simillimus ; sed capite longiore, glabella elongata, antice convexiore, lobis basalibus circumscriptis subtriangulatis nec transversis; sulco medio glabellart longiore, supremo distinctiore ; oculis elongatis subdepressis; angulis posticis capitis brevissime mucronatis ; caudaé ad apicem paullo compressa et in apiculum recurvum brevem producta ; -azi angustato. Localities——Common in the Llandeilo flags of North Wales, and in the Caradoc sand- stone of Hope Bowdler and Acton Scott, Shropshire. [Geol. Surv. and Woodw. Mus. | Heads of this species have also occurred in the hard quartzites of the coast of Corn- wall, at the Great Peraver, in company with Calymene, Orthis and other Silurian forms. 10 BRITISH FOSSILS. 2. Phacops Brongniarti, Portlock (1843), Geol. Rep. Tyrone, pl. 2. fig. 8. (excel. ref.) P. Murchisonii, ib. fig. 9. P. biuncialis, elongatus granulatus, modice converus ; capite longo trigono, fronte angulato subrecurvo ; glabella ad basin contracté anterius valde dilataté nec convexd, lobis utrinque tribus radiantibus ; lobo antico maximo triangulato, a frontali sulco valido—a medio sulco leviore—sejuncto ; lobis infimis minutis hemisphericis circumscriptis sese remotis; lobo verti- cali eminentiore ; oculis maximis, a lobo frontali usque ad sulcum verticalem tractis ; angulis genarum obtusis; thorace axi convexo angustato, lateribus parallelis abrupté deflexis; pleurarum apicibus rotundatis, fulcro intra medium posito ; caudad trigona, axi longe conico angustissimo fere ad finem caude extenso, decies annulato; apice prominulo; lateribus 5-costatis, costis per totum divisis, nec marginem levem attingentibus. Col. Portlock had united with this species both the P. macrophthalma of Brongniart, and P. Downingie, Murch. They are however, as above stated, quite distinct species. The present is well characterized by the pointed front and contracted base of the glabella, as well as by the large eyes, which have each 170 lenses, Localities.—Bala and Llandeilo Rocks : Tyrone; Carrickadaggan, Wexford; Llan- fyllin, and other places, N. Wales. 3. P. Dalmanni, Portl. 1. c. f. 7. Omnino precedenti simillimus—caudé multi-annulata, oculis maximis, glabella ad basin contracta, granulosa; sed capitis fronte rotundato, nec producto; [an forsitan fomina inermis ? | This neat species occurring with the last, and of the same or of rather less dimensions, so much resembles it in form, proportion, and sculpture, that we are compelled to regard it as of the same species, and as indicating either a variety with a rounded front, or, what is more likely, the female form. Portlock’s original specimens are all of one character, and the front appears to have been really rounded, not broken off. Locality.—Desertcreat, Tyrone. 4, P. Jamesit, Portlock, G. Report, pl. 3. fig. 10, (mala). P. unciam latus ; capite semicirculari, bis quam longo latiori, fronte angulato, marginato, crasso; glabellé fere pland tuberculata antice latissima postice ad dimidium contractd, lateribus rectis ; lobo frontal late triangulato, oculis impendente ; ceteris radiantibus,—supremo maximo triangulato, medio lineari obliquo haud abbreviato, basali transverso ; lobis omnibus fere ad medium glabelle, spatio angusto interjecto, conniventibus ; genis lente declivibus marginatis, angulis obtusis ; oculis abbreviatis valde curvatis; (thorace — ?) cauda [und cum capite congregata | rotundatd, quam longa tertiam partem latiori, depressa ; axi satis magno conico, marginem nullo modo attingente,—annulis 8-9 ; luteribus sulcis 6-7 equalibus, leviter inter- lineatis. Portlock’s figure but imperfectly expresses the great width and flatness of the glabella, which is not the result of pressure ; the tuberculation covers the glabella only, while the cheeks are merely granulated. The shape of the glabella and its radiating lobes, and the short curved eye, approximate this species nearly to the next, from which the glabella and pointed front of the head readily distinguish it, ‘The head too is not so broad in proportion. Locality.—Tyrone; in calcareous sandy schist, Waterford; also in sandstone at New- town on the Suire, in the same county. [Geol. Sury. Coll.] 5. P. alifrons, Salter, in Appendix to Sedgwick’s Brit. Pal. Foss. Le. ii. t. 1G. f. 12-14, M‘Coy, ib. 159. P. capite sesqui-unciam lato, gibboso, tuberculoso, antice truncato, bis quam longo latiori; glabellé elevataé sed paullum convexa, ad basin angustata, superne dilatatd obtusd, lateribus subrectis; lobo frontali brevi transverso linbum crassum impendente, et utréque angulis | ee ae ees BRITISH FOSSILS. 11 tumidis cum margine genarum confluentibus; lobis lateralibus tumidis, supremo sub- triangulato anticé obliquo, reliquis fere rotundis brevissimis ; genis declivibus tuberculatis marginatis, angulis rotundatis; oculis elevatis brevibus curvatis; pygidio semicirculart tumido; azxi lato convexo 8—9-annulato, apice obtuso nec marginem attingente; lateribus convexis, costis 7-8, radiantibus simplicibus, margine angusto. The peculiar character of this species, which a good deal resembles P. sclerops Daman, consists in the absence of any separating furrow between the upper lobe of the glabella and the outer margin of the cheek, the glabella thus seems to be drawn out into it on either side. Localities.—Capel Garmon, Llanrwst; near Penmachno; Pont-y-Glyn Diffwys ; and Bala; all in the Bala or Llandeilo rocks of North Wales. 6. Phacops Jukesii.—n. sp. [P. sclerops, var., DALMAN, Pal., t. 2. fig. 1 g. (mala) ?] P. capite unciam et plus lato, fere quam longo ter latiore, convexo (granuloso ?) ; glabella haud elevaté antice valde dilatata, postice contracta, utrinque tri-loba; lobo basali transverso lineari, secundo paullo majore rotundato, supremo magno triangulato, frontali maximo transverso toto oculo elevato brevi curvato imminente, lobo cervicali elevato nec lato; genis latis marginatis, [angulis rotundatis ?] ; sulco verticali forté exarato ; linea faciali impressa ; sulcis _axalibus profundis. This curious species, which we have only just now detected in the collections from Bala, differs materially from the next, in the comparatively equal size of the lateral glabella lobes. The upper one is large and triangular, but not nearly so large as in P. conophthalmus, and the second is distinctly rounded and larger than the basal lobe, instead of being contracted and almost lost, as in that species. Lecality.—Bala limestone, west of Gelli grin, Bala. [Survey Coll. ] 7. P. conophthalmus, Boeck. sp. [ Calym. sclerops, var. Dalman, Pal., t. 2. fig. 1d?] Tvril. conicoph. Boeck Goea Norveg. (1838), 1. 4. Phacops con., Emmrich Dissert. 21. Asaphus Powisit (head only), Murch. Sil. Syst., t. 23. £9. Calym. Odini (Kichw.), De Vern. Geol. Russ., t. 27. f. 8. P. sclerops, Burm., ed. 2. (1846), t. 4. f. 5. excl. syn. (icon bona, ab editione prima multo emendata.) P. conophthalmus, ib. p.91. Chasmops Odini, M‘Coy, le. t.1 G. f. 22,23. P.conophthalmus, ANGELIN, Pal. Suec. (1852) t. 7. f. 5, 6. P. ovatus, magnus ; capite valde transverso, fere quam longo ter latiore, granuloso, convezxo ; glabella convex, anticé valde dilatata, postice angustatd, utrinque biloba, lobo mediano omnino contracto obsoleto, basali transverso lineari, supremo maximo triangulato, supra paullum sinuato ; frontali rhombo-trigonali maximo nec oculo imminente; lobo cervicali lato; genis convexis laté marginatis ; angulis in cornua lata extensis [interius rotundatis] oculo brevi valde curvato; linea faciali impressé; cauda (associata) lata punctata, vix marginata, axi conico, lateribus angustiore, 9-10 annulato; costis lateralibus 8 arcuatis, omnibus duplicatis. This remarkable species is abundant in the Silurian strata on the Baltic coasts ; it is equally common in Britain, but although fragments are abundant, we have only seen perfect specimens of the head in the Woodwardian Museum. I collected these in company with Professor Sedgwick, and with them was associated the tail above described, which could hardly belong to any other species. It is found with fragments of the head in some other localities, and agrees well also with that figured by Professor Burmeister. But the figure given by Angelin represents the tail as considerably more pointed, and we have specimens from Wales more of this character ; there are other species of Phacops in which similar variations occur. The heads figured in the “Silurian System,” from the Caradoc sandstone, belong to this species. -Angelin has figured two other Phacops with very similar lobes to the glabella, but it is possible his P. ducculenta and P. macroura may prove but varieties of this. 12 BRITISH FOSSILS. We have seen the eyes of this species, and they are reticulated as in other species of Phacops. But from their greatly curved shape they are generally broken off, and this has led Professor M‘Coy to the establishment of his genus Chasmops, which had better be expunged, as this group is so closely connected with the ordinary Phacops by means of such species as P. Brongniarti and P. Jukesit. Localities—In Bala Limestone; Llansaintffraid Glyn Ceiriog, south of Llangollen ; Alt-yr-Anker, Meifod, North Wales [M‘Coy], Welshpool [Sil. Syst.] ; Llanfyllin, Montgomeryshire; Llanbedrog, Carnarvonshire [Survey Coll.] ; Applethwaite Common and Coniston, Westmoreland [M‘Coy]. Caradoc Sandstone; Cheney Longville, Shropshire [Sil. Syst., figured specimen]; Acton Scott, &c., abundant. Section OponTocuILE (Dalmannia), DecapeE II. Pu. 1. Additional British Species. P. mucronatus, Brongn. sp. Entomostrac. caudatus, Wahl. Nov. Act. Soc. Ups., v. 8, t. 2. £2. Asaphus mucr. Brongn., Cr. Foss. t.3. 9. Dalman, Pal. t. 2. f3a6. Phacops, Emmrich (1839), Diss. 24. N. Jahrb. 1845. Burmeister, ed. 1. p. 113., and ed. 2. (1846), p. 95. (excl. syn. Murch. “ Sil. Syst.”) Angelin, Pal. Suecica (1852), t. 8. fi 1. P. triuncialis et supra; glabella convexd, anticé parum dilatatd, utrinque lobis tribus subequalibus transversis, sulcts longis satisque profundis sese separatis; caudd laté tri- angulart acuto, axt subconvexo limbum planum haud equante, in 9-12 annulos et appendicem trigonalem diviso, appendice in apicem caude brevi-mucronatum percurrente ; lateribus costis 7 planis, sulcis angustis acutis valde curvatis et cum tot lineis intermediis profundioribus ad apices confusis ; margine angusto nec distincto. Portions of the head and perfect caudal shields of this rare species have been found in a stratum over the bed of volcanic ash at Pen-y-Rhiw, west of Bala, where it is ' to be hoped other collectors may obtain fresh specimens. The head is not complete enough to give the diagnosis. Our Bala specimens, as well as those from Sweden in Sir R. I. Murchison’s cabinet, have but 9 rings and a triangular terminal portion to the axis of the tail, but in a specimen from Haverfordwest part of this terminal portion is annulated, and there are 12 rings. ‘The lateral ribs are much arched at their ends, and strongly duplicate, of double furrows, eaeh pair uniting at their tips in a broad depression. The apex is recurved; the mucro varies in length. Localities—Pen-y-Rhiw, west of Bala [Survey Coll. ] ; Haverfordwest, Pembrokeshire [Mrs. Day’s cabinet] ; in Llandeilo flags. P. amphora, n. sp. P. caudé magna biunciali elongata, convexissima, fere semicylindrica ; sulcis axalibus fere obsoletis ; axi lato nec eminenti, marginem caude haud attingente, in annulos sexdecim sub- planos diviso, apice obtuso; lateribus valde curvatis deflexis, costis 14-15 planis, sulcis acutis separantibus,—costa quaque linea mediand levi elevatd (sub cortice impressa !); margine angusto inflexo, apice obtuso (emarginato ?). Very like in general form to P. truncato-caudatus, Portl., from which it is at once distinguished by its convex form (almost like that of a half cask or barrel), and the axis not at all distinct from the sides—the axal furrow being almost obsolete; this latter character is very unusual in Phacops. Along the middle of each of the flattened side ribs a narrow and but slightly elevated ridge runs the whole length ; on the internal cast this is represented by a depressed line of connected dots. Something similar, but less distinct, occurs in the allied species above quoted. Locality—Grug Quarry, near Llandeilo [Survey Coll.]; one fine specimen was presented by Mr. Williams, ofthat place. In Llandeilo flags. J. W. SALTER. August, 1853. Geologrieal Survep of the il uted Kingdom. GENERLRURUS (Silurian) LA - CHEIRURUS BIMUCRONATUS — Murcni sol, ; ci F W.AB aily elt .¥orbes direx* pe j JW Lowa fe. a BRITISH FOSSILS. DecaDE VII. Puarte II. ees CHEIRURUS BIMUCRONATUS. [Genus CHEIRURUS. Beyricu. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca. Tribe Trilobite or Paleade.) Head strongly trilobed ; glabella with three lateral lobes, the basal ones circumscribed ; eyes facetted ; facial suture ending on the external margin; a rostral shield: Barrande. [Cheeks scrobiculate] ; hypostome inflated, oblong, truncate, with a marginal furrow and lateral auricles; thorax of 11 joints, the pleure strongly nodular as far as the fulcrum, the ends free and pointed; tail of few, 3 or 4, segments, free at their ends. | Diacnosis. C. grandis; glabell& superne latiori, sulco frontal et ocu- . lari obliquis propé medium glabelle terminatis ; lobis inferis trigonis (@etate rotundioribus) sejunctis; genis glabella angustioribus, oculis medianis, spinis posticis parallelis ; thorace pleuris trituberculatis; cauda parvuld, utrinque pleuris tribus subequalibus ad basin brevisuleatis, apicibus robustis, arcuatis. Synonyms. Var.a. Bimucronatus—caudd mucrone central nullo. Calymene speciosa [DALMAN (1826), Pal., pp. 58, 76 ?] Hisincer (1840), Lethea Suecica, Suppl. 2d. t. xxxix. fig.2. Paradoxides bimucronatus, Mourcuison (1839), Sil. Syst., pl. 14. fig. 8,9. Mirnz Epwarps (1840), Crustac., vol. iii. p. 343. Arges bimucr. Gotpruss (1843), Neues Jahrb. 544. Cheirurus bimucronatus, BryricH (1845), tiber einige Bohmische Tril., p. 18, 19. Cheir. ornatus (Dalm.), 8, bimucronatus, Bronn. Ind. Paleont. (1848), 1. 286. C. spectosus, SaALtER (June 1848), Memoirs Geol. Survey, vol. ii. pt. 1. pl. 7. fig. 4, 5,6. Ceraurus Williamsii, M‘Coy (Dec. 1849), Ann. and Mag. Nat. Hist., p. 408, Pal. Foss. Woodw. Mus. (1851), pl. F. fig. 13. Var. 6. Centralis, fig. 16. —caudd mucrone centrali brevi, Mem. Geol. Surv., 1. c. fig. 7. The subject of our present notice received some degree of illustra- tion in the second volume of the Memoirs of the Eibaliyaiical Survey, and we need not repeat here the figures which indicate the large size to which the species grew, but take advantage of a beautiful and nearly perfect specimen, found near Aymestry, and lent to us by the Rev. T. T. Lewis, whose valuable labours are so frequently [ VIL. ii.] 7B v4 BRITISH FOSSILS. acknowledged in the “ Silurian System.” Messrs. Gray and Fletcher, of Dudley, have kindly enabled us to complete the details, and the figures in this plate are nearly all drawn from Upper Silurian specimens, while those previously given, with one exception repeated in this plate, were from the Llandeilo flags of South Wales. : The genus to which this rather common fossil belongs is highly interesting for the remarkable sculpture of the body rings, which are broken up into a number of prominent swellings divided by deep furrows, and have their ends freely extended into sharp points, — which are so widely distant from each other, that it would require the animal to roll up to bring them into contact. The tail is made up of a few similar rings, cohering only at their base, and having the ends also free and pointed. The nature of the eyes also is worthy notice, inasmuch as they are covered by a facetted cornea, like that of Phacops caudatus, and not, as in most trilobites, with a smooth one. The facial suture, in this and cone or two closely related genera, runs as it does in Phacops, to the outer margin of the head. The shell or crust is strong and calcareous, the furrows of the head well marked ; the hypostome or labrum has a considerable resemblance to that of the genus above mentioned, and the number of rings in the thorax is the same—so that it is almost certain, much as the general appearance resembles Paradowides, that there is a really close affinity between it and those species of Phacops which have the tail fringed with long spines. Descruption.—One of the largest of trilobites ; it measures oc- casionally 15 inches, and probably more, judging from the propor- tions of the large fragments previously figured* to that of perfect specimens of a smaller size. Those found at Dudley are not above one and a half or two inches long,—specimens from the Mal- verns are much larger. Length to breadth as three to two; the head occupies fully one third the length, and is a little broader than the body. General form moderately convex, and oblong, but narrowed suddenly towards the posterior end; the sides of the thorax and tail deeply serrated by the projecting ends of the seg- ments. ‘The animal is sometimes found half coiled up ; the pointed ends of the pleuree closing together and overlapping each other (fig. 2.) ) Head rather more than a semicircle,—the obtuse front project- ing; glabella gently convex, equal in breadth at the base to the cheeks, above considerably broader, marked with three strong furrows on each side besides the neck furrow, the lowest being * Mem. Geol. Survey, vol. ii. pt. 1. pl. 7. BRITISH FOSSILS. 5 directed obliquely downwards and joining the neck furrow before reaching the middle ; it thus encloses a spherical triangle as a basal lobe. In older specimens this lobe is somewhat squarer, and the furrow more curved. The other furrows curve but little downward, and are variable in length, but usually extend more than one third across the glabella on each side. The furrows on the glabella, as well as the axal furrows, are sharp, but not broad or deep ex- teriorly, although they are so on casts of the inner surface. Fore- head lobe of moderate size, half as long as the entire glabella, and on the sides overhanging the other lobes,—in front it is somewhat produced and occupies all the margin. The glabella is neither — gibbous nor depressed, a line taken from the front edge to the neck furrow presenting a regular and gentle convexity. Cheeks subtri- angular, not so wide as long, with a broadish margin distinctly sepa- rated by a furrow, which meets the strong straight neck furrow at the posterior angles ; these angles are spinous, the spine short and - directed backwards. The eye is placed more than half-way up the cheek, and not close to the glabella, it 1s opposite the middle fur- row,* and is rather small, supported by a raised rim below; the eyelid is narrow and indented,—the lentiferous surface (fig. 7) very convex, supine, and covered with minute, closely set, convex facets with no spaces between them. Our figure, 7*, represents each facet _as with a minute pit upon it, but this is due to wear, (at a, a lens is seen in the natural condition). Above the eye the facial suture takes - asigmoid curve, and cuts the margin exactly where the axal furrow ends on it; below the eye it turns directly downwards to the smooth border, which it cuts considerably in advance of the posterior angle, and in an oblique direction, so that it reaches further back on the lower side than on the upper. We do not know the course of the suture in front,—it is probably direct across, beneath the front margin, leaving the cheeks united there, as in Sphwrexochus, next described. The surface of the glabella is sparsely covered with small granules (fig. 1*, a); the cheeks are largely scrobiculate, (0, ¢), and the wings or free cheeks have their border smooth and only scabrous on its outer edge ; they sometimes, as fig. 10, dilate a little in advance of the facial suture. Hypostome (figs. 11 to 15) large, ovate, oblong, very convex, its length one fourth more than the width, but in appearance more ; broadest near the base of insertion, from which the central convexity rises immediately and reaches * Lovén calls the upper furrow “‘frontalis,” and the middle one “ ocularis,” and, though not always strictly correct, it would be a very useful designation. We have employed it above in the diagnosis. 4 BRITISH FOSSILS. nearly to the tip. A rather narrow ring or rim surrounds the apex and sides, terminating abruptly near the base on each side in what may be called an auricle, followed by a deep notch c¢, above which the ascending processes a, a, take their origin. The apex of the hypostome is truncate, the corners angular or even mucronate. A distinct sulcus separates the border all round, and within this there is a short oblique furrow on each side. Its whole surface is closely scabrous (fig. 15*) ; the convex portion has besides scattered larger granules. The organ is hollow when viewed from the inner and under side, and the structure there observable is such as has been often described.* These are two ascending processes, a, a, rising from the ends of the basal or front margin, and directed obliquely backwards ; and on the sides, b, 6, the inflated broadly triangular portions characteristic of the genus. These triangular curved plates give the appearance of thickness on viewing the organ from the side (fig. 12), but the general surface on the inner side is concave, answering to the great convexity of the outer side. Thorax much longer than the head, but narrower, and for most part of it parallel sided, of 11 gently convex rings which are very minutely scabrous ; the axis is narrower than the glabella, of nearly equal width all the way down, but scarcely so wide as the pleure. These are linear and directed straight outwards for two thirds their length, then curved a little backwards and tapering to a sharp point. The fulcrum, placed at about one third, is of singular structure,—a small semi-oval piece (fig. 8, a) 1s attached to the posterior edge of each pleura, and against this piece abuts a similar tubercle (0), placed on the front edge of each, and the two pieces, forming together a narrow oval tubercle, are insulated by a deep sulcus from the body of the pleura, which is also constricted and furrowed across at this point, so as to have the outer and pointed portion (c) quite distinctly separated from the small inner one. The latter (d) is very strongly divided into two tumid lobes by a short oblique sulcus, and just beyond the constriction the outer portion rises into a stout boss, (fig. 9, e) giving the tri-tuberculate form characteristic of the genus. * M.de Barrande, Neues Jahrbuch (1847), 389, has given a full description of the hypostome of Cheirurus. He describes the ascending processes a, a, (Fliigel), as bent upwards at right angles to the surface of the organ, and uniting with the upper crust along the line of the dorsal or axal furrow, with a broad base of attachment, reaching from the upper to the middle glabella furrow. In Phacops it has nearly the same position. He also describes a second organ, of the same size and shape, but less convex in all its parts, lying immediately behind the hypostome, between it and the upper crust of the head. This organ he calls epistoma ; and he has seen it both in Cheirurus insignis, and a species of Phacops. It has never yet occurred to our observation. BRITISH FOSSILS. 5 The line of the fulcral points is parallel to the axis for all its length, and the constriction beneath them, though not very marked on the upper crust (fig. 8), produces a longitudinal ridge on the under surface, and a strong furrow in casts (fig. 9). Tail, at least in Dudley specimens, very much narrower than the body, with three strong spinous lateral lobes on each side directed backwards, the outer ones a little divergent and longest ; all extend equally back- wards,—the tail is therefore truncate—but exclusive of the spines, it is broad triangular, following somewhat the shape of the axis; it is marked on each side by four short deep puncta or furrows, which do not run to the margin in young individuals. The axis is convex and short conical, of three distinct ribs and a small terminal piece —the last very obscurely indicated ; there is no mucro between the lowest spines in the ordinary Wenlock forms. Variations.—The following have been observed. In a Dudley specimen the front or forehead lobe occupies much more than half the length of the glabella, the side lobes being therefore more crowded. In a Dudley specimen, a large tubercle occurs in the middle of the forehead lobe. In some individuals the glabella widens more above, in others it is nearly parallel-sided, and the lateral furrows vary in length. The head spines occasionally reach the third thorax segment. The margin of the cheek in one specimen is notched at the facial suture (fig. 10,qa@). The axis of the thorax is, sometimes, though rarely, as wide as the pleure. The most im- portant variations occur in the tail,—in fig. 5, we have represented the spines as all directed backwards, and the two central ones closely approximate; they are so in the large Ledbury specimen figured in the “Silurian System,” where too they are shorter than the outer spines. In fig. 6, they are a little space apart; in a Lower Silurian specimen we have seen a small tubercle appear between, and in our var. 6 a decided, though short, mucro protrudes. Lastly, as a mon- strous variety from the Silurian rocks of Kildare,—we have reason to think it of the same species,—we have one with a wider interval, and a bifid mucro. In old specimens, as well as in var. 6, the spines diverge much more than in those we have here figured. Perhaps some of these variations are due to sex. A ffinities.—The considerable variations above mentioned lead us to believe that the Ch. insignis, Beyrich, may be but a variety of this-species. We have not materials enough to justify our recording it as a variety, as Beyrich describes and figures it as with a much wider glabella, the furrows reaching but a short way across. The hypostome is very similar, and the tail differs very little, except in [ VII. i1.] 7B3 6: BRITISH FOSSILS. the much greater central mucro and more divergent spines, towards which characters we have shown considerable approaches in some of our varieties. It was these close resemblances which induced us to say, 1n the volume already alluded to, that our British species occurred in Bohemia with the C. insignis. But I find the Bohemian specimens do not show any tendency to vary towards ours. Barrande, in his great work which has just been published, figures a fine new species, C. Quenstedti, closely allied to both the above, but the head spines are very much longer and slenderer, and so are those of the tail; the glabella too is parallel-sided, its furrows run quite across, and the lower pair of lobes nearly meet. Calym. ornata of Dalman, since fully described by Lovén, must’ be very nearly like our species; but the greatly elongated first pair of spines to the tail, and the parallel-sided glabella must separate it for the present; we subjoin a note giving a few of its prominent characters.* Ch. obtusicaudatus, Corda, is another nearly allied fossil. History—tThe history of the species dates clearly, we think, from Hisinger’s Lethzea Suecica, where the head of a large specimen is figured, and the species considered identical with the Calymene speciosa of Dalman, found by Nillson in the isle of Giland. There is, however, some doubt of the correctness of this reference. Dalman described in a supplementary note to his “ Palzeadze” two species, C. speciosa and C. clavifrons, comparing the former with the Trilobites Sternbergu.t ‘This comparison sufficiently indicates that a large species, with the glabella broad in front, must have been intended ; and we lay the more stress on this, because it proves that the species with a small oval glabella, narrowed in front, which was figured by M. Sars in Oken’s Isis, 1835, as C. speciosa of Dalman, is not that species, and could never have suggested the comparison above mentioned. We believe it was this erroneous reference by Sars, joined to Dalman’s rather loose description, “smooth, large, oval, and convex glabella,” which has thrown doubt on the identity of his species with Hisinger’s figure. But since there are several species of the genus found in Norway and Sweden, as indicated by the figures of M. Sars, above quoted, and those lately given by * Glabella zequilata; abdomen articulis 3, basi connatis ; primo secundum longé super- ante, in appendicem crassam teretem longissimam utrinque producto; secundo tertium excedente, hoc verisimiliter brevissimo. Loc. Husbyfjol, Ostrogothia. Lovén in Ofver- sigt Vetenskaps Akad. (1844), p. 64. + Sternberg, Verhandl. Vaterlands, Mus. Prag. 11th pt., p.45. tab, 13a. Dalman says, that in his species “ the glabella lobes are all connected down the middle, while in Sternberg’s they are separated by transverse furrows.” Ee oe BRITISH FOSSILS. 7 Angelin in the “ Palzeontologia Suecica,” we prefer with Dr. Bey- rich,* to leave the question undecided, and wait for the descriptions and references now in course of publication by M. Angelin. Sir R. I. Murchison first published it in this country, referring it to Paradoxides, as the only genus then published which it appeared to resemble, especially as he regarded the two lower prongs only as constituting the tail; he also figured the body rings, and commented on their remarkable rough sculpture; this figure of the body is accidentally reversed upon the plate, the portion nearest the head being turned downwards. | It is next mentioned by Lovén in 1844, describing two of Dalman’s species, the C. clavifrons, and C. ornata, and to the latter he referred the figures given by Murchison of the present species. But the comparison could be made only with the body segments, and these are far too much alike in different species. The description too of the head given by Lovén, though agreeing in the main with the perfect examples we now possess, is not sufficiently precise, and we are not therefore justified in reuniting ours with C. ornata, more especially sd, as the excellent figure of that species lately given by Angelin, Pal. Suecica, p. 21, fig. 1, represents the uppermost or fore- head lobe of the glabella as not wider than the rest, (“ equilata glabella,” Dalm.), or occupying nearly so much space in length as in our species. It is to be regretted that to these descriptions, the author has not added that of C. speciosa ; he does not even mention this disputed species. In 1845, Dr. Beyrich first described the entire animals of this genus, and introduced the British fossil as an undoubted species of Cheirurus, leaving for future observation its identity or other- wise with his C. insignis, to which, as above stated, it bears great resemblance. It was again published in the second volume of the Memoirs Geo- logical Survey, 1848, where the head of the species was described and identified with Calymene speciosa of Hisinger. And we still regard Hisinger’s excellent figure as a proof that our species is found in Gottland, in a stratum marvellously ike our own Wenlock lime- stone. In that notice the very large size the species attained was represented, and we accidentally repeated the error of reversing the position of the body ring by turning the front edge downwards. Lastly, Professor M‘Coy, in one of his useful contributions to the “Annals of Natural History,” described the entire animal, which he has since figured in the Synopsis of the Woodw. Mus. fossils, * Untersuch. tiber einige Bohm, Trilob, (1845), 1st part, 1. p. 17, 18. 8 BRITISH FOSSILS. retaining the generic name Ceraurus. We had previously selected this beautiful example from the collection of Mr. Williams, who found it near Llandovery, and we have since again examined it. It is much elongated and narrowed upon the cleavage of the rock, but is identical with the present species, and is very interesting as showing that the Lower Silurian form is somewhat intermediate, as regards the tail, between the ordinary Dudley form and our var. 6, for the lower prongs are but slightly distant, and have but a tubercle, instead of a prominent mucro between them. Barrande’s exquisite figures of the genus, fortunately now before us, show the structure of all parts of the body completely. He has figured the hypostome in several species ; we are fortunate in here being able to add the under side of that organ, and the sig ture of the eye. British Localities and Geological Range.—LLANDEILO FLAGS to AymesTRY Limestonr.—In Llandeilo flags; Sholes Hook, and Peleombe Cross, Robeston Wathen, and Llandowror, near Haver- fordwest; Goleugoed, Llandovery, (Cambridge Museum). In Bala limestone ; Rhiwlas and other localities, near Bala, North Wales ; Chair of Kildare, Ireland. In Lower Silurian rocks, at Mullock, Girvan, Ayrshire, (Coll. Sir R. I. M.) In Woolhope limestone ; Nash Scar, Presteign, (Coll. Mr. Davis.) In Wenlock limestone ; Haven, near Aymestry, (Coll. Rev. T. T. Lewis); Brand Lodge, Mal- verns ; Dudley ; Dormington Wood, Woolhope. In Aymestry lime- stone; Downton Castle, Ludlow. Var. 6.—In Wenlock strata; Nelson’s Tower Wood, east of Carmarthen. Foreign Distribution.—Gothland, in Upper Silurian (HistNGER) ; (Gland, Lower Silurian, DALMAN ?). EXPLANATION OF PLATE II. Fig. 1. Specimen, perfect except the tail, from Haven, near Aymestry; in the collec- tion of the Rev. T. T. Lewis, of Bridstow, Ross. Fig. 1*. Head of same, dissected, showing the granulate glabella, a, and deeply pitted cheeks, 6, c. (the eye is raised too much.) Fig. 2. From Dudley, collection of J. Gray, Esq. A fine half coiled specimen, showing the whole 11 rings, and the small tail. Fig. 3. Same locality and collection. ‘Very young coiled specimen. Fig. 4. Same locality and collection; showing the under side and incurved edge of the. tail, with the spines a little more apart. Fig. 5. Tail of young specimen, from Dudley; collection of T. W. Fletcher, ia It has the posterior spines approximate. Fig. 6. Same locality ; collection of J. Gray. BRITISH FOSSILS. 9 Fig. 7. Eye, magnified. Fig. 7*. Do., still more highly magnified ; the facets are convex ; and at a, one is in its original condition ; the pits on the others are due to wear. Fig. 8. Two thorax joints of Aymestry specimen (fig.1); at a and 8, the curious tubercles at the fulcral point are seen; c,is the outer spinose portion; d, the inner bilobed part; they are separated by a furrow, f¢ Fig. 9. Specimen from Nash Scar, Presteign, collection of J. E. Davis, Esq. This is an internal cast, and shows the outer tubercle e, and the furrow g, more strongly than in fig. 8, which has the crust on. Fig. 10. Under view of cheek from the same specimen (as fig. 9); it has an unusual swelling above the facial suture a. Fig. 11. Perfect hypostome (collection Geol. Surv.), from Dormington Wood, Wool- hope; a, the lateral ascending processes; 6, the marginal wings. Fig. 12. Side view of do. ; the incurved triangular plates are shown at 0, the lateral notch at c. Fig. 13. Under view; a, a, the “ ascending processes,” which are attached to the under surface of the glabella at its sides; 5, 6, the incurved triangular lateral plates, possibly for the attachment of muscles; c, the hollow space under the ascending processes, answering to the lateral notch in fig. 12. Fig. 14, Outline of the largest hypostome we have seen, from the Lower Silurian lime- ~ stone of Kildare, Ireland ; the letters are the same as in fig. 11. iS Fig. 15. Lateral view of the same. Ba Fig. 16. Var. 8, centralis, from the Wenlock strata of Nelson’s Tower Wood, Llandeilo. RS Sf Remarks on the Genus. It seems necessary to contend for the generic name adopted here, because a rigid adherence to priority would compel us to relinquish a name now familiar to naturalists, and = _ bestowed by Beyrich on a group which he had carefully investigated and fully described. <— 2 Now that Hall has given such excellent figures of Ceraurus, we know perfectly well “i? what was meant by the obscure and imperfect plaster cast published by Green under that ~ name, But the original description was scarcely more than sufficient to indicate that it * © wasa trilobite, and consequently it has been referred with doubt to various genera by Beck, % .©™ Beyrich, Lovén, Portlock, and Burmeister. A genus so ill constructed and imperfectly > oe described, can have no authority; and it would be unjust to substitute such names for << Y= those given by the first real describers. The same rule we think fully justifies us in 2 \J rejecting Zethus of Pander, a name lately revived by Dr. Volborth*; for the genus as 4 rr constituted by Pander consists of two species, to either of which the meagre and incorrect “’ = deseription will apply; the firstfof these being, by Dr. Volborth’s own admission, a ® <_ species of Cheirurus, the second a Cybele” He would restrict the name to the latter ; but = » — eustom and the opinion of naturalists in general would point in doubtful cases like this to ' the first as the typical species, and we should then have to apply Zethus to all we now call ona ~ — Cheirurus ; more especially as it was the Cheirurus only of which Pander knew the entire body. He describes it as having 16 ribs in thorax and tail together, the segments of the tail being free like those of the thorax ; this is untrue for either genus; and he denies any trace of eyes. Of the Cybele, a fragment only is figured, and Pander even doubts whether it belongs to the genus, so that he evidently intended the first for his type; and had either his figure or description been intelligible, or had he referred to Sternberg’s or Dalman’s Species as cognate, his name ought to have been retained. But we believe the right of priority of name, rather than that of description, cannot with advantage be so rigidly enforced, and we accept Cheirurus as the first intelligible description, as well as the clear definition of a remarkable group. With regard to the affinities of the genus, we have * Transactions of the Royal Mineralogical Society of Petersburgh (1847.) tJ Wntphicalns, Trader & ah talon “ss , Poor dey, a 10 BRITISH FOSSILS. come, as above stated, to the conclusion that it must be considered nearly related to Phacops. Barrande, in his ingenious and simple arrangement of the groups lately published,* places Cheirurus among the series which he defines as having the “ plévre 4 bourrelet ;” and certainly it is most closely allied to some genera, Spherexochus, Cybele, &c., which possess this character. But an inspection of our plate will show that the characteristic furrow (“ sillon”) of the pleure is only shortened, not absent in this genus. In several Bohemian species it is quite evident, and in the Cheirurus claviger, which Corda elevates to the rank of a genus, the furrow continues along the whole length, as it does in most trilobites ; and we may state generally, that we believe this character to be merely a special modification, since all pleure have the furrow, either bisecting them as in the ordinary form, or so near the anterior edge as only to separate a mere line for the front or fulcral portion.t In Spherexochus, the nearest ally of the genus we are considering, it is not, perhaps, indicated at all. We think, therefore, that the other characters which we regard as of more importance, viz. the structure of the eyes, and the course of the facial suture, will connect Cheirurus with Phacops. But with respect to the limits of the genus, we are strongly inclined to think Spherexochus ought not to be separated from it, since such species as Ch. clavifrons of Dalman, and Ch. globosus of Barrande seem exactly intermediate, having the head of Spherexochus and the tail of Cheirurus. How- ever, if we allow the striking character of the thorax rings to guide us, we shall find it agree with the habit in marking out three distinct genera already recognized, viz.— Eccoptochile. Corda. Cheeks scrobiculate; pleure 12, furrowed; hypostome with lateral furrows : Cheirurus. Beyrich. Cheeks scrobiculate; pleuree 11, nodulated; hypostome with lateral furrows : Spherexochus. Beyrich. Cheeks not scrobiculate; pleure 11, simple, rounded; hy- postome without lateral furrows : And the species which have globose glabella, but still have the 11 nodular pleure, will remain in Cheirurus, not in Spherexochus, just as we find this variation in the glabella of Phacops, while the characters of the thorax remain the same. The genus is Silurian and Devonian ; it does not rise into the Mountain Limestone. Other British species of CHEIRURUS. SECTION CROTALOCEPHALUS. Glabella furrows continuous across, all strong and distinct. 1. C. articulatus ? [Calym. articulata, Munst. Beitr. Heft, 3. pl. 5. fig. 72] Ch. Stern- bergit (Miinst), Puixiirs, Pal. Foss., fig. 247. I do not venture to characterize this species from the imperfect fragments we possess. The glabella is long, narrow, and scarcely clavate forwards, and not very convex. The upper and middle glabella furrows are very strong, and go right across, and the basal lobes are narrow, triangular, transverse, and they nearly meet in the middle of the glabella, leaving but a small space between. The latter character I suspect to have been much exaggerated by Minster, in the figure above quoted, who has represented the basal lobes as forming one transverse piece. Our rare British fossil is certainly more like this figure than the C. Sternbergii of the same author, in which the furrows are partially obliterated in the middle, and the glabella is broader. Locality—Barton, S. Devon (Phillips); Newton Bushell, in Devonian limestone. Pre- sented by R. A. C. Austen, Esq. * Systéme Silurien de la Bohéme, 1853. Also Ann. and Mag. Nat. History, Sept. 1850. } This narrow line may certainly be seen in Acidaspis and Cybele; in Bronteus it seems to have completely vanished. seed yee Pat cee te ae BRITISH FOSSILS. 11 SECTION CHEIRURUS proper. Glabella with the furrows all distinct, but not meeting across. 2. Ch. speciosus. Dalm. sp.—above described. 8. Ch. gelasinosus, Portlock. Amphion gelas. id. Geol. Rep., t. 3. fig. 4. (head) ; and Arges planospinosus, pl. 5. fig. 9. (tail). Chetrurus, BEyRIcH (1845), Bohm. TriL, 1. p. 19. Salter (1851), Quart. Geol, Journ., vol. vii. pl. 8. fig.1. Chetrurus planispinosus, Bronn. Ind. Pal. (1848). Ch. depressus, capite transverso, glabellé rectangulari sulcis brevibus transversis, lobo frontali brevi, basalibus oblongis transversis vix circumscriptis, uno ab altero spatio equali sejuncto ; genis latis, marginibus depressis, spinis brevibus ; cauda (hic haud dubie refertd) lata, seqgmentis utrinque tribus latis, ad basin longe adnatis, acuminatis ; primo in appendicem longam producto secundum longe excedente, hoc tertium brevem superante ; axi 4-annulato, articulo ultimo minimo angusto, nec apicem caude profundeé emarginatum attingente. The upper lobe of the glabella is not at all broader—sometimes it is narrower— than the rest; and in the furrow beside it there is a very deep indentation. On the under side of the crust this would be a strong ridge, to which, as Barrande has shown, the processes of the hypostome are attached, The transverse form of the head, especially the wide cheeks, easily distinguish this from any other species. The surface of the glabella is smooth, or nearly so. There can be little doubt that, as Beyrich has suggested, the head and tail belong to one animal, They are alike broad and depressed, and agree in size, while no other species of the genus occurs with them. Locality—Co. Tyrone, head and tail ; limestone of Ayrshire, head only. [Presented by Mr. C. Moore. } 4, Ch. cancrurus. sp. u.—Ch. satis magnus, caudé lineas 20 lata transversd, apice abrupté iruncato premorso ; axi lato, annulis quatuor subequalibus, tertio & quarto punctis binis remotis solum separato; lateribus spinis quatuor longis sub-parallelis, ad basin adnatis, transversis, apicibus lente decurvatis; basalibus utriusque lateris longo intervallo remotis. A most remarkable species, in which the four lateral lobes of the tail start hori- zontally from the broad axis, instead of gradually converging beneath it, and leave its apex bare; the breadth of this space being increased by the outward direction of the spines themselves, which begin to curve downwards only when when they have attained half their length. ‘The appearance of the perfect tail is just like that of a crab; premorsus might have been an appropriate specific name. C. obtusatus, a Bohemian species, somewhat resembles this, but the spines are radiating, not parallel. There is a rare cephalic shield in the Chair of Kildare limestone, which may very probably belong to this species ; it is as unusual in its character as the tail we have described. It is the Ch. gelasinosus of M‘Coy’s Synopsis Sil. Foss. Ireland, 44. The cheeks are scrobiculate, and the eyes forward, the glabella smooth, clavate, long, and narrow; the neck furrow trends upwards towards the middle on each side ; the basal furrows curve downward, but do not meet the neck furrow, or quite circum- scribe the subtriangular basal lobes; the middle furrows are strong and transverse, the upper pair apparently obsolete (probably some faint traces of them may be found.) But there is enough to distinguish the species as a very curious one, and provisionally I refer it to the C. cancrurus, with which it agrees well in size. Locality— Limestone of the Chair of Kildare in Ireland. [tail in Survey coll.; sup- posed head in the cabinet of Mr. R. Griffith. ] 5. C. octolobatus. M‘Coy’s Synopsis Pal. Foss. Woodw. Mus., t.1G. f. 10. [Mem. Geol. Surv., vol. ii. pt. 1. pl. 7. fig. 36, without name. | C. pygidio transverso elliptico semiunciali, bis quam longo latiort, margine octolobato ; axi depresso, annulis tribus, duobus superioribus subequalibus, tertio lato a limbo terminali punctis Ve BRITISH FOSSILS. binis solum distincto, lateribus planis, lobis anticis curvatis et distinctis, nega ad basin connatis, apicibus ovatis. Locality.—Bala limestone ; Bala, frequent ; Hendre wen, Cerrig-y-druidion, Denbigh- shire. SECTION ACTINOPELTIS. Corda. Glabella inflated, the upper lobes indistinct. 6. Ch. elavifrons, Dalm. sp.? [Calymene, Dalman, Palead. 59. not of Hisinger. Lovén Ofv. Kongl. Vetensk. Akad. (1844), 63, 64?] Spherexochus juvenis, Salter (June 1848), Mem. G. Surv. vol. ii. pt. 1. pl. 7. fig. 1-3 (exclude 3 6). S. clavifrons, ib. Errata, p. viii. Chetrurus clavifrons, in Appendix, Pal. Foss. Woodw. Mus., t. 1 F. fig. 11, and 1G. fig. 9. Ceraurus, M‘Coy, ib. 154 (1851.) C. capite sesquiunciali semi-elliptico, in juveni rotundiore, convexissimo ; glabella maxima ovali gibba, genis latiore, granulosa; sulcis duobus anticis brevibus obscuris, basali profundo fere ad cervicalem decurvato lobumque subovatum ambiente; genis declivibus scrobiculatis brevi-spinosis; cauda axi longo, 4-annulato, articulo ultimo rotundo, lateribus utrinque trispinosis, spinis valde inequalibus vix bast connatis, primo ad basin lato, brevisulcato, secundum longe superante, héc integro angusto tertium brevem sepe obsoletum multo excedente ; spinis omnibus retrorsis subparallelis. The glabella, when perfect, shows small regular granules or tubercles widely scattered all over it. The punctations too on the cheeks are rather small, and scattered. The terminal spines of the tail in some specimens are very short and obtuse, and the whole tail is in some shorter and broader than in others, even from the same locality, and the spines consequently more divergent at their bases. There are some points of difference between our fossil and that which Lovén has carefully described from Dalman’s original specimen and we may have again to recur to the name juvenis as above quoted. ‘The Swedish species is described as having long straight head spines, the glabella nearly as wide as the cheeks. Ours, now that we have more perfect specimens of the head and caudal shield from Ireland, shows short head spines, and the inflated glabella is certainly wider than the cheeks. In all other respects Lovén’s description applies well. By the description also of the tail of the C. ornatus, Dalm., given by the same author with the above, it would appear that this species had a caudal shield precisely similar to — that of ours. Localities.—Llandeilo and Bala rocks; in South Wales, Sholes Hook, Haverfordwest. In North Wales, Bala, abundant ; Cader Dinmael, Denbighshire ; near Llanfyllin, Montgomeryshire—in Upper Bala beds; in Westmoreland, Applethwaite Common ; in Ireland, Chair of Kildare,—frequent, and of large size. J. W. SALTER. — August, 1853. i ‘ ' + \ t om athe “ . . | | ‘ y) ‘ ree) t + n ‘ DECADENT fer liven SPH ZEREXO CHU S: ( Silurian.) Geological Survep of the United Kingdom. De a ee Nasa meiy we NY Tas yf Any # 4 fy» SPHAREXOCHUS MIRUS_ Bevrtch. _ I WLowzy fe Ji Forbes ditrex: CA Bone BRITISH FOSSILS. DecapDE VII. Puare III. ae SPHZREXOCHUS MIRUS. [Genus SPH HREXOCHUS. Beyrzicu. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca. Tribe Trilobite or Palade.) Eyes facetted? ‘‘ Head very convex, the cheeks not scrobiculate ; facial suture ending on the external margin near the angles, in front continuous and submarginal; glabella large and nearly spherical, with three furrows on each side, the two upper very obscure, the lower strong and curved down to the neck furrow; thorax of 11 joints, without any furrows; tail of 3 segments, free at their ends;” hypostome subtrigonal, with a marginal furrow, but without lateral furrows. No rostral shield. | Draenosis. S. granulosus; “glabelld lobis infimis profunde circum- cinctis, paullum tumidis,—spatio interjecto diametrum eorum superante ; caudd pleuris tumidis.” Synonyms. Calymene clavifrons, Histncrr (1840), Leth. Suec., Supp. 2d. t. 37. fig. 1 (mot of Dalman.) Spherexochus mirus, Beyricu (1845), ber einige Bohm. Tril., p.21. S. mirus, ibid., Zweite Stiick (1846), t. 1. fig. 8. S. calvus, M‘Coy (1846), Syn. Sil. Foss. Ireland, pl.4. fig. 10. S. mirus, Corpa (1847), Prodrom. einer Monog. Bohm. Tril., fig. 72. BaRRANDE (1853), Syst. Sil. de Bohéme, vol. i. pl. 42. fig. 11-18. Weare indebted to Mr. John Gray for the fine Dudley specimens which figure in this plate, and to Mr. Fletcher for those from which the details are drawn. Fragments and detached heads are not uncommon ; but these are the only perfect British specimens we are acquainted with. The species is cosmopolitan, at least it ranges -from Bohemia to the Western States of America, and in our own country is found both in Upper and Lower Silurian rocks. Description.—The animal is capable of rolling itself into a com- plete ball, of which the large head forms a very conspicuous part. The general form is oblong ; the length of English specimens usually about an inch and a half, and the breadth ten lines; they never appear to reach the length of two inches. The head is more than one third the whole length, and the glabella is very large, occupying, as seen from above, four fifths of the width, [ VII. iii.] 7c 74 BRITISH FOSSILS. and quite overhanging the narrow front margin. It is, excluding the neck segment, nearly a true hemisphere, and has a pair of large orbicular lobes at the base, deeply circumscribed, and further apart from each other than their own diameter. The furrow that bounds each of these lobes is broad, sharp, and equal in depth all round, leaving no communication with the body of the glabella (fig. 3, a, 11a). Above these lobes on each side are two faint impressed lines which represent the upper furrows (in fig. 4); of these (a) the one next to the round basal lobe is placed at a less distance from it than the diameter of that lobe, at about the point of the head’s greatest width, and the upper one (6) at an equal distance in advance of it towards the front. The cheeks are small in comparison with the glabella, and hang vertically from its sides (fig. 4, cc), like a pair of lappets from a cap or helmet ; they are oblong and have a thickened margin. The small convex eye is placed very near the glabella, and below the middle of the head; the facial suture runs from it out- wards, and reaches the exterior margin which it cuts obliquely a little in front of the posterior angle, as at fig. 3,¢; in front of the eye it continues parallel to the glabella, and runs along the edge of the narrow front margin, leaving the free cheeks connected beneath by a narrow band (fig. 4, d). Hach free cheek is hatchet-shaped, and the small eye (fig. 5, a) occupies the inner corner, supported on a fold of the crust, b, which truncates, or even indents it below. The eye is thus pushed up into a supine position ; it is short, oblong, and very convex. The lenses are numerous, larger in size than the granulations of the general surface, and placed near together, less than half their diameter apart. In this specimen we have not the outer surface sufficiently perfect to enable us to say whether the cornea is raised into facets (as Barrande thinks) or not; the surface is therefore left blank (fig. 6, a); from the inferior surface, b, the lenses have fallen out, leaving pits which indicate their size. The posterior corners of the head are rounded off and contracted to a less width than the free cheeks, and they bear instead of a spine, only a small tubercle (fig. 3, d), which is placed far inwards. The hypostome has not yet been found in England, but it is figured in M. de Barrande’s* plates. It is subtrigonal, straight at the base, where it is much broader than it is long, and the apex is * If this figure be as complete as M. de Barrande’s figures usually are, there is no lateral notch nor any visible ascending processes. M. Corda’s figure, however, exhibits a narrow rim at the base, with a small lateral process on each side. The notch would then exist between the lateral border or wing (fliigel), and these small processes and the resemblance to Chetrurus, in other respects so closely allied, would be more complete. BRITISH FOSSILS. _ 3 rounded and slightly emarginate. A broad shallow furrow runs round the end and sides, leaving only a small central convexity of the same shape as the hypostome ; this convexity is not indented by any lateral furrows. The surface of the head is covered by a fine close granulation (fiz. 11), which occupies also the free cheeks or wings (fig. 5) ; it is therefore one of the generic distinctions from Cheirurus, in which the cheeks are always pitted or scrobiculate. Thorax parallel sided, scarcely tapering backwards, of 11 thick rounded rings; the axis as wide as the sides, and of equal breadth throughout, very convex ; each joint much raised and rounded (see fig. 10). Pleurze horizontal as far as the fulcrum (fig. 7, a), and then abraptly deflexed, and from this point the pleura tapers outwards to a conical blunt point, which at the extreme tip is a little bent forwards. The fulcrum is placed at rather less than half-way from the axis, but in the last segment (fig. 8) it approaches much nearer,— to about one third. Its place is indicated by a protuberance both on the forward and hinder edge of each segment (fig. 7, a and b), but these swellings are not isolated tubercles as in Cheirurus, nor are there any oblique or longitudinal furrows on the pleure, as in that genus, to break up the uniform convex surface of the segment. Tail about semicircular, truncate ; the axis conical, its base of two depressed close-set rings, its apex of one long triangular joint, which is separated from the second joint by a deep depression ; from thence it is flattened, or even depressed for some distance, but suddenly rises to an obtuse and elevated tip (fig. 9, a); which, seen sideways, presents the appearance represented in fig. 2, where @ is the obtuse tip of the axis. The sides are composed of three obtuse convex lobes which scarcely project on the margin ; the upper one follows the bend of the hindermost pleura, the second is less curved, the third parallel to the axis ; all are deflected so that an end view ot the tail (fig. 13) presents an angular figure. The entire surface of the thorax (fig. 10) and tail, like that of the head, is covered with a fine granulation, the grains of equal size throughout. Variations. — Our Dudley specimens have the tail somewhat shorter and wider, and the terminal joint of the axis therefore shorter, than those from Bohemia. Irish specimens (figs. 14, 15) are more like the foreign ones in this respect. The space between the lower glabella lobes is least in these Irish specimens, though some of them have it consideraby wider than the diameter of the lobes; in a Wexford specimen, the space is proportionally as wide 4, BRITISH FOSSILS. as in those from Dudley, which often have the lobes as far apart as in Bohemian examples. A ffinities.—But one species, and of that only a caudal shield, has been described, which at all closely resembles this,—we allude to a species published without name by Dr. Beyrich, from Gott- Jand, in his second paper (1846, pl. 1. fig. 9); it has the side lobes of the tail lengthened out into spines of some length. The terminal joint of the axis too is shorter. There is a second species in Britain, found at Haverfordwest, to which if it were perfect enough, a new name might be applied. It differs from S. mirus in this respect, that the large basal lobes of the glabella are more really tumid, especially outwards, less than their diameter apart, and connected with the body of the glabella by a narrow depressed neck on the inner side, the boundary furrow not com- not completely circumscribing the lobe as in our species. But only a fragment of the head has yet been found, and I may say, that it is singularly like a fragment apparently of this genus lately dis- covered by Captain Strachey in the Silurian rocks of Tibet. There is a species figured by Sars in Oken’s Isis, 1835, tab. 9. fig. 8, as the Cal. clavifrons of Dalman, which has a nearly globose glabella with the basal lobes very small; but it is probably a Cheirurus, and would, we think, be found to possess punctured cheeks. History.—That Hisinger’s figure of Calym. clavifrons does not represent the species so described by Dalman, though very probably, as Beyrich suggests, it may have been associated under the same name in his collection, has been shown by every author who has since written on the subject; and the great similarity between it and the species we are describing must be evident to all. Dr. Beyrich supposes it may be the head of the other species we have mentioned above from Gottland ; but, as Hisinger’s specimen came from Furu- dal in Dalecarlia, this is not certain, and we think we cannot be wrong in referring it to the present cosmopolitan species, of which it is a very good representation. Dr. Beyrich, when he formed the genus in 1845, had only the head and caudal shield, but these were sufficient to show him the generic distinctions, which we think are now confirmed by characters drawn from the hypostome and thorax rings, since figured by M. Corda and Barrande. Professor M‘Coy next described the head from Irish specimens, considering it a distinct species from the Bohemian one, but identi- cal with that of Hisinger. His description is very clear, but having found among the Irish specimens considerable variation in the point he marks out as distinctive, viz. the breadth between the lower — rcog lt atian ae 2 oa « BRITISH FOSSILS. 5 lobes of the glabella, we have here ventured to unite them ;—the species agrees in all other essential characters. M. Corda in his Prodromus, 1847, next figured an outline of the entire animal and its hypostome, and Barrande’s accurate figures complete the illus- trations of this trilobite. British Localities and Geological Range—LiLANDEILO FLAGs to WENLOCK Limestone. In Lower Silurian, Chair of Kildare, county of Kildare, Ireland ; and in beds of the same age, Carrickadaggan, county of Wexford. In Wenlock strata, Dudley Castle Hill; Trindle near Dudley ; Walsall (Survey Coll.) Foreign Distribution.—In Bohemia; Komorau, Hills of Listice, Kolednik, &c., in Etage E, Upper Silurian, and also in one of the ‘ colonies” in the Lower Silurian, Etage D, (BARRANDE). In Sweden, Furudal, Dalecarlia ; in Lower Silurian (HIsINGER). In North America, Springfield, Ohio, Upper Silurian. (De Verneuil and Sir C. Lyell.) EXPLANATION OF PLATE III. Fig. 1. Coiled specimen from Dudley; Mr. John Gray’s collection. Fig. 2. The same specimen viewed sideways; a, the terminal boss of the axis of the tail. Fig. 3. The head, dissected ; a, a, the strong basal glabella furrows ; 6, the small eye ; c, termination of the facial suture in front of the posterior rounded angles ; d, the rudimentary cheek spine ; e, e, connecting portions of the free cheeks. Fig. 4. Front view of ditto; a, is the middle glabella furrow; 6, the anterior one; c,c, the free eheeks; d, the connecting portion, here separated from the glabella along the line of the facial suture; the dotted lines at 6 indicate the natural position in this view of the fixed cheeks, which are much bent down. g. 5. Free cheek, with the supine eye (a) actached ; 4, the fold of the crust which supports the eye, the “ palpebra inferior” of some authors; the surface of the cheek granulated equally all over. Fig. 6. Magnified portion of the eye; a, upper surface, obscure in these specimens, but probably facetted ; 5, lower suface, the lenses fallen out. (Figs. 3 to 6 also from Mr. Gray’s collection). Fig. 7. Third or fourth thorax ring ; at a, the fulcrum, and 4, the prominence against which the falerum of the succeeding segment abuts. Fig. 8. Last thorax segment, the fulcrum near the axis. In this and the preceding figure the pleure are represented as flattened out to show their characters ; they would appear much shorter on viewing them from above. Fig. 9. Tail ; at a the prominent tip of the axis is shown, Fig. 10. Part of thorax joint ; a, the axis magnified. Fig. 11. Basal lobes of the glabella, magnified to show the fine granulation that covers the whole head; a, the deep circumscribing furrow. (Figs. 7 to 11 are taken from Mr. Fletcher’s specimens, Dudley). Fig. 12. A group from Dudley, Mr. J. Gray’s collection. Fig. 13. End view of the tail. Fig. 14. Head, from the limestone of Kildare; it is a little elongated by pressure. Other specimens show a rounder form. [Survey collections. ] Fig. 15. Tail, more elongated than in the Dudley specimens, also from Kildare. Ki 1 tC} 6 BRITISH FOSSILS. Remarks on the Genus. When originally described by Beyrich, in 1845, he naturally included in this genus the species of Cheirurus with an inflated glabella, in which the anterior furrows are nearly obsolete, such as C. sphericus of Esmark (which Sars described and figured as the C. clavifrons, Dalm.), and the true C. clavifrons, of which Lovén has since given so excellent a description. But the latter species has the nodular and furrowed thorax rings, spinose cheeks, and the long spined tail, characteristic of Cheirurus, so much so, that Dr. Beyrich asserts that portions of separate trilobites must have been combined in the description. We have, however, in England, as above described under Plate 2, the same or a very closely allied species, showing these characters, which we formerly described as Spherexochus, but now consider a true Cheirurus. The Cheirurus globosus of Barrande, and the C. (Actinopeltis) Caroli Alexandri of Corda, are examples of this section, to which for convenience sake, the sub-generic term Actinopeltis might be applied. [See Cheirurus, ante. | J. W. SALTER. August, 1853. DECADE 7.PL4_ Orologicl Surbev of the Mnited Ringdom. ENCRINURUS — ( Silurian ) Vi Muar 9 ae etn. Gian meres figs. 14 Q(ENCRINURUS (Limonertch) Lids. /4, 73. £. VARIOLARIS _ Brongraare. | sex-costatus— Sadter. figs. (O16. &. punctatus Brizaady. C.R. Bone del. i. Forbes direx* BRITISH FOSSILS. DEcADE VII. Puate IV. ENCRINURUS SEXCOSTATUS. Figs. 1 to 17. [Genus ENCRINURUS. Emmrrcn. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca. Tribe Trilobite or Palade.) Glabella inflated, clavate, with 3 indistinct lateral lobes, and a large forehead lobe; eyes pedunculate, smooth (finely facetted, Kutorga) ; the facial suture posteriorly ends in advance of the head angles, and in front runs above the margin; the cheeks are separated in front by a vertical suture, enclosing a narrow vertical rostral shield ; thorax segments 11, equal, without pleural grooves, notched at the ends, but not produced into spines; tail with the ends of the pleure free, the axis many ringed. Evxpivos a lily-shaped animal; ovpa a tail, in allusion to the resemblance between the many-jointed axis of the tail and the stems of the Crinoidea. | Disenosis. LE. latus; glabellé anticé subsphericd et ad marginem frontalem fascid latd crassdé circumeincta ; genis scrobiculatis, angulis spinosis ; cauddé trigond, obtusd, axt annulis crebris, per medium |(non- nullis anticis exceptis) obliteratis ; pleuris 6, rarius 7, subplanis. Synonyms. Cybele sexcostata, SALTER (June 1848), Memoirs Geol. Surv., vol. ii. pt. 1. pl. 8. fig. 10 (not fig. 9). Zethus sexcostatus, M‘Coy (1851), Synops. Pal. Foss. Woodw. Mus., fase. 1.156. Encrinurus sex- costatus, SALTER (1852), ib. Appendix A. vol. iv. pl.1lg, fig. 6, 7. _ We are induced to figure this trilobite, although it is not quite perfect in all its parts, because it completes the illustration of the same species formerly given in the second volume of the Memoirs, where the tail only was figured ; and it is the more desirable to pre- sent it in illustration of the genus, as the two species which are best known, the EF. punctatus, and variolaris, are chiefly Upper Silurian, and have been fully illustrated lately in the “ Geological Journal.” In the general appearance, in the structure of the remarkable elevated eyes and of the. hypostome, the coarse tuberculation of the head,—the many-jointed axis of the tail, and its few lateral ribs, there is the greatest similarity to Cybele,* with which genus * Zethus of Pander and Volborth, a name which we cannot adopt, because Pander’s ill-defined genus was chiefly founded on a Chetrurus. [vu iv.] 7D a 2 BRITISH FOSSILS. we have hitherto considered it identical, although there are 12 body rings to the latter, and only 11 in Encrinurus. But the delineations of the facial suture given by Drs. Volborth and Kutorga in the Transactions of the Royal Mineralogical Society of St. Petersburgh, 1848, show that in this important particular, as well as in the number of body rings, the two genera differ; and when to this is added that the hinder segments of the thorax are not in Hncrinwrus produced into long spines but are all equal, we have a combination of characters sufficient te justify the separation. But there are species of Cybele whose habit is so like that of Encrinurus, that should a species hereafter be found with the facial suture of one of these groups, and the number of body rings distinctive of the other, we should recommend their reunion as sections of one natural genus. Description.—Length about an inch and a half, breadth an inch. Some specimens must have been larger. General form broad-ovate ; the head and tail convex, the body rather flat. Head about equal in length to the tail, but shorter than the thorax; its shape triangular, the lateral angles produced, the front rounded, gibbous, and overhanging. The glabella occupies full one third of the width of the head in front, where it is much infiated and more than hemispherical ; it overhangs the margin, which, as is usual in the genus, is not distinctly separated from it in front, but within the margin and above it on the glabella, there is a strong furrow which runs quite across the glabella, separating from it a thick prominent ridge (fig. 3, a) so completely that it appears not to form a part of the glabella, but to belong to the thickened front margin.* The entire glabella is pyriform, constricted behind to half its width, and separated by a strong sulcus from the neck segment, which is broad and prominent. It is indented half-way up by three short furrows on each side. ‘The cheeks, though convex, are much less so than the elabella, and they bear the eye in the middle of the cheek. In our specimen the eyes are broken off, but in all probability they were elongated, and directed forwards and outwards, as we have indi- cated by the dotted lines in our fig. 2. The outer margin of the cheek is thick, and separated by a furrow; and the posterior angles are produced into spines; the posterier edge also has the strong neck furrow continued along it. The glabella is covered with tubercles of unequal size, mixed with granules, but the specimen * This singular furrow is probably the place of the facial suture, which in this genus crosses the front of the glabella. This suture isnot visible in our specimens; but its course in front is well seen in &. variolaris, figs, 138 and 14, aa. ee ee SL ee aie > BRITISH FOSSILS. > does not show whether these tubercles have each a pit on their summit; it is probable they are so constructed, like those of the other species in the genus. The raised fascia, too, in front, has so worn a surface that tubercles are not visible, if they ever existed. The cheeks, instead of being tuberculate, are pitted like those of Cheirurus or Amphion, and the raised interstices are covered with fine granules. The margins appear smooth, or only finely granular. We have no specimens of the hypostome, or indeed any part of the under surface of the animal. The thorax consists of 11 segments; the axis moderately con- vex, of nearly equal breadth throughout, and considerably nar- rower than the pleurez. These are quite horizontal as far as the fulcrum, which is placed more than half-way from the axis ; and from this point they curve backward and downward to the tip, which is again a little bent forward, so that the line from the fulcrum outwards is‘a sigmoid curve; the hinder pleurz curve less backward. Each pleura is nearly semicylindrical, with three or four tubercles along it, and there is little or no space anteriorly for the narrow flat rim which exists in the species of Cybele, and which we have called sometimes the fulcral portion.** We have not the extreme ends preserved ; but from what has been observed in LE. punctatus and i. variolaris, there is little doubt it was terminated by a bilobed tip, such as we have indicated by dots in fig. 7; the notch c being in front of the blunt outer tip, and indenting the end of the facet 0. This facetted or flattened portion, which passes beneath the pre- ceding ring in rolling, is shown in fig. 8, a. Tail of a triangular form, wider by one third than the length, with an obtuse rounded apex, and flattened above, the sides and the tip deflected, so that the tail is moderately convex ; the axis at the upper part is about one fourth the width of the tail, and tapers to a point at some little distance within the blunt apex ; it is convex at its broadest end, and there the rings are continuous across, but from about the upper third it becomes flatter, and the rings are effaced along the middle; its apex is quite flat. There are about 20 rings in all, and no tubercles down the smooth central portion. The sides of the tail have six strong ribs, which are broad and somewhat flattened, divided from each other by narrow deep furrows, and have the tips squarish and obtuse. The ends of the * Tn this genus, as in Amphion, Acidaspis, and some others, the pleura is not divided by a groove along its middle as it is in Calymene; the division into two parts, an anterior or fulcral portion and a posterior portion, exists, but the latter occupies nearly all the outer surface of the pleura. 4. BRITISH FOSSILS. four upper ones are free (or rather much overhanging the margin) 5, the remaining two are distinct nearly as far as to the margin, but they there become fused with those from the opposite side, and. extend in a very blunt point beyond the tip of the axis. The uppermost ribs arch strongly outwards, the next less so, and the last pair lie parallel to the axis. | On the internal cast, the furrows, especially those which bound the axal lobe, are all stronger and deeper, but there is no other difference. Externally the whole surface of the tail is covered with a close scabrosity (see fig. 10). Variations.—In the cast from Sholes Hook (fig. 12) the rings on the axis of the tail are effaced down the middle for a broader space, and there are but few of the upper rings continuous across. Our ficure in this case does not show the uppermost rings. There are sometimes (fig. 11) seven rings on each side of the tail. Affinities—When perfect specimens are obtained, there is no published species with which ours can be confounded. The sub- globular shape of the glabella, with its small tubercles, and the pitted, not tubercular cheeks, will easily distinguish imperfect portions of the head from all other British species. The separated tail, especially internal casts of it, may possibly be confounded with the same portion of EL. punctatus, but the want of a central row of tubercles down the axis, and the arched lateral ribs, will enable observers to distinguish it. The other Lower Silurian British species, H. multisegmentatus, Portlock, is diametrically opposed in all its characters ; it has a large coarsely tubercular head, and many- ribbed tail. Nor can the detached tail of our species be confounded with that of Cybele verrucosa, Dalman, so abundant in company with it, if the four tuberculate lateral ribs of that species be attended to. Ours has six or seven smooth ones. : History—We first described this in 1848, in the work above referred to, under the name Cybele sexcostata. In those figures there was associated with the tail, but only provisionally, a coarsely tubercular head, which occurred so frequently in company with it, © that the two might reasonably be supposed to belong to each other. The figure we now give justifies the caution there expressed, for it is the “ more clavate form of head rarely occurring,” which properly belongs to the species ; the head figured in company being, we are now all but certain, that of the C. (Calym.) verrucosa, Dalman, a species which we hope hereafter to illustrate as the British type of the genus Cybele, Loven. It had been previously described in manuscript for. Professor Sedg- BRITISH FOSSILS. | 5 _wick’s intended memoir on the fossils of Westmoreland and Wales ; and a short description of it will be found in the Appendix to the second fasciculus of his large work on the “ British Palzeozoic rocks ;” it is also described by Professor M‘Coy, in the first fasciculus, as Zethus sexcostatus. _ British Localities and Geological Range—LLANDEILO FLAGs. Rhiwlas and Llwyn-y-ci, north-west of Bala Lake ; and Llechwedd Ddu, east of the lake, North Wales; in the former locality very abundant ; Sholes Hook and Pelcombe Cross, Haverfordwest. Not yet found in Ireland. EXPLANATION OF PLATE IV. Fig. 1. Coiled specimen ; from Rhiwlas. _ Fig. 2. Do.; back view, to show the 11 thorax segments. Fig. 3. Do.; showing the raised fascia a. Fig. 4. Do. ; side view. Fig. 5. Imperfect head ; the dotted lines are added from other specimens ; the cheeks show the pitted surface. _ Fig. 6. Magnified portion of head. Fig. 7. A thorax segment enlarged ; at a, the fulcral point ; 3, the facetted surface, and ce, the blunt indented tip, as usual in the genus ; they are added in dotted lines as the specimens are not perfect enough to show them. Fig. 8. Side view of the pleure in the coiled state ; at a, one of the facetted surfaces is seen by the breaking away of the other segments, Fig. 9. Tail of a Rhiwlas specimen. Fig. 10. Part of the same, magnified, to show the scabrous surface. Fig. 11. Variety of tail with 7 side ribs. Rhiwlas. Fig. 12, Internal cast of variety with the central part of the axis more free from ribs, Sholes Hook. Fig. 13. Front view of the head, slightly enlarged, of E. variolaris, to show the course of the facial suture in front of the head, and the vertical suture 6, which divides the cheeks, filled at its lower end by a narrow triangular rostral shield. Wenlock limestone of Dormington, Woolhope. Fig. 14. The same, aside view ; a a, facial suture. Fig. 15. Under view, somewhat enlarged, of the tail of E. punctatus,* to show the incurved scabrous margin which unites the lateral ribs of the tail; their free points are seen projecting beyond it. Walsall, near Dudley. Fig. 16. Hypostome of do., enlarged ; a, sinuated margin ; 0, cucullate base ; c, the points of the extended base of attachment. Walsall. The above figures are all from specimens in the collections of the Geol. Survey. The last four figures are enlarged to once and a half their natural size. Notes on the other British species of the Genus. If the strict rule of priority were observed, irrespective of clear definition, we should be compelled to adopt the name Cryptonymus for this genus, as that of Zethus for Cybele. Dr. Kutorga, indeed, in the journal above quoted (1848), advocates this course, and has * See description at the end. 6 BRITISH FOSSILS. restored the name Cryptonymus, under which Eichwald at first described several varieties of the common Asapfhz of the Russian Silurian Rocks. Subsequently, aware of his error,. he restricted Cryptonymus to such trilobites as the Calym. variolaris, Brong., including the C. punctatus, and some forms of Cybele. But, though thus marking out the group he intended, he gave no description of the amended genus; besides which he was now applying the name to a totally different set of fossils to those for which it was originally intended. Under such circumstances it is impossible to retain his name in opposition to the genus clearly indicated, though not sufficiently described, in Emmerich’s scientific arrangement, 1845. ‘The latter name has been adopted, and the typical species fully characterized by Professor M‘Coy (Synopsis Sil. Foss. Irel., 1846). The genus Encrinurus has a nearly universal range, being found in Silurian rocks from Russia to North America, and from the Arctic regions to Australia; and it has rather an extensive geological distribution, being found in Lower and Upper Silurian, and in the Devonian strata of Germany. Cromus, Barrande, a Bohemian fossil, is probably of the same genus ; it has, however, four lateral lobes to the glabella, instead of three. 2. E. punctatus. Brinn. sp. Pl.4.f14-16. 4 Syn. Entomolithus paradorus, Linneus, 1759, Act. Reg. Acad. Sc., Holm.,'p. 22. t. 1. f.2. Tril. punct., Briinn., Kjobenh, Sellsk. Skrivt. nye Samml. 1. 394. Entomostrac. punct., Wahl. (1821), Act. Soc. Se. Ups. v. viii. 32. t. 2. f. 1.—tail only. Calym. variolaris, Brongn., Crust. Foss., t. 1. f.3 A. (not B.) Cal. punctata, Dalm. Pal. 47. t. 2. f. a, b. Murch. Sil. Syst. (1839), pl. 23. £8. Phacops variolaris, Emmrich. Diss. (1839), 20. Asaph. tuberculatus, Buckl. Bridgw. Tr., pl. 46. f. 6. Encrinurus punct., Emmr. (1845), Neues Jahrb. 42. Encrinurus Stokesii, M‘Coy (1846), Syn. Sil. Foss. Irel., t. 4. £15. Pal. Foss. Woodw. Mus. (1851), p. 158. E. punctatus, Corda (1847), Prodr. Tril. Bohm, 91. fig. 55. bona. Cybele punct., Fletcher, Quart. Geol. Jour. (1850), vol. vi. pl. 32. f. 1-5. E. ovatus, biuncialis ; glabella clavatd convera sed parum inflata tuberculosa ; tuberculis anticis paullo majoribus, in arcu dispositis, sulcis glabellaribus brevibus vix inter tuberculos magnos visis ; genis convexis profunde marginatis, tuberculis sub oculo valde elevato angusto collocatis, angulis spinosis ; hypostomate bast subcompresso, rostro apiculato; thorace axt pleuris curvatis paullo angustiore, segmento septimo decimoque brevi-spinosis ; cauda longe triangulatd, lateribus ante apicem nunc planum recurvum, nunc deflexum obtusiorem contractis ; costis lateralibus 8 obliquis, ad apices prominulis ; axi nec convexo, annulis crebris per medium omnino obliteratis, tuberculis quinque vel sex in serie longitudinali dispositis. Var. a. Calcareus—Caudé in mucronem planum seu recurvum producto. Var. B. Arenaceus.—Cauda apice deflexo obtusiori. The original Swedish species appears certainly to differ in no respect, so far as the tail is concerned, from that common in the Dudley limestone; the tubercles on the lateral ribs, on which so much stress has been laid, being always present, either at the origin of the rib or on its surface. And the species is pretty well represented by M. Corda from Swedish specimens. The thorax rings we have not seen from Sweden, but they are tuberculate as ours are, according to the figure above quoted. The variety we have called arenaceus appears to differ only in the abrupt ending of the tail, which, instead of being horizontal and drawn out into a mucro of variable length, as in the limestone specimens from Dudley and elsewhere, is deflexed and blunt. But the specimens from the Caradoc and Llandeilo sandstones agree so well in all other particulars, the tubercles collected round the eye, the number of ribs and tubercles on the tail, &c. &c., that it cannot be separated as more thana variety. Its name indicates its usual habitats, and the deficient development of the tail may be connected with the deficient supply of calcareous matter. Upper Caradoc specimens are almost always smaller; occasionally, as at Bogmine, in Shropshire, they are of full size. Some Ludlow specimens have the glabella nar- rower, aud but four tubercles down the axis of the tail. BRITISH FOSSILS. A Lecalities—In Bala Rocks, Pwllheli, Carnarvonshire ; Mathyrafal Wood, Mont- gomeryshire ; also Westmoreland and South Wales. In Upper Caradoc Sandstone, var. 8, May Hill and Tortworth, Gloucestershire, in great abundance, first observed at the latter place by T. Weaver, Esq.; Bogmine, Shelve; in the “ Pentamerus Limestone” of the Hollies, and of Buildwas, Shropshire, abundant. In Wen- lock Shale; Var. a Woolhope. In Wenlock Limestone ; Dudley, Walsall. In Upper Ludlow Rocks; Pilliards Barn, Woolhope. Ludlow Rocks of Marloes Bay, Pembrokeshire, var. 8. Foreign Localities Sweden, Norway, Russia, in Lower Silurian ; Gottland, in Upper Silurian. p Y) 113 3. E. variolaris, Brongn. s Sp. Monee Bronen. (1822), Crust. Foss. t. 1. f. 3 B. (not A.) Parkinson, Org. Rem., th. pl. 17. f. 16. Murcutson, Sil. Syst. (1839), pl. 14. f. 1. mala. (not of Emmr.) Satter, Mem. Geol. Surv. (June 1848), vol. ii, p. 1. 344, FLETCHER, 1850, Quart. Geol. Journ., vol. vi. pl. 32. 6-10. Zethus, M‘Coy (1851), Pal. Foss. Woodw. Mus. p. 157. E.. ovatus, obtusus, sesquiuncialis, capite et thorace E. punctato simillimis, sed glabellé tnflatad, nec anticé tuberculis in serie transverso dispositis, genis per totum tuberculatis, angulis rotundatis ; hypostomate basi convexo ; thorace axt inermi, pleuris rugoso-tuberculatis ; cauda convexd brevi trigono, axi convexo pauci-annulato, annulis subequalibus 9-12 inter- ruptis et in tuberculos varie dispositos insectis, lateribus costis 7, deflexis, sepe tuberculatis; apice abrupto deflexo. Professor Burmeister in the supplement to his valuable work (ed. 2. p. 115), pointed out the obvious discrepancy between the two figures referred by Brongniart to his Cal. variolaris, and in a great measure set the synonyms right. But he was wrong in quoting the figures in the Bridgwater Treatise and Emmrich’s description as for this species, which has obtuse and rounded, not spinose angles to the head. The characters of the tail are amply sufficient to separate the two common species ; and I may add that those of the head, even if the angles are broken, are also well marked, the glabella of EH. variolaris being inflated and equally clothed with large tubercles, whence the name “Strawberryheaded Trilobite ;’’ while in E. punctatus it is convex, but not inflated, and in front has the tubercles distinctly gathered into a tranverse series or crest, a character more marked in our next species. There should be no more confusion as to the names, since the publication of Mr. Fletcher’s figures and description quoted above. Localities. — Wenlock Limestone and Shale. Dormington Wood, Woolhope ; Dudley and Walsall (abundant.) 4, E. multisegmentatus, Portl. sp. Amphion, Portlock, G. Rep., pl. 3. fig. 6 (too many side ribs.) Ampyx baccatus, id. (head), fig. 11. . multisegm., Emmr. (1845), Neues Jahrb., p. 43. E. sesquiuncialis, depressus? glabellé valde clavatad, ad basin angusta, tuberculosd, a genis convexis profundé separata ; tuberculis magnis anterius in cristam transversam arcu- atam collocatis ; genarum tuberculis (nisi duobus mazximis), minoribus, caudd longé triangulaté, apice acuto nee producto deflexo, axi angusto annulis numerosis circiter 30, solim prope apicem obliteratis ; lateribus 12-costatis, costis arcuatis deflexis. The crest of large tubercles, parted in the middle, along the font of the glabella, as well as the numerous ribs of the tail, are good marks of this elegant species. There can be no doubt the two portions above cited belong to each other. Localities. Lower Silurian [head and tail], Tyrone ; Montgomeryshire [tail only]. J. W. SALTER. August, 1853. vita ug iS Viger io | CR. Bone del* Geological Surbep of the Maited Iemngionr. CYPEASPIS | (Silurian) CYPHASPIS MecaLors_ MM’ Coy, E. Forbes direx® JW Lowry & >| go) BRITISH FOSSILS. DrcaADE VII. PLATE V. CYPHASPIS MEGALOPS. [Genus CYPHASPIS. Bormetster. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca. ‘Tribe Trilobite or Palade.) Head tubercular, strongly mar- gined ; glabella very convex, resembling half an egg, much shorter than the head, without lobes, except a small basal pair which are longitudinal, oval, and deeply divided from the base of the glabella (and an obseure furrow above these on each side) ; cheeks very gibbous, the smooth eyes rising to a high level, without an ocular ridge ; facial suture direct forwards to the margin from the eyes, and behind cutting the posterior margin near the angle, which is long-spinous; a small rostral shield present ; thorax of 11 to 17 rings (or more ?), the sixth joint of the axis frequently bearing a spine ; pleure grooved ; tail small, of few rings. Kudos, a convexity ; aom)s, a'shield, in allusion to the inflated carapace. | [Section Cyphaspis; glabella moderately large, thorax of 11 rings. } Disenosis. C. parvulus ; capite undique granuloso, fronte rotundato ; glabellé subhemispherica, nec gibbd, oculos maximos vix supereminente ; lobis posticis obovatis angustis ; genis latitudine glabellam equantibus ; angulis longi-cornutis ; limbo ante glabellam declivi angusto—vix margini incrassato latiori ; thorace segmento sexto armato, spind crassa appressd caude apicem attingente ; pleuris inermibus ; caudé lateribus unisulcatis. Synonyms. Harpes? megalops, M‘Coy (1846), Synopsis Sil. Foss. Irel. pl. 4. fig. 5. Harpidella megal., Ann. and Mag. Nat. Hist. (1849), vol. iv. 412. We have figured, for the first time in Britain, a complete specimen, of this genus ; it has been known for some years on the continent, and is one of those genera which are common to the Lower Silurian, Upper Silurian, and Devonian rocks, while it does not ascend into the carboniferous rocks. | Descrvption.—One of the smallest known species of the genus ; its length is never more than half an inch: the head, which is the widest part, is rather more than five sixteenths broad. The usual length is not above three eighths of an inch. General form convex and truly ovate, with the extremities obtuse. Head very convex and strongly granulose, in form about a semicircle, but contracted at the [VII v.] a) 2 BRITISH FOSSILS. posterior angles just in front of the strong curved spine, so that the sides are somewhat square. The spine is about equal in length to the head ; it is directed first obliquely outwards and then curved a little towards the thorax again, reaching as far as to the 7th seg- ment. ‘The glabella is very convex, parallel sided or slightly para- bolic if its whole contour be taken into account, but half egg-shaped if the small lateral lobes are excluded ; it occupies about one third the width of the head, and extends forwards only about two thirds its length, a considerable though not very broad space being left between it and the thickened front margin. ‘This space, together with the margin itself, about equals one third of the length of the glabella. Only one pair of lobes are present, which lie at the base of the glabella; they are convex, longitudinally ovate, narrow, each about one fifth the entire width of the glabella, and circumscribed by a deep sulcus, which divides them as much from the glabella as from the cheeks. These last are high-conical, and at about half-way up the head and near the glabella, bear the large, prominent, smooth eyes, which rise nearly to a level with the highest part of the glabella; a thick margin, continuous with the front margin, surrounds the cheek, and is separated from it by a strong sulcus, which does not quite reach the termination of the neck furrow ; there is no abrupt hollow or any depression at the angle. The facial suture, contrary to its usual course in this genus, turns considerably outwards above the eye to cut the front margin—along which it runs; beneath the eye its course is abruptly outwards to the end of the posterior margin— a little within the base of the spine. The neck segment is tolerably broad and prominent, and the neck furrow deep and straight. The thorax is much less convex than the head, and is always a little longer than it; it consists of 11 joints, with the axis moderately convex, tapering quickly backward, and of rather greater width than the pleurz, especially at its anterior and posterior ex- tremities ; in front about equal to the width of the glabella. The 6th segment of the axis is greatly swelled and produced back- wards, giving rise to a straight horizontal spine, which lies upon the surface of the posterior rings, and nearly reaches the end of the tail. Pleuree short, flattish, divided nearly to the tip by a strong, straight groove, the fulcral portion being of the same width as the posterior half. The ends are thickened, truncate, and very faintly bilobed ; the fulcrum is placed at about half-way along the pleurse in the middle segments,—at a less distance posteriorly, and beyond it the forward edge of the pleura is sharpened or facetted for the purpose of rolling up. Tail small, transverse, and but slightly convex, much so, ee settee BRITISH FOSSILS. 3 less than half a circle, its entire width being but little more than that of the glabella ; the axis is short conical, occupying one third its width, with one distinct rg, another more obscure, and a ter- minal joint; sides with one distinct upper furrow, which does not reach the margin. All the prominent parts of the surface of the body are rough with small tubercles; but these are by far most evident on the glabella, cheeks, and neck segment; they are wider apart than their own diameter, and pretty regular in size. Variations—The forehead portion of the glabella in our figs. 3 and 3* is much smaller and less inflated than usual, giving the glabella a parabolic instead of sub-rectangular form ; and the same variation is less conspicuous in fig. 7. In other respects they seem to be identical. Some Lower Silurian specimens have the space in front of the glabella a little wider than in those from Dudley, but even in Dudley specimens the anterior margin is sometimes narrower than this space and sometimes broader. Sex.—Under the genus Remoplewrides, described further on, at plate 8, the possible indication of sex by certain ornaments or appen- dages to the dorsal surface is adverted to. Of the small number of this species hitherto examined, we have met with no individuals ' destitute of the spine at the 6th segment, and it is therefore quite possible that it may be characteristic of the species, and not of one of its sexes. In the collection of Mr. Fletcher, of Dudley, one specimen (fig. 7 ) has the spine nearly double the ordinary length, or twice the length of the five anterior thorax rings. And this varia- tion, which we can hardly help regarding as indicative of the male, is accompanied by a less inflated glabella, the basal lobes being set more widely apart, as above mentioned, and by a somewhat more pointed form of the head. In C. Burmeisteri, the large Bohemian species, the curved dorsal spine always occurs on the same 6th seg- ment, and is always long.* But it is at least worthy of remark that the possession of such a dorsal spine is characteristic of the male of some of the Cymothoade, a group of Isopod crustacea very analagous, though probably not closely allied to, the Trilobites. In the genus Sphowroma, the male of one species, S. diadema, is characterized by the presence of a spine very much like that of Cyphaspis, and occurring too on the 6th thoracic segment; in the * In Encrinurus punctatus, described above, pl. 4, such spines, but much shorter, occur on the 7th and 10th segment ; and there are certain trilobites, Sao hirsuia and Bronteus spinifer, Barrande, for example, that have a prominent spine on every thorax ring: so that we must estimate this character at no more than its proper value. 4 BRITISH FOSSILS. female of that species, a rudimentary spine or tubercle is all that occurs. Several others are described, S. armata, &c., distinguished by such an appendage; it may perhaps be proved that some of these are males of the unarmed species. Affinities. - As nearly all the known species are double the size of this, a close comparison is not necessary ; and Cyphaspis Bur- meistert, Barr., besides its very much larger size, has 7 to 15 thorax rings according to its age, and the tail with five rings to the axis; the space, too, between the glabella and front margin is very wide: the posterior head spines short, reaching only to the 4th ring. Like our species, it bears a spine on the 6th thoracic segment. C. Barrandei, Corda (the species called formerly, with doubt, C. clavifrons, by Barrande) has 11 rings, but the glabella is vastly more inflated and the head margin narrow; the posterior head spines, too, are one and a half times the length of the body. C. cerberus, of the same author, has the head fringed with spines ; and the Devonian species, C. ceratophthalma, Goldf., besides its greater bulk and much more convex head, has a scrobicula or pit at each of the posterior head angles. The pretty Swedish species, C’. elegantulus (Proetus eleg., Angelin), is more like ours, but has an elongate head and 12 unarmed thorax rings. In fact there is no published fossil which can be confounded with it. The genus is more rich in species than might be supposed, but they have only been discovered of late years. C. ceratophthalma, Goldf., of the Eifel, furnished Professor Burmeister with the type, which he described in 1842, in his original work ; since which time Barrande, Lovén, and Sandberger have made us acquainted each with a few species. M. Corda has largely swelled the list, divid- ing the genus into Goniopleura, with 12 rings, Cyphaspis, with 11, and Conoparia, with 13; but the differences he notices are by no means sufficient for the establishment of distinct genera, though possibly the species with a very wide space in front of the glabella, and with more than 11 body rings, may form a sub- genus. Now that we possess the work of M. Barrande, who has discovered the several species with great variations in the number of thorax rings according to their age, (in C. Burmeisteri, from 7 to 15), the limits of these sub-genera may perhaps be arrived at. Our species, at all events, will fall into the same group of 11-ringed species, with that originally described by Burmeister. History.—Abundant but very imperfect specimens of the head of this little trilobite were detected by Professor M‘Coy, and carefully described by him in his account of the Irish Silurian css ioe by sieeie etal eee BRITISH FOSSILS. 5 fossils. His specimens were not perfect enough to enable him to see the true position of the large eyes on the head, nor the strong granulation of the glabella, and he referred it therefore, with a doubt, to the genus Harpes, suggesting that it might form a new group allied to that genus ; this idea was carried out in his classifi- cation of the British Trilobites, in the Annals of Natural History, for December 1849, in which this trilobite stands as the type of a proposed new genus, Harpidella, and the granulated surface is mentioned. In a communication from him lately, he is agreed with me in identifying these perfect specimens with those described by himself. It is mentioned by myself, Proceed. Brit. Assoc. 1852, Sect. p. 57. British Localities and Geological Range.—LLANDEILO FLAGs to Lower Luptow Rock. In Llandeilo flags ; sandstones of Ardaun, Boocaun, Cappacorcogue, and Tonlegee, Cong, county of Galway (Mr. Griffiths’ collection); limestone of Portrane, county of Dublin; sandstones of Mullock quarry, near Girvan, Ayrshire (M‘Coy); Bala limestone of Cader Dinmael, near Corwen, North Wales; in the Wenlock limestone and shales of Dudley and its neighbourhood (figs. 2-6); in the Wenlock shale, west of the Worcester Beacon, Malvern Hills; Lower Ludlow rock, of Hole Farm, near Philsley Beauchamp, Abberley Hills (fig. 1). [Survey Collection]. EXPLANATION OF THE PLATE. Fig. 1. A nearly perfect specimen, from the Lower Ludlow Rock, Abberley ; natural size. Fig. 1*. The same, enlarged. The tail in this figure is rather too large, both as to length and breadth. Fig. 2. A fine specimen from Dudley, in the collection of T. W. Fletcher, Esq. Fig. 2*. The head, magnified, and dissected at the suture. The glabella and its basal lobes are in this of the usual form, Fig. 3. A variety from Dudley (Mr. Gray’s coll.), in which the glabella is shorter and more parabolic in outline ; it is a rare variation. Fig. 3*. The same, magnified. Fig. 4. A fragment from Dudley, placed laterally in the rock, and showing the dorsal spine parallel to the body, and reaching to the tail. (Mr. Gray’s cabinet.) Fig. 5. Magnified dissections of the thorax; a, the anterior segment, with its pleure obliquely truncate at their ends ; 6, the 6th segment, showing the broad deep pleural groove and the long dorsal spine ; ¢, the last or 11th segment ; e, the small transverse tail. Fig. 6. A lateral view of the head, magnified. Fig. 7. A specimen, from Dudley, with the dorsal spine greatly elongated. Natural size, and enlarged. (Mr. Fletcher’s coll.) Fig. 8. Ahead from Cader Dinmael, Denbighshire ; Bala limestone. Natural size, and enlarged. 6. BRITISH FOSSILS. Other British Species. Only one other certain species of the genus has yet occurred in England, and that so like the C. (Proetus) elegantulus from Gottland, that if it were not for some differences in proportion, long head spines, &c., it would have been thought the young of that species. Its characters may be thus given :— C. pygmeus, sp. nov. [Proetus elegantulus, Angelin (1852), Palontol. Suec., t. 17. fig.7. Lovén (1845), Ofvers. Kongl. Vetensk. Akad., t. 1. fig. 4. junior ? C. minutus, ovatus; capite granuloso fronte paullum producto; glabella depressd genis angustiori, lobis basalibus rotundatis; oculis parvis; limbo antico angusto tumido, angulis posticis longispinosis ; thorace segmentis 12, azi angusto, pleuris acuminatis—posticis re= eurvatis, fulcro anticé ultra dimidium posito ; caudé minutd, lateribus costatis. Not two lines long, (while C. elegantulus grows to an inch and a half,) depressed, the head rather more than one third the entire length; glabella round oval, the small basal lobes full twice their diameter from each other. A narrow and tumid space lies between the glabella and the somewhat produced and narrow front border. ‘The cheeks are considerably wider than the glabella, and bear the small eyes at a short distance from the latter ; their angles are produced into long diver- gent spines, which reach as far as to the 7th or 8th thorax segment. The pleure are wider than the axis, and have in front the fulcrum very remote, behind it is not quite one third away from the axis. The tail is very small, the axis and sides are ribbed, but it is too imperfect to be described properly. The characters above mentioned may be those of a young specimen ; but it has the full number of rings, and in this genus they increase in number with age ; the head is not nearly so produced in front, nor the glabella so convex as in C. elegantulus, _ and the head spines are proportionally much longer ; above all, the Gottland species has blunt pleure, and in ours they are decidedly acuminate, the hinder ones being even recurved at the tips ; the pleura are grooved nearly to the ends, Locality,—Eastnor Castle, Malvern Hills ; in Wenlock shale. J. W. SALTER. August, 1853. 2 . # ACIDASE ¢ it (Silurian ) a Con, ? d King v f th e Ba ( urbep of ( slogteal S DEL (ils SOME. 12.8 AQCPOASFUS daivin sat pispinosus M’Coy. 4.6 ree E.Forbes direx* one del* eaetls) Sg OS aS | eee ee te Seales ae oe : aay BRITISH FOSSILS. DECADE VII. Puate VI. Fig. 1, 2, 3. aD ACIDASPIS JAMESII. [Genus ACIDASPIS. Morcutson. (Sub-kingdom Articulata. Class Crustacea. Order Entomostraca. ‘Tribe Trilobite or Palade.) Capable of rolling up, or even contractile into a ball. Head short, broad, truncate in front ; the glabella broadest at the base, with a median portion strongly separated from the three lateral lobes, which are obscurely divided from the cheeks (and often connate with them); cheeks thickened, generally Bpinose at the margin, and with the angle produced into a spine ; éyes smooth, convex, (occasionally elevated on a long peduncle) connected with the front of the glabella by a strong ocular ridge ; neck segment much enlarged, and generally produced into spines ; body of 9 or 10 segments (fewer during the metamorphosis), with a narrow convex axis, and horizontal pleurze which are produced at their ends into spines ; tail small, axis abbreviated, limb multidentate, with one strong lateral rib on each side produced beyond the margin. axis, mucro ; ams, scutum.] Driscnosis. A. latus, depressus, granulosus; capite haud convexo, glabella triangulari, utrinque lobis duobus ovatis d gena dilatata fere dis- tinctis—tertio obscuro; oculis medianis; jugo oculari obscuro; angulis brevispinosis ; thorace segmentis 9 unispinosis, caudd spinis 12, primariis fortibus parallelis, reliquis minutis,—terminalibus sex, externis utrinque duobus. Synonyms. tH r is vat S a ea cal 719 ie Ct ucts Aree Thet Bale Led Sy ee ONT Nm oe anes ae. BRITISH FOSSILS. DeEcADE VIII. Puate I. ASTERACANTHUS GRANULOSUS. [Genus ASTERACANTHUS. Acassiz. -(Sub-kingdom Vertebrata. Class Pisces. Order Placcidei. Family Cestraciontide.) Dorsal spine large, tuberculate, with a double row of processes on the posterior margin ; base smooth. | Asteracanthus granulosus, Sr. Nov. Description.—The characters assigned by Professor Agassiz to the genus Asteracanthus, are striking, constant, and unmistakeable. The Jeading features of these Ichthyodorulites are the tubercular surface of the dorsal ray, and the stellate ornament of the tubercles. In the typical species, Asteracanthus ornatissimus, found in the Kimmeridge clay, these characteristics avtain their maximum de- velopment—in the species under consideration, from the Tilgate beds, they are reduced to theminimum. The specimen represented (fig. 1. of the Plate) isthe only one approaching a perfect state I have met with. It probably belonged to a young dividual. The other figure is taken from a fragment of a much larger ray, in the British Museum, belonging to the same species. The length of the former is nearly 1 foot; when perfect it probably measured an inch more. The base at the front of the ray is only 4 inches in length, but the cavity at the back extends upwards of 8 inches. It is scarcely pos- sible that the whole of this can have been imbedded in the muscles ; it 1s more likely that it supported a large adipose or membranous fin, attached to the hinder surface, and embracing the cavity, but leaving the rough outer part of the bone exposed for offensive or defensive operations. The whole texture of the bone is remarkably coarse and fibrous. It is traversed by inosculating canals, inter- spersed with pores, arranged in longitudinal series, and showing a reticulated pattern, when examined with a lens. The root and the hinder surface as high as the termination of the cavity are smoath, and free from ornament. The remainder of the ray is covered by numerous smooth tubercles, isolated, but arranged in longitudinal [ VIII. 1.] 8B v4 BRITISH FOSSILS. series, parallel to the long axis of the bone. They are smaller in this species than in any other yet discovered, resembling coarse grains of sand; they, nevertheless, have the radiating lines on the apex, so constant in all the Asteracanthi. The specimen in the British Museum is a fragment of the lower portion of the ray. It measures 7 inches in length. A second fragment, also in the British Museum, measures 5 inches. In these specimens, as is usual in the rays of full grown individuals of the genus, the asteroids are more distant than in the younger ones. They are small in size, and patelliform in figure, the apex being eccentric, and approaching the upper periphery. ‘Their bases are smooth, the stellate rays becoming obsolete before descending so far. The general outline of the ray is very slightly recurved. ‘The anterior margin is rounded, and without carina. The sides expand considerably, so that the back of the fin is broad, as seen in the transverse section (fig. 4). There is no evidence to lead to any conjecture as to the form of tooth belonging to this species ; the only Placoid teeth hitherto discovered in the Tilgate beds being referable to the genera Hybodus and Acrodus. . Locality—The original of figure 1. of the Plate is from the — ferruginous grit beds of Tilgate forest, and was presented to me by the late Mr. Dixon. The specimen in the British Museum (figs. 2, 3, 4,) is derived, apparently, from the same beds, and formed part of the Mantellian collection. EXPLANATION OF PLATE. Fig. 1. Asteracanthus granulosus, size of nature. Fig. 2. Asteracanthus granulosus, size of nature. Fig. 3. Interior of ditto. Fig. 4. Transverse section of ditto. Fig. 5. Portion of No. 1 magnified. e DECADE 5 PL 2 Orologiral Surven ofthe Variked Bangham ASSESS ENS 5 gi f Oobtie) BRITISH FOSSILS. DecaDE VIII. Prats II. ASTERACANTHUS VERRUCOSUS. ei [Genus ASTERACANTHUS. Acassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Placoidei. Family Cestraciontide.) Dorsal spine large, tuberculate, with a double row of processes on the posterior margin ; base smooth. ] “a aeeractint his verrucosus, SP. Nov. Deser uption.—The genus Asteracanthus, although for the most part an oolitic form, extends nevertheless upwards ca the Tilgate _ beds, as shown in the preceding article. The typical species, _Asteracanthus ornatissimus, 18 a fossil of the Kimmeridge clay. The remarkable character of this Ichthyodorulite attracted the notice of collectors at a very early period. On the 29th of March 1753, a paper, by Mr. Henry Baker, was read before the Royal Society entitled, “An Account of some uncommon Fossil Bodies.” This paper is printed in the Philosophical Transactions of the Royal ; Society for that year. The specimens described and figured are a spine of a Hybodus, from Aust Passage, and several examples of the Shotover-hill Asteracanth. The alan descriptions, as also the repre- sentations, are tolerably accurate, but the conclusion drawn is, that “the general appearance of these fossil bodies gives reason to conjec- ture, that they are bones belonging to the head or snout of some animal of the fish kind, or perhaps of some lizard, alligator, or crocodile.” The credit of determining the true nature of these curious fossils is due to Doctor Buckland and Sir Henry De la Beche, who some years ago prepared a joint paper on the subject, which unfortunately was never published. The facts and materials collected by these authors were liberally conceded to Professor. Agassiz, when engaged on his valuable publication on Fossil Ichthyology, and he stamps with his authority the correctness of their opinions. The very elegant fossil which forms the subject of this article belongs undoubtedly to the genus Asteracanthus, but differs specifically from all those btherts described.. The length of the lies is 102 inches, but the apex is wanting to the extent of perhaps 4 an inch. Taking the length as 11 ‘inches, the base of the front of the spine occupies [ VIII. ii. ] Sc 2 BRITISH FOSSILS. barely 3, but the cavity on the posterior surface extends for 7 inches. It is, therefore, probable that the membranous fin concealed more of the spine on the back than on the front, a feature found in some of the recent Placoids, with spine-bearing fins. The line of junction between the base and the ornamental portion is less oblique than ordinary, which proves a. more erect position of the fin in this than in the other species of the genus. The external surface is closely beset with tubercles, smaller in size and far more numerous than in Asteracanthus ornatissimus. They are arranged in very regular longitudinal series, parallel with the front edge of the bone. They become less numerous as they recede from the front, and cease altogether on the posterior re The tubercles are oval, the larger diameter coinciding with the direction of the rows; on the distal portion of the spine they become smaller and more elongated. They are all ornamented with deep grooves, radiating (in some in-— stances spirally) from the apex, the stellate surface being of harder material than the base of the tubercle. The substance of the spine bearing these ornamental projections is very coarse and fibrous. The base is also composed of similar material. It has been already stated that the cavity of the spine extends for nearly two thirds of the back aspect; the surface beyond this point, which marks the determination of the cutaneous investment, was armed with a double row of falcate processes, in alternating order, a feature common to other species of the genus. Professor Agassiz conjectures that this form of Ichthyodorulite probably belonged to the genus Strophodus, in consequence of the frequent occurrence of teeth of this genus in association with Asteracanthus spines, in the Kimmeridge clay of Shotover, and the oolite of Stonesfield. [I am not, however, aware that teeth of Sirophodus have, as yet, been discovered in the Swanage beds. Locality —tThis form of spine is not uncommon in the Purbeck strata of Swanage and the neighbourhood. The specimen I have selected for the figure and description, belongs to the Dorchester Museum, and was, 4j believe, obtained with many other fine Pur- beck fossils from Mr. Wilcox, of Swanage. Note.—Mr Beckles, of St. Leonards-on-Sea, possesses an Ichthyodorutite, found in the Paludina beds, near Hastings, which varies in some respects from the species deser bed in this article, but it has suffered so much from attrition, that the evicence of specific difference is insufficient. - EXPLANATION OF PLATE. Fig. 1. Asteracanthus verrucosus, size of nature. Fig. 2. Tubercle, magnified. P. DE. M. GreY EGERTON. Muy 1853, . . % - \ ¥ eS 4 or) - a Ee © oe 2 4 2 9 Zz ie = 3 = (i oe at ba Cs.) Pena ee bs oa Peery Se ee ee = ke my Sik tA : ee 2 BRITISH FOSSILS. a Ts DeEcADE VIII. Puate VIL. — Fics. 1—»5. PHOLIDOPHORUS HIGGINSI. [Genus PHOLIDOPHORUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces Order Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerci. 2d Group, Body elongated, more or less fusiform.) Dorsal fin small, opposite the ventrals ; caudal fin forked; the lobes equal; the base of the upper lobe invested with scales; teeth villiform.] — SynonymM.—Pholidophorus Higginsi. StTurcuBury. Description.—This diminutive member of the genus Pholido- phorus was named by Mr. Stutchbury, of the Bristol Institution, in compliment to the discoverer; but as no figure or description of the species has yet been published, I have selected it as an appro- ‘priate subject for this Decade. It is one of the smallest species of the genus; the largest of all the specimens hitherto found not exceeding 2 inchesin length. It is remarkable also for the large size and great solidity of the scales. The specimen I have selected for representation is not so complete as some others, but it gives -_the best idea of the form and characters of the head and scales, features which are for the most part either crushed or deficient in the other examples. It differs remarkably from the other small Pholidophori in the thick and short-set proportions of the body, in which respect it contrasts strongly with the elegant outlines of Pholidophorus gracilis of Count Mimster—the smallest species hitherto described. The head measures rather less than one third of the entire length, and is about equal to the largest diameter of the body. The muzzle is pointed, and the gape wide. The bones of the head and opercular appendages are smooth and lustrous. Those appertaining to the maxillary apparatus are more or less distinctly characterized by fine longitudinal plaits running parallel to the larger diameter of the bones. The surface of the lower jaw is pierced on its under side by seven or more large punctures for the passage of the mucous ducts. Both jaws are furnished with [ VIII. vii] © 8H Zz, BRITISH FOSSILS. a single row of smooth thick-set villiform teeth. These are well seen in the enlarged representation of a detached head (fig. 2 of the Plate). The pre-operculum is more uneven superficially than the associated bones, the undulations becoming very strongly marked as they approach the posterior margin, which, however, is not in- cised. The operculum is triangular, the apex directed downwards ; the sub-operculum is nearly as large as the operculum, and both are traversed by indistinct concentric lines of growth. ‘The scales couveying the mucous duct are quadrilateral in the anterior and middle parts of the body, but as they approach the tail the posterior angles are bevelled off, and the long diameter of the scales gradually reduced until they assume the lozenge form. The canalis unusually large, and its course is prominently raised above the surface of the scales. The apertures are for the most part in notches at the poste- rior margins, but occasionally there is, in addition, an orifice in the centre of the scale. The scales immediately below the lateral line are the largest, and are also quadrangular. Those below this series, as also those above the lateral line, diminish rapidly im size, and lose at the.same rate their angular outline. The surfaces of all the scales are perfectly smooth, and invested with a dense covering of ganoine. The free margins of the larger scales are armed with two-or three sharp cusps, but in the smaller scales these are either reduced to a single point or are altogether absent. The fins are mutilated in all the specimens. ‘The pectoral fins appear to have been broad, and to have contained not less than 16 rays. The position of the dorsal fin is rather remote. The ventrals are small, and are placed about the middle of the body ; the anal fin is about the dimensions of the dorsal fin, and is situated nearer to the ventrals than to the tail. The latter fin is not preserved in any of the specimens. Cae Locality.— All the specimens yet discovered of this and the two following species of fossil fish, where found by Mr. Higgins in a single block of Cotham marble from the lower lias of Aust Passage There are not less than 14 or 15 individuals all grouped together in a matrix not larger than the plate which accompanies this description. Owing to the liberality of the discoverer, specimens. of this species are in the collections of the Bristol Institute, the Rev. P. B. Brodie, the Earl of Enniskillen, and my own; and I am indebted to him and the other possessors for the loan of their specimens for the purpose of comparison and description. BRITISH FOSSILS. 3 PLATE VII. Fig. 6-8. Pholidophorus nitidus. Spe. Nov. : | , _ Description.—Associated with the preceding group of fish, two specimens were found, which although very imperfect, incontestably constitute a new and distinct species of Pholidophorus. Among the numerous members of this overcharged genus, many of which are remarkable for graceful forms and proportions, none can vie with the subject of this memoir for symmetry and elegance. As compared with Pholidophorus Higginsi, the head is smaller, the body more slender, and the shape and proportions of the scales dissimilar. The imperfection of the specimens precludes a very de- tailed description of the species, at the same time enough remains to establish specific characters which may be safely relied on. One specimen, belonging to the Bristol Institution, shows the impression of a portion of the head and the opercular apparatus. It was evidently small in relation to the body, and the surface of the bones was smooth and highly polished. The other specimen, of which a re- presentation is given double the natural size, belongs to Mr. Higgins. It shows the greater part of the trunk, together with the dorsal and one ventral fin. These are situated opposite each other, and are composed of a small number of fine fin rays. The scales are beautifully preserved, without either dislocation or fracture, and present the following characters. The principal series, or that constituting the lateral line, contains the largest scales. They are oblong in form, being considerably higher than they are wide. The posterior angles are slightly rounded. The central area of each seale is traversed by a ridge indicating the course of the mucous tube, and in addition to the notch at the posterior margin for the exudation of the lubricating secretion, there is also on each scale a foramen on the upper margin of the tube (Plate 7. fig.7.) The row of scales immediately below the lateral line is next in importance. In this set the vertical diameter is much reduced, and in the suc- ceeding rows, about four in number, this diminution is progressive, the scales in the vicinity of the ventral fins being nearly equilateral. _ Above the lateral line one row of large scales occurs, and this is succeeded by four or five rows in which not only are the dimensions exceedingly reduced, but the posterior margins, by the elongation of the lower angles, assume the lozenge form. They are all highly lustrous, and the only irregularities of surface discernable with a pocket lens are the concentric undulations recording the successive growths of the scales. [VIIr. vii. | 8H 2 4 BRITISH FOSSILS. Locality.—These specimens were found in the same block of Cotham marble at Aust as those described in the preceding memoir. PuATE VII. Fig. 9—12. LEGNONOTUS. Gen. Nov. [Genus LEGNONOTUS (Aeyvoy, a fringe, vwros, the back). Ecrrton. (Sub-kingdom Vertebrata. Class Pisces, Order Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerci.) Dorsal fin extending from the nape to the tail; teeth conical. ] Legnonotus Cothamensis. Sr. Nov. Description—The same block of Cotham marble which con- tained the two preceding species, yielded also the curious little fish represented in the accompanying plate (fig. 9.), of twice the natural size. The head and detached jaw, of which enlarged views are given at figs. 10. and 11., probably belonged to the same species, at all events they differ entirely from the characters of Pholido- phorus, the only other genus associated with them. It is not without some hesitation that I have ventured on the slender evi- dence afforded by a mutilated specimen, and a few fragments to establish a new genus; and I should not have done so, could I by any licence of interpretation of the characters of genera already acknowledged have referred this fish to any one of them. The dorsal fin is a feature of such paramount importance, that it cannot be disregarded ; and the peculiarities cf this organ in the subject before us, are quite irreconcileable with any genus hitherto dis- covered. It commences immediately behind the nape and extends nearly to the tail, and contains about 30 rays all supported on strong perpendicular interapophyses. Six or seven of the anterior rays are single spines, rather arched and shorter then the succeed-. ing rays. The latter are thicker than the anterior ones, and although single for some distance from the body, are subdivided at their extremities and traversed by transverse articulations at rather distant intervals. The nearest approach to this construction of the dorsal fin is found in the Sauroid genus Macrosenwus, but in other respects Legnonotus resembles a Pholidophorus, or still more nearly the genus Votagogus. The former has a small single fin on centre of the back, the latter has a double dorsal fin; features quite sufficient to distinguish them from the subject before us. ‘The fish measures 14 inch from the insertion of the pectoral fin to the base of the tail, and =%, of an inch in depth. The dorsal fin occupies an inch of the back, and the anal fin is nearly an inch distant from a ch Se eg Ae Me cn eee ene ee ee *, # i ¥ ie & wy 7 + 5 EY % Me 54 ¥ 4 i rs My i od Ps % oF a x By ° e 3 LE a ‘a te a % Rey aed Si 15> ate Pir. ee o. 4 x a re : BRITISH FOSSILS. a the pectoral fin. These fins are both small, and the rays continue the greatest part of their length without subdivision ; they are, _however, fimbriated at their extremities. The scales are very thick and solid, and of variable and rather irregular forms. The ganoid investment is very dense and lustrous. The posterior margins are coarsely serrated. A large fulcral scale occupies the base of the upper lobe of the tail. The latter organ is mutilated, but it is probable from what remains, that it was blunted in form, or at all events not deeply forked. The lateral line is nearly horizontal. The head figured as probably appertaining to this fish shows the operculum and the lower jaw. The former is characterized by a rough pattern of flattened tubercles of enamel, very different in this respect, as also in form, from the corresponding part in the genus Pholidophorus. ‘The lower jaw is strong, and armed with a single row of stout incurved teeth, in the form of elongated cones, with rather blunt points, not unlike the outer row of teeth of some of the more slender toothed Lepidoti or dichmodi. They are well seen in a detached jaw represented at fig. 11 of the plate. On comparing this figure with the Pholidophorus head (fig. 2.), the difference of the dentition of the two genera is easily appreciated. Locality.—This Ichthyolite was discovered by Edmund Thomas Higgins, Esq., at Aust, in the same block of Cotham marble which contained the two species of Pholidophorus figured on the same plate. It is in his possession, and I am indebted to his liberality for the opportunity afforded me of making it available for this Decade. EXPLANATION OF PLATE. Fig. 1. Pholidophorus Higginsi, size of nature. Fig. 2. Head of ditto enlarged, twice the size of nature. Figs. 3. 4. 5. Scales of ditto, 4 times the size of nature. Fig. 6. Pholidophorus nitidus, twice the size of nature. Figs. 7. 8. Scales of ditto, 4 times the size of nature. Fig. 9. Legnonotus Cothamensis, twice the size of nature. Fig. 10. Head of ditto ditto ditto. Fig. 11. Lower jaw of ditto ditto ditto. Fig. 12. Scale of ditto, 4 times the size of nature. P. p—E M. Grey EGERTON. July 7, 1853. Be is Ma LO aad : a Sei eat ae a . e + - | i fs 1 eS = a z ‘ . - Cee ee is Au Zeb i , a i 3 a ) ae ile af t a . Pret le a i : 2 ‘ a R ' « ry Uasah OYA (C2) LLL] Oo” ) 3} (Qs ts =O aid I TD dull 2 LaVON ea es ARES: 2 Wi 3 if UT TU 8 O (2 BRITISH FOSSILS. DeEcADE VIII. Puats VIII. ee —— PTYCHOLEPIS CURTUS. - [Genus PTYCHOLEPIS. Acassrz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. Ist Group. Tail forked.) Scales thick, elongated, plicated transversely on the base, and deeply furrowed longitudinally ; under-surface smooth, and devoid of rib; pectoral fins pointed; dorsal fin opposite the ventral fins ; anal fin remote. ] t Ptycholepis curtus, Se. Noy. ~ Description.—The beautiful little specimen figured in the plate accompanying this description affords another proof (were further ___ evidence requisite) of the value of dermal characters in the deter- mination of fossil fishes, more especially those of the secondary formations, where the internal skeleton is so rarely preserved. Were a mere outline of the fish before us submitted even to Professor Agassiz himself, I very much doubt whether he would recognize or acknowledge in it a species of his genus Ptycholepis, so little do its short and thickened proportions resemble the slim, elegant forms of the Sauroid family in general, or correspond with the known species of its own genus ; and yet the inspection of a single scale, or even a fragment of one, would at once reveal to him its true generic affinity. The fish has retained its natural form without distortion of the body or dislocation of its parts. The pectoral, ventral, and a portion of the caudal fin are wanting ; with these ex- _ ceptions, it is in perfect preservation. The length from the nose to _ the insertion of the tail is 42 inches, of this measurement the head. occupies nearly 13 inches, more than a third of the entire length. : “In Ptycholepis Bollensis, the head meastres only a fourth of the total length. The depth of the body at the dorsal fin is 1-2, inches. These proportions. serve to distinguish this from the previously — known species; they are, however, associated with other distinctive features to be mentioned in the sequel. The head, as noticed above, is large; the outline forms a very regular isosceles triangle. The [vit viii] 8 I 2 BRITISH FOSSILS. orbit is of moderate size, and placed in a forward position. The snout is thickened and rounded at its extremity. The mouth is large, and capable apparently of great distention. The operculum is quadrilateral, and the sub-operculum triangular. The line of junction between them runs obliquely upwards and backwards The pos- terior border of these bones is nearly perpendicular. All the cranial bones and their appendages are highly ornamented by deep grooves, arranged in a variety of elegant patterns. On the upper part of the head they are grouped longitudinally, running in sinuous, and sometimes inosculating lines, from the occiput to the snout. On either side the latter, they are retroflexed with a sigmoid curve, exactly resembling the common tattoe pattern on the alee of a New Zealander’s nose. On the premaxillary bone they are parallel to its lower margin, and on the lower jaw they run obliquely downwards and backwards. The opercular bones are less deeply sculptured, and the furrows are more distant. On the posterior angles they become almost obsolete. ‘The scales (with the exception of a few immediately behind the thoracic arch) (Plate viii. fig. 2.) are long and narrow. The base of each is marked by three or four distinct bars. The surface of each scale behind the base is cut by two (or sometimes more) grooves, always varying in length, but rarely extending to the posterior edge of the scale, which is deeply notched. They are all incrusted with a thick and lustrous coat of ganoine. The an- terior insertion of the dorsal fin is equidistant from the nose and the commencement of the tail. The fin itself 1s moderately long, and contains 22 rays. Of these the sixth and seventh from the front seem to be the longest, The transverse articulations of the rays are very frequent near the base, but become more and more distant. After the fourth articulation the rays are grooved, but they do not dichotomise, so far as the fin is preserved in the specimen. It is devoid of fulcral scales. The base of the pectoral fin is all that remains of this organ. The anterior rays are disproportionately strong. The ventral fins are deficient, but they seem from the impression on the shale to have been small. They are inserted below the hinder part of the dorsal fin. The anal fin is small, and very distal in position. Its hinder rays almost reach the tail. The latter is of moderate size, and forked. It has a strong fringe of oblique rays along its upper margin, and a similar one, though finer, protects the lower edge. A few of the terminal vertebree of the column are preserved. They diminish gradually in size, and terminate at the commencement of the upper lobe of the caudal fin. BRITISH FOSSILS. 3 A ffinities—The dermal characters of this species associate it very closely with Ptycholepis Bollensis ; the individual scales, however, are proportionately longer and narrower, and differ in the arrange- ment of the sculpture. I have evidence of a third species occurring with the two former, in the lias of Lyme Regis, in which the scales are still more elongated ; but the subject of the present memoir is easily distinguished from the other members of the genus, by the striking proportions of the fish described above. Localities.—The only specimen I have seen of this species was found in the lias beds, between Lyme Regis and Charmouth. It is the property of Mr. Beccles, of St. Leonards-on-Sea, to whom I am indebted for permission to figure and describe it. EXPLANATION OF PLATE. Fig. 1. Ptycholepis curtus, size of nature. Fig. 2, 3. Scales magnified. P. pE M. Grey Ecerton. May 1853. bs hasty = Bia Gtk pe UTNE a posit Pens ain CADE & » 5 ’ : 1 ORTON AMIENS Hroalogieal Surven of the Vaaked King ont . (Oolitic : OXYGNATHUS ORNATUS Egerton r +ike nom ye me nahi > Tara) Dy VEC A i Pp) eS bx SP at ape - . — YY eI oe nS SS mm 7 ONG cs = ' ater BRITISH FOSSILS. DecaDE VIII. Puate IX. oe OXYGNATHUS. Gen. Nov. [Genus OXYGNATHUS. Lasertron. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. Ist Group. Tail forked.) Body elongated; head pointed ; jaws furnished with numerous small in- curved teeth, intermixed with larger ones; scales thick, small, rhomboidal, and covered with sinuous longitudinal furrows; pectoral fins short and broad ; ventral fins large ; anal fin small. | Oxygnathus ornatus, Sp. Nov. _Description.—This fish has so many striking peculiarities, that it e _has been necessary to create a new generic title for its designation. ‘The slender lanceolate form of the body resembles some species of Eugnathus, the characters of the teeth and jaws approach those of Sauropsis, while the peculiar ornamentation of the scales can only be compared to that found in the heterocerque genus, Acrolepis. The combination of these characters, and the addition of others not found in the above cited genera, establish the propriety of selecting for this form a new generic appellation. The specimen measures 91 inches, from the snout to the base of the caudal fin, of which the _ head occupies 3 inches. The greatest depth of the body was probably not more than 2 inches, but the attitude of the fish is such that this measurement cannot be ascertained with precision. This, however, is clear, that the deepest part was immediately behind the nape, from which point the body gradually tapers to the tail. The dorsal and caudal fins are both absent. The form ‘of the head is more pointed than in any of the Sauroid genera, except those with elon- gated muzzles, such as Aspidorhynchus, Belonostomus, and Saur- ichthys. In consequence of the extreme tenuity of the bones of the head few are preserved entire, with the exception of the dentigerous bones, and the hyoid and branchiostegous apparatus. These are all covered with a surface ornament, composed of fine vermicular plaits of enamel, arranged for the most part in longitudinal direc- [ VIII. ix.] : 8 K 9. BRITISH FOSSILS. tions. The remnant of one of the opercular bones shows that this | pattern did not extend to those bones; they seem, however, to — have been covered with a fine and rather indistinct granulation, intermixed with raised lines, running parallel to the posterior margin of the flap. The teeth are numerous in both jaws. The larger ones are conical, sharp, and hooked at the extremity. The smaller ones are of the same form, and fill up the irregular interspaces between the larger ones. They together form a single row, fringing the margins of the mouth. The symphisis of the lower jaw is remarkably ~ acute. The branchiostegous rays are beautifully displayed, occu- pying the angle between the jaws. There appear to have been about twelve on either side. The pectoral fins are composed of a series of flattened rays, about thirty in number. They are deyoid of transverse articulations, but dichotomise when near their ex- tremities. The ventral fins are situate nearer to the anal than to the pectoral fins. They are smaller than the latter, although larger than the corresponding organs in the allied genera. ‘They contain, in addition to three or four small marginal appendages, about 24 rays. These are rounded, have frequent transverse articulations, and bifurcate at their extremities. The anal fin is short and small. It occupies a position midway between the anterior insertion of the ventral fins, and the commencement of the tail. It contains 16 or 18 rays of similar character to those composing the ventral fins. - The scales are small, and very numerous. They vary in form and size, on different parts of the body, but they all correspond in the character and distinctness of the surface ornament. This consists of elevated ridges of enamel, arranged for the most part in longi- tudinal directions, in reference to the outline of the fish; but obliquely as regards the individual scales. On the nape a few granulations are interspersed with the ridges. The latter, however, predominate in all other regions of the body. The scales near the tail are thicker than those on other portions of the trunk, and the ornament more coarse. Each scale has a thick rib on its under surface, which locks in reciprocally with that of the adjoining scale, and secures the continuity of the series against accidental dis- location. Affimities—The character of the scales alluded to above marks out the genus Oxygnathus, as distinct from all others. The only approach to it is in the genus Acrolepis, but (in addition to the latter being a heterocerque fish, which alone would forbid the union,) the differences in the form of the scales, and the arrangement of the sculpture, sufficiently distinguish it from that genus. A slight re- BRITISH FOSSILS. 3 semblance may, perhaps, be traced between these scales and those of Gyrolepis; but, here again, we have probably a heterocerque fish, it being restricted to beds older than the lias. As compared with the Liassic Sauroid genera, already described, this fish differs from them all, nor can it be ascribed to any of those genera named, but not yet described, viz, Thrissonotus, Centrolepis, Endactis, or Cosmolepis. Locality.—The figure and description are taken from a specimen in the collection of the Earl of Enniskillen, found in the lias at Lyme Regis. | EXPLANATION OF PLATE. Fig. 1. Oxygnathus ornatus, size of nature. Fig. 2, 3, 4. Scales of ditto, magnified. P. DE M. Grey EGERTON. May 1853. Bs aa) Ow IN Oolitic, @ rtOn . € at Mes ‘esud ‘orb Bo PYC NGOS Li ASS hC uss. 1g¢ lL. I , lit dos Dmikel ese “ ~~ a Se eee PAS BRITISH FOSSILS. DecADE VIII Puare X. PYCNODUS LIASSICUS. [Genus PYCNODUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Pyenodontide.) Body short, deep, and adpressed ; three or five rows of smooth, flattened, oblong, tritoral teeth, on each ramus of the lower jaw; five rows of similar teeth on the vomer; incisive teeth in both jaws. | Pycnodus liassicus, Sp. Nov. Description—The announcement of the occurrence of fishes belonging to the family Pycnodontide, in the las of Great Britain and Wurtemberg, recently made in a memoir read at the Geological Society,* has been quickly followed up by the discovery of a true Pycnodus, from the same formation. This interesting specimen was brought to light during the operation of transferring the fine collec- tion of fossil fishes in the British Museum, from the cases in Room 6, to their new position in Room 2. It is supposed to have been derived from the lias of Barrow-on-Soar, and, although far from perfect, is, nevertheless, sufficiently so to leave no doubt as to its natural affinities. In referring it to the genus Pycnodus, I have been guided mainly by the characters of the dentary apparatus. The general contour of the body has more resemblance to a Microdon, or a Gyrodus, and wants the elongated caudal pedicle of the typical Pycnodi ; but the characters of the teeth are so decisive, that I have no hesitation in referring it to the latter genus. The specimen fioured in the plate measures from the symphisis of the lower jaw to the commencement of the tail, 4 inches. The greatest depth, following the direction of the dorso-ventral series of scales, is 33 inches. The anterior portion of the trunk is highly vaulted; the summit of the nape being nearly 1 inch higher than the occiput. The frontal and facial line is straight, and steeply inclined. The lower jaw is unusually large (fully 1 inch in length), and renders gies * Quarterly Journal of Geol. Soc,, 1853, page 276. [ VirT. x.] 8 L 2 | BRITISH FOSSILS. _ the prognathic character very decided. The orbit is situated in a high and very forward position. The upper limb of the operculum is nearly horizontal ; the posterior margin slopes downwards and forwards, in an easy curve. The preoperculum is high and narrow. Wherever the surface of the cranial bones is preserved, it is covered with small flattened granules, distinct from each other, and not grouped in radiating or other patterns. The anterior or incisive teeth are elongated cones, slightly flattened at the apices; the succeeding teeth are shorter and broader. The outer row only is visible, and these being comparatively small, we may conclude from the general rule applicable to this genus, that each ramus had five rows of teeth, those comprised in the second row being considerably larger than the remainder. One large tritor is seen in a position which indicates that it belonged to the central or principal row of the vomerine teeth. Several smaller ones scattered about may have belonged to the lateral series, of which there were probably two on either side of the central one. The form of all these teeth is more or less oblong, and the crowns are smooth, devoid: alike of the inequalities of the Microdon teeth, and the rugosities of the Gyrodi. The dorsal and anal fins are large, and opposed to each other. The former has 20 rays, the latter about 15. These are all articulated to dilated extremities of strong interapophyseal osselets. The ‘rays are single at first, but they soon dichotomize, and are marked by very closely arranged transverse articulations. The course of the spinal column is nearly straight, and does not coincide with the arched form of the dorsal outline. The vertebral centra were cartilaginous, but the apophyses strong and keny. The scales are much mutilated. Those of the nuchal region are the largest. The impression left on the stone proves them to have been orna- mented with diverging curved lines of small tubercles, sweeping downwards and outwards from the central area of each scale. The succeeding scales below are of smaller dimensions, but they all partake of the high narrow character so generally prevailing in this family. They are covered with small flattened tubercles, similar to those found on the bones of the head. No evidence remains of the form or position of the pectoral or ventral fins. It has been stated . above that the form of this fish differs from that recognized as typical of the genus Pycnodus, but this remark must be taken as having reference to the state of our knowledge of the genus. Agassiz founded its generic attributes on the well-known Pycnodus platessus, of the Monte Bolca beds, and in this tertiary form the elongation of the pedicle of the tail is very striking. The only | re OS ao OARS re ee ; ut 3 by BRITISH FOSSILS. 3 other species of which the trunk is preserved, with the exception of the species of Pycnodus orbicularis, in the Paris Museum, is the small Pycnodus rhombus, found in the Jura (?) beds of Torre d’Orlando, near Castel-a-Mare; and in this older form this peculiar character is less prominent. The remaining thirty-two species enumerated and partly described in the “ Poissons Fossiles,” ranging from the tertiary formation down to the Keuper, are only known by their teeth. It is, therefore,” quite possible that the Oolitic species may have resembled the other Pycnodonti of that period, in the more rounded outline of the body, and that this must therefore be considered a specific rather than a generic condition. Be this as it may, the characters derived from the dentition are of so much greater moment than the mere outward form of the fish, and they coincide so entirely with those of the well-known dental apparatus of the genus Pycnodus, that no duubt remains upon my mind as to the propriety of assigning the subject of this article to that genus. Locality.—The only specimen I have met with of this species is the one represented in the plate. EXPLANATION OF PLATE X. No. 1. Pyenodus liassieus, size of nature. Nos. 2, 3. Front teeth, magnified. Nos. 4, 5. Vomerine tritor, ditto. No. 6. Nuchal scale, ditto. P. pE. M. Grey EGERTON. July 7, 1853. ed Heer ear ar Hamid add > bens Vics Ae SAU RICE el veey | enttenriak ¥ ER Bian hi: ts pd eatiatinee whe rg ae RE Re ee ee en ae ae ee ee > Yo “_ a Sa Fe Se eet ee ry Lt ae F ae Am) : Ye "i ae Fr. ‘ y pity 3 ee: * t ig # i [ nf Bis x SUPPLEMENT TO DECADE VIII. Tue delay which has occurred in the publication of this Decade has been so far fortunate, that in the interval which has elapsed since the completion of the manuscript, several specimens have been discovered, of species described therein, substantiating the characters already given, and supplying others which were deficient in the materials originally examined. As several of the species were founded upon single specimens, it is of con- _ Sequence that the opportunity of recording this additional evidence should not be lost, although it would not be advisable to incorporate it in the descriptions completed two years since, and which are now in type. ARTICLE V.. PLATE V. EMistionotus angularis—This genus and species was determined by a single specimen, in my own collection. ‘The Museum of Practical Geology has now two specimens of the genus, one of which belongs, no doubt, to the same species. ‘The other is a portion of a much larger fish, and may possibly indicate a second species, but it is too imperfect to afford any reliable evidence of distinctive character. Both these specimens are from the Swanage quarries. ARTICLE VI. Prater VI. Aspidorhynchus Fishert.—The British Museum and the Museum of Prac- tical Geology now possess good specimens of this species. The original of Plate 6 is so perfect, that no further evidence was necessary to complete the specific description. ARTICLE X. Puate VIII. _Ptycholepis curtus.—This species depended on the evidence of a single specimen, in the possession of Mr. Beccles. A second specimen has recently been sent to me from Lyme Regis (whence the first was also derived), showing some details which were wanting in the one originally described. The pectoral fins are here preserved. ‘They are composed of from 18 to 20 rays each. ‘These are strong, and closely arranged. They are single as far as they are preserved, and show no transverse articulations. The anterior margins of these fins were bordered. The ventral fins are placed nearer to the pectoral than to the anal fins. They are small, and composed of 10 or 12 slender articulated rays ; the articulations only commencing near the extremities. The caudal fin contains about 20 rays in the upper, and 30 in the lower lobe. The former is strengthened by a ridge of elon- 47 2 BRITISH FOSSILS. gated scales, overlapping its base. Five or six of the upper fin rays are much stronger than the succeeding ones, and have no transverse articula- tions until near their extremities ; the remaining rays of the upper lobe, and all those composing the lower lobe, have very frequent articulations from the base to the extremity. The length of this specimen is 5} inches from the nose to the commencement of the caudal fin; the depth from the nape, 12inches. The length of the head from the nose to the posterior edge of the operculum, 2 inches. ARTICLE XI. PLATE IX. anv [X*. Oxygnathus ornatus.—The fortunate discovery of a most perfect example of this rare fish enables me to complete the description of those parts that are either mutilated or wanting in the specimen originally examined. The recent acquisition measures 11 inches from the snout to the fork of the tail, and 3 inches in depth between the nape and the dorsal fin. The position of the fish is such that all the fins of the left side are shown, and by a lucky upturning of the lower jaw, both rami, together with the hyoid and branchiostegous apparatus are displayed. The parts shown in this spe- cimen, which were deficient in the former one, are the dorsal and caudal fins. The more perfect condition of the anal fin renders some cor- rection requisite in the description formerly given of this organ. It is, in fact, not so small as I was led to suppose, but is in full proportion to the other locomotive organs. It commences anteriorly with a few graduated jointed rays, and not with the single fulcral rays frequently found in this position; these are succeeded by the principal rays, about 30 in number, which decrease in length rapidly as they recede towards the tail. The transverse articulations of the principal rays are frequent near the base of the fin, but occur at greater intervals on the more distant portion ; on the posterior rays they are also frequent, but uniform through- out. The dorsal fin is situated immediately above the interspace between the ventral and anal fins. It was furnished, like the anal fin, with a few soft slender rays on the anterior margin, The succeeding rays corre- spond also in size and character with those of the anal fin. In consequence of a slight mutilation of the hinder extremity of the fin, the exact number of the rays cannot be ascertained ; it was certainly not less than 30. The most remarkable and wholly unexpected character of this fish is pre- sented by the form and structure of the caudal fin. This organ is deeply cleft into two lobes ; the upper one measures 3} inches in length, the lower one only 24. The former has a scaly investment from the base to the extremity, below which issues a fringe of innumerable fine rays, with frequent transverse articulations and longitudinal bifurcations. The lower lobe contains about 24 rays; of these the strongest occupy the middle of the lobe, those of the upper and lower margins becoming gradually finer as they recede from the centre. The transverse joints are nearly equi- distant, but the intervals are greater than those on the dorsal and anal fins. It results from these peculiarities that this fin in Oxygnathus not 4 : 4 .f oy iq ’ 2 SUPPLEMENT TO DECADE VIII. 3 only simulates the tail of a true heterocerque fish, but carries the resem- blance to an extent only found in the most heterocerque genera. I question whether any one on seeing a drawing of this fin would hesitate a moment in pronouncing it a paleozoic form. The solution of this pro- blem depends upon a single point, viz., whether the rays constituting the upper lobe of the tail are all short rays, given off from the lower elements of the vertebral column, or whether any of them are continued under the scaly integument to the upper part of the column. The evidence the specimen affords is this: the centrum in the vertebre of this genus was ossified, a fact proved by the occurrence of several of these bodies, seen in the specimen, where the integuments have been removed. Being thus qualified to resist decomposition, while the softer parts perished, the course of the spinal column becomes evident by a slight elevation of the surface where the scaly integument rests upon it. In tracing its direction in the posterior part of this fish, it exhibits no tendency to mount into the upper lobe of the tail, as in the typical heterocerque fish, and, to a certain extent, in Ophiopsis, Eugnathus, and some other homocerque forms; but, on the contrary, it seems to terminate abruptly at the base of the tail. For this reason I am inclined to think that, without more conclusive evidence, it would be unwise to consider this an exception to the general rule, with reference to the fish of the lias, although the actual resemblance of this tail to that of a heterocerque is so striking as almost to warrant a contrary conclusion. ARTICLE XII. PLAate X. Pycnodus lassicus.—The opinion I ventured to express in the descrip- tion of this specimen, that the more shortened contour of the body as compared with the typical Pycnodus platessus ought not to exclude it from that genus, has been fully confirmed by the discovery of several new species of Pycnodus in the oolitic slates of the Bugey. Monsieur Thiolliere, in one of the most splendid works ever contributed to paleeon- tological literature,“ has described and figured, together with other new and interesting forms, five species of this genus. Of these two are more elongated than Pycnodus platessus, and of the three shorter species two, viz., Pycnodus Egertont and Pycnodus Bernardi, correspond in form with liassic species described in this Decade. There seems to be some doubt as to the locality from which the British Museum example of this fish was derived. In the course of last autumn I saw a second specimen of this species presented to the Worcester Museum by the Rev. W. Symonds, which was found in the lias of the neighbourhood of Tewkesbury. P. pe M. Grey Ecerton. April 16, 1855. * Descriptions des Poissons Fossiles provenont des Gisements corallines du Jura, dans le Bugey. ro) e , CBE ett hS aN LOPES MEMOIRS OF THE GEOLOGICAL SURVEY OF THE UNITED KINGDOM. Figures and Descriptions BRITISH ORGANIC REMAINS. —eeee DECADE IX. FUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY’S TREASURY. LONDON: PRINTED FOR HER MAJESTY’S STATIONERY OFFICE: PUBLISHED BY LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. 1858, y aha . LONDON : PRINTED BY EYRE AND SPOTTISWOODE, HER MAJES | | | ; Pass i * Bs na pe, yg ‘ pe i i : @ ae y q Ys . a * SS ee Bi ce tare yp Se ere SAR RR baa ens disetecetees ete Te Saat ph EE a ee Se NT eee ee Se Pn PREFACE. In issuing this Decade to the Public, justice requires that I should express the great obligations of this Establishment to Sir Philip de Malpas Grey Egerton, who had previously undertaken and completed two similar works at the request of my predecessor, Sir Henry T. De la Beche. The present Decade contains descriptions and figures of six new genera of Fossil Fishes, three of which had been named by Agassiz, but not described or figured. In these three Decades of Fossil Ichthyolites, Sir Philip Egerton has described nine new genera and thirty-five species ; and in call- ing attention to his valuable labours, I beg especially to notice the very skilful execution of the Plates by Mr. Dinkel, whose truthful delineations of detail, combined with artistic effect, cannot be surpassed in this branch of Paleeontography. RoDERICK I. MURCHISON, Director. Museum of Practical Geology, 16th November 1857. ie Vera ate Fee Pe OK Sra hi a PBR tet LUE + WES ‘ 4 Wo « + « : oa . f vA vt y , oh Ae ‘ by se ee ks = be eng A in Lg See wre ee BRITISH FOSSILS, Drcipe 1X, Prare i SS COSMOLEPIS, Gen. Nov. [Genus COSMOLEPIS. Acassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. Ist group, tail forked.) Body oval. Head small. Scales thick, small, numerous, and rhomboidal ; sculptured on their surfaces. Pectoral fins large ; ventral fins near the pectorals ; dorsal fin in advance of the median line, over the interspace between the ventral and anal fins ; anal fin extended; caudal fin large, springing from a broad pedicle.] Species Unica. Cosmolepis Egertoni. Acassiz, MS. Morris, Cat. Brit. Foss., 1854. In the generic characters here given, I have endeavoured to express those features which distinguish Cosmolepis from the several sauroid genera with which it has affinities in other respects. The form of the trunk corresponds with that of Pachycormus, the advanced position of the dorsal fin with Caturus, the extent of the anal fin with Sewropsis, and the character of the scales and caudal fin with Oxygnathus. It differs from Pachycormus and Caturus in having thick sculptured scales, in the form of the tail and in the proportions of the anal fin; from the former in the position of the dorsal fin. It differs from Sawropsis and Oxygnathus in the ereater depth of the trunk in relation to its length, and in the arrangement of the locomotive organs ; and from all in the forward position of the ventral fins. The genus was established by Professor Agassiz, immediately before his departure for America, from the examination of a single specimen belonging to Lord Enniskillen, and found in the lias quarries at Barrow-on-Soar. A second spe- eimen has been found since (now in my possession), which agrees in generic and specific details with the original. Description.—The anterior half of the head is deficient in both specimens; in other respects they are in a good state of preservation. The type specimen is selected for the general description, as being the most perfect, but some of the details are derived from the last found specimen. The form of the body is elliptic, the dorsal and iz, i, 9B a BRITISH FOSSILS. ventral lines forming graceful and symmetrical curves. The pedicle of the tail is sightly prolonged and gradually contracted, but not to so great an extent as in Pachycormus. The length of the body from the nape to the base of the upper caudal lobe measures one foot ; the greatest depth in front of the dorsal fin is four inches and three quarters ; the pedicle of the tail two inches; from the nape to the dorsal fin is five inches, and thence to the tail seven inches. From the pectoral to the ventral fins is three inches and a quarter; from thence to the anal fin, three inches and a half, and thence to the lower caudal lobe four inches. The pectoral fin is compused of about twenty-five rays, the first of which is much stronger than those behind it. The ventral fins are much dislocated ; the number of the constituent rays cannot therefore be ascertained. They appear to have been broad, and the rays were thick, flattened, and frequently subdivided transversely. The dorsal fin had a few slight fulcral scales at its base, but neither in this or the other fins is there any evidence of the first ray having a fringed margin. It contained not less than fifty rays, closely arranged, flattened, and composed of very numerous ossicles. The longest, forming the apex of the fin, measure two inches and a quarter in length; from the apex to the hinder margin of the fin the rays decrease rapidly in length, forming with the base line and anterior outline of the fin a nearly equilateral triangle. The rays of the anal fin are too numerous and indistinct to be accurately numbered. They correspond in character with the dorsal rays, but are shorter, and decrease in length more gradually towards the tail. The base of the fin measures two inches and three quarters, and it may be computed to have contained at least seventy rays. The caudal fin is broader and not so deeply cleft as that of Oxygnathus, but it corresponds with it in having the upper lobe invested with scales. So strongly marked is this character in both genera, that the doubts I have already expressed in the description of Oxygnathus as to the propriety of considering that a homocerque form, are much strengthened by the examination of Cosmolepis. The rays composing the caudal fin of Cosmolepis are far more numerous and frequently jointed than those of the corresponding organ of Oxygnathus. Those of the upper lobe decrease in length and substance as they approach the extremity, and are supported by the prolonged upper limb of the organ, features quite at variance with homocercal structure. There is no evidence in this genus of the prolongation of the vertebral column into the upper limb of the tail; on the contrary, there are symptoms of the abrupt termination of the ossified vertebrae at the fork; it BRITISH FOSSILS. 3 may be, however, that the embryonic character was persistent in the hinder extremity of the column, notwithstanding the ultimate development of its other parts. The scales of this fish are remark- able for their great number and the beauty of their sculpture. The dorso-ventral rows on the flanks contain nearly sixty scales in each. Those on the flanks in the vicinity of the line of the vertebral column (which was nearly straight and equidistant from the back and belly) are larger than the dorsal and ventral scales; but on the after part of the body they are all of uniform size. The under surface of each scale has a strong process on the upper margin, which corresponds with a pit on the lower margin of the scale above it; in addition to this, these margins are bevelled, so that additional strength is secured by the overlap of the juxtaposed scales in the dorso-ventral series. The external surface of each scale is orna- mented with five or six raised lines of enamel, some single, some bifurcate. These are most frequent on the scales of the anterior parts of the fish, but they are distinctly developed upon all. These dermal characters agree closely with those of Oxygnathus. The small portions of the jaws which remain show the bases of strong sauroid teeth ; the other parts of the head are deficient. Locality.—Lias of Barrow-on-Soar, Leicestershire. EXPLANATION OF PLATE. Fig. 1. Cosmolepis Egertoni, size of nature. Fig. 2. Tail of another specimen. Fig. 3. Outer surface of scales, magnified. Fig. 4. Inner surface of scale, magnified, P. pE M. Grey EGERTON. February 1857. Rc ae ro ‘<2 —. =I — \ = | jd \ \ art if | Ny er ! ry 18) \ L SN Ss. = a -\\ i ut “ a> \ lo ip De \ Pb. 2 ¢_cuen of Me lantted Samad. : = WW OUWS THRISSONOTUS COLEI Agasstx BRITISH FOSSILS. DECADE TX. PLATE: Uf. —— THRISSONOTUS. Gen. Noy. [THRISSONOTUS. Acassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. Ist Group, tail forked.) Body elongated ; dorsal fin opposite the interspace between the ventral and anal fins ; anal fin extended ; scales rhomboidal, small, ganoid. ] Thrissonotus Colei. Acassiz. Poiss. Foss. vol. 2, part 2, p. 128. The tapering head, gracefully elongated body, and well propor- tioned fins combine to render this the most elegant of the sauroid fishes of the liassic period. The specimen, which is unique, was discovered many years since, and is in the possession of Lord Enniskillen. The generic and specific appellations were given by Professor Agassiz, who alludes to this specimen in the following paragraph :—“ The genus Thrissonotus is in some degree inter- mediate between the genera Sauropsis and Thrissops. In general appearance it also resembles the Pachycormi, but it is decidedly a new type, for the dorsal fin is situated in the middle of the back, and yet it has the extended anal fin of a Thrissops.” With reference to these affiliations, I may remark, in corroboration of its generic distinction, that the body is more elongated than in the Pachy- cormi, the dorsal fin more distal, and the scales entirely dissimilar both from that genus and Thrissops. The extended anal fin re- sembles that of Sawropsis and Thrissops, but the dorsal fin is more advanced than in either of these genera, corresponding more nearly in this respect with the dorsal fin of the genus Oxygnathus. The scales have the nearest resemblance to those of the latter genus and Cosmolepis, but are devoid of the surface ornament common to those genera. : [1x. ii] 9¢ 2 BRITISH FOSSILS. Deservption.—Lord Enniskillen’s specimen, the only one hitherto found, measures ten inches in length. The parts anterior to the eye socket and behind the termination of the anal fin are deficient. The depth is nearly uniform from the nape to the anal fin, being about two inches and a half. Behind the anal fin, the depth is one inch and a half. From the gradual convergence anteriorly of the outlines of the head, it is probable that the muzzle was elongated, after the fashion of an Hugnathus or Sauropsis. The gape was large, and both jaws were furnished with numerous sharp conical teeth. The branchiostegous rays are flattened, and ap- parently not so numerous as those of Pachycormus. Twelve are distinguishable, of which the middle ones are the broadest. The opercular flap is crescentic in form, and extends some distance behind the line of union of the vertebral column with the occiput. The preoperculum is strong and prominent, and is invested with a thick coat of ganoine, plicated longitudinally. The surface orna- ment of the operculum and sub-operculum is finer and more granular in its arrangement, and does not conceal the lines of successive erowth running parallel to the free margin of the flap. The pec- toral fin is broken off at a short distance from the base. It con- tains about twenty-six rays; these, as far as they are preserved, are single, without transverse sutures. The rays of all the other fins correspond in being compressed and imbricate. The ventral fin has a few short anterior rays, and about twenty principal ones. They are so closely crowded together, that it is impossible to dis- tinguish the precise number. The rays of the dorsal fin are grace- fully curved backwards; they are in number about twenty-four. The transverse joints are at distant intervals. The anal fin is remarkable for its extension towards the tail; it measures one inch and three quarters along the base, and probably contains. between fifty and sixty rays. The squamation of Thrissonotus is very elegant, with regard both to the shape and beauty of the component parts, and the graceful arrangement of the dorso-ventral lines. The scales are all comparatively small, but vary much in relative size. The largest, as is generally the case, occur in the neighbourhood of the lateral line, and the smallest, on the abdominal region. The former are rhomboidal in form, the latter are long and narrow, resembling elongated parallelograms. The surface orna- ment is, for the most part, due to the permanence of the successive lines of growth; but, in the anterior part of the body, and especially in the vicinity of the nape, a few small vermicular pro- on P. pE M, Grey EGERTON. ass ayy Se Pi aE 2 Na Ay VO) a WW re Wa a = Ab ASM AS 1) UL 1 A Pe rT Ay Prearen wa CG» NODAL LY AY AG ass bao LcAGriaalit2 stssI NU Nao 2s PoC Y. G.O oR Mues BRITISH FOSSILS. DECADE IX. Pate III. PACHYCORMUS LATIPENNIS. [Genus PACHYCORMUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces, Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. 1st Group, tail forked.) Body deep ; vertebrae normal ; pectoral fins large; dorsal fin opposite the ventral fins; scales thin. | Pachycormus latipennis. Agassiz. Poiss. Foss. vol. 2. pt. 2. p. 114. In detailing the generic characters of his genus Pachycormus, Professor Agassiz remarks that the dorsal fin is situated opposite to the interspace between the ventral and anal fins. This is strictly the case in the genera Oxygnathus and Cosmolepis. In Sauropsis the dorsal fin is opposed to the anal fin. In Hugnathus the large dorsal is inserted opposite the ventral fins, and extends backwards as far as a point coincident with the commencement of the anal fin. In Caturus the dorsal fin is opposed to the ventral fins, and in Pachycormus its position is intermediate between that of the like fin in Caturus and Eugnathus. The first ray is imme- diately over the insertion of the ventral fins, and the after part of the fin stretches a short distance over the interspace between these fins and the anal fin. Of the predacious ganoid fishes of the Liassic period, the Pachycormz form an important group, well charac- terized by their short and deep form, and the delicacy of their scales, features which contrast powerfully with the lanceolate shape and solid scales of the associated Hugnatht. Professor Agassiz has only described four species in the “ Poissons Fossiles,’ but he notifies by name several other species as worthy of more detailed examination. Of these the subject I have selected for this article is one of the best characterized, although the specimens hitherto brought to light show only the anterior portion of the fish. Descrvption— Of three specimens under notice referable to this species, I select for description the only one seen by Professor Agassiz, and which is therefore the type of the species. It com- prises the head, a portion of the scapulocoracoid arch, the pectoral [TX. i1.] ; | 9D 2, BRITISH FOSSILS. ‘fin, and a confused mass of scales and vertebra. The form of the head varies much in this genus. At Whitby, where the species are more numerous than in any other of our British localities, we find a gradation from the small and pointed form of head of Pachy- cormus gracilis and acutirostris to the short and deep head which characterizes Pachycormus latirostris. Professor Agassiz considers the species under notice to be most nearly allied to the latter species, an approximation which is hardly borne out by a more strict comparison of the two than he was enabled to institute from the materials he had at his disposal. The head of Pachy- cormus latupennis is deeper and broader, and has the snout more blunt than in any other species. It measures four inches in length by two and a quarter in depth; the breadth across the frontal bones is one inch aud a quarter. The lower jaw measures two inches and a half in length from the symphisis to the articulating condyle. Jt is furnished with numerous conical, incurved teeth, varying in size, the largest being situated on the anterior portion of the jaw. The condyloid process is strong, and articulates with a very broad hypotympanic bone. The upper maxillary bone is more slender than the lower jaw; it is dentigerous, the teeth corresponding with those of the lower jaw opposed to them. The large laniary teeth of the latter probably reciprocated with similar teeth on the premaxillary bone and vomer. ‘The frontal bones are broad and very compact in structure. Their surface is covered with slightly elevated sinuous rugze interspersed with frequent minute punctures, the former prevaling on the posterior, and the latter on the anterior parts of the head. The opercular bones had a somewhat similar surface character, with the addition of a few distant granulations on the upper portion of the operculum. The coracoid bones are very strong, and coarsely plicated longitudinally. The ascending ramus forms nearly a right angle with the lower horizontal branch, this curvature being more abrupt than in other species of the genus. The pectoral fin is very broad, and its constituent rays are flattened as in the genus Sauropsis. It differs from the pectoral fin of Pachycormus latirostris, in being much shorter and less pointed at the extremity. It contains more than twenty rays. Of these the first is very strong, and single; the succeeding rays remain single for more than half their extent ; they then dichotomize, and show frequent transverse joints. In consequence of the great breadth of the constituent rays the surface of the fin when expanded was very large, a character happily seized upon by Professor Agassiz for the specific definition. The BRITISH FOSSILS. o vertebrae, as seen in another specimen, were osseous, the neura- _pophyses short and slender, and the interneural spines continued over the region anterior to the dorsal fin. In these respects the genus greatly resembles Catwrus, except that in the latter the vertebral appendages are more robust. ‘The scales are exceedingly thin and overlaid with a very delicate coat of enamel finely sculp- tured in concentric rings. The free margins were more or less curvilinear, resembling in this respect the scales of Caturus and Leptolepis. Locality—All the specimens of this species hitherto found are from the lias of Lyme Regis. EXPLANATION OF PLATE. Pachycormus latipennis, size of nature. , P. DE M. Grey EcGErton. February 1857. Uovlabg —|ZASSWOW SILOVGNG MMM ratte ae tr cl Torti SS Ti frit eer tic ————————— - = = ie BRITISH FOSSILS. DECADE IX. Puate IV. ENDACTIS. Gen. Nov. [Genus ENDACTIS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. 1st Group, tail forked.) Head small and pointed ; dorsal fin opposite the ventral fins ; anal fin approxi- mated to the ventral fins; base of the tail deep; scales minute, curvilinear, ornamented with raised surface markings. | Species Unica. Endactis Agassizi. The subject of the following description is the last fossil fish named by Professor Agassiz before his departure for the United States. 1 had incorporated it in my cabinet as a new species of Pachycormus, but his discriminating eye detected evidences of generic discrepancy which induced him to make it the type of a new genus, which he called Hndactis from the peculiar character of the scales. It certainly is very nearly allied to the Pachycorm in general figure, and in the arrangement of the fins; the most evident distinctions being the larger size of the dorsal fin, the greater thickness of the caudal pedicle and the surface ornament of the scales. It is, perhaps, hazardous to trust to characters so slight, and to the evidence of a single specimen, and that an imper- fect one for generic isolation; the more so when we find some of these characters variable and considered as of only specific value in the several species of Pachycormus with which we are acquainted. A very important element for deciding the ques- tion is unfortunately deficient, namely, the caudal fin. One of the most striking and constant peculiarities of the genus Pachy- cormus is a very large and deeply cleft caudal fin springing from a narrow pedicle, caused by the rapid contraction of the dimensions of the after part of the trunk. This contraction is much less rapid in Hndactis, as far as the specimen shows, and I am inclined for this reason to believe. that future discoveries will reveal a form of caudal fin which will substantiate this as a generic type. Should it prove otherwise, the genus must lapse, but there is no doubt Le ive] 9E vA BRITISH FOSSILS. whatever but that the species is distinct from all the Pachycormi hitherto discovered. Description.—The species of Pachycormus to which Endactis has the nearest resemblance is Pachycormus curtus, from the lias of Whitby. The figure given of this species in the “Poissons Fossiles ” represents a fish nine inches in length by three inches in depth. The specimen under description is also nine inches in length, but was probably an inch longer when perfect ; the depth is only two inches and three quarters. ‘The diameter of the caudal pedicle at a corresponding point in the two specimens is one inch in Pachycormus curtus and two inches in Lndactis. The dorsal fin in the latter is longer and the rays thicker, and the ventral and anal fins are more approximated. Compared with Pachy- cormus gracilis, the body is shorter and the head comparatively smaller. It has no resemblance to any species of Pachycormus found associated with it in the Lyme Regis beds. The bones of the head are much crushed, and the operculum is thrown upwards from its position; the latter disturbance makes the head appear larger than it is in reality. It is in fact small for the size of the fish. In form it approaches that of an isosceles triangle, the lines of the forehead and lower jaw being very slightly curved, the snout forming the apex of the figure. The mouth is large, the lower jaw measuring an inch and a half in length. The teeth are wanting. | The branchiostegous rays are numerous. Judging from what re- mains of the pectoral fin, it probably corresponded in size and structure with the analogous organ of Pachycormus. The dorsal fin is situated six inches from the snout, and is immediately over the insertions of the ventral fins. It contains at least twenty rays. Of these the four or five anterior ones are single, and increase consecutively in length. They are, however, true rays, carried upon interneural spines, and not fulcral scales. The principal fin rays are transversely jointed at rather distant intervals. The ventral fins are small and indistinct. The anal fin commences one inch and a half behind the attachment of the ventral fins. The interhzemal spines supporting the anterior rays of this fin are very strong. The fin rays are thicker than in any of the Pachycormi. The number cannot be discerned, but those that remain correspond in character with the dorsal fin rays. The scales are very numerous. In the neighbourhood of the scapular arch they are rhomboidal, with the posterior angles slightly rounded. In the afterpart of the fish they become curvilinear. They are invested with a thin layer of enamel, on the surface of which an elegant pattern is produced BRITISH FOSSILS. 3 by a series of fine diverging rays rising in relief and radiating outwards towards the posterior margin of each scale. A somewhat similar ornament is seen in some species of Hugnathus, but no instance has occurred of its presence in any species of Pachycormus. Profegsor Agassiz gave no specific name to this specimen; I there- fore dedicate it to him in grateful remembrance of the last of the many happy days it was my good fortune to enjoy in his society. Locality.—Lias of Lyme Regis, Dorset. EXPLANATION OF PLATE. Fig. 1. Endaetis Agassizi, size of nature. Figs. 2 and 3. Scales magnified, outer view. P. DE M. Grey EGERTON. February 1857. WOELTO AGIOS SC, OY ehh a ra tren Pitwrtsit FOSSILS. DECADE IX. PLATE V. CENTROLEPIS. Gen. Nov. [Genus CENTROLEPIS (kev7poy, calcar ; Aems, squama). Ecrertron. (Sub-kingdom Vertebrata. Class Pisces. . Order Goniolepidoti. Family Sauroidei. Sub-family Sau- roidei homocerci.) Head large ; teeth conical ; body short ; pectoral and anal fins very broad ; scales rhomboidal, rugose, with strong spurs on the posterior margin. | Specius Unica. Centrolepis asper. Poiss. Foss. vol. 2. p. 304. Walking, many years ago, with Lord Enniskillen, on the beach under Black Ven, to the eastward of Lyme Regis, we met a well- known character, by name Jonas, who had just split open a lias nodule which contained a fossil fish, The specimen changed owner- ship for a few shillings, and from that day I have in vain searched for another fragment to elucidate the affinities of this most singular fish, The family to which it appertained was for some years doubtful. Professor Agassiz, who examined it more than once, was inclined to refer it to the Lepidoidei. More recently, by delicate manipulation, the form of the jaws and characters of the teeth have been discovered, and they unquestionably betoken its affinity to the Sauroidei. Description.—The distorted position of the fish, and the deficiency of the dorsal portion, render the restoration of the actual proportions a matter of conjecture. The head is large, and the mouth especially so; the body short, and the pectoral and anal fins unusually broad. It is fair to presume, from these features, that the depth of the fish was considerable, and the dorsal fin large. By restoring the head to its natural position, the length of the fish from the nose to the base of the tail is ascertained to be seven inches. Of this dimen- sion the head occupies nearly three inches. The cranial bones are dense, and are ornamented externally with a raised pattern, varying from a granular to a ridge and furrow figure. On the opercular flap the pattern is less prominent, and is associated with what appear to be lines of successive growth, corresponding with the existing outlines of the constituent plates. The mouth measures two inches in length. The teeth are numerous, sharp, and conical ; the intervals between the larger ones being beset with smaller ones. No fish of the Lepidoid family has the dental apparatus similarly Lixs Val OE De BRITISH FOSSILS. constituted. The pectoral fins are composed of numerous broad flattened rays. They have frequent transverse joints, and are re- markable for having their surface invested with a corrugated layer of ganoine, corresponding in character with that covering the head bones and scales. This character is common to all the fins. The only similar instance I am acquainted with occurs in the genus Platysomus. The first pectoral ray is fringed with scales on its anterior border. The position of the ventral fins is seen about midway between the pectoral and anal fins; the fins themselves are defective. The space between the pectorals and the anal is so confined that the ventral fins were probably of small dimensions. The anal fin is very large, and the rays composing it unusually long. The first ray has fulcral scales and a fringed margin ; the subsequent rays are flattened, expanded, and transversely jointed | at short intervals; in number they cannot have been fewer than thirty. A few rays of each lobe of the tail are preserved ; the multiplication of the transverse articulations is the most striking peculiarity they present. A single broad scale occurs at the base of the lower caudal lobe, but beyond this no fuleral scales seem to have existed in this region. The scales are unlike any I have elsewhere met with; they are rhomboidal, of medium size, and extremely solid. The exposed surface is covered with coarse ruge, arranged, not, as is commonly the case, in the longitudinal direction, from the anterior to the posterior margin of the scales, but trans- — versely. The free edges of the scales are armed with strong spurs. On the under surface the scales are smooth, and destitute of the midrib so common in the generality of the Sauroid genera. The substance of the scales is so thick that the strong articulating pro- cesses of the upper margins are formed out of the uniform thickness of the scales themselves, the extra material provided by the midrib not being requisite. Iam not without hopes that the publicity given to what is already known respecting this genus may be the means of bringing to light other specimens, to complete the anato- mical details of this most interesting form. Locality.—Lias of Lyme Regis. EXPLANATION OF PLATE. Fig. 1. Centrolepis asper, size of nature. Fig. 2. Scales, magnified. Fig. 3. Caudal scale, magnified. P. DE M. Grey EGERTON. February 1857. y Oewlogua | Sat \y all) Vas thy \ Yaby b 3 : y a ILO) ACEO) Ss) c ( Oolitie CT , a> NOTHOSOMUS OCTOSTYCHIUS.. Agassryz ad jose Ei fea y , Cet ALK on! ~~ ts 4 j F ; - — Ws 7 ‘he ‘ ty e iS poem te : F ee ee ee ee ee PrRiTisHh FOSsi1s. DecADE IX. Puate VI. ———— NOTHOSOMUS. GEN. Nov. [Genus NOTHOSOMUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerci. 2nd Group, body elongated, more or less fusiform.) Fins small, with fulcra on the first rays. Caudal fin forked. Scales smooth; four rows of broad scales on the flanks. ] Yothosomus octostychius. Acassiz. Poiss. Foss. vol. 2, page 292. The genus Nothosomus is notified in the “ Recherches sur les Poissons Fossiles” of Agassiz in the following terms :—“ After the genus Ophiopsis must be placed a new generic type, which I have distinguished by the name Nothosomus, and which is characterized by a long dorsal fin and scales higher than broad.” The specimen from which the genus was established was found in the Lias at Street, and presented to me by Mr. Hawkins. It only shows the posterior half of the fish, but as it is the ‘type of the genus, and so far as | am aware the only example of it which has yet been found, it is worthy of being described, the more so that in consequence of the brief notice of Professor Agassiz, it has been quoted by other authors, and is included in all the catalogues of liassic fossils. - Description.—The specimen is broken off immediately in front of the dorsal fin, and the anterior portion is wanting. What remains is, however, in a good state of preservation, and exhibits the dorsal, ventral, anal, and caudal fins, together with the scales of the right flank seen from within. A few impressions of the outer surface of the scales are seen in the anterior part of the specimen. The dorsal fin is situated a little in advance of a perpendicular line extended from the attachment of the ventral fins; the anal fin is inserted about midway between the ventrals and the base of the tail. The interspace between the first ray of the dorsal fin and the upper lobe of the caudal fin measures two inches and a half, and from the ventral fin to the lower lobe of the tail two inches and one tenth. The depth of the trunk from the dorsal fin to the ventral fins is one inch and three quarters; from this point to the spring of the caudal fin, where the diameter is half an inch, the contraction is very regular. In these details Nothosomus bears [Ix, vi. ] 9G 2 BRITISH FOSSILS. a close resemblance to Pholidophorus, and should the positions of the fins in relation to the anterior parts correspond, the general form of the fish would come very near that of one of the shorter and deeper species of that genus. There is also an approximation in the character and mechanism of the scales, and I am therefore inclined to place the genus next to Pholidophorus, rather than after Ophiopsis, as suggested by Professor Agassiz. The locomotive. organs differ essentially from both these genera. In advance of the dorsal fin are five strong fulcral scales, and the first true fin ray has a fringe of short spines along the anterior border. The true rays are six or seven in number, curving backward from their insertions. They are stronger than the fin rays of Pholidophorus, and differ also in having the transverse articulations more numerous, and continued nearly to the base of the component rays. The distal extremities are finely fimbriated. The ventral fin contains six rays, more slender than those of the dorsal fin. “Ehe anterior one is similarly fringed. The anal fin is composed of twelve rays at least, but they are inserted so closely together, that the exact number cannot be ascertained. The anterior ray is bordered in unison with the corresponding member of the dorsal and ventral fins. The component rays are extremely slender and delicately fimbriated in their distal parts. All the fins, although small with reference to the size of the fish, are comparatively larger than the corresponding organs of Pholidophorus ; they differ also materially in having bordered margins, and being transversely sub-~ divided to a much greater extent. The caudal fin is deeply forked. The upper lobe contains sixteen rays; the lower one is composed of a like number. Both upper and lower margins are fringed, and a few strong fulcral scales occur at the base of each. The body scales extend rather further on the upper lobe than on the lower. The styles supporting the rays are short and slender, and of equal length in each lobe ; in the tail of Pholidophorus, the styles of the upper lobe are very considerably longer than those of the lower lobe. The fin rays are stronger in the upper lobe than in the lower. The transverse articulations occur at shorter intervals than in the tail rays of Pholidophorus ; in the lower lobe the divisions of the ossi- cles are so nearly coincident that they form continuous elevated lines sweeping across the fin, while in Pholidophorus and the ‘allied genera, the articulations of one ray generally impinge between the articulations of the adjoining ray. The result of this arrange- ment, combined with the frequency of the sub-divisions of the rays of this and the other fins, would be to afford a greater amount of en a ui oi t: P A: ab ee BRITISH FOSSILS. 3 lateral flexure in the organs of locomotion in Nothosomus, while ’ the necessary support was provided for by the fulcral scales and strengthened borders of the anterior rays. The dorso-ventral series contain eight scales, slightly inclined backwards. The mucous duct pierces the third row from below, this being the position of the largest scales; the row next below it being the next also in size. These and the two rows above the lateral line are considerably larger than those above and below, until near the region of the tail, where all the scales are nearly uniform in size. The scales are thick, compact, and highly lustrous. The outer surface is smooth, and the free margins entire. The inner surface is provided with a broad perpendicular band, occupying the centre of the scales on the flanks, but extending over the entire inner area of the caudal scales. Each band terminates above in a strong pointed process, which locks into a corresponding depression on the lower margin of the scale next above it. Receding towards the tail, these processes become gradually more and more obtuse, until they disappear altogether, and the few most distal scales are united by apposition of the broad margins of the bands. In Pholidophorus and the allied genera the scales covering the centre of the flanks are commonly larger than those on the upper and lower margins of the body; but there is always a more or less graduated passage from the one form to the other, by the interposition of scales of intermediate dimensions, even in Pholidophorus pachysomus, where the extremes are most exaggerated. The details above given show that in Nothosomus, the flanks are protected by four rows of large scutiform scales, suc- ceeded above and below by small scales, the transition from the one form to the other being abrupt. In this respect Nothosomus has some resemblance to the sauroid genera Aspidorhynchus and Belonostomus, but in all other respects it appears to be a legitimate member of the Lepidoid family. Locality.—The Lias of Street, Gloucestershire. EXPLANATION OF PLATE. Fig. 1. Nothosomus octostychius, size of nature. Fig. 2. Dorsal fin, magnified. Fig. 3. Ventral fin, magnified. Fig. 4. Anal fin, magnified. Fig. 5. Caudal fin, magnified. Fig. 6. Tail of Pholidophorus, magnified. P. DE M. Grey EGERTON. February 1857. i “ wv 1 x ee ve) peyubou gD SIIWIS © 8 Cassoby -SAWISSIAAVT SLTOHAOUN ANd uoyabT SNANVOISSYAD SITOHdOUNAld Z unsere STANWOLONO1 GTAOlon Game <7 undleby “SINANILIN SITOHdDONN ANd | Palen rt HOPPE ante aa so 5S vOndOuma Vee 2 Ors Vieng eee — > —— 7 “ ur.ep ofthe Varied 2 ination J PIG OIRO? Oolt 1 PLEUROPHOLIS ATTENUATUS. KAgerton PLEUROPHIIOLIS LONGICAUDUS Egertun 2. PLEUROPHOLIS RASSICAUDUS. Agerton 5.6.7 PLEUROPHOLIS SERRATUS Egertor 3. PLEUROPHOLIS LAEVISSIMUS. Agassrz 6 SCALES @4 magnified : SON I A MT Se Rr vig Pe mS as 14 Ki ie 4 eo ay B E i ay Be the » OR ig M BRITISH FOSSILS DecaDE IX. Puate VII. Fig. 1. — a a PLEUROPHOLIS. Gen. Nov. _ [Genus PLEUROPHOLIS. sAcupa, the side ; podus,ascute. EGerron. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerci. 2nd Group, body elongated, more or less fusiform.) Caudal fin forked ; dorsal fin’opposite the anal fin ; anal fin eeeate® head small; body slender ; scales of the flanks arranged in a single series. ] Pleuropholis attenuatus. Morris. Cat. Brit. Foss., 1854. I propose the generic designation Plewropholis for a small group of fishes of diminutive size and limited geological range, but pos- sessing characters singularly well defined and very distinct from those of any genus,of fossil fishes hitherto described. In the form of the head, the position of the mouth, and general outline of the body, they somewhat resemble a small Thrissops or Leptolepis. The arrangement of the fins also corresponds to some extent with that of those organs in the former genus. The characters of the tail resemble those of Ophiopsis. The dermal peculiarities, however, are so remarkable that they forbid the association of Plewropholis with any known genus. If we except the isolated family of the Acan- thoder, the multiplication of the scales in the dorso-ventral series is greatest in the genera Pachycormus, Endactis, and Cosmolepis. In the latter we find not less than sixty scales in each series on the anterior and middle regions of the trunk. In Nothosomus the number is reduced to eight, and in the sauroid genus Aspidorhyn- chus the flanks are protected by large scutes, the dorso-ventral series being completed above and below by a few scales of much smaller dimensions. These characters are subject to occasional variations in the latter genus, and the single scutes are sometimes replaced by two or three scales. In Pleuropholis the dorso-ventral series are also composed of a single row of scutes, completed above and below by a few small scales, the latter being more numerous in the caudal region. In this respect it resembles the cretaceous genus Priono- [IX. vii. ] | 9H TE Fee Se meres sea Se) Po Te 7 ; 3 Ce oo ee ae , : ; 2 BRITISH FOSSILS. lepis. I am cognizant of several species, probably referable to this genus, all of which will be noticed in the sequel. Description.—The beautiful little fish which I have selected as the type of the genus was found by Mr. Bristow in the Middle Purbeck beds at Apsel Lane, north of Sutton Mandeville. It measures two inches in length from the nose to the extremity of the tail, by three-tenths of an inch in depth. The latter measure- ment is taken at a point midway between the pectoral and anal fins, from which point the body tapers symmetrically to the tail. The head measures four-tenths of an inch in length. The mouth is small and opens upwards, as in Thrissops and Leptolepis. The relative size and position of the orbit correspond also with these genera. The opercular bones are of moderate size and smooth exterior. The rays of the pectoral fin are strong in relation to the size of the fish. Their number cannot be ascertained. The ventral — fins are small, and situated midway between the pectoral and anal fins. The dorsal fin commences at a point two-thirds of the dis- tance from the nose to the fork of the tail. It contains ten delicate rays, single for half their length, and then bifurcated and trans- versely articulated. They are preceded by a few elongated fulcral scales. The anal fin is opposed to the dorsal fin. It contains twelve rays, rather distant from each other. They correspond in character with those of the dorsal fin. The anterior ray is bordered, a character probably also common to the dorsal fin. The caudal fin is deeply cleft. The upper lobe is invested with scales at its base, and contains nine principal rays, closely set at their insertion. The lower lobe, is also composed of nine rays, more distant from each other than those of the upper lobe. All the rays have frequent transverse joints, more numerous on the lower than the upper lobe. The borders of both are fringed with fine elongated fuleral scales. The scales are smooth. Those on the back, belly, and tail are small and lozenge-shaped. The remainder of the body is covered with a single row of high, narrow scutes, inclining backwards and downwards in slightly sigmoid curves; each scale has a broad elevated band extending from the apex to the base of the inner surface (fig.9). It is broader above than below, and terminates upwards in a short process, which connects it with the scale next above it in the series. Locality.—tThis, the only specimen I have seen of Pleuropholis attenuatus, was found by Mr. Bristow in the Middle Purbeck beds at Apsel Lane, north of Sutton Mandeville. Shes ee ee CP eh a ee A Se BRITISH FOSSILS. 3 Piate VII. Fig. 2. PLEUROPHOLIS CRASSICAUDUS. Sp. Nov. The specimen figured on the same plate with the above, No. 2, was found some years ago by Mr. W. Brodie in the bed known in the Durdlestone Bay section as the Insect Bed. It is now the property of the Rev. P. B. Brodie, of Rowington. It agrees with the genus Plewropholis in the large size of the lateral scales, and in the extent and position of the anal fin; but differs from the species last described in the more massive proportions of the hinder part of _the body, and in the characters of the caudal fin. The specimen measures one inch and three quarters from the nose to the base of the tail, and is three-tenths of an inch in depth. The latter mea- surement falls short of the actual dimensions of the fish, as the dorsal and ventral portions are wanting, and the larger scales alone remain. ‘The head agrees for the most part with that of Pleuro- pholis attenuwatus. The operculum is, perhaps, relatively larger, and the ganoid external layer thicker, characters which are re- peated in the squamation. ‘The scales comprised in the principal series are broader, thicker, and straighter, those in the vicinity of the tail are longer and more irregular in form. The position of the anal fin is discernible, but its characters are indistinct. The caudal fin has some strong fulcral scales on its lower margin, and appears to have been much stronger and less furcate than in the other species. A small fish discovered by the late Count Miinster - in the quarries of lithographic stone at Kelheim has a very close resemblance to this species, but the scales are more delicate and greatly more numerous. The tail is more like that organ in Plewropholis attenuatus. A figure of this species is given on the Plate, No. 3. Professor Agassiz originally named it Pholido- phorus levissimus ; he subsequently removed it to his new genus Nothosomus ;* but it must now be considered a Plewropholis. — Locality.—Plewropholis crassicaudus is from the Insect bed of the Purbeck strata in Durdlestone Bay, No. 106 of Mr. Austen’s table.+ Pirate VII. Fig. 4. PLEUROPHOLIS LONGICAUDUS. Sp. Nov. When engaged in examining materials for describing the several species of fossil fishes from the Purbeck strata published in the Eighth Decade of the Memoirs of the Geological Survey, I found | * Poiss. Foss., vol. 2, p. 288. J Guide to the Geology of the Isle of Purbeck, by the Rev. J. H. Austen, page 17. 4, BRITISH FOSSILS. two specimens in the Museum in Jermyn Street, which, although very imperfect, gave evidence of another species of the genus Plewro- pholis. I have recently received from the Rev. John Austen (whose abours in the Purbeck beds are well known to geologists) three ad- ditional specimens of a species of Plewropholis apparently different from that indicated by the specimens in Jermyn Street. Of these, one, and that the most perfect, belongs to Mr. W. Brodie, of Swanage, and was found by him in the bed numbered 69 in Mr. Austen’s table of the Purbeck strata; a less perfect specimen of a larger individual of the same species was furnished by Mr. Lister, of Langton Purbeck, and the third, asmaller one, is from Mr. Austen’s private coliection. As the specimens in the Jermyn Street Museum are not sufficiently perfect for detailed description, 1 may here briefly state that my reason for considering them specifically dis- tinct from the subjects of this and the foregoing description rests upon the character of the large scales covering the flanks of the fish, which, in these specimens, are distinctly serrated on the posterior margin. Mr. Brodie’s specimen, of which a figure is given in the plate, measures three inches and three tenths from the nose to the ex- tremity of the tail; the head and tail each measure seven tenths of an inch, and the greatest depth of the body is six tenths. These comparative dimensions attest the slender proportions of the fish, and, combined with the small size of the head and the large size of the tail, give evidence of its having been a swift and agile swimmer. The head is narrow, and somewhat pointed at the muzzle, the gape small, and with no traces of teeth discernible. In these respects, and in the relative proportions of its constituent members, it re-, sembles the corresponding parts in the genus Leptolepis. The pectoral fins contain at least a dozen rays; the anterior one is armed with a border of long sharp spines; the succeeding three or four rays are very strong; all these have the transverse articu- lations rather distant. The remainder of the fin is composed of smaller bones, not very distinctly preserved. The ventral fins are small, and situated halfway between the snout and the extremity of the tail fin. The anal fin, commencing a little behind the ventral | fins, extended almost to the insertion of the caudal fin. The number of rays constituting this organ cannot be ascertained from any of the specimens. The dorsal fin is small in this species, and situated immediately above the anal fin, a position for this fin very unusual in the members of the Lepidoid family, and very characteristic of the genus Plewropholis. ‘The base of the upper BRITISH FOSSILS. 5 lobe of the caudal fin is covered by an oblique prolongation of the scales of the tail. The upper margin of the fin is roofed with a series of elongated, imbricated scales, similar to those seen in the genus Ophiopsis, and common to most of the heterocerque fishes. The rays composing the fin are from twenty to thirty in number, and are long and powerful for the size of the fish. The pedicle of the tail is narrow, allowing great latitude of motion to the pro- pelling organ. The general arrangement of the large scutiform scales investing the flanks of the fish corresponds with that described in the foregoing memoir; and is, in fact, a generic rather than a specific character. The scales on the back and belly are small and lozenge-shaped ; these are connected, above and below, with the prin- cipal longitudinal series of high and narrow scutiform scales covering the parietes of the thorax and abdomen. Beyond the hinder part of the dorsal fin, the smaller scales encroach more and more on the principal series, and the latter diminish in altitude, until, in the proximity of the tail, all the scales are nearly uniform in size. The outlines of the scales in the principal series are waved in double curvatures, representing a series of parallel sigmoid lines of very graceful appearance, the curves becoming gradually less, until, in the caudal region, the scales are nearly rectilinear. A!!! the scales are invested, on the outer surface, with a thick and shining coat of ganoine, without sculpture, and unbroken at the posterior margin. The under surfaces have broad, slightly elevated bands, occupying the median area of each scale (fig. 9). The connexion with the lozenge-shaped scales of the back and belly is provided for by a small process at the upper and a slight depression at the lower extremities of these bands. Locality.—The specimen belonging to Mr. Lister is from near the bottom of the Downs vein of the Purbeck section, which, as I am informed by Mr. Austen, corresponds with the bed No. 69 in his tabular arrangement. Mr. Brodie’s specimen is from the same region of the section, and Mr. Austen’s is from a thin shale sub- ordinate to bed 48 of his economic table, which corresponds with No. 69 of the Durdlestone Bay section. PLEUROPHOLIS SERRATUS. Sp. Nov. PuaTE VII. Fig. 5—49. I have recently ascertained that the specimens in the Museum of Practical Geology indicating another species of Plewropholis, to which I alluded in the description of Plewropholis longicaudus, 6 BRITISH FOSSILS. were derived from the Purbeck strata at Hartwell, near Aylesbury. Through the kindness of Dr. Lee, who has obtained a large number of specimens from the same locality, and who most liberally for- warded them to London for my inspection, Iam enabled to com- plete the characters of a fifth species of this genus, which I have named Plewropholis serratus. The specimens are for the most part so fragmentary that I have found it necessary to compile the specific characters from the examination of several individuals. The most perfect specimen (the only one indeed which conveys the form of the fish) is represented in the accompanying Plate, Fig. 5. The head and tail are both imperfect, and the body is a mere impression, the counterpart of which has, unfortunately, not been preserved. This Pleuropholis resembles the other members of the genus in the arrangement of the scales and the disposition of the natatory organs. It differs in its more massive proportions, and in having the posterior edges of the scales serrated. The body is short and deep, compared with the other species resembling in general outline the Pholidophort. The dorsal line is nearly straight, the ventral line rounded. The head as seen in the specimen figured No. 7 is small. The mouth opens upwards, and appears to be edentulous. In this character, and in the position of the orbits and form of the opercular fiap, it is so like the heaa of a Leptolepis, that apart from other evi- dence it might be plausibly assigned to that genus. The pectoral fins seen in the same specimen are of small size, containing about ten rays. The ventral fins are deficient in all the specimens ; the point of attachment, however, of these organs is seen, in Fig. 5 to have been nearly medial. The dorsal and anal fins, as in the other species of the genus, are opposite to each other, and very similar in form and size. The base of the tail is broad, and the scales do not extend so far on the upper lobe as in Pleuropholis attenuatus and longi- caudus. The dorso-ventral series of scales are about forty in number ; of these the first thirty are composed of large scutes, with a few small lozenge-shaped scales above and below. In the ten posterior rows, the scales are more uniform in size. The most appreciable distinctive character of this species is found in the serrated margin of the scales. This is more or less seen in all the specimens I have examined, but generally in the impression of the scales; the scales themselves being in so brittle a condition that they are never well preserved. The specimen I have selected to show the dermal characters is figured No. 6. on the plate. Figs. 8 and 9, show the outer surface of the scale a, and the inner surface of the scale b, enlarged. ee ee ee ee eo ae oe SS ee ee ee ee ee ee ane — Sa ee. FOSSILS. ie Beta th EXPLANATION OF PLATE. srophohs attenuatus, magnified. erassicaudus, size of nature. , Pee ps size of nature. . ae a, A ). Seale b, magnified. BES ORTH? . | - P,. pe M. Grey EGERTON. ; fe att $e Uuoza0"| —~"\NOWVA SNUYNTVOAN * ; Si " ‘ =) ; . KS “3 % mie a . a eB Mice mari = ' Ta +! 3 whe Rin ath : Baan Hi . Nee a ty \ { OE a Fags aes | Liege P AM c 7 \ ' 4 ry ean 1 BeLLEISH. POSSILS. DrcaDE IX. Puate VIII. ee MEGALURUS DAMONI. fGenus MEGALURUS. Acassiz. (Sub-kingdom Vertebrata. Class Pisces, Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. 2nd Group, tail more or less rounded.) Caudal fin very large and rounded; dorsal fin opposed to the interspace between the ventral and anal fins; head large; jaws furnished with large conical teeth, intermixed with smaller ones. Vertebral centres ossified. ] Megalurus Damoni, Se. Nov. This remarkable genus is placed by Professor Agassiz in a small group at the end of the Sauroid family, comprising in addition one fossil genus Macrosemius, and the recent genera Lepidosteus and Polypterus. The characters common to these four genera are the upward tendency of the termination of the vertebral column, and the rounded form of the caudal fin. In other respects they differ widely from each other. M. Pictet, laying greater stress upon the dermal peculiarities, has proposed a new order, “les ganoides eycliferes,” for the reception of the fossil ganoids having rounded, imbricated scales. He divides this order into four families; the first comprises the recent Amia, and the fossil genera Notewus and Cyclurus ; the second, “les Leptolepides,” the genera Leptolepis, Tharsis, Thrissops, Megalurus, Oligopleurus, and Coccolepis ; the third and fourth, “les Celacanthes” and “les Holoptychides,” embrace the Ceelacanthoid family of Agassiz. This is not the place to discuss at length the validity of the proposed new arrangement. The objections to it are manifold, and until some more satisfactory solution of the admitted incongruities of the old system is pro- pounded the lesser evil will be to abide by the latter, rather than in- troduce new elements of discord of greater magnitude than those complained of. The ordinal titles proposed by M. Pictet involve a contradiction, for he associates together as “ Ganoides cycliféres ” several genera, some having and some devoid of the true ganoid character of the scales. Again, in his second order, “les Ganoides rhombiféres,’ he includes Pachycormus and Caturus, genera in which the rhomboid form of scale becomes nearly obsolete, and the [IX. vill. | ae 2 BRITISH FOSSILS. curvilinear character begins to be appreciable. The reasons adduced in favour of the new scheme, from the teeth and other structural details, are still more untenable than those derived from the dermal characters ; but the subject is too large to be further pursued in this article. The genus Megalurus is unquestionably a member of the Ganoid order as defined by Agassiz, the scales being invested with a coat of enamel, which, although thin, is unmistakeable. I have ascertained that the scales of Leptolepis are similarly coated, a fact which is disputed by M. Pictet, and other continental ichthyologists. The large teeth of Megalurus designate its position as a genus of the Sauroid family. The structure of the vertebral column and its appendages, with the exception of the caudal portion, resembles that of the corresponding parts in Caturus. | The distal extremity of the column and the caudal fin are most like those parts in Macrosemius and Lepidosteus, with some affinities to the Celacanthoid family, more especially to- the genus Undina of Count Munster. The genus Oligopleurus of Mr. Thiolliére appears to be intermediate in character between Caturus and Mega- lwrus, and affords an easy transition from the one to the other. Description.—All the species of this genus hitherto described are from continental localities, their stratigraphical position being limited to the upper region of the Oolitic system. The subject of this article was discovered last year by Mr. Damon in the vicinity of Weymouth. It is intermediate in size between Megalurus lepi- dotus and Megalurus elongatus of Agassiz; it differs from the former in having the head comparatively shorter, the body more slender, and the scales more elongated ; and from the latter in being a shorter and deeper fish. The specimen measures six inches from the nose to the extremity of the vertebral column, by one inch and a half in depth from the dorsal to the ventral fins. The body diminishes very slightly to the tail, the smallest diameter being one inch and one tenth. The head is one inch and seven-tenths in length, by one inch and two-tenths in depth. The scapulocoracoid bones are strong and smooth, having a thick prominent rip on the inner anterior margin. The vertebral column traverses the centre of the body. It is straight until it nearly reaches the tail, where it has an upward curvature. It contains about fifty bi- concave vertebree. The apophyses are short for the proximal two thirds of the column, but in the distal third they increase consecu- tively in length to the base of the caudal fin, and thence decrease towards the extremity of the column. The pectoral and ventral fins are small and indistinct. The first ray of the dorsal fin is imme- Pre te et ak BRITISH FOSSILS. 3 diately over the attachment of the ventral fins. The middle of the fin is coincident with the centre of the dorsal line. It is supported upon seventeen strong interneural spines, and contains a like number of rays. These are entire for some distance from the base; they then bifurcate, and are transversely jointed at small intervals. The anal fin is situated nearer to the ventrals than to the lower lobe of the caudal fin. It is attached to eight ossicles, and is composed of as any rays, agreeing in all respects with those of the dorsal fin, except in being shorter and more slender. There are traces of border scales on the first rays of both. The caudal fin is broad and rounded posteriorly. In form it resembles the tail of the recent Lepidosteus. A few fin rays, constituting the upper lobe, spring from the neurapophyses of the sixth, seventh, and eighth vertebre, reckoning from the caudal extremity of the column. These are single, without bifurcations or transverse joints; the remainder, about twenty in number, are supported by the flattened extremities of the elongated heemapophyses. They are coarse, with three or four bifurcations and frequent joints. The fin is completed below by a few single rays springing from the hemapophysis of the fifteenth vertebra. This is the longest of these processes ; those behind it decrease in gradation to the extremity of the column. The scales are large, and rounded posteriorly ; they differ from the scales of Megalurus lepidotus in having the longitudinal diameter greater than the transverse. They are thick, and of a coarse texture, and are covered exteriorly with a thin coat of enamel, ornamented with fine concentric rings. They have no rib or articulating process on the inner surface. In this respect, and in their imbricated arrangement, they very much resemble the scales of a Colacanthus. This very interesting addition to our list of British fossil fishes I have designated by the specific name of Megalurus Damon. Locality—Found by Mr. Damon in the Purbeck strata at Bin- ombe, about three miles north of Weymouth. EXPLANATION OF PLATE. Fig. 1, Megalurus Damoni, size of nature. Fig. 2. Counterpart of do., size of nature. Fig. 3. Scale, magnified. P. DE M. Grey EGERTON. February 1857 Uuoj4IUT “\NALSMV SNUNIVDIAW c STATS Ie POOL NG Elen Phitisi POSsiLs. DECADE [Xe PLATE. EX. ee MEGALURUS AUSTEN] [Genus MEGALURUS. Aaassiz. Sub-kingdom Verebrata. Class Pisces. Order Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. 2nd Group; tail more or less rounded.) Caudal fin very large and rounded ; dorsal fin opposed to the interspace between the ventral and anal fins ; head large ; jaws furnished with large conical teeth, intermixed with smaller ones ; vertebral centres ossified. | Megalurus Austent. Sp. Nov. Description.—The discovery of the very perfect specimen de- scribed in the preceding article has furnished the clue to the true nature of a group of icthyolites not uncommonly occurring in the quarries of Purbeck stone at Swanage, but for the most part ™m a very fragmentary condition. Many of these specimens have come under my notice from the collections of Mr. Austen and others, who have turned their attention to the Purbeck fossils; but I have hitherto failed to recognize them as belonging to the rare genus Megalurus of Agassiz. The parts most commonly preserved are the vertebral column and some of its spinous appendages, and such specimens have generally been considered as belonging to the Lepidotus minor, so common in the Swanage quarries. Last year I obtained a specimen, more perfect than any I had before seen, of this fish, but as the tail, so characteristic of the genus was deficient, I passed it over without a detailed examination, in the hopes that more satisfactory evidence of its generic affinity might be brought to light. While examining the specimen described in the last article, and comparing it with other specimens, I became aware of the affinity between it and the Swanage specimens, a result which subsequent investigation proved to be correct as to general relation- ship, the species, however, being distinct. The portion of the fish preserved in the specimen comprises about two-thirds of the entire length, the hinder third being deficient. The pectoral, ventral, and dorsal fins are seen in situ, but the anal fin is wanting. The fish, when entire, would probably measure ten or eleven inches in fis, dx} 9K 2 3 BRITISH FOSSILS. length. The greatest depth is two inches and a half. The head is proportionately smaller than in the other species of Megalurus, and the posterior edge of the opercular flap more angular. The dorsal line is nearly straight, while the abdominal line has a con- siderable downward curvature. These lines are nearly parallel in Megaturus Damon, and in Megalurus lepidotus the dorsal line is more curved than the abdominal line. Thirty-five vertebree are preserved, of strong osseous texture. The length of each is rather greater than the diameter. The peripheral pits are deep and strongly marked, but the size of the intervertebral cavities cannot be ascertained. The processes of the anterior vertebre are short, thick, and curved, those of the posterior part of the column straight, long, and slender. The scapulocoracoid arch appears to have been slight, and the pectoral fins of moderate size. The component rays are subdivided transversely into a great number of ossicles, a structure which must have given great pliability to the fin. The ventral fins are small, but strengthened by a thick anterior ray to each fin, having considerable curvature at its pelvic extremity. The dorsal fin is situated over the ventral fins, and extends as far backwards as the insertion of the anal fin. The three or four anterior rays are short, strong, and pointed, the succeeding rays are long, dichotomous, and articulated transversely at short intervals. The number of rays composing the fin was not less than seventeen, and these are supported on a like number of interapophyseal ossicles deeply inserted in the integumentary tissues. The position of the — anal fin is seen by a slight impression of the anterior rays in the matrix of the specimen, but an unfortunate fracture has removed the fin itself. The scales more nearly resemble those of Megalurus lepidotus than those of Megalurus Damoni; they are, however, too imperfect to be accurately examined. I have named this species Megalurus Austeni, in recognition of the labours of the — Rev. John Austen in working out the pheepebcrae details of the Purbeck beds. oe Locality.—The specimen figured and described was found in a quarry of Purbeck stone in the neighbourhood of Swanage, and is now in my possession. DESCRIPTION OF PLATE 9. Fig. 1. Megalurus Austeni, size of nature. P. DE M. Grey EGERTON. April 20, 1857. Bu We all Hyrvey wc CK ema ANN MN I MAGROPOMA EGERTON! AG asst 1 ' | hen ore i” So OT LL ot eS pied 0 «ator eld DPelipon. Puss... DECADE [X. PLATE X. ————t MACROPOMA EGERTONI. [Genus MACROPOMA. Agassiz. (Sub-kingdom Vertebrata, Class Pisces. Order Goniolepidoti. Family Celacanthi.) Caudal fin very large, rounded. ‘Two dorsal fins, one over the interspace between the pectoral. and ventral fins, the other opposed to the interspace between the ventral and anal fins. The rays armed with marginal spines. Seales enamelled, imbricated, rounded posteriorly, and tuberculate. Teeth large and conical, intermixed with smaller ones. Vomer and palatines dentigerous. | Macropoma Egerton. Acassiz. Poiss. Foss. vol. 2, part 2, page 186. At the time when Professor Agassiz was engaged upon his great work on the Fossil Fishes, the materials crowded in upon him in such abundance that he found it impossible to comprise them all in one publication, with any prospect of completing it in reasonable time. He therefore determined to finish his original work in five volumes, and to postpone the descriptions of those species he could not incorporate, to form a series of supplementary monographs. He was only able to issue one of these, that on the fishes of the Old Red Sandstone, before his engagements in the United States put a stop to his ichthyological labours on tbis side the Atlantic. As there seems to be little chance now of his resuming the subject, it appears to me desirable that some of the most characteristic genera and species which were named by him, but not described, should no longer remain in our catalogues undefined. I have therefore selected a few of the most striking forms for description in this Decade. The genus Jacropoma is one of the most singular in the whole range of fossil ichthyology. We owe its discovery to the inde- fatigable zeal and scientific skill of the late Dr. Mantell, who described the only species then known under the name of Amia Lewesiana. Professor Agassiz subsequently determined it could not be considered as belonging to that genus, but that it constituted a new generic type, to which he gave the name now adopted. The specific name given by Dr. Mantell ought to have been continued, but a departure from the rigid rule of scientific nomenclature was fix. x] Oe be BRITISH FOSSILS. justifiable in this case for the purpose of perpetuating the name of the talented discoverer of Macropoma Mantelli. The remains of this fish are most numerous in the chalk formations of the south of England, and are all referable to one and the same species. The subject of this article constitutes a second species of the genus found in the Gault at Speeton, in Yorkshire. The specimen which is in my possession is unique, and Professor Agassiz did me the honour of naming it after me. Description.—The reasous assigned by Professor Agassiz for considering this a distinct species in the short allusion he makes to it in the “ Poissons Fossiles,” are, ‘the more uniform character of the scales, and differences in the form of the head.” These and other specific peculiarities will be treated of in the sequel. The specimen exhibits only the anterior half of the fish; comprising the head, the pectoral fin, and the first few rays of the dorsal fin. It evidences a fish of the largest dimensions attained by the Mantellian species. The head from the snout to the posterior edge of the operculum measures seven inches; the depth at the occiput is five inches and a half, and the breadth across the frontal bones three inches. The inclination of the profile line of the head is very steep from the occiput to the orbit, far more so than in the allied species ; the orbit is situated in a more advanced position, and the facial line thence to the snout falls much more rapidly. The opercular apparatus covers a far larger area, and the breadth of the cranium is comparatively ereater. The orbit in this species is large, and a portion of the capsule of the eye is preserved. The frontal bones are wide, coarse in texture, and bear a few scattered granules on their exterior surface. The borders of the upper jaw are formed by the superior maxillary bones, which are very broad; they are beset with very numerous sharp pointed teeth, closely arranged and of uniform size. The lower jaws are also very broad, and the space between the rami is closed by a single glossohyal plate, as in Lophiostomus, Arapaima, and Amia. The lines of demarcation between the oper- cular bones are not discernible, but the entire apparatus is consider- — ably larger than the corresponding parts of Macropoma Mantells. The pectoral fin is of large dimensions. This organ is not mentioned in the description of Macropoma Mantelli, nor is it well seen in any of the specimens of that species | have examined. It may or may not, therefore, be a distinctive and specific character. The fin is by no means perfect in my specimen, but it measures four inches and a half in length, by two inches in breadth. The rays are very numerous, and differ from those of the dorsal fin by being dichotom- [ae ae hacen / Set . , yy “Om PS hy a3 a a = yi BRITISH FOSSILS. 3 ized, transversely jointed, and devoid of spines. The base only of the dorsal fin is visible; it is situated three inches from the occiput. The scales are smaller and more uniform in size than those of the other species ; they are rounded posteriorly, and are higher than long. The surface ornament is very different ; instead of the distinct tubercles so characteristic of that species, it is composed of minute eranules united into longitudinal rows, with only a few small tubercles, interspersed occasionally, on some of the larger scales. The characters above detailed fully warrant the specific distinction of this from the species described by Dr. Mantell. Locality.—Found in the Gault strata at Speeton, in Yorkshire. DESCRIPTION OF PLATE. Fig. 1. Macropoma Eyertoni, size of nature. Fig. 2. Maxillary bones of the opposite side. Figs. 3. Scales, magnified. : P. DE M. Grey EGERTON. February 1857. Note.—Since the above description was written, I have received from Mr. Beckles a specimen of a Macropoma found in the quarries of Purbeck stone near Swanage. The : specimen is not sufficiently perfect to determine the species; it seems to be a shorter and deeper fish than Macropoma Mantelli. It is interesting to know that the genus was in existence previous to the deposition of the cretaceous system. P. pe M. Grey EceErron. April 20th, 1857. ee Mer ty é se a oe hed Ts ath Nine yl Tae OR _ ASPIDORHYNCHUS : Fisheri - _ ASTERACANTHUS : si Granulosus Papillosus - _ Verrucosus CENTROLEPIS : Asper CHIMERA : A Hunteri - COSMOLEPIS : Egertoni ELASMODUS : Hunteri _ENpACTIS: Agassizi HIsTioNOTUS : Angularis LEGNONOTUS : _ Cothamensis ‘LEPIDOTUS : - Pectinatus - -Leproeris : _ Constrictus Macropthalmus LOPHIOSTOMUs : Dixoni.. < Semiverrucosus ~ INDEX Decade. VI and Sup- plement - VI. oe VIll. - VII. - VITi. - IX. - VI. - IX. - ee b IX. VIII. and Sup- plement - VIII. - VI. - VI. - WE. - VI. DECADES VI., VIII, AND IX. 6 bo 0 & Ou Cn 10 ‘Article. Page. bt et OD a INDEX TO DECADES VI., VIII., AND IX. MACROPOMA : Egertoni - Nov. Spee. MEGALURUS : Austeni - Damoni_- NOTHOSOMUS : Octostychius OPHIOPSIS : Breviceps - OXYGNATHUS: Ornatus - PACHYCORMUS : Latipennis - PALZONISCUS : Egertoni - Monensis = PHOLIDOPHORUS : Crenulatus Granulatus Higginsi - Nitidus -- Pachysomus PLEUROPHOLIS : Attenuatus Crassicaudus Leevissimus Longicaudus Serratus - PTYCHOLEPIS : Curtus - Minor - PYCNODUS: Liassicus - 'THRISSONOTUS : Colei ~ { as Decade. Article. IX. 10 IX. 10 IX. 9 IX. 8 IX. 6 VI. ‘6 VIII. , and Sup- plement | - IX. 3 VI. 2 VI. 2 VI. 5 VIII 4 Vill T Vill 7 VI. 4 IX. 7 IX. 7 IX. 7 IX. (< IX. 7 VIII. 8 and Sup- plement | - VI. 7 VIII. 10 and Sup- plement | - IX. 2 Page, a) bS = OD et a pe Gr Oo © SS = MEMOTRS OF THE GHEOLOGICAL SURVEY OF _ THE UNITED KINGDOM. Higuees and Aeseriptions BRITISH ORGANIC REMAINS. — DECADE X. DIPOLES SLL SLD SSDP IYO Ta PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY’S TREASURY. LONDON: PRINTED FOR HER MAJESTY’S STATIONERY OFFICE: PUBLISHED BY LONGMAN, GREEN, LONGMAN, AND ROBERTS. 1861. 3052, i Fab ie # * : ‘an Bo 21 4 ae ee Ms \ Si é * en * Seat % ; ‘ : ; ny . P a: ihe i fA oe i sda Pe —[4,964.—1,000.—11/61.1 « : — |; ee sai bd z i ¥ Se : ra \ ' ri whe Rie eo ae i He th ASS AS Wes Ly a ee ee CC ( ie Kage . To BRITISH FOSSILS. DECADE THE TENTH. PRELIMINARY Essay upon the SysreMATIC ARRANGEMENT of the FisHes of the DEvontAN Epocu, by THos. H. Huxtey, F.B.S., Professor of Natural History, Government School of Mines. THE endeavour to determine the systematic position of Glypto- lemus, a genus of Devonian fishes, first described and figured in Dr. Anderson’s interesting work upon “ Dura Den,”* and more fully discussed and illustrated in the course of the present Decade, has oradually led me to reconsider the whole question of the classifica- tion of the fishes of this epoch and, eventually, to arrive at results which seem to necessitate an important modification of the received arrangement of the great order of Ganoidei. I propose, in the course of the pages of this preliminary essay, to take the reader through the various steps of the argument which terminates in this conclusion ; and, commencing with a brief enu- meration of the most important characters of Glyptolcenvus, I shall proceed to the discussion of the peculiarities of other genera, more or less nearly allied to it, with the view of demonstrating, finally, that Glyptolemus is a tolerably typical member of a large and well defined family of Ganoids, which abounded in the Devonian epoch, but whose members have been less and less numerous in more modern formations, until, at present, its sole representative is the African Polypterus. Fig, 1. aS a Ue ha ET Ten ee Mea cA hee ae Gi iM Hi WK (Ke cae “4 De Restoration of Glypiolemus. Glyptolemus Kimnairdé (fig. 1, and Plates l.andIL.), the only known species of its genus, is a fish with an elongated body, a depressed head, * Dura Den; a Monograph of the Yellow Sandstone, and its remarkable Fossil Remains. 1859. LOW Ae 2 BRITISH FOSSILS. and a conically tapering caudal extremity. The orbits are situated forwards, while the gape extends far back. The frontal bones (fig. 2) are distinct from one ‘another and from the parietals, which last are not shorter than the frontals, and, though in contact throughout the whole length of their inner margins, are perfectly distinct from one another. Three bones, or scales (for they seem to partake as much of the nature of the latter as of the former), a median and two lateral, roof in the occipital region. The middle of the jugular region, or that comprised between the two rami of the mandible upon the under surface of the cranium, is occupied by two large, triangular, squamiform, bones—the principal jugular plates (j’) ; while the interval left between them and the mandibular rami, on each side, is taken up by a series of smaller, quadrate plates, which increase in size from before backwards—the lateral jugular plates (j’). There is no rhomboidal median jugular plate interposed between the anterior part of the inner edges of the principal jugular plates. The teeth are of two kinds ; smaller, set in a close series along the edges of the jaws; and larger, placed at intervals along the palate, and perhaps along the inner side of the mandible. The larger teeth have grooved bases, and appear to be composed of dendrodentine.* Diagram of the Head of Glyptolamus.—For an explanation of the letters, see p. 40. * Prof. Pander applies the term “ Dendrodonts ” to those fishes the pulp cavities of ' whose teeth appear branched, in consequence of the folding of their walls; and such folded dentine may be conveniently termed ‘‘ dendrodentine.” CLASSIFICATION OF DEVONIAN FISHES. 3 The pectoral arch is covered by two triangular, sculptured, osseous plates (Pct?, Pct”), which meet in the middle line below and are superficial to the so-called coracoids. The paired, or pectoral and ventral, fins are lobate ; that is, the fin has a central axis, or stem, covered with scales. There ave two dorsal] fins, placed in the pos- terior half of the body. The ventral fins are situated under the first dorsal, and are succeeded by a single anal. The caudal fin, whose contour is rhomboidal, is divided into two equal lobes by the pro- longed conical termination of the body ; in other words, the fish is diphycercal, or truly homocereal.* Every ichthyologist will admit the singularity of this combination of characters, but a careful analysis of the structural peculiarities presented by other fossil fishes of the same age, will show, that, so far from isolating Glyptolemus, they closely unite it with several other genera. That genus which appears to me to approach it most closely is the Gyroptychius of M‘Coy, whose structure has received admirable elucidation from Professor’ Pander in his beautiful monograph “Ueber die Saurodipterinen, Dendrodonten, Glyptolepiden und Cheirolepiden des Devonischen Systems” (1860), to which I may refer those who desire to obtain a more particular acquaintance with the details of its organization. Here I must content myself with reproducing in a reduced wood- cut (fig. 3) Professor Pander’s restoration of the fish, which may Hie. 3: oes == Restoration of Gyroptychius (after Pander). be compared with the restored woodcut of Glyptolemus (fig. 1), and with the Plates, and with stating that the head, the body, and the fins of Gyroptychius might be described in the terms which have just been applied to Glyptolemus. Pander, however, makes no * TI have endeavoured to show elsewhere (Quarterly Journal of Microscopical Science, Oct. 1858) that the so-called ‘‘ homocereal” Teleostet of the present epoch are in reality excessively heterocereal; but the word “ homocereal” is now so generally understood te signify a tail like that of most existing Teleoste?, that I prefer to employ Prof. M‘Coy’s term “ diphycercal ” for truly homocercal tails. See, on this point, Kolliker, “ Ueber das Ende der Wirbelsiiule der Ganoiden, 1860,” and Van Beneden, “ Sur le Développement de la Queue des Poissons Plagiostomes,”’ Bull. de l’Acad. Royale Belgique, 1861. 4, BRITISH FOSSILS. mention of lateral jugular plates; the scales, which are as often oval as rhomboidal, are sculptured in a very different manner from those of Glyptolemus, and, according to Pander, the anterior edges of the median fins are provided with fulera. Glyptopomus (Agassiz) is another genus whose close alliance with Glyptolemus is evidenced by the structure of its skull, of which there is a fine specimen in the British Museum. It is very depressed and has two distinct frontal bones, separated anteriorly by a small rhomboidal plate; there are two long and distinct parietals, and three bones, one median and two lateral, behind these, covering the occiput. The orbits are situated far forward, the gape is greatly elongated, there are two principal jugular plates, and the pectoral arch is as in Glyptolemus. om n i = 4 2 a 7: 2 & i ° zy a - 7 — a ( i La : ’ an L 6 1 7 my oo £ 7 en - J 7 i : , : -_ H te if i a i, :y = =e 7 r , i ‘ : je n 1 _ 7 i). Wo 7 ey wT. : a fod a a oO ‘ 7? oy & (a V. - lé A ROPLEURON ANDERSONI_ “uz N-E ®) aS P H A ¢ United Ringdow. th Geological Survey of BRITISH FOSSILS. DECADE X. Puate III. PHANEROPLEURON ANDERSONI. [Genus PHANEROPLEURON. Hoxtey. (Sub-kingdom Vertebrata. Class Pisces. Order Ganoidei. Sub-order Crossopterygide. Family Phaneropleurini.) Body elon- gated, tapering to an acute point posteriorly, compressed from side to side. Dorsal fin single, extending for nearly the length of the posterior half of the body; the paired fins acutely lobate ; the ventrals very long, apparently longer than the pectorals, and situated beneath the anterior end of the dorsal fin. Tail ineequilobate, the upper lobe being by far the smaller. Scales cycloid, very thin. Teeth numerous and conical: Neural arches, ribs, and interspinous bones well ossified. ] Phaneropleuron Andersoni. Sv. Unica. All the specimens of this species and genus at present known have been procured from the Old Red Sandstone at Dura Den, associated with Holoptychius, the two genera being constantly found associated in the same slabs of sandstone. A. fine series of examples is to be seen in the British Museum and the Museum of Practical Geology, the whole of which, I believe, were collected by Dr. Anderson, in whose work upon Dura Den the first description of the present species appeared. ‘The fish had received the name of Glypticus from Agassiz long before, but the name was unac- companied by any description or definition, and has been used for a genus of Hchinodermata. The most complete specimen I have seen is that figured (two-thirds of the natural size) in Plate IIT. fig. 1, which occurs among a number of other examples of this genus and of Holoptychius, in a fine slab marked 26120 in the collection of the British Museum. The length of body equals about 53 lengths of the head. It remains of tolerably equal thickness from the pectoral region to that of the ventral fins, and then gradually tapers off to a finely pointed caudal extremity, which is, usually, slightly bent upwards. When the mouth is shut, the head also presents a triangular contour, both its upper and its under outlines rapidly shelving towards the snout. The scales are exceedingly thin, and, apparently in consequence of containing very little bony matter, they are apt to run into one [x.] 10 D 48 BRITISH FOSSILS. another and lose their distinctness when fossilized. But so far as the — best preserved specimens enable me to judge they were large and circular, and their outer surfaces were marked by very slight and delicate, granular, radiating strive, which may, however, be indica- tions of internal structure and not of ornamentation (Pl. IIT. fig. 7). These differences from the scales of Holoptychius become particularly obvious when, as in theslab in the British Museum above referred to, specimens of the two genera lie side by side in the same matrix, or when, as in fig. 3, Plate III. detached scales of Holoptychius have become imbedded in the midst of a specimen of Phaneroplewron. The cranial bones are smooth, or, at most, present irregular and scattered grooves. The cranium seems to have been much more com- pressed from side to side than m most Devonian fishes, but I can say little else respecting its structure, as it is much injured in all the specimens I have seen. In no specimen are the boundaries of the cranial bones defined. The operculum, however, is large. The orbit seems to have been situated far forwards, and the gape is long. Both the upper and the lower jaw are beset with a single series of sharp short conical teeth. One specimen on the slab 21620 in the British Museum, exhibits the only view of the under surface of the head I have met with, and proves that the jugular region was pro- tected by bony plates. Whether there were more than the two principal ones, or not, however, I cannot make out with certainty. The pectoral arch is well developed, but I can say nothing as to its individual components, nor are the pectoral fins thoroughly well preserved in any specimen. Such parts of them as exist lead me to the belief that they were shorter than the ventrals, but like them | acutely lobate. No pelvic bones are discernible, but the ventral fins are beautifully displayed in two examples on the slab 26120 in the British Museum, and in another specimen marked 26117 in the same collection. Their length exceeds the greatest vertical diameter of the body. A taper central lobe extends through the whole length of the fin, ending in a point at its fine end. It is covered throughout with cycloid scales, having the same characters as those of the body, and both edges are fringed with delicate fin-rays. The notochord was persistent throughout the whole length of the vertebral column, while the superior and inferior arches were well developed and thoroughly ossified. The neural spines are long, and are curved, so as to be somewhat concave forwards and upwards. In the posterior moiety of the body, elongated interspinous bones, narrow in the middle and PHANEROPLEURON ANDERSONT. 49 expanded at the ends, are adapted to them. ‘These interspinous bones increase in length from before backwards to beyond the middle of the dorsal fin, and support the fin-rays, whose bases are broad and solid, while they divide into a series of branchlets at their ends. There may be more than one fin-ray to each interspinous bone. The dorsal fin, commencing with the posterior half of the body, gradually increases in height posteriorly, as its upper margin remains parallel with the axis of the body, while the dorsal line of the body converges towards that axis; the fin terminates posteriorly in an almost vertically truncated extremity. The ribs attain a considerable length, even close to the head, and are continued through the whole length of the abdomen, passing eradualiy into the subcaudal bones. They are well ossified, and hence, in the fossil state, they stare through the thin integumentary scales of the fish so as to suggest its generic name. The anal fin is somewhat lanceolate in shape, inclmed downwards and backwards, and so long that its lower extremity is as distant from the axis of the body as the upper edge of the dorsal. It is supported by interspinous bones lke those of the dorsal fin. The inferior lobe of the caudal fin commences immediately behind the anal, and its rays appear to be supported by similar interspinous bones, at least anteriorly. It can be traced backwards to near the extreme end of the body. The superior lobe, on the other hand, seems to have been obsolete. EXPLANATION OF PLATE III. Fig. 1. Phaneropleuron Andersoni, two-thirds of the natural size. From a specimen in the British Museum, No. 26120. Fig. 2. Head of a specimen in the Museum of Practical Geology. The upper contour of the cranium seems to be slightly distorted. Natural size. Fig. 3. Caudal extremity of a specimen in the British Museum, exhibiting the anal fin. bi Dy i Ns Yaa - = i ; f ie We Fj ; = Le : ' 4 : 4 ; hoa ; : ' > un ae ’ i : pa ae - : = : “o> ‘ : cA uy 2 Pe | oe ‘ ae . ~_ “80 7a! -1 , a . as se 4 : D i - a ’ 7 her 7 25 a Ds aly ) eal PAI x Et 4 C.ADI [ae S) @e ey dima: sy ia Om & = (ry! Oe ir lao} © Pls (2p) ed Kingdom. i } at sn the fi UrDLDY gr S Geological een °to the Que o fe) 1g Day & Son, lath’ gerton 7 Tats TticCHhOrTeRUS AvATUS. “ th el b ik ag Di Jos. RAR ASE ree art BRITISH FOSSILS. DECADE X. PLATES IV. AND V. TRISTICHOPTERUS ALATUS. [Genus TRISTICHOPTERUS.* Ecxerton. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Ceelacanthi.) Body fusiform. Cranial bones sculptured. Two dorsal fins ; one anal fin; the rays of the second dorsal and the anal fin springing from three strong interspinous bones in each, Caudal fin springing from eight or nine similar bones. Vertebral centres ossified and prolonged through the upper lobe of the caudal fin. ] Tristichopterus alatus. Sp. UNIcA. This is one of the many interesting additions made to the fossil Fauna of Scotland by the zeal and intelligence of Mr. Peach. Two specimens only have been obtained, one showing the general form of the fish, with the exception of the extremities of the head and tail, the other, with its counterpart, exhibiting in perfect preservation the structural and other characters of the fins and tail. The expanse of the latter and the opposition of the second dorsal to the anal fin are characters which might lead one to refer this form to the genera Diplopterus or Gyroptychius, but a rigid ex- amination of the specimens convinces me that it formed a member of the Ccelacanthoid family, although presenting some important discrepancies from the other genera of that family. The points of resemblance are seen in the number and position of the fins, the curvilinear outline of the scales, and the prolongation of the central portion of the tail. The differences consist in the structural details of the fins and the ossification of the vertebral centres; but in these respects the deviation from the Sawroidet-dipterini is quite as great as from the Calacanthe. Description.—The more perfect of the two specimens measures seven and a half inches in length; if to this we add two anda * From tpeis tres, orixy series, mrepov ala, a2 BRITISH FOSSILS. quarter inches, the dimensions of the tail supplied by the second specimen, and three-quarters of an inch for the absent portion of the head, the entire length of the fish will be ten and a half inches. The depth at the greatest diameter is two inches. The body is irregularly fusiform, the dorsal line being less curved than the ventral outline, and the anterior half of the body more obtuse than the caudal portion. The bones of the head (with the exception of a small fragment of the operculum) are wanting, but the impressions distinctly left upon the matrix show that they were sculptured in rather a bold pattern, not. unlike the ornament on the cranial bones of some of the Holoptychit, and consequently differing in this respect from the corresponding parts in Dipterus. The pectoral fins are very indistinctly seen. They appear to have had a short obtuse lobe forming the base, and extending therefrom a set of numerous fin-rays more elongated than those forming the pectoral fin in Dipterus. The small anterior dorsal fin is situated at the commencement of the last third of the body, and is opposed to the ventral fins. The latter are broad and composed of numerous rays expanding from a short lobate base. Both these and the pectoral fins differ from the corresponding organs in Dipterus in having more numerous and longer rays. The structure of the other fins is very singular and requires a more detailed description. The second dorsal fin is placed immediately opposite the anal fin, and resembles it so. closely that one description will serve for both. In each of these fins the component rays spring from three interspinous bones, and these are attached to a single broad spinous apophysis. The latter bone is probably a composite one, formed by the union of three or more spines. The interspinous osselets have cylindrical shafts expanded at each extremity, the one for attachment to the vertebral spine, the other for affording a base for the insertion of the fin-rays. In the anal fin the anterior bone of the triplet is shorter than the others and than the corresponding bone in the dorsal fin. The fin-rays springing from the first bone are the strongest. The anterior ones are the shortest and they lengthen in succession until the maximum extent of the fin is attained. They are single at first, _ bvt bifurcate in the distal part of the fin. The transverse joints are numerous. The group abutting upon the first interspinous bone contains about six rays. The second bone carries about eight rays, more slender than the former and more frequently subdivided. The anterior ray of this group is the longest, the subsequent ones decreasing in length in succession. The third TRISTICHOPTERUS ALATUS. 53 bone gives attachment to at least a dozen rays, finely fimbriated, and forming the posterior fan-like portion of the fin. The integuments extended over the interspimous bones as far ag the commencement of the true fin-rays, thus forming the lobate base so characteristic of the fins in all the Ceelacanthoid fishes. The upper lobe of the tail contains numerous rays, the anterior ones being short and fulcral, forming a marginal fringe along the upper edge of the fin. A few of the upper fin-rays are given off from a set of short neurapophyses, but the terminal rays seem to abut upon the vertebral axis. This is prolonged through and beyond the caudal fin, and is furnished at its extremity with a few fine rays forming a kind of supplemental fin projecting beyond the terminal margin of the normal caudal fin. This peculiar form of tail is common to many of the Czelacanthoid genera, and is most fully developed in the genus Colacanthus from the Permian and Carboniferous beds. It differs from the “ diphycercal tail” of Prof. M‘Coy, in which the upper and lower rays of the true caudal fin form the terminal point. This form is characteristic of the genera Diplopterus and Gyroptychius belonging to the Sauroidei-dipterint. The lower lobe of the tail is constructed upon a plan similar to that above described as occurring in the second dorsal and anal fins, but the interapophyseal osselets are more numerous. ‘They are eight or ten in number, and each carries four or five rays. These rays are stouter than those of the upper lobe and are more frequently jointed and subdivided ; the rays, above the upper interapophysis, forming the central area of the tail, impinge upon the lower periphery of the vertebral column, and decrease successively in length so as to form a vertical termination to this lobe of the tail. The condition of the vertebral axis in this fish forms a remarkable exception to the general law hitherto applicable to the greater part (if not to all) the fishes of the Old Red Sandstone, and to all the Celacanthi hitherto described. If we except the genus Dipterus (some specimens of which show a tendency to ossification in the caudal region) all the Devonian genera have been considered Notochordal fishes, that is to say, the chorda dorsalis has persisted in its embryonic condition without , any trace of segmentation. In the present subject, however, the whole of the vertebral axis has left its impression distinctly on the matrix in one specimen, and in the other the vertebre of the caudal region are preserved entire. There can be no doubt entertained therefore that in this genus the ossification and seg- mentation of the column was complete, in which respects it stands alone among the contemporaneous fishes. The scales more nearly 54a. BRITISH FOSSILS. resemble those of Dapterus than any other, but the surface orna- ment is differently arranged. The enlarged representations of two scales, one from the flank, the other from the lateral line, most carefully drawn by the skilful pencil of Mr. Dinkel, show the characters more clearly than any description can do. The posterior margins of the scales are all curvilinear, differing in this respect from Gyroptychvus.* Afinities—tIn assigning this new form to the Ccelacanthoid family, I have been mainly influenced by its resemblance in many respects to Dipterus. The latter genus was arranged by Professor Agassiz with the Sawroidei-dipterini, but I have long ago seen sufficient reasons for considering it a Ocelacanth, approximating more nearly to Glyptolepis and Holoptychius than to any other genera. Professor Pander, however, in his work on Fossil Ichthy- ology, a publication remarkable alike for the labour it evinces and the extraordinary beauty of the illustrations, has issued a monograph on the genus Dipterus, in which he disagrees with this arrange- ment (first published by Professor M‘Coy), and seeks to establish a new family for its reception, which he designates “Ctenodipterim.” Hugh Miller, so long ago as the year 1848, made known the curious discovery that the fossil crania named by Professor Agassiz “ Polyphractus,’ belonged to the genus Dipterus, and furthermore, that the palatal teeth called “ Ctenodus” by the same author, con- stituted the dental apparatus of the same genus. Professor Pander seems to have arrived at the same conclusion in 1858, not being aware of the previous discoveries of Hugh Miller, whose claim to priority, however, he acknowledges in a postecript. At the same time, Hugh Miller exposed the fallacy of assigning two anal fins to Dipterus, proving the so-called anterior anal fin to be one of a pair of ventrals. Professor Pander entertains the same opinion, but does not allude to Hugh Miller’s correction, nor does Professor M‘Coy seem to have been aware of it, as he describes the genus as having two anals. The genera Osteolepis, Duplopterus, and Glypto- lepis are also rightly deprived of the anterior anal fin in Professor. -Pander’s publication. The term Ctenodipterim is intended to express the association of the dental apparatus called Cienodus with the genus Dipterus, but it is an objectionable term, inasmuch as it * Professor M‘Coy figures a scale (Plate 2 c. Fig. 2a. British Paleozoic Fossils), which he describes as a scale from the back of Gyroptychius angustus. It very much resembles a scale of Tristichopterus. + Witness Newspaper, December 23, 1848. TRISTICHOPTERUS ALATUS. — 55 suggests the idea of a Dipterian fish with Ctenoid scales. If the family is proved to be well founded, the title Ctenodo-dipterini would be preferable. The genera Ceratodus of Agassiz, and Con- chodus and Chirodus of M‘Coy are referred by Pander to this family. The absence of all evidence as to the dental apparatus of Tristichopterus is much to be regretted. On other points the affinities between this genus and Dipterus are so striking that they cannot be classified in separate families. Locality At the meeting of the British Association at Aberdeen in 1858, Mr. Peach read a short notice of several new forms of fossil fishes discovered by himself in the north of Scotland. The subject of the present Memoir is thus alluded to: “The great “ interest attaching to the next arises from its having a short “ vertebral column running from head to tail, and also strong in- “ ternal supports to the fin-rays. Whether these and the vertebral “ column are of bone is still an open question. The scales are “ large and coarse ; it is about ten inches in length ; and came from “ the red and blistered sandstones near John o’Groat’s House.” The second specimen, contributing materially to the knowledge of the genus, is not mentioned by Mr. Peach. Both these specimens now form part of the collection in the Museum of Practical Geology. EXPLANATION OF PLATES IV. AND V. Plate IV. Vig. 1. Tristichopterus alatus, size of nature. Vig. 2. Structure of the tail, magnified. Plate V. Fig. 1. Zristichopterus alatus, size of nature. Fig. 2. Seale of the flank, magnified, Fig. 3. Seale from the lateral line, magnified. P. bE M. Grey EGeERron. Oulton Park, Nov. 15, 1860. La Eig ee ie mrt eh te fer" NDS 1X yoni xX: PLS AC AIRE ODIES . (Devonian.) ? @eslonical : surven of the Umitel ACANTHODES PEACH! — Agerton ACANTHODES CORIACEUS__ Agerton Ser S to the Queen. BRITISH FOSSILS. DecaDE X. PxuatTe VI. Figs. 1 and 2. ACANTHODES PEACHI. [Genus ACANTHODES. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Acanthodei.) Body fusiform. Mouth large, opening upwards, Orbits encircled by four bony plates. Branchie exposed. Fins membranous, supported by strong spines. One dorsal spine near the tail; one anal below and slightly in advance of the dorsal ; pectoral spines strong ; ventral spines small. Scales minute. | The genus Acanthodes forms the subject of the first article in Professor Agassiz’s volume on the Ganoid fishes. At that time only one species was known, Acanthodes Bronnt, from the Coal-measures of Saarbruch. Before the completion of the work, two others had been discovered, Acanthodes sulcatus, from the Coal-measures at Newhaven, and Acanthodes pusillus from the Old Red Sandstone near Gordon. Castle. , In the description of the latter species, in his later publication on the fishes of the Old Red Sandstone, Professor Agassiz supplements the characters of the genus given in the former work, with all the information derived from these subsequent dis- coveries. It was reserved, however, for Ferdinand von Romer, of Breslau, to complete the anatomical details of this singular fish, by the examination of hundreds of specimens (as he himself recounts) of anew species, Acanthodes gracilis (Holacanthodes of Beyrich), discovered in the Permian strata of Klein-Neundorf, near Lowen- berg.* Since the publication of this memoir (to which I must refer the reader for the many curious structural details therein - described), the Old Red Sandstone of Scotland has contributed three additional species to this genus. These will be considered in this and the following chapter. ‘T'wo of these novelties were dis- covered by Mr. Peach, and in recognition of the great services he * Ueber Fisch-und Pflanzen-fiihrende Mergelschiefer des Rothliegenden bei Klein- Neundorf unweit Lowenberg, und im Besonderen iber Acanthodes gracilis den am haufig- sten in denselben vorkommenden Fisch.—Von Herrn Ferd. Roemer in Breslau, 1857. eM 5 Gk 58 BRITISH FOSSILS. has rendered to Palzeontology I propose to designate the subject of this article by his name. Descruption.—Although somewhat longer than the Acanthodes pusillus from Tynet Burn, this is, nevertheless, one of the smaller species of the genus. The length of the only specimen found in tolerable preservation is about 21, inches. The depth of the the body is four-tenths, and caudal pedicle two-tenths of an inch. It differs remarkably from Acanthodes pusillus in these relative dimensions, being a thicker fish and less elegant in its pro- portions. The latter species is usually found doubled up upon itself, as if it had died a violent death. The Caithness species is also recurved, as if it had met with a similar fate; but, owing to the greater rigidity of the body, the distortion has been less excessive. The head seems to be large in proportion to the body, but this appearance may be due to the mutilated condition of this portion of the specimen. Owing to a forcible disruption of the integuments at the junction of the head and thorax, the former has been thrown up and crushed vertically, in consequence of which its natural proportions are disfigured by the lateral projection of the component bones. The pectoral fins remain in their proper position. They are supported by two strong spines, slightly recurved. The portions of the thoracic arch, to which these spines are attached, are seen sloping upwards from the articulation. They probably repre- sent the coracoid bones. They are of slighter proportions than the corresponding bones in the genera Cheiracanthus and Diplacanthus. The ventral fins are situated about midway between the pec- toral and anal fins. They are furnished with two spines, more slender than the other fin spines, but longer in proportion than in any other species of this genus. The dorsal fin is placed in a more forward position than the corresponding organ in the allied species. Instead of being slightly more remote than the anal fin, it is immediately above it. The spine which carries the fin is the strongest of the set. I+ is more curved than the dorsal spine of the other species of contemporaneous origin. ‘The anal spine is also strong and curved. All the fin spines are ornamented with three or four longitudinal grooves. ‘The tail is very broad for the size of the fish. The upper lobe projects: beyond the lower lobe to a con- siderable extent, but does not taper off so gradually as in other species. The appearance of a bifurcation at the extremity is due to a separation of the integuments, either trom pressure or decomposi- tion. The scales are very minute, at the same time they appear to have been coarser than the scales of Acanthodes pusillus. ACANTHODES PEACHI.— BRITISH FOSSILS. ra DECADE X. PLATE X. CHEIRACANTHUS LATUS. [Genus CHEIRACANTHUS. Acassiz. (Sub-kingdom Vertebrata. Class Pisces. Order Goniolepidoti. Family Acanthodei.) Body fusiform. ‘Tail heterocercal, Fins membranous, each supported by a strong spine. One dorsal fin, one anal fin, two pectoral fins, and two ventral fins. The dorsal spine situated above the interspace between the ventral and anal fins. Pectoral spines articulated to two strong coracoid bones. Scales minute. Teeth small, conical. | The generic characters of Chevrucanthus are so clearly defined by Professor Agassiz in the “Poissons Fossiles du Vieux Gres Rouge,” and the differences between this and the other Acanthodean genera so fully elucidated, that neither amendments nor additions are re- quired notwithstanding the rapid progress of discovery since the publication of this standard work. Three species are therein de- scribed, Cheiracanthus Murchisont from Gamrie, Cheiracanthus microlepidotus from Lethen and Cromartie,and Cheiracanthus minor from Orkney. Professor M‘Coy has since described two species, Cheiracanthus pulverulentus and Chevracanthus grandispinus, both from Orkney, the latter being the largest and most striking species of the genus. In consequence of the stimulus given to the exploration of the Old Red Sandstone deposits of Scotland by the meeting of the British Association at Aberdeen in September 1859, localities which had been previously but slightly examined were opened up, and yielded a rich harvest to the scientific labourersin Palzeontology. Amongst others, the quarries at Tynet Burn were extensively explored through the liberality of the late Duke of Richmond, who employed a gang of workmen expressly for the purpose. Some of the best specimens discovered were forwarded to me by his Grace for examination, and amongst other novelties and many well-known species, I detected a new species of Cheiracanthus, which I have named Chevracanthus latus. 74 BRITISH FOSSILS. Descroption.—On separating all the specimens of Cheiracanthus from the other genera with which they were associated it was evident that they indicated two distinct forms, one with a long tapering body and the fins rather distant from each other, the other short and thick, and having the fins closely approxi- mated. The former is probably identical with Cheiracanthus microlepidotus, so common at Lethen; the latter I consider to be new. Both species appear to have been very abundant in the Tynet locality and to have been gregarious, but Cheiracanthus latus seems to have been most numerous. The collection forwarded to me contained above fifty examples, more or less perfect, of this fish. The length of an average-sized specimen is about six inches from the nose to the extremity of the tail, and the depth in front of the ventral fins one inch and a half, being an excess of one quarter of an inch as compared with a specimen of Chevracanthus microle- pidotus of similar length. The head is seen in profile, and measures an inch and a quarter in length from the point of the lower jaw to the posterior edge of the operculum. The mouth is large and horizontal ; the teeth are not preserved in any of the specimens. Judging from the character of the dentigerous bones they were pro- bably small and in single rows. The branchiostegous rays are very numerous, and extend high up in the opercular space. They are composed of a harder substance than the surrounding parts, being almost as dense as the fin spines, and are consequently preserved in most of the specimens. The pectoral fins are large and triangular. They are supported by a pair of strong spines, slightiy curved and measuring one inch and a quarter in length. These are attached toa pair of coracoid bones, broad at the point of articulation and tapering upwards. A short process extends downwards from the same point on either side, meeting its fellow in the median line, and completing the thoracic arch. The large expanse of the pectoral fins required a powerful fulcrum such as this to enable them to fulfil their functions. The ventral fins are situated midway between the pec- toral and anal fins. The spines supporting them are straight, and have their bases inserted in the intecuments without any trace of pelvic bones. The dorsal fin occupies the middle of the back, the point of insertion of the dorsal spine being opposite the interspace between the ventral and anal fins. It is a large triangular fin attached to a long and straight spine deeply implanted in the muscular tissue. The anal fin spine occurs midway between the ventral spines and the base of the caudal fin, the membranous portion extending as far as the anterior margin of the latter organ. CHEIRACANTHUS LATUS. 75 The pedicle of the tail is very deep, and terminates in a broad fin, of which the upper lobe greatly exceeds the lower lobe in extent. The scales are smooth, umbonated below, and neatly sculptured on the outer surface with four or five parallel grooves. They are of uniform size over the entire body. The broad tail, large fins, and close arrangement of these on the ventral surface distinguish this species from all those hitherto described. Locality— All the specimens I have seen of this species are from Tynet Burn, where they occur in nodules similar to those found in the contemporaneous deposit at Lethen Bar. EXPLANATION OF PLATE X. Fig. 1. Cheiracanthus latus. Size of nature. Fig. 2. Seales magnified. P. DE M. Grey EGErToN, Oulton Park, November 1860. LONDON : Printed by Grorcr E. Eyre and Witt1am Sporriswe oO Printers to the Queen’s most Excellent Majesty. For Her Majesty’ fS Stationery Office. MEMOTRS OF THE GEOLOGICAL SUI OF VEY. THE UNITED KINGDOM. Figuees amd Descriptions ILLUSTRATIVE OF BRITISH ORGANIC REMAINS, ——_—— DECADE XI. ——E TRILOBITES. (CHIEFLY SILURIAN.) WII wey PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY’S TREASURY. LONDON: PRINTED FOR HER MAJESTY’S STATIONERY OFFICE PUBLISHED BY LONGMAN, GREEN, LONGMAN, ROBERTS, G&G GREEN; AND BY EDWARD STANFORD, 6, CHARING Cross, 8.W. —E 1864. 10435. eget Sag rained sha ane “er a i ‘ [761 PREFACE. a THE plates of this Decade were engraved a year ago, but the pressure of other duties compelled Mr. Salter, the late Paleeontologist of the Geological Survey, to postpone the descriptions. That gentleman has now completed the work at my request, he being at present engaged on a Monograph of all the British Trilobites for the Paleontographical Society. Following our usual plan, those genera only have been illustrated which are rich in material for the engraver, or those which, though less perfect, are so rare and interesting as to render it desirable to publish them, even from fragmentary materials. The genus Olenus, characteristic of the lowest Silurian rocks of all the northern parts of Europe, is an instance in point. All the British species, save one or two, are fragmentary, but these fragments illustrate several of the important sub-genera into which this genus of the primordial Silurian of Barrande is divisible; hence a second plate of it is given. Aglina, pl. IV., is another case of the same kind. The genus was previously illustrated in Decade 7, from imperfect pieces of the head and body. We now possess the entire form of this genus, which is eminently Lower Silurian in its range. The genera Stygina, Salteria, Trimerocephalus, Angelina, Agnostus, and Staurocephalus have not before been illustrated in the Decades. Asaphus, before given in Decade 2 as to one of its sub-generic groups, now presents us with a British type of the sub-genus Isotelus, which 1s so common in America, but rare in Europe. Lastly, a fresh discovery, by the author of this Decade, of a gigantic Paradowides in the Lingula flags of Pembrokeshire, has made it possible to figure this characteristic genus from perfect materials, RoDERICK I. MurRcHISON, Dvrector-General. Geological Survey Office, 28, Jermyn Street, London, Novenber 1864. (pi NOTE. The reader must understand that the numerous references to Memoirs Geol. Survey, vol. 111. (ined.) throughout this Decade apply to the forthcoming Memoir on the “Geology of North Wales,” by Professor Ramsay ; with an Appendix on the Fossils by Mr. J. W Salter. Sa Ta Geological Surrey of the Hurted tinghour. 11> sally Figs. 1-6, KGNOSTUS PRINCERS, J alter. Jone delt GS 8_L0, Me COYII, TRINODUS, 1a. 7a. IW. Salter direx* Ltd. ss Le ees AGNOSTUS . (Lingula Flags and ~ Tower Silurian) a AGNOSTUS TRISECTUS, JSaller. cela SHEP ns MOREA, 7 BRITISH FOSSILS. DErcADE XI. Piatre i Fies: 1-5, ae AGNOSTUS PRINCEPS, [Genus AGNOSTUS. Bronentart. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Agnostide.) Minute trilobites, with caudal and cephalic shields nearly equal. No eyes, no facial suture. Two body rings.—Ranges from Lingula flags to Caradoc rocks. | Draenosis. A. latus, 7 lineas longus, scutis rotundato-quadratis, ad limbum ru goso-radiatis. Glabella subconica, tuberculo centrali antico, sulcis duobus transversis, lobis basalibus magnis instructa; sulecoque verticali ad marginem ducto. Annuli corporis valde nodosi. Cauda axe magno rotundato, fere per totum caude extenso ; margine edentulo. Synonyms. A. pisiformis, SALTER (1859), in Siluria, pp. 45, 53, foss. 4 and 9; A. princeps, id., * Memoirs Geol. Survey, vol. iii. (ined.), pl. 5. Certainly the lowest and most rudimentary form of Trilobite, and greatly resembling in some respects the young stages of higher sroups. But Agnostus shows at once its mature character in the possession of a large caudal shield, well developed, and generally quite as large as the head. The surface is sometimes much orna- mented, especially the border, and the lobes are often well marked out both in the cephalicand caudal portions. The leading character of the Trilobite family, the facial suture, is altogether absent, and there are no eyes in any of the species. When Brongniart described this fossil for the first time, he evidently could not tell what to make of it. To describe the head and tail as distinct animals was natural enough, but when he turned the hinder part of the head forwards, and suggested that the basal lobes of the glabella might be eyes, and the forehead lobe the abdomen, &c., one feels that he was justified in payin, “On ne sait a quelle fee des régnes organiques le rapporter.” Beyrich first gave the entire form in his treatise, “ Ueber einige Bohmische Trilobiten,” 1845. * The reader must understand that the numerous references to Memoirs Geol. Survey, vol. iii. (ined.) throughout this Decade apply to the forthcoming Memoir on the “Geology of North Wales,” by Professor Ramsay ; with an Appendix on the Fossils by Mr. J. W. Salter. [xr 1] Tis 2, BRITISH FOSSILS. It is instructive to find this, the most rudimentary form, asso- ciated with other genera in which all the characters of the group are fully developed, in the same primordial zone. But it is to be noted, that either by excessive reduction, as in Agnostus, or exces- sive multiplication of segments, as in Paradowides, the genera at this early period exhibit a defective organization as compared with those of later formations. There is no sort of equality between an Agnostus or Olenus and a Phacops or Phillipsia. The figures we give of A. princeps possess more than an usual interest, for they represent some of the oldest fossils known in N. Wales which occur in the lower part of the “ Lingula flags,” considerably below the characteristic Lingule of the formation. They are in countless numbers in the black slates near the waterfall of Felyn Rhyd, near Maentwrog, and are there associated with a new Olenus, and with rare specimens of Lingula. That they are characteristic of the formation is evident from the fact that with the reappear- ance of black earthy slate in the upper division of the formation, the Agnostus reappears also in abundance, and our figure 3 is from that part of the series. In S. Wales other and new genera accom- pany the Agnostus in the lowest portions of the deposit. Description.— Not half an inch long, though frequently elon- gated by pressure beyond that length. The general form of the head and tail is about two-thirds of a broad oval, truncated next the thorax, pretty regularly convex, and strongly trilobed; the thorax joints do not together occupy one-third the length of the head, and are narrower than its width. The head is a little longer than broad, smooth, with a narrow distinct border. The glabella about as wide as the cheeks below, ' but tapering forwards ; and divided, at more than two-thirds its height, by a transverse furrow which separates it into two parts, the lower oblong oval smooth, without lateral indentations, and the upper a spberical-triangular lobe, from the end of which a dividing line runs forward to the margin. A conspicuous pair of triangular lobes lie at the base of the glabella, in part subtending ~ the convex cheeks, which are narrow below, broadest above, but narrower again in front, where they are separated by the dividing line. . Thorax of two nodose joints, the anterior largest. Hach is strongly trilobate ; the pleuree convex, and with a strong groove toward the tips, making them appear notched (fig. 1 a). The axis too is trilobate, the central lobe very prominent, and strongly dis- BRITISH FOSSILS. 3 tinguished from the lateral and more forward portions ; these are obliquely ovate,—the centre lobe is pyramidal. Tail nearly of the same shape as the head ; the margin furnished, toward its hinder edge on each side, with a prominent tooth. The axis is very broad and convex, somewhat clavate, and reaching nearly to the margin, a space the width of the latter being left between ; it is of greater breadth than the sides (even including the narrow margin). The front pair of lobes are distinct, rounded- triangular, and their own diameter apart; the second pair (fig. 3, 4) occupy a less width, are not very distinctly circumscribed, and are divided from the large terminal lobe by a faint transverse furrow. The tubercle on the intermediate pair is prominent but short ; it scarcely invades the terminal lobe, and is of nearly the same shape in all our specimens, however distorted. Variations.—-Our larger specimens fig. 1, 4, (fig. 5 is magnified) from the lowest and upper Lingula Flags have the axis of the tail rather longer and somewhat more pointed than in fig. 3, but this may be entirely due to elongation from pressure. The terminal lobe of the glabella too is shorter in proportion in the former, but there seems to be no other real difference. The rugose veins which ornament the limb are always conspicuous in well-preserved speci- mens, but are much obliterated in less perfect ones, as our figures will show. A finities.—Compared with Angelin’s incorrect figures of A. pisi- fornis and A. planicauda (I have Swedish specimens of those species before me), A. princeps has the axis of the tail (though Angelin’s figures have it too short) decidedly longer, and reaching so far as to leave a space, between it and the margin, of only the breadth of the latter; and the tubercle, which Angelin represents as elongated and reaching far down the middle of the axis in his A. planicauda, is very short and prominent in our species. In both these respects they agree better with Swedish specimens of A. pisiformis than with Angelin’s figure ; and if it were not for the longer glabella and tail axis, the larger size and the decided radiation of the limb in our fossil, we should have united ours with the weli-known Scandinavian form. Our second variety 6 is more like it than the first and more ornamented one, «. In size Agnostus princeps nearly rivals the largest of the Swedish forms, A. reticulatus and A. aculeatus, Angelin, pl. 6, fic. 10, 11. These, however, show a strong reticulation of the 4 BRITISH FOSSILS. surface, instead of the more or less faint radiations of the British fossil. And A. exsculptus (fig. 8), which is still more like ours, has no posterior spines, and a very short glabella. ! We may notice two distinct varieties, possibly species. 1. A. princeps, «. ornatus,—glabella fere trilobaé antice obtusd, limbo radiato-sculpto, pl. 1, figs. 4, 5. 2. A. princeps, 8. rudis,—glabelld bilobd, antice acutiors; limbo vie radvato, pl. 1, figs. 1, 2, 3. British Localities and Geological Position.—Var. a. LOWER AND Upper LincuLa FLaas, figs. 4, 5, from Carreg Wen, near Borth, Portmadoc. Var. 6. Lower Lineuia Fuaas, figs. 1, 2, Pen-y-foel, a hill close to the Waterfall, Maentwrog, N. Wales (in great abundance). Upper LincuLa Fuags, fig. 3, Penmorfa Church, near Tremadoe. The species is also found in the Upper Linecuna Fiaes (Black Shales) of Whiteleaved Oak, Malvern, where it was first collected by the late Mr. Hugh Strickland. Upper Tremaboc Stats, Port- madoc. Lowrr LLANDEILO, St. David’s Head, rare. If I were disposed to divide the genus, as Corda and MeQoy have done, the Agnostus tardus, Beyr., A. glabratus, Ang., and A. trvnodus, Salter, would form a separate group. I prefer to regard them as forming a sub-genus only, Trimodus, while the species with transverse lobes to the glabella and caudal axis may stand as Agnostus proper, and Condylopyge, Corda. lastly, the smooth forms with all but undivided caudal and cephalic shields (A. integer, Beyrich, A. glandiformis, Angelin), &¢, would form a fourth division, Phalacroma, Corda, as follows : Section 1. Condylopyge, Corda.—Glabella distinct and lobed, the forehead lobe wider than, or as wide as, the pos- terior ones. Ex. A. Rew, Barrande; A. McOoyii, A. Morea, Salter, &c. : Section 2. Agnostus, Brongn.—Glabella distinctly lobed, the forehead lobe narrower. Ex. A. pisiformis, Brong., A. princeps, Salt. ’ Section 3. Trinodus, McCoy.—Glabella not lobed. Ex. A. tardus, Barr., A. trinodus, Salter, &c. Section 4, Phalacroma, Corda ?—Glabella or caudal axis scarcely marked out at all. Ex. A. integer, Beyr. English examples doubtful. BRITISH FOSSILS. ; 5 The foregoing Species belongs to Section 2.—AGNostuS proper. | AGNOSTUS PIsIFoRMIS, Linn. I subjoin a description of the Swedish species, as it is necessary to show in what respects this long-known primordial species differs from the preceding, and also from the A. McCoyiti, under which name I have designated the species common in the Llandeilo flags of Britain, and which was formerly published in the Silurian System as A. pisiformis. Synonyms. Lntomostracites paradoxus and E. pisiformis, Linn., Iter Scan. 122; Syst. Nature, ed. 16, vol. ili. 160; EF. pisiformis, Wahl. ; Agnostus pisiformis, Brongn. (1822), Crust. Foss. pl. 4, fig. 4; Angelin, (1852), Pal. Suec. t. 6, fig. 7 (A. planicauda, ib. t. 6, fig. 9, variety). Dracnosis. A. elongatus, 5 lineas longus, valde trilobus, capite et pygidio ovali-truncatis, levibus. Glabella longiconica, in duas partes, anticam trigonam parvam, posticam oblongam, divisa. Cauda axi magno, longo, lobato, apice obtuso ; marginibus angustis brevidentatis. Locality. —Lingula flags of Sweden. Comparing, then, the Swedish figure with that given of our next species, it will be seen that the general shape of A. pisiformis is much longer, and the glabella narrower and more pointed; its upper lobe, instead of being larger than the lower, is much smaller, and from its apex a longitudinal furrow runs to the front margin. In these respects it agrees with our A. princeps, as before said, but differs. from the Llandeilo fossil A. McCoyz. There are also considerable differences in the caudal shield, as will be seen by referring to the following figures. | Section 1.—CONDYLOPYGE. AGNOSTUS MACCOYII. Puate I. Frias. 6, 7. Diaenosis. A. oblongus, depressus, capite pygidioque rotundatis, et ad thoracem contractis. Glabella oblonga, antice vix incrassaia, in duas partes sub-equales, posticam circularem, anticam lunatam, sulco curvo divisa. Limbus undique equalis, lineis impressis radiatis sepe notatus, margine angusto. Cauda capiti simillima, sed axi clavato brevi, lobo terminali majori semielliptico, mediano transverso drevituberculato, lobis anticis prominulis. Margo distinctus, brevidentatus. Synonyms. A. pisiformis? Murch. (1837), Sil. Syst. pl. 25, fig. G (fig. 4 in text), not of Brongniart ; Diplorrhina triplicata, McCoy hl do Sees 6 BRITISH FOSSILS. (1851), Pal. Foss. Woodw. Mus. pl. 1 E., fig. 11 [not of Corda]; Agn. Me Coyit, Salter (1854), in Morris’s Catal. Brit. Foss., 2nd ed.; id., Mem. Geol. Surv., vol. 3 (ined.), pl. 13, fig. 8. A very frequent fossil in the black Llandeilo flags of Builth, in Radnorshire, but, as far as I know, not found elsewhere. It accompanies the Ogygia Buchit and Ampyx nudus, figured in a former decade, and seems, like many others of the genus, to have delighted in a habitat of black carbonaceous mud, now converted into shale. Description.—A minute species, never half an inch long, even when head and tail are taken together (the body rings have not yet been found). The head is rounded, not oblong, forming about two-thirds of a circle, the base being contracted where it joins the thorax. The tail is nearly of the same shape, a little more oblong. In both the convex limb is nearly equal all round, and the glabella and caudal axis are short and obtuse. The outer marginal rim is — narrow but prominent all round, and the two short marginal teeth are placed far back on the caudal border. The general shape thus given, we may notice a few details, The glabella in front is remarkably broad and obtuse, always as broad, and sometimes (fig. 7) broader than in the hinder moiety. A curved depressed line separates the front portion from the hinder lobe, and the two portions are about equal in length. The basal lobes are small and inconspicuous. The limb is gently convex, and slopes equally on all sides away from the central lobe, from which a sharp furrow separates it all round ; one or two faint depressed radiating lines occur on the limb. The margin is strong and continuous, an narrowest poste- riorly, where it ends on anh side with a projecting tubercle or minute spine. The small basal or neck-lobes are transverse. Body rings unknown. (They might surely be found at Builth by collectors.) Tail ofthe same shape as the head, broadest posteriorly, margined all round distinctly, and with a pair of spines which occur on the sides, so far back as to be on a level with the hinder margin. The axis is short and obtuse, not reaching much above halfway down the tail, and leaving a broad equal limb. The axis is divided very unequally by a transverse line into an upper and a lower lobe, at the junction of which is the prominent tubercle characteristic of the genus. The lower or terminal lobe of the axis is as broad as long, the upper lobe twice as broad as long; a pair of minute lateral BRITISH FOSSILS. ¥¢ transverse lobes at the margin of the axis lie above this, one on each side. Locality and Geological Posituon—UpPeR LLANDEILO FLAGs. Builth, Radnorshire; Llandeilo, Caermarthenshire; Marrington, Wilmington, and Shelve, Shropshire. AGNOSTUS MOREA. ) PuaTe I. Fie. 13. Diacnosis. A. minor, capite radiato, radiis profundis bifidis. Gla- bella angusta subclavata. Description._—A. small species, and the only one detected by Mr. Lightbody and myself in the black shales west of the Stiper stones. Jt is remarkable for the strong radii on the limb, which are bisected halfway out by intermediate furrows. About seven of these principal radii occur on either side. The glabella is narrow and rather short, somewhat clavate, the sides constricted below the upper third, where the transverse furrow occurs. The basal triangular lobes are of rather large size. Named after the Rev. J. More, of Linley Hall, under whose hospitable guidance it was found in the following-— Locality and Geological Position.—LowER LLANDEILO (Arenig eroup) of Cefn Gwynlle, W. of the Stiper Stones, Linley, Shropshire. Section 3.—Trinovus, McCoy. A, LIMBATUS. Synonyms. A. frinodus, Mem. Geol. Survey, vol. ii. pt.1, pl. 8, fig. 11 (not figs. 12, 13, which belong to A. trinodus proper), A. limbatus, Salter, Mem. Geol. Surv., vol. iii. (ined.) p. 41. I only introduce the references to this imperfect fossil to coim- plete our account, and induce collectors to pay attention to a rare form. Locality and Geological Position.—Caradoc, Wexford. (Survey Coll.) 8 BRITISH FOSSILS. AGNOSTUS TRINODDS. Pirate I, Fires, 8—10. Diaenosis. A. brevis, semiuncialis. Caput suborbiculare, glabella Moonh y 2 ss Pees se Coad convexa, nec ultra 2 capitis extensa, integra; limbo convexo. aUuad transversa, convexa; axi miruto conico, vix dimidium caude efficiente ; utringue biloba, tuberculoque magno. Limbus posticus convexus, 4 margine — bispinoso et ab axe profunde sejunctus. Synonyms. Trinodus agnostiformis, McCoy, Sil. Foss. Ivel., pl. 4, fig. 3; in Pal. Foss. Woodw. Mus., t.1E., figs. 12, 13 (mot fig. 11); 7. tardus, ib., fig. 9 |.A. glabratus, Angelin, Pal. Suec., t. 6, fig. 5 |. The original figure in the Memoirs of the Survey was not quite satisfactory, for the tail segment (from decomposing limestone near Haverfordwest) had lost its axis furrows and its marginal spines. It is replaced by better specimens in our Museum from Ayrshire. The head has been found more abundantly than the pygidium, and is at once distinguished from all other British published forms (except the kindred species, A. limbatus) by the simplicity of its glabella, in which, and many other points, the species closely re- rembles A. tardus, Barrande. There was a wrong reference in my first description of this species, for I quoted Professor McCow's synonym for the A. lam- batus next described, regarding both as varieties of the A. trinodus, and giving the present one the varietal name, 6. convexus. McCoy corrected this error in the Cambridge work, where he again figured two imperfect heads of the species. I hope now to have remedied all our deficiencies by these excellent specimens, chiefly obtained by Professor Wyville Thomson from Ayrshire. Description—A. small species, not above five lines long and three lines broad, very convex for the genus. The head and tail rounded, with a narrow equal border all round, very distinct and separated by a sharp sulcus. In the head the limb is equal in breadth in front and on the sides, separated by a sharp line from the short parabolic glabella, which has no lobes or furrows of any kind. It is a little constricted about the middle, and is rounded at its base, just above a pair of small transverse basal lobes. . The posterior angles are contracted and minutely mucronate (fig. 8 a). The body rings are not known. The tail (fig. 10, 10 a) is semioval, the upper angles not contracted like the base of the head, but rectangular. The central lobe is BRITISH FOSSILS. g shorter than the glabella of the head, and hyperbolic rather than parabolic in outline; its breadth at base is greater than the whole length. A sharp sulcus surrounds the central lobe, which has two pairs of furrows faintly marked out; the upper ones transverse and reaching far inwards, the middle pair of furrows rather below the middle. A prominent round tubercle ornaments the centre of the lobe, of larger size than usual in the genus. The limb is very con- vex, and the marginal rim is broader than that surrounding the head ; it has a pair of strong short spines on its outer and lower border, which are placed higher up than in A. McCoywi and A. privnceps, before described. Affinities.—There is no trace in A. tardws (Barr. Boh. Trilob., pl. 49) of the slight lateral indentation in the glabella, which indi- cates the position of a furrow. Nor are there any traces in his specimen of the lateral spines to the tail, any more than in the allied Swedish form, A. lentiformis, Angelin. But the A. glabratus of Angelin, a Caradoc form from Besstorp, in Vestrogothia, is far more like, and if | might suppose that his artist had made the form too elongate, and drawn the tail axis too large, I should consider it identical. The body rings in his species are very clearly shown (and ours should be sought for). The second ring differs a good deal from the anterior one. Localities and Geological Position.—Haverfordwest, S. Wales ; Bala and other localities in N. Wales; Shineton, near Cressage, Shropshire, &c.; Chair of Kildare, Ireland ; Penwhapple Burn, &c., Girvan ; Ayrshire. Foreign.—Probably Vestrogothia (D.), as A. glabratus, Angelin. Section 4.---PHALACROMA ? AGNOSTUS.—Sp. Prats. To Wie, 12: We have only the caudal shield of a species resembling the 4. mudus of Beyrich (more like that species than any British one). The central portion is but faintly marked out ; it is, however, smaller in proportion to the limb than in the Bohemian species. The length of the pygidium is less than two lines. It is long- semioval, the border concave, and is nearly as broad as the axis, 10 BRITISH FOSSILS. which is half the length of the tail, not very strongly marked out, and has a small anterior prominence. The Caradoc or Llandeilo flag species, A. lambatus, Salter, is somewhat like it in the broad and somewhat duplicated border, but differs in the much smaller axis, and more backward position of the central tubercle. Our species, imperfect as it is, is distinct from and lies midway between this species and the Bohemian A. nudus, a primordial form. Locality and Geological Range.—LowER LULANDEILO (Arenig eroup). Tai hirion, west of Bala, collected by J. W. Salter in 1853. Section 1.—AGNOSTUS ? AGNOSTUS TRISECTUS. PLATE. 1, Baie ae Diacnosis. A. cauda subrotunda inermi, axi longo trilobato, multi- segmentato. Axis fere percurrens, latus, ad medium constrictus et tuber- culatus, sulcisque longitudinalibus binis approximatis exaratus. Two specimens only have been sent to Mr. Tennant of this rare species. It is very like A. princeps, from which it differs, at first glance, by the central narrow ridge on the axis, running down throughout its whole length. It is, besides, apparently a flatter species, and has no trace of the posterior spines, but in their place a simple swelling of the margin on each side. This character is unusual. It is a small species, the tail not being above a line and a half in diameter. It is about as broad as it is long, much rounded in out- line, very slightly convex, but the flatness may perhaps be due to pressure. The axis is very broad, and the basal lobes—those next the thorax—are broader and longer than usual, and nearly equal and similar to the second lobe of the axis. The large terminal ovate lobe is longer than the other two put together. All three are deeply divided along the middle line by a pair of parallel furrows, which divides the axis into three strong lobes ; hence the trivial name. Locality and Geological Position—UPrPeR Lineuta FLaes. Black Shales of Whiteleaved Oak, Malvern. Probably not un- common ; it is a conspicuous species. BRITISH FOSSILS, 1] EXPLANATION OF PLATE I. Figs. 1-5. Agnostus princeps, Salter, specimens from various localities and in different states. Figs. 1, 2, are from the Lower Lingula flags of Felyn Rhyd Waterfall near Maentwrog, and only show the radiations faintly. [Fig. 1. is the most perfect known, and fig. 1 a is the same magnified. Mus. Pract. Geology]. Fig. 2 is a piece of the compressed slate, showing the ordinary condition of the fossils. Fig. 3. Variety from the Upper Lingula flag of Penmorfa, under the church. ’ 5 * ' 5 ‘ a + ’ nt ' b : t - e ¥ + i? ‘os ‘ - = i ’ it ‘i r * F 7 ea . bs - A 1 i a ’ ' ¥ t F - + ; ‘ Fr, A i 1 = = ‘ i i 3 : t ) i ‘ i . ‘ y - . , . 7 f i | - ae A) . . DECADE 11. PLATE 2. (beological Surbep of the Tuited Kmydont. STYGINA | (Lower Silurian) a STYGINA LATIFRONS Salter. C.R.Bone,delt JW Salter direx* BRITISH FOSSILS, DrEcADE XI. PuateE II. en STYGINA LATIFRONS. [Genus STYGINA, Satter, 1852. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Asaphide.) Body ovate, flattened ; head and caudal shield nearly equal ; body of nine rings ; eyes small, placed far backward and inward, near the base of the glabella, which is quite distinct above, and much contracted below. Facial suture marginal along a wide space in front, and below the eyes curved outward and - ending on the posterior margin. No rostral shield. Labrum convex, entire. Axis of body narrow. Pleure without furrows. Caudal shield with a long axis. ] Diagnosis. S. sesquiuncialis, ovalis, axti angusto; spinis capitis brevissimis. Caput semiovale, obtusum, glabella ad basin angustissima, oculis retrorsis, fere ad basin capitis retractis, Cauda semiovalis, obtusa, axt subannulato. Synonyms. Asaphus latifrons, PortLock, Geol. Rept. Londonderry and Tyrone, pl. 7, figs. 5,6. A. marginatus, ib., fig. 7. Stygina latifrons, SaLTEeR (1852) in Rep. Brit. Assoc. Trans. Sect. p. 59. Id. “ Siluria,” Ist ed. 18, and 2nd ed. 1859, p. 184, Foss. 26, fig. 2. Among the many new and interesting forms of Trilobites de- scribed by Colonel Portlock in his work on Londonderry and Tyrone, a small species of Asaphus is recorded from the Lower Silurian of Tyrone, which he named 4A. /atifrons, distinguishing it from some other species by the breadth of front included within the curve of the facial suture. The species is remarkable for the position of the eyes, which are placed far backward and inward, so as to be close to the base of the small and narrow glabella. This peculiarity of habit is associated with some other characters which will remove the species from Asaphus. The flattened oval form, long axis to the tail, and the head spines, much resemble those of Asaphus, from which the nine ungrooved pleure effectually distinguish it. In the partial obliteration of the glabella, number of body rings, and course of the facial suture, it is closely allied to Illenus, from which its habit differs so much ; and there is enough of the under side preserved to show there was no rostral shield, which last is an essential character of Ille@nus. [X1. 1] ibs Z BRITISH FOSSILS. Description.—The general form is depressed and elliptical, the length about 14 inch, the breadth 1 inch. The contour of the head, which is exactly as long as the caudal shield, and more than one- third the whole length, is nearly a true semi-oval, evenly convex except on the median line behind (which is abruptly raised), and slopes on all sides to a concave border. The glabella, scarcely defined at all in front, though faintly indicated (more strongly so in young specimens), is of a pyriform shape. Posteriorly it is much con- tracted, and again suddenly expanded upon the neck border. Its greatest width behind is not above one-fifth that of the head. The eyes are small, convex, much curved, placed at less than their own length from the hinder margin, opposite the contracted part of the glabella, and rather further apart than the width of the thoracic axis. The facial suture runs out nearly at right angles beneath the eye, and in front of it describes a large arc, diverging from the eyes at an angle of 70°, and cutting the anterior border far outwards, in a line overhanging the fulcral points. The facial suture is strictly marginal in front, and the hypostome, fig. 4, appears to be quite con- tinuous, without a rostral shield as in Jl/lenus, or a vertical suture, as in some Asaphi. Two good specimens in Dr. Wyville Thomson’s cabinet show the labrum, but its margin is broken off. It is wide at its attachment, considerably convex in the middle, more so than in Asaphus, and is marked with concentric lines on the sides. There is not enough to show that there was no marginal groove, or whether the tip was rounded and entire, as in [llcenus, which is most probable. Thorax of nine rings, not so long as the head, and with its axis only two-thirds as wide as the pleurze, convex. Pleure flat as far as the fulerum, which is about the width of the.axis remote from it. Thence the pleuree are bent down and a little back, and facetted for rolling up. There is no groove whatever to the pleure, which thus resemble those of Jilenus. Tail semi-oval, blunt, not convex, the conical axis about half the width of the sides, and reaching fully two-thirds the length of the tail. Our figure 24. has it too long. The axis has about eight faint furrows. The sides are gently convex at first, and then broadly concave, with a somewhat sharply defined margin; it is without any furrows,—even the usual upper one is obsolete, or nearly so. The apex is very blunt, more so than the front of the head. The incurved striated portion is broad, and not indented by the point of the axis. BRITISH FOSSILS. 3 By some accident my name is attached to this species on the plate. Our specimens are those figured and described by Portlock. Locality and Geological Position.—-Carapoc of Desertcreat, Tyrone. OTHER SPECIES OF THE GENUS. I only know one other British species, and no foreign ones. Ss. MURCHISONIA, Murch.—S. converus, trilobus, capite longo semi- ovato, spinis productis. Cauda longa, axe prominulo levi. Synonyms. Ogygia Murchisonia, Murcu., Silurian System, 1837, pl. 25, fig. 3. Stygina Murchisonia, SALTER in Siluria, 2nd ed. 1859, pl. 4, fig. 1. Morris, Catal. 2nd ed. p. 115, 1854. Although only a single specimen of this has been found, there can be little doubt of the genus to which it should be referred. The contracted axis of the head and body, and the smooth tail with its strong axal lobe, are at all events extremely like those of Stygina. Locality—In LLUANDEILO FLAGS? Mount Pleasant, Carmarthen. It is, however, probable these are Caradoc strata. J. W. SALTER. November 1864. EXPLANATION OF PLATE II. Fig. 1. Portlock’s original specimen figured in the Geological Report on Tyrone. Fig. 2. Dissected head of the same, showing obscure pyriform glabella, its base (a) only convex, and part of the striated incurved portion c, d, continuous with the hypostome to the short posterior angle, where it is obliquely folded. At b, the termination of the facial suture beneath the eye. Fig. 2. e, f, thoracic rings of the same; g, tail showing the fulcrum. Fig. 3. Larger specimen (the figured specimen of A. marginatus, Portl.), showing impression of the labrum Zn situ. Fig. 4. Under surface of one of Prof. Thomson’s specimens, with broken labrum showing concentric lines. ao i SMieAy ee a 2, pees BA Oe alla WEIL ie caieps alba aap ASAPIEU'S Seologisal Surbep of the United Kingdom. ; Lower Silurian. ASAPHUS (ISOTELUS) Gicas_ DeLay. TW Vows BRITISH FOSSILS, DecaDE XI. Prats III. - ASAPHUS GIGAS. [Genus ASAPHUS. BRONGNIART. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Asaphide.) Eyes large, smooth. Facial suture marginal or supramarginal in front, and ending o1 the posterior margin. No rostral shield. Labrum strongly bifurcate. Body rings eight. | [Sub-genus Jsotelus. Dm Kay. Facial suture imtramarginal in front, and with a vertical suture beneath ; head scarcely at all lobed ; pleure much bent down ; tail large, with faint axal furrows and no lateral ribs. | Diaenosis. L. ovali-oblongus levis, laieribus rectis ; capite pygidioque equalibus subtrigonis hyperbolicis. Caput suleis axalibus minime pro- fundis. Oculi modict pone medium capitis positi. Sutura facialis intra marginem frontalem parallela; labro* ad basin angusto, furcis longis parallelis, Thoracis axi pleuris equali, fulero ad tertium posito. Cauda axt indistincto angusto conico longo, limbo sulco unico superiore, reliquis nullis. Synonyms. Asaphus platyceph., Strokes (1822), Trans. Geol. Soc., London, i. 8, p. 208, pl. 27. Isotelus gigas and I. planus, Du Kay (1824), Annals of the Lyc. of Nat. Hist. of New York, vol. i. p. 176, pl. 12, 13, fig. 1. Asaphus gigas, Daum. (1826), Palead. 71. Isot. gigas, GREEN (1882), Mon. of Tril., p. 67 ; also I. planus, p. 68, I. stegops, p. 71, I. cyclops, p. 69, and I. megalops, p. 70. Brongniartia isotela, Eaton (1832), Geol. Text Book, pl. 2, fig. 19. Asaph. platyceph. Bronn. (1835), Leth., vol. i. p. 115, pl. 9, fig. 8. Asaph. gigas, Emr. (1839), Dissert. 32, 12. Isotelus gigas, Mitne-Epw. (1840), Crust., vol. iii. p. 298. Asaph. platyceph., BucKLAND (1840), Bridg. Treat., vol. ii. p. 76. Asaph. platy- ceph., Burm. (1843), Org. Tril., pl. 2, fig. 12, Ray, ed. (1846), p. 110. Portt. (1843), Geol. Rep. Jsot. gigas, pl. 7, figs. 1-4, pl. 8, fig. 7 ; I. planus, pi. 7, figs. 2, 3 (except pl. 8, figs. 2, 3); £. ovatus, pl. 8, fig. 5 ; I. sclerops, pl. 10, fig. 2; £ Powisi, pl. 6, fig. 1. I. megistos, LocKE (1842), Amer. ~ Journ. Science, vol. xlii. p. 366 ; Trans. Assoc. American Nat. and Geolo- gists (1843), vol. i. pl. 6. J. gigas, Haru (1847), Pal. New York, pl. 60, fic. 7; pl. 61, figs. 3, 4 ; pl. 62, figs. 1,2; pl. 63. J. gigas, Brtiinas (1868), Geol. of Canada, p. 184, fig. 182 (and L. platycephalus, ib. fig. 183?) * I prefer this term to hypostome, used in the former Decades. ‘The hypostome of - Dalman is the incurved front margin. (Se iit ai © 2 BRITISH “FOSSILS. I have figured this fine species from General Portlock’s original specimens, and I follow most writers in adopting De Kay’s name, because it must have been contemporary with the publication of Stokes’ paper (though the latter was read early in 1823). Even were A. platycephalus a little the earlier name, it was published without any description. And it is just possible that the fossil ~ described by Stokes may belong to a different species. Description.— General shape oval-oblong, with the sides rather straight, the head and tail nearly equal, and both subtriangular, the head pointed, the tail more obtuse at the tip. The surface is convex when the fossil has not undergone compression, a line taken from the snout to the apex of the tail being a regularly convex one, uninterrupted by any neck furrow, depression, or convexity of the smooth and even body rings, or furrows on the axis of the tail. The axal furrows are very obscure in the head ; they are neatly marked but shallow along the body, and only very faint along the tail. All the surface is smooth. The sides are strongly deflected, but not steep. , The head has the shape of a broad and pointed Gothic arch, the breadth at base being to the length as three to two. The margin is very narrow and flat, rather than recurved. ‘The facial suture forms a broad ogive arch in front, running for some distance close within and parallel‘to the front margin ; and, beneath the eyes, which are large, placed near the glabella, and rather behind the middle of the head, the suture curves gently out and cuts the posterior margin mid- way from the axal furrow. The hinder angles are blunt pointed, not rounded. On the under side of the cheek near the point is a convex space, containing an oval depression, which receives the apices of the front pleurze in rolling up (fig. 6, and see also fig. 5 for the cast of this depression on the matrix). The labrum (fig. 7) has a narrow base, then a strong constriction, and thence the sides are parallel. The apex is deeply furcate, the parallel forks occupying nearly half the entire length of the organ. Body rings smooth, rounded at the apices, deflexed at the fulerum, which is placed rather beyond one-third, and with a broad strong groove. Tail sub- trigonal, with straight sides, and rounded blunt tip. The faint axis rapidly tapering, broad conical, and reaching three-quarters the length. Sides quite sixooth. In young specimens, says Hall, the caudal extremity is more pointed, and exhibits marks of eight articulations ; in older spe- cimens these increase in number. But the crust presents many BRITISH FOSSILS. 3 traces of them when viewed from within ; they are often distinct (Hall, 1. c, 231). Burmeister also calls attention to this character. It appears to be frequent in the genus and its allies, for I have seen Swedish specimens, both of Asaphus and Illwnus, which exhibited it strongly, chiefly on the axis. In like manner the lobes of the glabella often show internally, though quite obliterated on the ex- ternal crust. I have not seen them in this species, but Burmeister gives them in his figure, of which he boasts the absolute accuracy. We can at least say as much for ours, so far as the specimens exhibit character ; and our plate of this species is alike creditable to the artist, Mr. Bone, and the engraver, Mr. Lowry. Variations.—There seems to be some reason to think there may be two species in the American limestones; one rarer, of broad form and with small eyes—the true A. platycephalus of Stokes ; the other very common, of elongate form, and with variably large eyes, to which nearly all the above synonyms belong. See figures of both forms in the “ Geology of Canada,” 1863, by Sir W. Logan and E. Billings, p. 184. I have quoted these above. On the other hand, I should have no difficulty in referring these differences to sex, the broad A. platycephalus being the 2 form. History.—It is not necessary to refer to the American authors, who have profusely illustrated this common species. But I feel persuaded that Prof. Hall is right in uniting all Green’s casts under one name; the more so as Hall had several hundred specimens at command in every degree of perfection. Prof. Green’s species are chiefly due to differences of position, and in attempting too closely to identify each of these, Gen. Portlock separated the Irish specimens he de- scribed into more forms than can be now admitted. J. gigas and I, planus of Portlock he himself considers identical. J. ovatus, id., differs in nothing but its size; the head is really not more elongate than in his specimens of J. planus; and with regard to his I. Powisw, the more depressed form is entirely due to pressure; and the fulcrum is at the same proportional distance,—about one- third from the axis (not more distant, as stated); the appearance is due only to the before-mentioned cause. The true A. Powisit, Murch., has distinct ribs to the tail, square ends to the pleure, and a swelled glabella, but the Irish specimens all resemple J. gigas in these respects. I do not know that the true A. Powisii occurs in. Ireland, while [. gigas is not known in England. The large Isotelus megistos, which is certainly the same species with J. gigas, has been reconstructed in the form of a cast by Laon A, BRITISH FOSSILS. American authors, as of enormous size. The cast which is com- monly sold for lecture purposes indicates a form 21 inches long ; but there is no pretence for making it more than two-thirds this length. Asaphus gigas is not one of the largest of Trilobites. Locality and Geological Position.—CaRanoc of Tyrone (Port- lock). The species ranges from Canada to Tennessee, and it is rather remarkable that it should abound in N. Ireland without reaching further to the eastward. Some other American species appear to range to Ireland, but are not otherwise members of the British Silurian fauna. OTHER BRITISH SPECIES OF THE SECTION ISOTELUS. 2. I. rectifrons, Portlock, Geol. Report, 1843, pl. 9, fig. 1 a, b; also pl. 8, figs. 2, 3, 7, only referred to under J. planus. These belong to the head. J. arcuatus, ib., pl. 9, figs. 2, 3 (tail of same species). I. entermedius, ib., pl. 9, fig. 5. Head semicircular convex; the angles rounded, and showing the characteristic pit for the pleurze some distance above the angle. Glabella between the eyes about equal in width to the cheeks. Eyes large, placed much behind the middle of the head, and very much curved. Eye-line straight and directed outwards above the eye to the front margin, along which it runs. Beneath the eye it runs outwards, nearly parallel to the posterior margin. In the front of the head there is no vertical suture, the front being striate and showing rather a narrow base for the attachment of the labrum. The tail and body Portlock called J. arewatus. The body seg- ments have the axis broader than the pleurz, which have the fulerum close in, and are bent back from it and rounded at the ends. The tail is wider than a semicircle; the upper angles are much bent down for the facet. The axis is marked out at its origin by two rather deep 1 impressions, and is here rather wider than the side lobes. Thence it is not indicated, except by a slight promi- nence at its apex, which reaches to three-fourths the length of the tail. A broad shallow furrow beneath the fulcrum is all the marking that shows on the smooth convex sides. Incurved portion narrow, concave ; its edge not indented by the © point of the axis; strongly lineate, the lines abutting sharply against the margin. I. intermedius is too like the species just imoripned to be catalogued as distinct. It is much pressed out of shape and BRITISH FOSSILS, D obscured. But the L. leviceps of this author, though not the same as the As. leviceps of Dalman, is probably a member of the section Cryptonymus, a group which has the axis and glabella lobes well -marked out, and often has very prominent eyes. It is very rare in England and absent in America, but is the common form of the genus in the Swedish area. Asaphus levigatus, Angelin., Pal. Succ. pl. 29, fiz. 1, in many respects resembles A. rectifrons. Locality.—Caradoe of Desertcreat, Tyrone. 3. I. sp. Salter, in Quart. Geol. Journ., vol. vii. pl. 8, fig. 2. A caudal portion of an undetermined species has been figured by Sir R. I. Murchison in his paper on the Silurian Rocks of the 8. of Scotland. It is probably distinct from I. gigas. 4,? Another is quoted in Prof. Nicol’s paper on the Peeblesshire Silurians, Quart. Journ., vol. iv. p. 205, which is lost now, but was stated by myself to be allied to Asaphus (Lsot. megistos) gigas. Both these species require further illus- tration ; but they seem to show the gradual dying out of the American type Jsotelus in its range eastward, as above noticed. Possibly both are referable to Megalaspis. The distribution of subgenera over the northern zone is as foliows:—. N. American Types. British Types. Scandinavian Types. ee Isotelus, rare, N. and N. [ Jsotelus, absent. | Isotelus, common. West only. Basilicus, rare. Basilicus, common, also in Cryptonymus, common. Mid-Europe. Nileus, common. Ptychopyge, rare. Cryptonymus, very rare, in Megalaspis, do. N.W. area. Ptychopyge, do. EXPLANATION OF PLATE III. Fig. 1. Asaphus gigas, De Kay, the original specimen figured by Portlock as Jsotelus planus, De Kay. It shows the vertical suture to the hypostome and the labrum in place. | Fig. 2 Do. (Portlock’s original of J. ovatus.) Fig. 3. Do. (Portlock’s figured specimen of I. sclerops.) Fig. 4. Tail of do. Fig. 5. Cast of under surface of side of head, showing the eye, and the pit for the reception of the ends of the pleure. Fig. 6. Gutta percha cast of the same specimen, showing the real under surface. All the above are from the Caradoc of Desertcreat, Tyrone, and are in the Mus. Pract. Geology. J. W. SALTER. November 1864. “i! Ell PLATE CADE x 4 dD By PSO} ft cial a a m 8 Se =e) mh 8 wae: (@} I As | 4 We H at SEER y AT Wt SO — SSNS > IgQVoM. ia ? te v oO ss Ae etn 2 / y | ly natal wa BINODOSA _ Salter GRANDIS ? _G. AGLINA Tae. Be se Gy Ue ok SEP. J.W.Lowry fe. divrex* JW. Salter 1 elt Home ¢ RJ r BRITISH FOSSILS. DECADE XI, Puate LV: Fes. 1-6. AGLINA BINODOSA., Genus “EGLINA. BaRRANDE, 1847. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Asaphide.* Body oblong, the extremities equal, rounded. Head convex, glabella large, rounded or parabolic, not distinetly lobed ; eyes very large, - occupying the whole, or nearly the whole cheek, coarsely granulated (externally ?); facial suture ending on the posterior margin close to the axis. No rostral shield. Thorax with five or six rings, the axis broad, the pleuree facetted and grooved. Tail large, the axis of ‘two or three rings, abbreviated ; the sides few-ribbed, or nearly smooth. Cyclopyge, vieoons ] -- -Dracnosts. 4. lata, biuncialis et ultra, convexa, capite grandi inflato, levi; segmento thoracis tertio binodoso ; cauda triangulata profunde 6 ispee ‘SynovyMs. | -Aglina binodosa, SALTER, Siluria, 2nd ed., p. 50, Foss. 8, fig: 6. Id. Mem. Geol. Surv., vol. iii. ined., pl. 11 8. fig. 3. The genus has been previously ‘illustrated in Decade VIL, but from less perfect materials. Descriptiow.—About an inch long, and three-quarters broad in the widest part; the head very blunt in front, and the tail taper- ing acutely. The glabella is round and inflated; the axis of the body tapers quickly backwards, and the tail is truly triangular. These characters and the tubercles on the third body segment will easily enable the collector to identify it. The head is seldom perfect, but, from many specimens, must have been transverse-oblong, while the glabella is perfectly round, in- flated, and showing no trace of lobes or furrows. It has a narrow border down the aales marking the course of the facial suture, and separating the glabella from the broad lunate eyes, which are coarsely granular (fig. 3) and occupy the whole cheek. As usual in the genus, the inflated glabella shows no trace of a neck segment. * For the present I do not wish to cut up this large natural group. But a better knowledge of the primordial forms of it will doubtless render it necessary to do so bye and bye. iglina has some relation to Remopleurides ( Olenide). [XI. iv.] ene if, 2 BRITISH FOSSILS, Beneath the head the hypostome is- continuous *(fig. 2a) and tumid, without rostral shield or any suture, and the convex labrum has rather a broad base, as in I[llenus. The thorax is convex, and has a wide and much tapering axis, broader than the sides. It is greatly wider in front than its pleure, and behind is not quite so wide .as these. Its rings are gently arched, and the third one bears a pair of those enigmatical tubercles which are of so common occurrence along the, central lobe of Trilo- bites.* The front pleurge are very short, and the hinder elongated. They are more curved forward than our figure indicates, at least in the central and hinder rings. The fulcrum is near the axis, the groove broad, not deep; the apices truncate, and a little pointed behind. The facet is long and narrow. The tail is truly triangular, and except that the apex is rounded off, would be an equilateral triangle, deeply and strongly margined all round, and with a narrow conical axis which reaches two-thirds and rather more of the length. Its tip is rounded, and it is marked by a single broad ring at the base, and very faint traces of two or three others. Variations.—Young specimens, which I have seen since the plate was engraved, in the choice cabinet of Mr, H. W. Edgell, show the metamorphosis. In a specimen which is barely two lines in length, the number of rings to the body is only four, and the fourth ring 1s scarcely separable from the caudal shield. The axis of the latter is narrower than in full-grown specimens ; but I do not see much other difference. This is one of the most conspicuous species of the genus, and in great plenty in the black slate of one locality. It differs so markedly from all the other species, in the triangular tail with a prolonged axis, that it is unnecessary to compare it with any. It appears to have grown to a less size than 4. grandis next described. Locality and Geological Position—LowER LLANDEILO FLAGS (Arenig group), Cefn Gwynlle, in the district west of the Stiper Stones, Shropshire; in black slate, abundant. My friend, Dr. A. Fritsch, of Prague, tells me he has found the same species in the Lowest Llandeilo beds (d. 1) of Prague. I suppose it a closely allied, not identical, form. * They have been specially noticed in my memoir on the Phacopide, Paleont. Trans- act., vol. for 1862, p. 52. And they are conspicuous under various forms in Encrinurus, Cheirurus, Sao, and a host of other genera. Probably they indicate the places of cutaneous glands, but their purpose is not yet evident. BRITISH FOSSILS. 3 EGLINA GRANDIS. PuatTe, LV. Fas. 7, 8. Draenosis, 2. ovalis, 2-3-uncialis, depressa, tuberculata, axe corporis angusto ; cauda rotundata levi, lateribus unisulcatis. Synonyms. Aglina grandis, SALTER, Siluria, 2nd ed., p. 53. Foss. 9, fic. 6. Id. Mem. Geol. Surv., vol. iii. (ined.) pl. 12, fig. 11. Description—Oval (rather depressed?) 12 inch long; head more than two-fifths the whole length, with a large glabella without lobes, covered with rather prominent tubercles. This character is so remarkable in the genus that no long description is necessary to enable us to recognize the species. The eyes are very large, as long as the head, and there appears to be a larger border beyond them than usual in the genus. Body of six rings, the axis narrower than in most of the species, broadest in front, contracted behind, where it scarcely equals the pleurze in width. These are bent at the fulcrum, which is placed rather more than one-third out from the axis in the front rings, and nearly at half in the hinder ones. The tail is semicircular, and has rather a conical axis of two joints, rather long in our figure 8, which I believe is the same species. One obscure lateral furrow (the uppermost) is all that. is visible on the smooth sides. A distinct margin runs all round the tail, neatiy defined, but not by a broad or deep furrow. The shape of the tail in fig. 7 is much rounded, and more than a semicircle. In fig. 8 it has been compressed longitudinally, and has a shorter aspect; but I believe this is only due to compression in the slaty rock. 1 The largest specimen I have seen appears to have the fulcrum of the pleuree further inwards, but agrees in other respects with the remaining specimens ; at least it has the tubercular glabella, a character in which our species differs from all others. Of the two British species previously described; &. mirabilis, _ Forbes, has a parabolic and lobed smooth glabella. 4. major, Salter, has a wide body axis, and two lateral furrows in the tail. All Barrande’s species have a smooth glabella, and are very much smaller than ours, except his 4. speciosa, which has a very broad axis and short marginal eyes. Locality—Lowsr LiLANDEILO FiLaGs (Arenig group ?), South side of St. David’s Head, Pembrokeshire. A BRITISH FOSSILS, EGLINA, Sp. (EYES OF). y PLATE LV, Fie. 9. This large species is perhaps not the largest “glina known; M. Barrande has an enormous one from the Llandeilo rocks of Bohemia, with a projecting front to the head. Ours probably was six inches long, and the great eyes an inch and a quarter long (no other part occurs with them). The eye of this species lay for a long while in the Museum as an undescribed Bryozoon from the Llandeilo flag. Contrary to the usual arrangement in the eyes, the lenses are in quincunx, instead of hexagons (see fig. 9b), and very closely set ; but in some parts the normal hexagonal arrangement is seen (fig. 9c). Locality—Urrer LLANDEILO FLAGS of Abereiddy Bay, Cardigan- shire. The rest of the body should be sought for there. EXPLANATION OF PLATE IY. Fig. 1. Aiglina binodosa, Salter, nat. size, Lower Llandeilo (Arenig) group of Cefn Gwynlle, Stiper Stones, Shropshire. Fig. 2, 2 a, magnified. Labrum and hypostome of do. Same locality. Fig. 3, 3a, magnified. ye of do. Fig. 4. Body rings, showing the tubercles on the third segment. Fig. 5. Tail, nat. size. Fig. 6, All the above portions are enlarged in this figure. . Fig. 7. dglina grandis, Salter. A small specimen from the Lower (?) Llandeilo rocks of Whitesand Bay, St. David’s, Pembrokeshire. Fig. 8. A compressed tail. Same locality. ; Fig. 9a. Aiglina,—sp. An enormous species, of which we have ouly the great eyes in their natural position. The slate is much compressed and folded. 9 b,c, magnified parts of the eye. Upper Llandeilo, Abereiddy Bay, Pembrokesh. All the above are in the Mus. Pract. Geology. J. W. SALTER. November 1864. ... Aas i's ‘ : DECADE 11 PL.5 ow . WG “t & o Z ou a - | Geslogreal Survep of the Varited Kingdom. STAVROCEPHALUS ( Silurian ) 4 2 figs.1 4/5?) STAUROCEPHALUS MuRCHISONI — Barr 6 mistake _ GLOBICEPS _ Fortto cle * C.RBone del JW. Salter, direx’ . IW. Lowry fe. BRITISH FOSSILS, DECADE XL PLATE V. STAUROCEPHALUS MURCHISONI. [Genus STAUROCEPHALUS. Barranpn, 1847. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Cheiruride.) Head cruciform, with long clayate glabella, greatly swelled in front into a hemispheric lobe, the base narrow cylindric, with three pairs of furrows. Cheeks convex, with pedunculate eyes and serrate margin. Facial suture ending on the external margin. Body rings.10, without pleural grooves, pointed. ‘Tail of few segments, the apices of the pleure free. Birrdnde.| Draenosis.—S. ovatus, tuberculosus, oculis remotiusculis, margini genarum spinoso. Cauda quadrata, pleuris omnibus equalibus retrorsis parallelis, haud divaricatis. Synonyms. Staurocephalus Murchisoni, BARRANDE (1852), Syst. Sil. Bohéme, pl. 43, fig. 28-32. S. Murchisoni, Sauter, in Siluria, 2nd ed. 1859, p. 540; Id., Morris’s Catal., 1854, p. 115. One of the most curious, though not most conspicuous, of our British species. The globular head, or rather glabella, set on its narrow stalk-like base, the gibbous cheeks, projecting eyes, serrate border, and spiny comb-like pleuree and tail, combine to give an extravagant and unusual appearance to the fossil. It is seldom found perfect. But the skill of the Dudley naturalists has long been exercised on it, and specimens are now to be found in many cabinets. Mr. Hollier’s specimens are the principal ones figured. Mr. Ketley has some fine ones, and our figs. 1, 2, are from the Museum of Practical Geology. They were formerly part of Mr. E. Dayis’s collection at Presteign. Deseription.—About an inch long, of which the gibbous head occupies more than two-fifths. This is longer than broad, roughly triangular in general outline, but not truly so. It appears rather four- lobed, or like the heraldic “ fleur de lis,” the truly globular front occupying more than half the length of the glabella, and being at least three times as wide as its semi-cylindrical base, from which it is abruptly cut off by a transverse furrow ; the base is marked by two distinct lateral lobes besides the feck furrow. The cheeks reach forward about-half way up this globular portion, and the [XI v.] Il & 2 _ BRITISH FOSSILS. central part is necessarily raised, so as to be nearly on a level with the glabella. The cylindrical eyes are on the most convex part of the cheeks, and are directed outwards, scarcely forwards. The margin is distinct in front of the head as a very narrow prominent ridge, and furnished on each side with about 14 truncate spines; the cheek spine is directed backwards, and but slightly outwards, abrupt at its origin, and not reaching beyond the two ovr three first body rings. The facial suture cuts the outer border in a direct line from the base of the eye. All the prominent parts of the head are covered with larger and smaller tubercles ; they only fail on the deeper furrows, and the truly vertical outer half of the cheeks. They are conspicuous on the border, and even on the cheek spines. The body and tail united are slightly longer than the head, the thorax of 10 rings many times longer than the short square tail, and the axis about one-fourth the whole width, and highly convex, especially in front. There are no axal furrows to separate the gibbous axis from the horizontal portion of the pleurze, and these soon curve downward, and are abrupt and steep on the sides.’ The pleurze are semi-cylindrical, the front portion, separated by the pleural groove being very narrow in this and allied genera, placed on the forward margin, and scarcely visible.* The apices curve much backward, and in the hinder pleure a little outward again, and are produced into strong spines beyond the ovate facetted portion. And all along these pleurze and over the axis tubercles are placed at equal distances, except that the central prominent tubercle fails on alternate rings of the axis, and the intervening ones, especially the ninth, are stronger than any other behest and remind us of the spines on Lncrinurus. The tail is nearly square, concave rather than flat, the short conical axis, of four rings, not easily distinguishable from the sides, which are composed of three flat broad spinous pleuree directed back- wards, and quite parallel, so as to give a comb-like appearance. A few tubercles are scattered on the surface. Locality and Geological Position—Carapoc Rocks, near Bala, N. Wales (fig. 5) ; WOOLHOPE ‘LIMESTONE AND SHALE, Corton, Presteign (figs. 1, 2); Wrntock Limestone, Dudley and Malvern. * Yet I doubt the propriety of making this character so important in classification as Barrande has done. ‘The pleural groove is always present in one form or another. In this case it is anterior, in Cheirurus it is very short and oblique. BRITISH FOSSILS, 3 STADROCEPHALUS GLOBICEPS. Plz Voc Bie6. Synonyms. Ceraurus globiceps, PortLock (1843), Geol. Rep., Tyrone, 257, t. 1. f. 7. Staurocephalus globiceps, Sauter, in Morris’s Catal., Qnd ed. (1857), p. 116. Diaenosis. S. ovatus granosus, cauda elongata, spina utringue unica divergenti. Glabella stipite brevi vix lebato. Oculi approximati. Spine ‘genales et pleurales diffuse. Cauda brevis, pleuris primarits longeé extensis, latis ; reliquis—? A much smaller species than the preceding, and distinct from it by abundant characters of shape and habit. The divergent spines of head, thorax, and tail enable us at once to recognize it; and of the latter, the remarkable extended first pair of pleurze (the rest of the tail is lost) show a near connexion with the S.? Maclareni,— afterwards described. Only one good specimen, 10 lines long, is known. The head is equal to the thorax in length, and longer than the caudal portion. It has a very large globular front, longer than the square stipes, and granular all over. This stalk or base seems to be without furrows. The cheeks granular, gibbous, with a prominent eye on the front edge, near the glabella, and directed forward, not outward ; a broad plain margin, and widely divergent spines. The axis of the thorax is cylindrical, and as wide as the stalk of the glabella. The pleure flat as far as the fulcrum, which is less remote than the width of the axis, with patent not recurved spines as long as the portion within the fulcra. The thorax tapers back- ward rather rapidly to the tail, which has a short three-ribbed axis, and the upper pair of its pleurz are very much expanded, widely divergent, and more arched than in our figure, which also represents the thoracic pleurze as less curved than they really are. The hinder portion of the tail is absent on our specimen ; and I know of no other. Locality and Geological Position.—CaRrapboc Rocks of Desert- creat, Tyrone (Mus. Pract. Geology). A third form, very abnormal in its characters, and of large size, has been named S. Maclarent by Prof. Wyville Thomson, after the veteran Scotch geologist, in whose company he found it. It is, however, Prof. Thomson’s previously described Acidaspis wirica. As he has mislaid his own full description, I may supply the follow- ing notes, from his specimens and others presented to the Museum of Practical Geology by himself. A BRITISH FOSSILS, STAUROCEPHALUS ? UNICUS. Draenosis. S.14 uncialis, oblongus, sparsé granulosus, glabella gibba eminentissima, corpore plano, cauda expansa transversd. Caput latum, glabella clavata elevata frontem longé impendente, a genis punctatis distinctissima ; margine crasso utringue bispinoso. Pleure subplane, sulcate, recte, apicibus abruptée recurvis. Cauda lata brevis, axi appen-— diculato, pleuris primaris latissimis spatulatis, margine postico truncato. [Synonym. Acidaspis unica, Wryv. Tuomson, Quart. Geol. Journ., vol. xiii. pl. 6, fig. 13. | | In the absence of a figure sufficiently complete (for the one quoted above is very defective), it is necessary to give a rather full diagnosis of this remarkable form, which tends to show the passage of the Chevrurid into the Acidaspid family. Indeed, if Prof. Thomson be correct in figuring 12 segments to the body, the species is abnormal for either Acidaspis or Staurocephalus. The shape of the head clearly enough shows that it is to Stawrocephalus, or else to one of the sections of Cheirurus, that this strange fossil must be referred. Cheirurus often has 12 segments, Acidaspis 9 or 10, Staurocephalus only 10. The grooved pleurz are unlike Stauro- cephalus, but like the section ELecoptochile among the genus Chei- rurus. But no Chevrurus has so clavate a plabelle though a tendency towards it is exhibited in some species, and Spheerocoryphe of Angelin 1 is very near to ours. There is an evident analogy too in this form with Lichas, both in the shape of the tail and the character of the pleure. But the external position of the facial suture far up the cheek easily dis- tinguishes it from that genus. I do not further describe it, as it will appear in a very ne plate in the volumes of the Palzonto- graphical Society. Localities. —CARADOC SCHISTS, at the base of the “ Hig and Graptolite flags,’ Penwhapple Glen, Ayrshire (W. Thomson). EXPLANATION OF PLATE V. Fig. 1. Staurocephalus Murchisoni, Barrande, coiled specimen, natural size. Wool- hope Shale, Presteign. (Mus. Pract. Geology.) Figt 2. Head of ditto, same locality and cabinet. Fig. 8. Magnified figures from the above specimens, completed from Dudley specimens. Fig. 4 a, 6. Magnified specimen from Dudley. Mr. E. Hollier’s cabinet. Fig. 5. Lower Silurian specimen. Rhiwlas, Bala (Mus. Pract. Geol.), nat. size and magnified. Fig. 6. Staurocephalus globiceps, Portlock (his original specimen, magnified three diameters). November 1864. ° J. W. SALTER. \\ i , DECADE IL. PI.6 Geological Survey of the Voted Kingdom. SAW TERIA (Lower Silurian ¥ Fig. 7-2 SALTERIA PRimava — Wyv thomson 4 - a ey AW. Lowry fe TW. Salter direst wry C.R Bone delt Y BRITISH FOSSILS. DEcADE XI. PLATE VL. SS SALTERIA PRIMAVA. [Genus SALTERIA. Wry. Tiromson. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Trinucleids.) Body oval, tapering backwards. Head large, semi-lunar, margin very narrow, simple, surrounding a broad limb. Glabella inflated, furrowed. Facial suture following the edge, except through a small portion on either side, where it becomes nearly vertical and slightly emarginates the upper surface, cutting off a narrow free cheek. [Eyes minute, linear.] Thorax of few segments. Tail of many segments. | Diaenosis. S. fere uncialis, lata, ovata. Caput semilunare limbo angusto brevi convexo marginato; glabella ovata pyriformi depressa, genis multo majori, utringue puteis tribus brevibus notata ; sutura facialis sub fronte ambitui parallela, dein per quaritam partem externam limbi conspicua subverticalis. Thorax articulis truncatis. Cauda triangularis multiseqmentata. We have no hesitation in placing Salteria among the Trinu- cleide. It is evidently closely allied to Dionide, especially to Angelin’s species D. euglypta. They have nearly the same form of glabella with longitudinal grooves ; the same narrow, smooth, concave limb; the same structure of body rings and tail. The great difference between them consists in the presence in Salteria of a distinct though linear free cheek, and apparently of a true eye in its normal position. In these characters our fossil at once recalls Cyphowscus, placed by Mr. Salter, apparently with much reason, among the Olenide. It also resembles this genus in the peculiar character of a delicate striation on the cast of one portion of the head, while the remainder is smooth. We have a specimen of Cyphoniscus from the game beds in Ayrshire retaining the free cheek, and showing a well marked narrow rim, ending in a long, straight, genal spine. The specimen is unfortunately too imperfect to show the eye. In Cyphoniscus the structure of the body rings is quite characteristic, and the small Olenoid tail is very different from the compound tail of Salteria, [XI. vi.] ae 2 BRITISH FOSSILS. Deseription.—Length of adult about three-quarters of an inch. Form broadly oval, tapering backwards. Head large, semi-lunar, slightly but regularly convex. The central shield, composed of glabella and fixed cheeks, is widely semicircular, emarginate exter- nally, with a contour nearly corresponding with that of the head. The head is bordered by a distinct but not very broad, smooth, slightly concave margin, which is continuous with the central shield through the anterior half of the margin, but is cut away at the exterior fourth on each side by the curving inwards of the facial suture. The glabella is rounded-trigonal, in front trans- versely oval and very convex, and slightly prolonged and contracted behind, where it is much flattened; the crust is perfectly smooth. The two posterior glabella furrows on either side are represented by shallow pits, arranged nearly in a square, and occupying the posterior third of the glabella; the anterior pair of furrows by similar depressions more remote, placed near the anterior and outer angles of the middle third. Two aay grooves connect the posterior giabellar depressions with the neck furrow, only shown in our upper figure. The tergal portion of the neck segment is small and convex. ‘The fixed cheeks are large, shehtly at coalescing before the glabella in a narrow ridge, bordered by a still narrower margin. ‘The lateral portion of the occipital groove passes forwards and outwards two-thirds across the fixed cheek, then shghtly back- wards to the lateral margin, cutting off nearly one-third of the cheek. The portion of the cheek before the groove is smooth like the glabella, the portion behind it (the neck segment) is marked with delicate striz parallel to the furrow and to the posterior margin. In all our examples the free cheeks and the eyes are absent, but from the portions which we possess, and from the analogy of closely allied forms, we may safely supply a facial suture coinciding with the outer edge of the anterior margin, appearing upon the upper surface nearly midway between the centre of the frontal edge and the genal angle, passing gently inwards, and then outwards and backwards through the limb, slightly emarginating the semicircular contour of ie head, and so curving downwards and outwards towards the genal angle. The linear free cheek, pearls probably a linear eye, is absent. In our specimens the posterior angles have an imperfect truncated look, and we should be inclined to believe that, following the analogy of Trinucleus, Dionide, Cyphoniscus, &e., the lower edge oe eS foe ge oe eee en ee oe a ba i BRITISH FOSSILS. 3 of the free cheek was prolonged into a genal spine. The labrum is unknown. The body rings are few? in number. The axis is rather wide and more convex than the pleure (epimerals). A deep groove passes diagonally across them, curving slightly backwards from behind the anterior and inner angle of each epimeral portion to the outer and forwards to the outer angle.* The distal ends of the pleure are truncated obliquely forwards. Of the tail we have only a fragment, but enough to show that it was somewhat triangular, marked with.many segments, but fewer than in the tail of Dionide (Polytomurus of Corda). We regard the structure of the head in Salterza as intermediate between that of Trinucleus and some of the Olenidw. We may expect to find a series, beginning with the distinct facial suture and erescentic eye of Remopleurides, then the suture gradually approach- ing the edge of the head, passing through its position in Salteria, Ampyx, and Cyphoniscus, till it reaches the edge in Dionide and Trinmucleus, the eye becoming more and more linear as it ap- proaches the margin, till when it reaches it, the suture being constantly immersed in mud, and its function in abeyance, it becomes altogether obsolete, and is sometimes replaced by stemmata ? jutting out on the epimerals of some of the other head segments. We have much pleasure in dedicating this remarkable genus to our friend, lately the Palzeontologist to the Survey. Varieties—The only. variations which we possess of this species depend on age and size. Our largest specimen (fig. 1) may have been about an inch in length. The glabella is slightly carinated on the posterior third, and the longitudinal erooves are well marked. In smaller examples the glabella ridge is absent, and the longitu- dinal furrows scarcely perceptible. Locality and Geological Position—We procured about half a dozen specimens of the head from Schists forming the base of the _ “Graptolite and Orthoceratite flags,” Penwhapple Glen, in the Girvan district ;—the equivalents of the “Upper Bala or CARADOC Rocks,” P. WYVILLE THOMSON. * The groove is more forward than in our figure, so as to leave a larger posterior half to the pleure, but the direction of the groove is correctly given. 4 BRITISH FOSSILS. OTHER SPECIES OF THE GENUS. 2. In the Museum of Practical Geology there is a head of a small species with a smaller and more pyriform glabella, a wider and more deflected limb (almost involute) in front of it, and a narrow neck segment. It was not found till after the plate was engraved, or should have been added to it. It may be called S. INVOLUTA. Diacnosis. S. minutus, capite vix 34 lineas lato, convexissimo, ad frontem decurvo gibbo. Glabella pyriformis, dimidium capitis efficiens, suleis transversis. Sulci cervicales vix arcuati. Oculi haud remoti. The involute limb in front is really about as broad as the width of the glabella, but is so much curved down that only a part of its breadth is seen on an upper view. The glabella, not equal to the width of the free cheeks at their base, is pyriform in outline, and marked by two pairs of transverse furrows, which indent it far inward, and one pair, the upper one, which is minute and very far outward. The furrow surrounding the glabella is very sharp and deep, but not broad. It separates an extremely tumid limb, which comprises the broad front margin and the convex cheeks. The facial suture cuts the front margin far outward, as in S. promeva, but, unlike that species, it then turns sharply inwards very near to the glabella, and then again abruptly outwards, in a wide curve to what must be the extreme end of the cheek. The neck furrow is sharp and deep, and reaches nearly to the end of the facial suture. It is nearly parallel to the posterior margin, instead of curving forwards as in that species. The species looks like a dwarfed variety of S. primeva, but is really a very distinct one. Locality.— LLANDEILO FLags, Newtown Head, Waterford, in the © cabinet of Major Austin. EXPLANATION OF PLATE VI. Fig. 1, 2. Salteria primeva, Wyv. Thomson; specimens, natural size, from the Caradoe schists of Penwhapple Glen, Ayrshire. (Mus. Wyv. Thomson.) Fig. 2a, 26, 2c. The same magnified, J. W. SALTER, November 1864. : eke ge a Pa ap re DECADE 1k, BL aaa We Seological Survev of the tuted thingdom. ANCELINA § Treniadoc Slates — |-5 ANGELINA sepewicnt, Salter [ Tremadoe Slate } 6 CONOCORYPHE wvira, td f/f Wp Tingula Flags/ ne del NWT ASaltreial Ganveac’ JW, Lowry * BRITISH FOSSILS. Decape XI. Pare VIL Fras. 1-5. es ANGELINA SEDGWICKI, [Genus ANGELINA. Satter. (Sub-kingdom Articulata,- Class Crustacea. Order ‘Trilobita. Family Conocephalide.*) Depressed, head smooth, and with long posterior spines; eyes small, sub-median, without ocular ridge ; glabella lobeless. Body segments 14-15, with an angular fulerum, facetted for rolling up. Tail of few (four or five) segments. ‘Labrum emarginate. | ‘Diaenosis. A. ovata, segmentis trunct 15, axi quam pleuris paullo ee. Cauda utrinque bispinosa. - SYNONYMS. A. Sedgwichi, SALTER, Siluria, 2nd ed., 1859, p. 53, foss. 9, fig. 2. A. subarmata, ib., fig. 8 (specimens pressed laterally and Tengthened). A Sedgwicki, Memoirs Geol. Sury., vol. ili. (ined.) pl. 7. “The new forms illustrated on our plate were part of the results of a survey by myself i in 1853 of the “ Lingula Fiags ” and overlying beds in the mountain region extending from Tremadoc to Ffestiniog, and thence to Arenig-fawr, west of Bala. They have since been collected by the hundred, and are really common fossils. The affinities of the genus are equally balanced between Olenus and Conocoryphe. Angelina differs from Olenus by having the pleuree grooved and facetted for rolling up, instead of flat and pro- duced into points; nor do we know of any Olenus that is totally without glabella furrows. It is this latter character, with the occa- sionally spinose tail, which distinguishes it from Conocoryphe ; but this is combined with some characters of habit, such as the long head spines, less marked cephalic furrows, both axal and marginal (indicating probably a thinner crust), and much less deflexed pleure, with the fulcrum nearer the axis. Angelina, too, wants the ocular ridges of Conocoryphe. From Arionellus the less number of body * The Conocephalide (Salter) differ essentially from the Calymenide by the variable but larger number of body rings, and the course (posteriorly) of the facial suture. They seem to have had a thinner crust, and, as a character of habit, resemble the Oleride in the long head spines and often sub-spinous tail border. [XI. vii.] lle 2 BRITISH FOSSILS. rings separates it, and that genus has so broad and expanded a margin, which is without a furrow, and the facial suture so far out- wards, that there evidently is but little affinity with Angelina. The genus is named in honour of the Swedish paleontologist, who is carefully illustrating the old rocks of Christiania. Two fasciculi of his quarto work are already published, and we wait anxiously for the remainder. His Calymene? lecostraca, Pal. Suecica, t. xix. fig. 3, may very possibly belong to this genus. Descryption.— Usually three or four inches long (one specimen fully six inches), of a broad oval contour, the head blunt, and the tail only moderately pointed. The head occupies less than one-third of the length, and is semicircular, but rather truncated forwards; a narrow equal margin, not raised or thicker in front, runs all round, scarcely broader than the occipital border of the cheek, and con- tinuous with it; an equal space separates this margin in front from the glabella, which is parabolic, much longer than broad, and quite destitute of any lobes. It is about equal in width to the cheeks (exclusive of their margin). The cheeks themselves are gently convex, smooth, and bear the small curved eye midway, but nearer ~ _ the glabella than the marginal furrow. The facial suture is nearly vertical to them above, and then turns sharply outwards to cut the posterior margin at its outer third. The labrum is seen on one or two specimens. It has a central raised portion, separated. by rather a deep groove from a flat margin, which is broadly and abruptly truncate at the apex.* Thorax of 15 segments; the axis narrower than the sides, gently convex, and tapering quite regularly backwards. The pleuree are nearly direct, shghtiy produced and bent back at their ends, and grooved throughout. They are bent down a little from the angular fulcrum, which is placed at rather more than one-third in front (our figure shows it too far out at this point), and at much less than one half in the middle segments. The hindermost segments are scarcely at all produced or curved backwards; and all the segments are facetted for rolling. The pleural groove is deepest beneath the fuleral point, and as beyond this the facet bounds it in front, and the posterior edge of the segment is convex beyond the fulcrum, the groove becomes an elongated rhomboidal depression: a feature * It is a little like that of Zichas, but is without the terminal notch and the “ auricles ” or lateral wings, and differs from that of Olenus by its broad margin. Conocoryphe has a Jabrum without so broad a margin, and not nearly so truncate. BRITISH FOSSILS. 3 not often seen in those genera in which the faculty of rolling up is lost or very limited. The tail is more pointed than a semicircle, the axis not-as broad as the sides, with two distinct rings, and a bluntish terminal por- tion not reaching the tip. The sides are marked by two lateral furrows which just reach the margin, opposite to the two short lateral spines. The upper furrows are duplicated. The incurved under margum * is very narrow, but convex. The compressed and elongated specimens (figs. 3, 4) were formerly considered to be of a distinct species, not, however, on account of the form, which I was aware might be due in great part to pressure, but on account of the spinose border to the tail, a character I had not at the time seen in figs. 1 and 2. A noble series of specimens, distorted in every possible way, have been lately transmitted by Mr. D. Homfray, of Portmadoc, who has collected the fossils of that district with much success. These specimens show 15 segments (our figured specimens only showed 14), and they prove clearly that the spinose border to the tail occurs in all well-preserved specimens, yet in some more distinctly than others. And the great difference in appearance between figs. 2 and 3 is entirely due to the different direction in which the fossils have been pressed in the stone. The pleural grooves in the one case are all but obliterated (fig. 3), in the other they are deepened (fig. 2), and the spinose border to the tail (in fig. 3) appears to be increased in length; in fig. 2 it is reduced. The somewhat greater space in front of the glabella, and the long head spines in fig. 3, are differences which may possibly (if they be found constant) be referable to sex. Locality and Geological Position —UPPER BEDS OF THE TRE- MADOC SLATES, Garth Hill, east side of Traeth Bach, Tremadoc, N. Wales ; also Portmadoc Quarries, and at the Ynys Tywyn, in similar beds. (Mus. Pract. Geol., and cabinets of Messrs. Homfray, F. Ash, and Mr. E. Roberts, surgeon, and many other collections.) Fenus—CONOCORYPHE. It isnot usual to include more than one genus in a plate; but accident having introduced a Conocoryphe upon the plate of * We want a term for this incurved striated under margin, which is always more distinct in the tail than elsewhere. Being always or most generally parallel-sided in the tail, it might conveniently be termed the “ caudal fascia ;” in the pleure, the “ pleural fascia,” but the term is hardly necessary for any portion but the tail, where the relative width of the fascia is of specific importance. lig2 4A BRITISH FOSSILS. Angelina, advantage is taken of it to present the English reader with the characters of a genus which is more common, or at least better known, in Sweden and Bohemia, than in England. Conocoryphe belongs to the same primordial family as Angelina, and differs from it chiefly in the lobed glabella. M. Barrande gives the following characters.” [Genus CONOCORYPHE. Corpa. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Conocephalide.) “ Glabella shortened, narrowed in front, with three or four pairs of oblique furrows. Axal furrows deep. Hyes (usually present) reticulate. Facial suture ending within the posterior angle. A rostral shield present. Labrum elongate truncate. ‘Thorax segments 10-15, furrowed and facetted for rolling. Tail entire, of two to eight segments.” Barr., p. 417.] [Section Conocoryphe proper. Eyes large, approximate. Glabelia large, well lobed ; 14 body rings ; tail small. Lingula flags only. | The other sub-genera, Solenoplenia, Ge. will be illustrated in future decades. CONOCORYPHE* INVITA. DeEcADE XI. Puate VII. Fic. 6. Diacnosis. C. capite (adhuc solim cognoto) lati-marginato, angulis brevispinosis ; glabelld urceolata, utrinque bisulcata ; oculis longis, ad glabellam appressis ; cauda angusta, axi conico 4-annulato. Synonym. Conocephalus invitus, SALTER, in Siluria, 2nd ed., 1859, p. 47, foss. 7, fig. 1. Id. Mem. Geol. Surv., ined. pl. 4, figs, 5, 6, 7; pl. 7, oa Oa Description.—Of the head we have only nee but they show that the facial sutures converge greatly from the margin to the eye, which is very long, reaching two-thirds the whole length of the glabella, from the middle of the large basal lobe to above the upper lobe. The glabella furrows nearly unite in the centre and both pairs are very oblique, the basal pair almost meeting the deep arched neck furrow. : This species resembles so nearly EL. Hmmrichii, Barr., that were it not for the glabella having only two pairs of funone the frag- * | think, much as we wish to preserve to M. Barrande all the honour of his careful nomenclature, that we cannot safely use the term Conocephalus or Conocephalites of Zenker, as the term has been employed in no less than three different genera of plants and animals. It is better to adopt Corda’s term, the more so, as it is really likely that the subdivision of the genus proposed by him will be hereafter sanctioned, BRITISH FOSSILS. 5 ments might readily be mistaken for that species. The glabella, however, is longer, of an urceolate shape, and with the furrows reaching much further into it. The eyes are not quite so long, as they do not reach to the base of the lower lobes, and they are set quite close to the glabella, which is not the case in LH. Hmmrichii. The tail is longer and narrower ; the axis conical, with the ter- minal segment developed. Our species is altogether an excellent British representative of a genus common in Bohemia and Sweden. Locality and Geological Position—UPprern LINGULA FLAGS. Penmorfa Church and Carreg Wen, Tremadoc, N. Wales. Ogof ddu, near Criccieth. (Mus. P. Geol.) ; It may be as well to mention here that 10 species of Conocoryphe are already known in Britain. Nine are described in the forth- coming Memoir of Professor Ramsay on the Geology of North Wales; and a fine species, with highly developed ornament, is found in the Lower Lingula Flags of St. David’s. As the genus must be illustrated hereafter, I only give the names and references. C. invita, Salter, Mem. Geol. Surv., vol. iii., ined., pl. 4, figs. 5, 6,73; pl. 7, fig. 6, above described. C. abdita, id. pl. 5, fig. 18, Upper Lingula Flag, Ogof ddu, near Criccieth. C. sp. id. pl. 5, fig. 14 (fig. 15 tail ?), same locality. C. sp. id. pl. 5, fig. 16, same locality. C.? simplex,id. pl. 5, fig. 17, Upper Lingula Flag, Penmorfa Church. C. vexata, id. pl. 8, fig. 7, Lower ? Tremadoc Slate, Penmorfa village. C. depressa,id. pl. 6, fig. 1, 2, 3, Lower Tremadoc, near Penmorfa Church, and Wern, Portmadoc. : C. ? verisimilis, id. pl. 6, fig. 13, Lower ? Tremadoc, above Penmorfa village. C.? olenoides, id. pl. 8, fig. 6, Upper Tremadoc, Garth, Portmadoe. C. variolaris, id. Quart. Geol. Journ., vol. xx., pl. xiii., figs. 6, 7, Lower Lingula Flags, St. David’s, Pembrokeshire. EXPLANATION OF PiatEe VII. Figs, 1-4. Angelina Sedgwicki, Salter, in various states of compression, according to ; ,the position in the slaty beds. (Mus. Pract. Geol.) Fig. 5. Labrum of ditto in Mr. Homfray’s cabinet. Upper Tremadoe, Garth Hill, opposite Portmadoc. Hig. 6. Conocoryphe invita, Salter. Upper Lingula Flag, Penmorfa Church, Tremadoe, N. Wales. J, W. SALTER. November 1864. ‘las! Woh Tag ks sake Seas ate: 7 Heological Survep of the United Singdom., Ligs. 7.3 OLENUS scarapforwEs, Wahl. 4 es Se Sie. LS a 5 ues awris) Sadiee eS 6 | SAS eee eas, L4 We LOG CR Bone, del* JW. Salter direx' are Swedtsl species for COTMPATTS OT, OLENUS | (Lincula flags ) Fags 7-8 OLENUS FLAGELLIFER Angeli! Humiiis, — Lhilleps. PECTEN , Satter. CATARACTES, — 7a. IW Lowry ite " BRITLSH. FOSSILS: DecaDE XI. Puatre VIII, Fie. 14. OLENUS CATARACTES, [Genus OLENUS. Daman, in part. (Sub-kingdom Articulata. Class Crustacea. Order Trilobita. Family Olenide.) Glabeila oblong, or usually narrowed anteriorly, lobed ; eye smooth, with a narrow prominent ocular ridge (Costula facialis, Angelin) connecting it with the upper part of the glabella; facial suture marginal in front, and cutting the posterior margin behind ; cheeks spinous, no rostral shield ; hypostome? labrum oblong, narrowed at base ; pleuree 7-15, (14 typically), pointed and curved ; tail with articulated axis and sides. ] [British sub-genera. Olenus, Darman. Body rings 11-15, head semicircular, spines moderate, tail entire——Spherophthalmus, ANGELIN (including Eurycare, id.) Body rings 7-15; head transverse, with remote eyes and widely curved long spines.— Parabolina, Satter. Body rings 12; head semi-lunar; eyes approximate ; spines diverging ; tail spinose.—Peltura, ANGELIN (not Milne-Edw.). Body rings 12; head narrew, with approximate eyes, and no spines ; tail spinose. | Dracnosis.. O. ovatus 14 uncialis et ultra, capite magno semilunari, spinis brevissimis. Gllabella ‘sulcis tribus fere perfectis. Oculi antici. Thoracis axis latus, pleure vix recurve brevispinose, fulcro remoto. Cauda minuta, transversa, semicircularis, axi latissimo. Several species of the well-known Olenus of Dalman are now added to the British list. The originally described British form is Olenus micrurus, in our Decade II., plate 9 (1849), also “Siluria,” 2nd ed., p. 45, foss. 4, fig. 2. That is not, however, by any means a common fossil, and it is necessary now to distinguish from it the present species, which appears to be the ordinary form in the lower black shales of North Wales. Description—Nearly an inch and a half long, ovate, blunt at poth ends, the head wide, nearly one inch broad, the body much narrower, tapering regularly to the tail. The head is sub-truncate, the glabella moderate in size, parabolic, not so broad as the cheeks, reaching forward nearly to the narrow front margin, and about the width of that margin distant from it, furnished with three pairs of furrows, of which the lower two are complete across, The eye is nearly as far forward as the front of the glabella, and somewhat [XI. vill. | 11 H 2 BRITISH FOSSILS. remote from it. The hinder angles of the head with the spines abrupt, short, scarcely reaching the fourth segment, directed back- ward, not outward as usual in the sub-genus. Body rings 15 (our artist has only represented 14 rings), their axis convex, nearly as broad in all the rings as the pleuree, which decrease regularly, not abruptly, in length from before backwards ; they are obliquely pointed, with short spines directed outwards, but very little backward. The fulcrum of the pleurze is placed beyond the half, even in the hinder rings. Tail short, semi-oval, with a very wide axis, of three rings, and the sides with two furrows. O. mcrurus is easily distinguished from O. cataractes by the oblique lower glabella furrows, the shape of the small smooth sub- truncate tail, and by the abrupt narrowing of the hinder body rings, which also have the fulerum placed nearer than half way out from the axis. The tail is even more easily distinguishable, the width of the axis being greater than that of the sides, and having three rings, including the terminal portion; there are two lateral furrows, not one only. O. cataractes has 15 body rings. O. m- erurus 14. The head is much like that of O. micrurus, but the lower glabella furrows run quite across. Compared with the Swedish O. trun- catus, the greater breadth of the cheeks, and the longer, more parabolic form of the glabella, will distinguish it. Ido not compare the caudal portions, for Angelin’s figure looks as if there were some mistake in this part. Possibly two of the caudal rings as figured by him belong to the body, which otherwise would have but 13 rings—a difference hardly to be expected in such closely allied forms. | O. truncatus is, 1 think, from higher beds, at Andrarum in Seania, than our Lower Lingula flags, but this is a point not yet sufficiently investigated. Localities and Geological Position.—LowER LINGULA FLAGs, Maentwrog Waterfall, Merionethshire, in black shaly strata full of Agnostus princeps ; also at Treflys, EK. of Criccieth, Carmarthenshire N. Wales, where I found the figured specimen in 1859. Specimens probably identical are found at the Dolgelly gold mines. BRITISH FOSSILS. O39 OLENUS (SPHEHROPHTHALMUS) FLAGELLIFER. ? PpArE: VLE KIes:..7 9,8: Synonyms. Spheroph. flagellifer, ANGELIN, Pal. Suecica, pl. 26, fig. 7.2? Satter, Mem. Geol. Surv., vol. iii. ined. pl. 5, figs. 8, 9. The only difference I can see between the Tremadoc specimens and the figure by Angelin is, that the glabella furrows in ours run quite across, while Angelin gives them as only lateral. But as this character of the complete transverse furrows seems to belong to the whole of the Spherophthalmz, perhaps the Swedish artist has not sufficiently represented it. The other characters of the sub- genus (for it can, I think, only be so regarded) are the short and wide transverse head, the cylindric glabella reaching the front margin, and the very large curved head spines. Again, Hurycare, Angelin, which I regard as only Spheroph- thalmus, has a somewhat broader front, and wider and more para- bolic glabella, thus leading from Spherophthalmus to the true Olent, of which O. gibbosus may be taken as the type. The cha- racters seem to me not to be absolute in any of these sub-genera, and hence they may all, I think (and Barrande seems to be of the same opinion), be conveniently retained in Olenus. Description.—Our specimens are so imperfect, that I do not pretend to give a true diagnosis, nor do IJ feel quite sure I have identified it rightly. The head is very transverse and has parallel edges. The glabella is nearly square, and has only two pairs of furrows. The lower reach far across, and appear quite complete in some specimens ; the upper, not represented in our scanty figure, only lateral and short. The ocular ridge is distinct and oblique. The margin very narrow. The neck segment also narrow. The free cheeks rotund, the eye large and prominent; the spine seeming to start from the outer edge above the angle. The thorax rings are strongly furrowed, their axis moderately broad. The tail is entire, sub-triangular, with a conical axis, and furrowed sides. Our specimen shows no trace of a spine such as Angelin figures and describes. I think the species is a distinct one, but in the absence of more complete materials, do not think it worth while to separate it from its near ally. Our figure is necessarily imperfect, but might have 4A BRITISH FOSSILS. shown more clearly the upper pair of glabella furrows and the outwardly placed head spines ; the eye is also too small. Locality and Geological Position—-Uprrr LineuLA FLAGs, Carreg Wen, Borth, Portmadoc. (Mus. Pract. Geology.) OLENUS (PARABOLINA) SERRATUS. PLatTe VEIT. Fie 'd: Diaenosis. O. modicus, 14-uneialis, convexus. Glabella oblonga equilata, haud parabolica, antice subtruncata, sulcis utrinque binis longis sere medium glabelle attingentibus, paullo obliquis. Sulcus cervicalis vix continuus. Oculi valde antici. Gene anguste. Cauda (hic haud dubie referta) semicircularis axt prominulo 4 costato, obtuso ; lateribus utrinque 5-dentatis, dentibus patulis limbo brevioribus; hoc 4-sulcato, sulcis omnibus distinecté interlineatis. Synonyms. Olenus (Parabol.) serratus, SautER, Mem. Geol. Surv., vol. iii. ined. pl. 5, figs. 6, 7. Description.—Glabella quite as wide in front as behind, with a broad neck segment, equal in breadth to the basal lobe. The second or middle lobe somewhat narrower. Fixed cheeks broad, sub-trigonal, equal to more than half the width of the glabella, the eye placed very far forwards, opposite the forehead lobe. Free cheeks not known, probably narrow. Tail, most likely of the same species, semicircular, serrate, with short, somewhat radiating spines. Axis thick, of four prominent rings and a blunt terminal piece; sides four-ribbed, the ribs duplicate, and produced on the margin into strong spines of less length than the limb, five on each side, the fifth pair of spines being set rather wide apart beneath the axis. Affinities—I much wish I could identify this with the common O. spinulosus, Wahl, for the head is very like. But the caudal shield is decidedly different, and as it in all probability belongs to the same species as the head, I feel bound to keep the two distinct. The glabella, moreover, differs, as above described, from that of the true O. sprnulosus, which tapers a little forward. In that species the tail spines also are greatly lengthened. History.—tThe section Parabolina, regarded as a genus by Angelin, was proposed by me in 1849 to distinguish the species of Olenus which have 12 body rings and a laciniate tail. O. scara- beoides might perhaps belong to this sub-genus as so defined, but BRITISH FOSSILS. 5 it has 13 body rings, and clearly belongs to a different natural group, in which the cheeks are much contracted, and the glabella enlarged ; in the majority of Oleni the reverse is the case. I believe Angelin has good reasons for supposing there are several distinct genera included under Olenus, but I do not quite see the way to their definition yet. The term Peltwra can only. stand by courtesy, for it was founded on a species of Lichas, as may be seen by reference to Capt. Fletcher’s description of the British Upper Silurian species of that genus.* Locality and Geological Position.--Upprer LInGuLa FLags, Carreg Wen, Borth, Portmadoe. OLENUS SCARABZXOIDES. PLATE VIII. Fries, 1-3. Synonyms. Vermiculites vagipennis, BromeLt, in Act. Lit. Upsal., 1729, pp. 525, 528, cum icone. Entomostracites scarabeoides, WAHLENB., Nova Act. Soc. Upsal., vol. viii. t. 1, f. 2. Olenus scarab., DALMAN, Paleade, p. 257. Olenus scarab., Histncrer, Lethea Suecica, t. 4, f. 4. Paradox scarab., Bronantart, Crustaces, foss. p. 34, t. 3, f. 5. Pel- tura scarab., Mitne-Epw., Crustaces, vol. iii. p. 344 (1840). Peltura searab., ANGELIN, Paleont. Suecica, pl. 25, f. 8 (mala), 1855. [ Olenus spinulosus ? Paity., Mem. Geol. Surv., vol. ii. pt. 1, pp. 55, 239.] 0. scarab., SALTER, Siluria, 2nd ed., Appendix, p. 540. 0. searab., Id., Mem. Geol. Surv., vol. iii. ined. pl. 5, figs. 2-5. In size, as well as form, these pressed and distorted Trilobites agree pretty well with Christiania specimens presented by Dr. Th. Kjerulf to the Mus. Pract. Geology. But ours show only one ring to the axis of the tail besides the terminal lobe. Wahlenberg’s fossil has two rings to the axis. The marginal spines are only clearly seen in one British example; they do not differ from the Swedish species except in being shorter (see fig. 3). The glabella im our specimens is broader, and the lobes less distinct. It is mani- fest, therefore, that there are sufficient differences to render it probable that better specimens will require us to distinguish it. I shall at present call it— Var. OBESUS. The following characters appear to me to be constant, and I find them both in N. Welsh and Malvern specimens. * Quart. Geol. Journ., vol. vi. p. 235. PS 6 BRITISH FOSSILS. General form broad oval, seldom reaching in length above an inch; of this the head occupies fully one-third. It is semi-oval, without the fixed cheeks (fig. 1), but with them (and perfect heads in Mr. Edgell’s collection show them well) it becomes transverse- oblong. The broad parabolic flattened glabella is more than equal to the width of the cheeks, and has usually straight sides, sometimes in Malvern specimens a little contracted in the middle (fig. 4). Lobes very slightly marked (our fig. 4 has them toc strong). The neck segment enlarged at the sides, and quite distinct across. The three pairs of furrows obscure. A very narrow margin in front of the glabella. The fixed cheeks narrow triangular, the eye very far forward, and connected with the front of the glabella by a low ocular ridge. The neck-furrow on the cheeks very near the hinder margin. Free cheek semicircular, very convex on its outer edge, and with a strong but narrow margin, and no spine, the base losely contracted. Labrum (fig. 4a), in a Malvern specimen lent by the Rev. W. Symonds, squarish, urceolate, with the base not expanded, the sides convex, the apex broadly truncate; the lateral furrows oblique, broad, not deep. Body rings 14 (in a specimen lent by Mr. Ash, fig. 1). But this number is somewhat doubtful, as I find my notes say it has only 12 distinct ones. The Swedish fossil has 13, according to Angelin’s figure, but his description gives 12, probably the true number. Ours do not show a central tubercle. Tail semicircular, with broad blunt axis, showing one distinct ring, and a larger terminal portion. The sides as broad as the axis, and with three obscure furrows, the margin distinctly triden- tate on each side, with short spines, not much projecting beyond the border, which is not at all marginate. I believe we may safely identify with this the small species found at Malvern (pl. 8, fig. 4), and described by Phillips under the name of O. spinulosus. We have copied his figure, Mem. Geol. Surv.,. vol. ii. pl. 1, p. 55. It is certainly not Wahlenberg’s species of that name. The furrows of the glabella are far too plainly marked in our figure, but the slight contraction visible on the sides of the glabella is correct for Malvern specimens. Taking all the evidence together, I am inclined to think the British fossil distinct from the Swedish; and I am principally indebted to Mr. Edgell for the specimens which lead to this con- clusion. I shall retain the name under which our fossil is usually BRITISH FOSSILS. 7 known till we have more complete evidence that the var. obesus is distinct as a species from the well-known Swedish type. Locality and Geological Position—Uprrer Lincuta FLAGs, Carreg Wen, near Borth, and Penmorfa Church, both near Tre- madoc, N. Wales. Abundant at Whiteleaved Oak, Malvern, in the Upper LinguLa Fags (Black Shales) of that locality. OLENUS (SPHEZROPH.) HUMILIS. PuaTE VIII. Fias. 9-11. ‘Draenosis. O. (Sph.) minutus, capite angusto antice emarginato, pleuris 7, posticis solum spinosis, cauda sexcuspidata. Glabella convexa angusta parabolica, sulco basali completo, reliquis obsoletis, cervice spi- noso. Gene convexissime, oculis omnino posticis, magnis. Thorax 7- costatus, pleuris duobus anticis muticis, reliquis spinosis. Cauda brevis semicircularis, 6-spinosa, spinis externis majoribus. Synonyms. Olenus humilis, Poitt., Mem. Geol. Surv., vol. ii. pt. 1, pl. 55. Satter, Mem. Geol. Surv., vol. iii. ined. pl. 5, fig. 12. This minute species is well characterized by its very narrow instead of wide cheeks. Yet in other respects it is a perfect Spherophthalmus, and such a copy in miniature of the Olenoid type, with nearly all the characters exaggerated or reduced, as to show us that great variation is to be found within its limits, and to induce us to regard the various groups into which Olenus has been divided as sub-genera rather than distinct generic types. Description.—A minute form, not above a quarter of an inch in length, and of an ovate shape; the head broadest, as usual in this sub-genus, but rather squarish-oblong, with an emarginate front, the very convex cheeks projecting on either side so much forward as to bring their greatest convexity in advance of the narrow para- bolic glabella ! The facial suture follows this convexity in a sigmoid line, cutting the front margin at a short distance outside the axal furrow, then curving outwards widely, and then again at the lower third much contracted inwards to the place of the eye, which is near the base of the cheek. The eye-lobe which covers it is elevated and easily broken away, being divided by a deep furrow from the fixed cheek. The eyes are large and round, and placed quite at the base of the free cheeks, which are true semicircles, strongly margined, and com- pletely contracted to a point behind, showing (so far as I can see) 8 BRITISH FOSSILS. no trace of the curved spine characteristic of this sub-genus. Our figured specimens had not the free cheeks in any case. Mr. Edgell’s specimens show them well. Body short, of seven rings only,* with a broad axis, showing in the five front rings the central tubercle. The pleurz are short, strongly grooved; the two front ones without recurved spines, the rest spinous; the spines bent strongly back and about as long as the pleure. The tail is nearly a semicircle, and furnished with a strong conical three-ribbed axis, which reaches the end. The sides two-ribbed, with three spines on each side, the forward one longest, the other two short, and leaving a rather broad smooth space at the extremity of the tail beneath the axis. Locality and Geological Position.—Only known in the BLack SHALES of Malvern, Fowlet’s Farm,and Whiteleaved Oak Farm, &c., and very abundant there, with other species of the genus next described. OLENUS BISULCATUS. PLATE VIII. Fic. 6. Diacnosis. O.(Sph.) modicus, capite transverso, glabella bisulcata, genis latissimis. Thorax pleuris latis, profunde sulcatis, spinis validis rectts. Synonym. O. bisuleatus, Puiti., Mem. Geol. Surv., vol. ii. pt. 1, p. 55; fig. 1. The head of this species is remarkably wide, and thus differs at a glance from O. humilis, with which it occurs. The body rings have lately been detected in the cabinet of my friend, Mr. Edgell, and I am thus enabled to improve the description. The species is stouter in all its parts than is usual in the sub-genus. The species is a small one, not more than eight lines in length, and the width from tip to tip of the stout thorax spines seven lines, The head is very transverse, three times as wide as long, even ex- cluding the free cheeks, which we do not perfectly know, but believe to have extended somewhat further out, and to have been armed with a stout curved spine starting one third or thereabouts above the genal angle. The front is straight, or only slightly emarginate, and the * The species is abnormal for the genus, abnormal even for the sub-group to which it belongs. It contradicts most of the technical characters of Olenus, and yet evidently belongs to it. ? BRITISH FOSSILS. 9 margin narrow, the long sub-cylindrical glabella touching it. The axal furrows are deep; the glabella narrower forwards and rounded in front, with a strong neck-lobe, not spinous but with a central tubercle, a pair of complete basal grooves cutting off the lower third of the glabella, and an incomplete upper pair. The fixed cheeks consist of an oblong convex plate in front of the eye, which is placed far back, opposite the basal furrow, and about the width of the glabella apart from it. ‘The ocular ridge is very oblique, and only reaches the front edge of the broad eye lobe. The facial suture is sinuous, but nearly vertical to the eye, and be- neath 1t turns abruptly outwards in a line all but parallel to the neck margin, and reaches it at a distance from the glabella equal to twice the width of that organ. The neck furrow is narrow, but distinct all along. [The cheek, in a separate specimen of Mr. Edgell’s probably belonging to this, is a quadrant of a circle, with a round prominent eye, and a narrow margin on the outer edge. The spine starts con- siderabiy above the angle, and on the level of the eye, and appears to be short and not much curved. | Thorax of — ? rings. We have only six preserved; they are broad, straight, equal in width to the axis, excluding the strong patent spine, which bends very little backward, and is about as long as the pleurze themselves. The pleural groove is deep and broad, and reaches the base of the spine. The axis is convex, and has a spinous tubercle on each segment. Locality and Geological Position—Uvrrrer Lincuta FLacs, Whiteleaved Oak, Malvern. (Mus. Pract. Geol.) OLENUS (SPHER.) PECTEN. PLATE VIII. Frias. 12, 13. Diacnosis. O. parvulus monstrosus, capite contracto longispinoso, thorace multispinoso, cauda mira pectinata et in spinam longissimam cen- tralem producta. Caput ad frontem emarginatum, glabella brevi, gena angusta spinam medianam curvam gerente. Oculis omnine antrorsis. Thorax pleuris rectissimis, spinis aciculatis. Cauda spinis utringue sex parallelis, et mediana longissima. Oblong, the head contracted in width, emarginate in front, with narrow glabella, and furnished with convex projecting cheeks, 10 BRITISH FOSSILS, bearing very forward eyes. They are placed on the most prominent part of the cheeks, opposite the front of the glabella, and about midway from it. The fixed cheek is wider than the glabella, but the free cheek is not so wide, and much resembles that of O. humilis. And the facial suture, as in that species, is nearly vertical below the eye as well as above it. The head-spine does not in this species start from nearly the base, but quite up in the middle of the free cheek. It is only slightly curved ; but arising from so unusual a position, it has a most odd appearance. It reaches to the seventh thorax ring. The thorax-rings are much wider than the head, and remarkably straight across. The axis is not above one-third the width of the straight pleurse, which are even a little curved upward, and grooved throughout ; they bear a straight spine, directed obliquely back- wards, and longer in the hinder segments. We only know seven rings; there must have been several more. Mr. Turner, schoolmaster at Pauntley, Gloucestershire, was the discoverer of this curious species, and sent it to the Rev. W. Symonds. It has since occurred in greater plenty. Mr. Edgell has perfect heads and several caudal portions. The Rev. T. B. Brodie has an excellent specimen. Locality With the preceding. The group of species last described rather fully illustrate the curious sub-genus Spherophthalmus, and show how wide in these ancient genera the limits of variation are in a single group. As we ascend in the geological scale, the law of variation becomes more restricted, and characters which are of family value in the more advanced groups scarcely afford generic distinctions in some of the more ancient and less highly organized ones. The Olenide and the Asaphide have both of them wide limits, and it may be possible bye and bye to subdivide them. Locality and Geol. Position.—UPrPER LINGULA FLAgs, White- leaved Oak, Malvern. Fires. 15, 16, 17. I have figured the Swedish O. spinulosus (fig. 16,) to give the British student an idea of what form to look for when searching for fragments of O. serratus. Fig. 15 illustrates perfectly the sub-genus Spherophthalmus, while it is also a common Upper Lingula Flag fossil for Britain (see Mem. Geol. Surv., vol. iii. ined., pl. 4). Fig. 17 is Angelin’s sub-genus Leptoplastus, which I regard asa form of Spherophthalmus, and may illus- trate in part our O. pecten and O. flagellifer. Olenus proper and Peltura are sufficiently represented by our own species. BRITISH FOSSILS. ll OTHER BRITISH SPECIES. O. micrurus, Salter, Decade II., pl. 10, (section Olenus). O. alatus, Beck, our pl. 8, fig. 15, and Salter in Mem. Geol. Surv., vol. iii. ined., pl 4, fig. 3 (section Spherophthalmus.) EXPLANATION OF PLATE VIII. Figs. 1-4. Olenus (Peltura) scaraba@oides, Wahl.? (possibly a new species), var. obesus, Salter. Fig. 1. Natural size, uncompressed (Mr. Ash’s cabinet). Fig. 2 compressed (Mus. Pract. Geology.) Fig. 3, slightly enlarged ; specimens are, however, occasionally found nearly of these dimensions. Fig. 4. Malvern specimen, the same figured by Phillips in Mem. Geol. Surv., vol. ii., pt. 1, pl. 55. ‘The glabella furrows are far too strongly marked. Fig. 4a. Labrum, from Malvern. Upper Lingula Flag (Black Shales). Fig. 5. Olenus (Parabolina) serratus, n. sp., Carreg Wen, Portmadoc. Fig. 6. Olenus (Spherophthalmus) bisulcatus, Phill. His original specimen from Malvern, in Upper Lingula Flag. Figs. 7, 8. Olenus (Spher.) flagellifer, Angelin.? Carreg Wen, Portmadoc, Upper Lingula flag. Fig. 9. Olenus (Spher.) humilis, Phiil., Malvern. Dr. Grindrod’s cabinet (magnified). Figs. 10, 11. Heads of the same (the free cheeks lost). Same locality. (Survey collection.) Abundant in the Black Shales. Fig. 12. Olenus (Spher.) pecten., n. sp. Same locality. (Rev. W. Symonds’ cabinet.) Fig. 13. Thorax of do., natural size and magnified. Same locality and cabinet. Fig. 14. Olenus cataractes, n, sp., Lower Lingula Flags, Treflys, near Criccieth (Mus. Pract. Geol.) 146. Tailenlarged. 14a. Pleure. We have figured three Swedish fossils to illustrate sub-genera imperfectly represented by British specimens. All are from the primordial zone. Fig. 15. O. (Spher.) alatus, Beck, copied from Angelin. Fig. 16. O. (Parabolina) spinulosa,, Wahl. do. Fig. 17. O. (Leptoplastus) or Spherophthalmus raphidophorus, Angelin, copied from his Paleont, Suecica, pl. xxvi., fig. 2. J. W. SALTER. November 1864. = Gate: (es? e nine Bas ae Re. : DECADE 11 PLATE 9, ‘logical Svrbev of the United Kingdom. PHACORS ¢ a (SUBGENUS TRIM EROCEPHALUS Fy ( Devonian ) Figs. 1.5 PHACOPS-: (TRIMEROC) Lavis_Miunst. 6 ot eats CRYPTOPHTHALMUS. LMI. (from Sandberg er | paln Bone del! - J W. Salter direx’ J W Lowry fe BRITISH FOSSILS, a ead Prare IX. Fries. icd: ‘PHACOPS (@nimEnocerHanus) LEVIS. bene. PHACOPS. ~ Emuricu. (Sub-kingdom Avticnlatic ~ Class” Crustacea. Order Trilobita. Family- Phacopide.) Wyes largely facetted ; facial suture ending on the outer margin ; ; thorax 11-jointed. ] Be Se [Sub-genus: Trimerocephalus. Form compact. Glabella infidted : Sar 2 idea or wards, the lobes, except the basal ones, obscure. Eyes very small, of few large lenses (often lost by abrasion) or absent. Head angles not spinous. Facial sutures soldered. Thorax with pleure all rounded. ‘Tail small, of few segments, with even border, and not at all produced. | Draanosis. P. (Lrim.) cecus, laté ovatus levis, glabella latissimd, brevi, genas subsphericas trigonas superintendente ; lobis basalibus minutis distinctis. Thoracis axis angustus, fulcro pleurarum axin approximato, suleoque brevi. Cauda latissima br brevis, axi longo, 5-annulato, lateribus 4-suleosis, margint nullo. Synonyms. Trinucieus ot: 352 iWowsr. Beier. Heft 5, t. x. fig. 6 (1842). Calymene levis, PHitu., Pal. Foss., pl. 55, fig. 250 (1841), (not Cal. levis, Minst., lc. t. v. fig. 4). Asaphus or Trinucleus, Sowrrsy, Geol. Trans., 2nd Ser., vol. v. pl. 57, “e 30 (1840). Trimerocephalus levis, McCoy, Ann. Nat, Hist. vol. iv. p. 404, woodcut (1849). - Ibid, Synopsis Woodw. Mus., ‘p. 178 (1851). oe Palxont. Society, Monogr. CPDL? 16, pl. 1, is, -5, 6, 7. = It would perhaps be better if a new name were Fetewed upon _ this species. It is clearly enough the 7rinucleus levis of Miinster, and that fossil belongs to Phecoons. § But the Phacops (Calymene) levis of Miinster is quite another thing, and typical of another sec- tion of the genus; and if the letter were a good species, and not a mere synonym = P. granulatus, as 1 believe it to be, it would be imperative to change the name, and I would then propose the term P. trinucleus for this species. At present it had better stand as P. levis. | {Xt ax. | 3 a ee bo BRITISH FOSSILS. There is less difficulty about the name of the sub-genus. That bestowed by McCoy is convenient enough, the group being a really good one, distinguished by the soldered head sutures and especially the absence of eyes.* _ No trace can be seen of these organs in the present species. : Description.—Rarely exceeding an inch and a quarter long, of a broad oblong-oval shape, the head being nearly one-third the whole length, convex, and divided deeply into three tumid lobes, of which the lateral ones or cheeks are not above half the width of the glabella. This is “sub-rhomboidal,” or spherical-triangular, convex, smooth, twice as broad in front as behind, where a very narrow pair of basal lobes separates it from the neck-ridge; the upper furrows are quite obsolete. The cheeks are trigonal, the shortest side being the outer or marginal side, very evenly convex, and with no trace of an eye. They are bordered by a very distinct and rather broad smooth margin, which is continuous at the rounded posterior angles of the head, and lost in front, where it abuts against the — glabella. Thorax of 11 segments, with convex narrow axis and rounded pleuree ; the segments of the’axis tuberculate at the sides; the pleurze not much bent back, rounded at the end, the groove narrow and short, the fulcrum placed at less than half way out; the facet rather large. The tail is short and broad; its length not half its breadth, and both forward and hinder edges being curved, so as to give a lenticular outline. The axis is suddenly narrower than that of the thorax, conical and gently convex, attaining very nearly the border of the tail, blunt at the tip and marked with four or five transverse furrows. The sides have four radiating bent furrows, which are faintly interlined and nearly reach the edge; there is no distinet border to the tail. The species was first figured in England (from the only English locality I know of, viz, the Knowl Hill, near Newton Bushell,) in the plates executed by Sowerby for the Devonshire Memoir of Professor Sedgwick and Sir R. I. Murchison.t{ That figure is from - * Trimerocephalus has been lately made to include all the species with lobeless or very faintly lobed glabella and soldered sutures and superficial minute eyes, e.g., Phacops Volborthi, Barrande, and P. cryptophthalmus, Emmrich, which last is figured on our plate for comparison. But it will probably be hereafter restricted to the present species and kindred forms, since the most careful scrutiny fails to detect the least trace of eye or facial suture. ; {| Trans. Geol. Soc., 2nd series, vol. v., 1840. BRITISH FOSSILS. 3 an uncompressed specimen, but they are mostly distorted, and, as noticed by Mr. Pengelly, the head is generally disjointed from the body and inverted, as if the animal had habitually kept it bent under, and been preserved in the slate in that position. In that posture, and exposed to the accidents of slaty cleavage, it is often difficult to distinguish the parts correctly ; and the juxtaposition of two specimens, or the extra elongation along the line of cleavage, have often given rise to a specimen with apparently more than the proper number of body rings, and to all sorts of abnormal proportions of the various parts. Locality and Geological Positton.—UrPrerR DEVONIAN. Knowl Hill, Newton Bushell. It is quoted by Phillips from 8. Devon, at Mudstone and Durlstone Bay. I think there is much doubt of these Lower Devonian localities, but less doubt about Brushford, N. Devon, in the Marwood or Pilton group. EXPLANATION OF PLATE IX. Fig. 1. Phacops (Trimerocephalus) levis, Minster. Specimens from Knowl Hill, Newton Bushell. (Mr. Pengelly’s cabinet.) Figs. 2,3. From the same locality and cabinet. Specimens in which the head has been disjointed from the body and reversed in position. (See also fig. 5.) Fig. 4. Thoracic ring and tail from Mr. Vicary’s cabinet. Fig. 5. Original specimen figured by Sowerby in the Geol. Trans., 2nd series, vol. v. (Same locality.) Fig. 6. Phacops (Trimeroc. ?) cryptophthalmus, Emmr., from Nassau. Copy of Sand- berger’s figure to show the differences of the species. P. cryptophthalmus is often confounded with P. levis. DECADE 1L PLATE 10 PAUR AID OSOUIDIE S 7 ‘ ~ EF the Wyiteiy Gingdom. Geological Surbvep of the Miniteds Ring o PORCHAMMERI diiqedoy | Figs.2_8, PARADOXIDES pavrnis Salter: | ae ee. dome. eb} gar. e Geological Surbep of tl} # BRITISH FOSSILS. DECADE XI. PLATE X. ee PARADOXIDES DAVIDISE. [Genus PARADOXIDES. (Sub-kingdom Articulata. Class Crustacea. Order — Trilobita. Family Olenide.) Elongate, of many segments, with a broad head and spinous head-angles, often greatly extended. Glabella widely clavate, with the lower furrows complete across. Labrum soldered to the hypostome. Body rings flattened, 17 to 20 in number, produced into recurved spines. Tail small, of few segments. Range, primordial zone only. | Draenosis. P. sesquipedalis et ultra, maximus, glabella parum cla- vata, genis latiori, sulcis duobus solum perfectis, reliquis obsoletis. Oculi antrorsum positi. Thorax articulis 19, axe lato. Pleure subrecte, apicibus recurvis ; anticis brevissimis abrupte flexis, ultimis longissimis, fere parallelis. Cauda truncata, axi obscuro 2-3 annulato; gladiis latera- -libus longissimis. Synonyms. Paradoxides Davidis, SartER (1863), Quart. Journ. Geol. Soc. (1864), vol. XIX., p. 275, woodcut, and XX., pl. 13, fig. 1-8. The genus Paradowides, from its bulk, has necessarily attracted attention from the earliest times in which fossils have been observed and collected. Linnzeus figured it, from Sweden, and Count Kinsky from Bohemia, in the 18th century, and the Entomostracites para- doxissymus was still the name under which Wahlenberg noticed it in his résumé of the Swedish Trilobites in 1821. Brongniart added to the typical form several species afterwards known as Olenus by Dalman, who did no more than uselessly change the name of the whole genus. And while the species were distinguished by subse- quent observers, the new name Olenus seems to have been adopted till Bronn, in 1835, restored that which Brongniart had imposed. Zenker, in 1833, had suggested a division of this large genus, making the great Paradowides the type of Olenus, and so reversing the original nomenclature. But Emmrich’s essay did not second this idea, and it was left for Goldfuss, in his systematic review of the group (Jahrbuch, vol. v., 1843), to give their correct definition to these two genera, which have since been generally adopted. The broad club-shaped glabella, large head spines, and numerous [XI. x.| er 2 BRITISH FOSSILS. (17 to 20) segments to the body, easily distinguish this group, which comprehends the largest Trilobites known, and yet is the earliest or nearly the earliest type of the whole Trilobite family. Agnostus accompanies it in all countries where it has been observed, and it is known to have ranged from N. America to Russia, and from Sweden to Spain and Bohemia. Twenty years ago a single specimen was found in the British slate rocks, and it is only within the last year or two that it has been found in any considerable - numbers, in a single locality in South Wales. Thad myself the good fortune to discover the new species, which -was first figured in the Quarterly Geological Journal for 1863. Description.—Of the head we have now many specimens, and some of the fragments betoken a fossil not less than 16 or 18 inches long; one or two heads are perfect, and show that it was semi- circular, with very large, thick, cylindrical, and tolerably straight spines. The glabella rather long, reaching and overhanging the front margin, broader but not suddenly so in front, half its length being occupied by the great front lobe. There are obscure traces in some specimens of short anterior fur- rows, but I cannot be sure of more than the two complete posterior ones, which bend backwards in the middle, and are equally strong with the neck furrow. The eye is far forward, in advance even of the second or upper glabella-furrow, and is near the glabella,—not half its length distant from it. The cheek is coarsely granular, except toward the outer angle, and abruptly contracted beneath, at the base of the great cylindrical spine. The labrum is expanded at the base, and has a truncated end, with sub-spinous lateral angles. It is, as usual, separated by scarcely any suture from the hypostome, or rather is connate with it. I can, in a fine specimen lately found, count 19 body-rings, and believe this to be the full number. The axis is very wide (in the largest specimen 14 inch) and convex, fully as wide in front as the pleure, spine included, and so for the eight or nine front segments. ‘The apex of the pleurz in these is abruptly turned back, with a short sharp mucro, and there is no enlargement of the second or third pleura—a character of importance in this genus. All have a deep groove, which is considerably oblique, and reaches the hinder margin just at the base of the spine in all the pleure. But from the eighth or ninth segment the pleure lengthen, and the axis gradually tapers. The hindermost axial ring is about half the width of the front ones, and scarcely one-fourth as wide as its lone pointed pleare. | ee ee BRITISH FOSSILS. 3 All the middle pleurze have a strong curve backwards from the. fuleral point, but at the same time arch outwards, and gradually, as they approach the tail, close in upon it until the hindermost are parallel with it. These hinder pleurz are greatly lengthened, and are of two forms in two distinct varieties (possibly sexes?) In one form (fig. 4) the penultimate pleura is developed into a shorter spine than the preceding; and the last is suddenly abbreviated and in- curved. This may be by abortion of the segments. In another the increment is regular, but the last spines are not extravagantly developed. In a third variety, the ultimate and penultimate pleuree are greatly extended (fig. 7), and this is accompanied by a corre- sponding dilatation and lengthening of the caudal portion next to be described. The tail in this species is most remarkable, and for some time I was inclined to believe that its outer segment was the ultimate pleura, of the body. In fact, the front caudal ring is a very slightly metamorphosed body-joint, and is not very strongly connected with the tail piece ; but it nevertheless belongs to it. Exclusive of the great sabre-shaped lateral spines, which are three or four times its length, the tail is an oblong convex plate, with a short conical broad axis occupying about two-thirds of its length, and aunulated by two or three incomplete rings. The extremity of this plate is broad and sharply truncate, contrasting with the parabolic contour of its axis, which is not so long as broad. The sword-shaped appendages are broader as well as longer than the last pleura of the body rings, and at first bend strongly inwards beneath the tail, afterwards diverging again at the tips (fig. 4). In one variety they are, in a moderate sized specimen, four inches long, They are connate with the central plate of the tail, though sepa- rated from it by a deep groove, except at the actual base, where the character of a pleura is maintained by the usual pleural groove running out into it. The nearest approach to this structure is made by the Paru- doxides Bohemicus. But in that species the enlarged last appen- dages are true pleure, according to Barrande’s figure, and the tail itself is destitute of all appendages. Moreover, in that allied species the second pleura of the body is enlarged ; so we have an additional character of separation from the present species. In P. spinosus, Boeck, the glabella is shorter and the eye less curved and nearer the glabella. The unfurrowed portion of the pleuree is shorter, and the hinder pleuree are only straight, not sinuous. 11K 2 A, BRITISH FOSSILS. Paradoxides Davidis nearly equals in dimensions the great P. Harlani from Massachusetts, and exceeds the large Newfound- land species described by me under the name of P. Bennettw.* The three Swedish species are greatly inferior in size. The above description is chiefly taken from the Quarterly Geol. Journal for the present year. In the plate accompanying that Memoir all the varieties are figured. Locality and Geological Position—Lowest LinGULA FLAGS, Porth Rhaw and Solva Harbour, both near St. David’s, South Wales. It has been lately detected at the Dolgelly gold mines, close: to Pistyl-y-Cain, by Mr. Readwin, and by Mr. Ezekiel Williamson, an excellent observer. P. FORGHHAMMEBRIL. ? PLATE X. Fria. 9. Synonyms. Paradoxides Forchhammeri, ANGELIN, Paleontologia Suecica, t. 2? Paradox. Forchhammeri, Saut=Rr, Siluria, 2nd ed. 1859, p45; Foss. 5, fig. 2, ib. ; Mem. Geol. Surv., vol. iii. ined., pl. 4, fig. 12. Descrvption.—Our specimen must, when perfect, have been fully 34 inches long by 14 broad. Of this length the long head is fully one inch, semi-oval, and with a long clavate glabella, which reaches quite to the front, and is rather broader than the cheeks. Below, the glabella is sub-linear, and not much above half as wide as in front. And it appears to have only the two lower complete trans- verse furrows; the upper inflated portion, more than twice the length of the lower, being unmarked by any furrows, except a pair of very short ones marking the place of the middle lobes. The eye is larger and placed further back on the cheek. The border of the head distinct and broad. Spines —? (the outer angle of the cheek is lost, and we do not know what the spines may be). Body with a long cylindrical axis tapering very slowly back- wards, with straight sides. The axis-rings are not, even in the front part, more than thrice as wide as long, and at the twelfth ring not so much. We have only 15 of the body segments, and the pleure are equal and similar for the first eight rings at * Quart. Journ. Geol. Soc., vol. xv. p. 553. + Two pairs are marked out in the figure in Siluriaabove quoted. But there is hardly any warrant for this. The specimen is too imperfect to decide it fully. BRITISH FOSSILS, 5 least, the second or third not being at all visibly enlarged at the end.” ' The pleurze are wider than the axis by one-fifth, or less, and are but slightly curved, the tip acuminate, short, recurved, but not produced as in P. Davidis. We have only eight pleure, and cannot therefore determine the shape of the extremities of the hinder ones. But there is no appearance of enlargement in the seventh or eighth. The groove is very oblique, and runs into the short mucro, rather than ends abruptly behind its base. As M. Angelin’s P. Forchhammeri wants the front body rings, and ours the hinder ones, it is not possible to institute a closer comparison. Although very incomplete, enough remains to show that the species is distinct from any of the Bohemian ones, unless it may be P, Bohemicus, and from either of the three Swedish species described by Angelin, except P. Yorchhammeri. But there are several points in which it agrees with the latter species and differs from P. Bohemicus. The glabella is widely clavate, and the furrows across the base are parallel, or nearly so. The eye appears to be nearly in the right position, but this is obscure. The body rings, of which we have only 16 preserved, have the axis narrower than the pleure, and the latter have only short points, and very oblique grooves. The second pleura is not elongated, nor at all wider than: the third, another point m which it differs from P. Bohemicus, but in which P. Forchhammeri does not offer means of comparison. But in the proportionate length to their width, the pleurze agree much better with the Swedish species, the length being rather more than three times the width, while in P, Bohemicus it is rather less. In both P. spynosus and P. rotwndatus of Bohemia, and P. Tessini of Sweden, the two basal giabella furrows, besides the neck furrow, run quite strongly across. Our species does not need, therefore, comparison with them, as it has only one transverse groove above the neck furrow ; the rest are very obscurely indi- cated in this specimen, which has been much compressed in an oblique direction. This will account for the narrow glabella. Locality and Geological Position—LowrR LINGULA IFLAGs, North Wales (exact locality uncertain, probably near Dolgelly). Collected by A. Selwyn, Esq., 20 years back. (Mus. P. Geology.) * Usually Bohemian species have the second ring enlarged. N. American species the third pleura. In Anopolenus, an allied genus, the hindermost 3 or 4 are ali enlarged. BRITISH FOSSILS. EXPLANATION OF PLATE X. Figs. 1-6. Paradoxides Davidis, Salter, various fragments from the Lower Lingula Flags of St. David’s. Fig. 1. Large glabella, showing two complete furrows, and one incomplete pair (this Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. November 1864. 2. last is doubtful), and other specimens do not confirm it. Tolerably complete head, with the labrum, a, turned upward from the lower surface at 6 ; the suture between the /abrum and the hypostome is seen to be soldered. . Labrum of large specimen. . Hinder body rings showing the gradually lengthening points of the pleure, completed from more perfect specimens. (See Quart. Geol. Journ., 1864, vol. XX., pl. 13.) This variety has the last pleura abbreviated. . Posterior body rings. . (Not numbered on the plate.) Head spine of the largest specimen known, All the above, except fig. 2, are in the Mus. Pract. Geology. Fig. 2 is in the cabinet of Mr. J. E. Lee, Caerleon. The ornament of its pleure is seen in the magnified figure. . Outline, restored from the largest fragments, and nearly coinciding with the size of the largest and nearly perfect specimen since found, and placed in the British Museum. . : . Body rings of a very large individual. (Maus. Pract. Geology.) | . Paradoxides Forchhammeri, Angelin? From the black Lingula flags of N. Wales, Locality unknown, probably Dolgelly. (Mus. Pract. Geology.) a 3. W. SALTER. a MEMOIRS OF THE GEOLOGICAL SURVEY THE UNITED KINGDOM. Higuees and Descriptions BRITISH ORGANIC REMAINS. DECADE XII. ee ILLUSTRATIONS OF THE STRUCTURE OF THE CROSSOPTERYGIAN GANOIDS, : BY THOMAS H. HUXLEY, F.RS., NATURALIST TO THE GEOLOGICAL SURVEY OF GREAT BRITAIN. PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY’S TREASURY. LONDON: PRINTED FOR HER MAJESTY’S STATIONERY OFFICE. PUBLISHED BY LONGMANS, GREEN, READER, AND DYER. 1866. 16295, . : ~~ ; ae i 4s. Bh BM, cae . Beer emer bie Seles Wis 85 ye | | | ; 4 ree ow + : a at OSU ea Ga ae 7 es, 5 ee ¢ “ BRITISH FOSSILS. DECADE THE TWELFTH. ILLUSTRATIONS OF THE STRUCTURE OF THE CROSSOPTERYGIAN GANOIDS; BY THomas H. Hux ey, FBS. I.—THE GENUS GLYPTOPOMUS. At p. 57 of the “Poissons Fossiles du Vieux Grés Rouge,” Prof. Agassiz remarks, in establishing this genus, that he at first took the only specimen known to him for a Platygnathus; and it is figured in the 26th plate as Platygnathus minor. He de- scribes the unique specimen of Gilyptopomus minor in the following terms :— “‘ This fish, of which I know but a single specimen, obtained at Dura Den, and placed in the collection of Prof. Jameson, has the body wide and heavy, and resembling in form that of Holoptychius. It lies on its belly, and is turned a little to the left side, so that it is the back and right side which are visible. The head is proportion- ably small, and composed of enamelled and irregularly sculptured bones, which appear to be covered with a thick and very variable granulation. In the middle of the head it is easy to distinguish the frontals; in front, the nasals ; behind, the occipital ; and a great lateral enamelled plate, which indicates that the cheek was covered, as in Polypterus, by a single osseous lamella, below which ‘the great masticatory muscle was fixed. “The scales of the body are very considerable, very high on the sides, almost square on the back. They form oblique series, which meet at an acute angle in the middle line of the back. The scales themselves are very thick, placed side by side, apparently connected together only by the integument in which they were implanted. Their enamelled surface is not smooth, but adorned with a fine granulation, which gives them a velvety aspect. I have been unable to examine their microscopic structure. * Only a few traces of fins are preserved in the specimen figured ; probably a portion of the ventral near the throat, and a vestige of the dorsal, or caudal, near the end of the tail. The fin rays seem to have been short and delicate.” In the “ Preliminary Essay” of the “Tenth Decade” I de- scribed and gave a woodcut of the skull, represented in Plate I., fig. 2, of the present decade; and in a note at the end of that A 2 4, BRITISH FOSSILS. Essay, I briefly adverted to the addition mae to our knots of the genus by the specimen received from Dr. Tee ne iE im, which I now proceed to describe at io GLYPTOPOMUS MINOR. (PL 4G fig. 1 ‘(his is a cast, in tolerably fine-grained sandston , of an & specimen of Glyptopomus, the parts of which have undergone little derangement.. The sandstone block in which the been preserved is split into two slabs, along a plane tr the body of the fish, and, in general, midway between its dor and ventral surfaces. The one slab (fig. ds Pes the fore, contains, for the most part, the impression of the d surface of the fish, while the other exhibits the impressio its ventral surface; but the. plane of splitting has not traver the head, so that the impression of the jugular plates and lower — jaw is left on both slabs. On the one, or dorsal slab, howe ae it is the impress of the inner surface of the bone of these part Ni which is shown, while, on the other, the outer or es surfa has left its mark. attains its ee width (22 inches) in the middle a ie A Some allowance must be made, however, for the ugar i which the fish has been subjected. : The greatest length of the head, ead in the elddie Lin ie from the anterior end of the snout to the level of the posterior — margins of the opercular apparatus, is 22 inches, or about aes, the length of the body. The principal jugular plates (G) are each 2 Mee long. | about three-quarters of an inch wide at widest. The impressio of their surfaces shows that they had had a finely-ridged, more or — less granular, sculpture. There is no median jugular. plate, and — there is no positive evidence of the existence of ony. fatorat gare: : plates. oe Behind, and partially aslecaes by, the two ica joa ee plates there is evidence of two triangular sculptured plate: longing to the pectoral arch; and behind these commence the series of ventral scales, which are irregularly four-sided, ee a quarter of an inch wide by one- sixth of an inch long, and are disposed in transverse rows, which converge obliquely from above _ and without, downwards and inwards, to the middle line. The = surface of the cast of each scale exhibits a multivude of minute hemispherical elevations, corresponding with the pits whic constitute the peel: known ornamentation of the cae of this genus. . = la ieteas The median ees sealeg are irregularly hexagonal rows of lateral dorsal scales run from them as a cen -and backwards, on each side, to pass into the latera tr: ~The most anterior = laugest of en median grape : PR Pe ANTE CRN Ye ee Poe NEEL RE TEA ee al 5a + ~ Sah ii a ogee: DECADE Al: PLATE I —\ 's = > a Geological Surbep of the United Kingdom. 3 ; . DECADE XII. PLATE | Dirkeel delet lithy. Day & Sor{limited)Lithls Glyptopomus minor ( Agassix.) GLYPTOPOMUS MINOR. 5 The general character of the sculpture is the same on the dorsal as on the ventral scales. On the right side of the body some few of the scales in the position of the lateral line exhibit a grooved character, which is somewhat more prominent in the figure than it appears to my eye to be in nature. _ The impression of the anterior dorsal fin (D) commences at seven inches and three-tenths from the anterior extremity of the muzzle; that of the second dorsal (D") at about nine inches and a half from the same point. — | ‘The fin rays of the ventrals (V) are visible on one side in the dorsal impression (fig. 1), and, on both sides, in the ventral cast, just in front of the second dorsal. They seem to have been broad, but far shorter than the pectorals, and the impressions are so indistinct that I cannot say whether they are lobate or not. _ The pectoral fins (P, P,) are exquisitely displayed; each has- a broad scaly lobe, subacute at the extremity, and more than an inch long, by half an inch wide. The scales exhibit the same sculpture as those on the body, but are much smaller, and diminish in size towards the apex of the lobe. The many-jointed fin rays are attached all round the margins of the lobe, and become longer towards its apex, where they form fully half of the length of the fin. I see no trace of the anal fin in either slab. The impression of the well-defined upper lobe of the caudal (C) commences at. eleven inches and a quarter from the anterior extremity of the muzzle. The lower lobe is not well shown in either slab; but I suspect from the size of the upper, that the tail is diphycercal. The only tooth of Glyptopomus I have seen, fig. 4, is stout, conical, slightly curved, and deeply grooved longitudinally. The jugular plates and the mandibles have a coarsely pitted and ridged sculpture (PI. L., fig. 3). _ These facts leave no doubt as to the position of Glyptopomus in the Glyptodipterine family of the suborder Crossopterygide - among the Ganorder. - DESCRIPTION OF PLATE I, Fig. 1. The cast of a specimen of Glyptopomus minor. In Dr, Taylor’s Collection. aee Nat, size. 3 ; _ Fig. 2. The skull of a larger Glyptopomus viewed from above. It is described in Pe ee . Deeade X. “Introductory Essay,” p. 4. In the British Museum. Two- 3 thirds of the size of nature. _ Fig.3. x +. = ore ake < sy cael ake es CC i ahs, on hina eae Qiot CK (eatin, nS oa X@ * LE e< i Ck. ae —— re Ke CC ra * CM AK « Prarecc AME Me SME CREE RE NAS, a aeere °C MER FETE ; < : pe oS AO EE NRE ME RE WEE AE EE SG, CG AMS a ati nm a aT ERR es be meg CASE ~ wanda dl: Ma (Cin,