F 783 A7 S64 1905 UC-NRLF C 3 IflS Ifll THE BRITISH EOSSIL ECHINODERMATA. VOL. II, PART III. PAGES 67—90; PLATES XVII— XXVI. Ipalaeontoovapbical Society 1905. A MONOGRAPH ON THE BRITISH FOSSIL ECHINODERMATA FROM THE CRETACEOUS FORMATIONS. VOLUME SECOND. THE ASTEROIDEA. BY W. K. SPENCER, B.A., F.G.S. PART THIRD. PAGES 67—90; PLATES XVII— XXVI. LONDON: PRINTED FOE THE PAL^ONTOGEAPHICAL SOCIETY. 1905. PRINTED BY ADLARD AND SON, LONDON AND DORKING. MITEASTER COMPACTUS. 67 of length to breadth are in the case of the interradial supero-marginal plates as 5*6 mm. is to 3'7 mm. Further, the tuberculation in this specimen may or may not extend over the whole of the abactinal area, the variations being on adjacent plates, and the abactinal gibbosity is not strongly developed. In the example figured on PL IX, fig. 3, the proportions of length to breadth in the case of the interradial supero-marginal plates are as 4'5 mm. is to 3'6 mm. ; the granulated areas more generally stop short of the distal edge of the supero-marginal plate and the abactinal gibbosity is well pronounced. In view of these considerable variations it is difficult to refer these forms to more than one species. 3. MITEASTEE COMPACTUS, Forbes, sp. PI. XVII, fig. 2; PI. XXVI, figs. 3, 3 a, 3 I, 3 c. GONIASTER COMPACT-US, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 468. Forbes, 1850. In Dixon's Geology and Fossils of the Ter- , tiary and Ci-etaceous Formations of Sussex, London, p. 333, pi. xxii, fig. 3. ASTEOGONIUM COMPACTUM, Dujardin et Hupe, 1862. Hist. Nat. Zooph. Echin. (Suites ii Buffon), p. 399. GONIASTER COMPACTUS, Forbes, 1878. In. Dixon's Geology of Sussex (new edition, Jones), p. 366, pi. xxii, fig. 3. Specific Characters. — Outline pentagonal, slightly cycloidal. Eight supero- marginal plates on each side of the pentagon. Supero-marginal plates form a broad margin, and the breadth of each is about four times its length. Base of ultimate paired supero-marginal plate twice as long as the other, more proximal, supero- marginal plates. Ten corresponding infero-marginalia. Material. — Only one specimen of this species is known. This formed a portion of Mr. Willett's collection and is now preserved in the Brighton Museum. It apparently escaped the observation of the late Dr. Wright, for the figure on Plate XVII is copied from that in Dixon's ' Geology of Sussex.' As this figure is slightly inaccurate I have had it redrawn and further details added on Plate XXVI. Description. — The dorsal surface of the disc is covered with a number of small, subequal, closely-fitting plates. It is considerably sunk in the specimen known. The supero-marginalia bounding the disc form a uniform margin 5'15 mm. broad. They are eight in number along each side, exclusive of the odd terminal or ocular plates. The six middle plates are about 1'2 mm. long. Their breadth is rather more than four times their length, a feature which distinguishes them 11 68 FOSSIL ASTEROIDEA. from Mitraster Himteri and M. rngatus. A further distinctive feature is the size of the distal paired plate. This plate is triangular. The base of the triangle measures 2'7 mm., giving the plate twice the length of the more proximal plates. The plate is gibbous at its outer extremity as in M. Hunteri. All the plates are ornamented with a single or double marginal row of small spinelets. The ocular is a small conical plate barely visible in abactinal view. It fits into notches on the lower surface of the distal paired plates, and is, as usual, notched on its inferior surface for the purpose of protecting the unpaired terminal tube foot. The median infero-marginal plates are rather longer than the corresponding members of the superior series. The first two, reckoning from the median inter- radial line, are T85 mm. long, and 8'5 mm. broad. The third is only 1'8 mm. long and not quite as broad. The fourth has approximately the same length but is subtriangular in form. The fifth is a small triangular plate. Two infero-marginals and a portion of a third are situated underneath the distal paired supero-marginal plate. The ventro-lateralia visible are small hexagonal plates covered with a fine uniform granulation. The adambulacralia are small oblong plates. The margin of the disc is very abrupt, but the transition from infero-marginalia to the actinal surface is more gradual than that of the supero-marginalia to the upper surface. A number of small granules are irregularly distributed between the plates. Remarks. — Unfortunately, the specimen is slightly distorted, so that the pro- nouncedly cycloidal appearance in the figure is partially due to the unnatural position of the marginal plates, which has brought the inferior series into the dorsal view. The supero-marginal plates appear to have been straight and the inferior series but slightly cycloidal. This, together with the large comparative size of the ultimate paired plate, would bring the species very near to the genus Meto- paster. Forbes remarked upon the fact that it appeared to be intermediate between Goniaster (Metopaster, Sladen) uncatus and Goniaster (Mitraster, Sladen) rugatns. I have therefore considerable doubt as to the validity of the separation of these two genera. Locality aud StratigrapJtical Position. — Upper Chalk of Haughton, Sussex. COMPTONIA COMPTONI. 69 Genus— COMPTONIA, Gray. Gray, 1840. Annals and Magazine of Natural History, vol. vi, p. 278. — 1866. Synopsis of Starfishes in the British Museum. Body depressed, with produced tapering rays. Disc covered abactinally and actinally with numerous polygonal plates which possess a imiform granulation. Marginal plates numerous. Supero-marginal plates equal in number to the infero- marginals, and forming a moderately broad border to the disc. Infero-marginal plates (as well as all other plates) devoid of spines. Radialia present throughout length of ray. This genus apparently differs from Stellaster only in the absence of spines on the infero-marginalia. It is thus similar to, as well as prior to Of/master (von Martens, 1865) and Dorigona (Gray, 1866). 1. COMPTONIA COMPTONI, Forbes, sp. PI. XVII, figs. 3, 3 a, and 36; PI. XVIII, figs. 2, 2 a, 2l,2c,2d. STELLASTER COMPTONI, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 476. Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, pi. xxii, fig. 8, p. 335. Dujardin et Hupe, 1862. Hist. Nat. Zooph. fichin. (Suites a Buffon), p. 408. Forbes, 1878. In Dixou's Geology of Sussex (new edition, Jones), pi. xxii, fig. 8, p. 368, 370. Specific Characters. — Disc large and interbrachial arcs wide, giving the disc a distinctly pentagonal appearance. Major radius rather more than twice the length of the minor radius. Arms elliptical in cross section. Large valvate pedicellarise present. Material. — Two specimens (the two cotypes) of this species are in existence. One (formerly in the Bowerbank Collection) displays the actinal aspect (PI. XVII, fig. 3), and is preserved in the British Museum of Natural History (34311). The other (PL XVIII, fig. 2), which shows the dorsal aspect, is preserved in the Northampton Museum. This is the specimen figured in Dixon. Description. — The large pentagonal disc is covered dorsally with numerous 70 FOSSIL ASTEROIDBA. small closely-fitting plates. In the radial areas these plates are polygonal and are about 1*8 mm. in diameter. In the interradial areas the plates measure only 1 mm. in diameter and are rhomboidal. All the plates are covered with a fine uniform granulation (PI. XVIII, fig. 2 a). Upon very many of the plates are valvate pedicellarige. Post-mortem changes have produced a sinking in of the plates over the interradial areas. Depressions, doubtless due to similar causes, appear in recent forms when dried, as also in G. elegans. I have been unable to distinguish either the madreporite or the anus. The arms are not so much produced as in G. elegans. R : r : : 62 mm. : 29 mm. in the specimen at Northampton. R : r : : 55'6 mm. : 25'8 mm. in the British Museum (Natural History) specimen. The width of the arms at the sixth supero-marginal (reckoning from the inter- radius) is 11 '5 mm. The supero-marginalia are oblong in shape. In the interradial areas they are of fairly constant size, measuring 5'2 mm. in breadth and 2mm. in length. They diminish in size distalwards. They are eighteen in number, and often bear one or more valvate pedicellarige. The margin is rounded and is about 8 mm. high. The infero-marginalia are equal in number and similar in appearance to the superior series. The actinal interradial areas are large and filled proximally with a number of small rhomboidal plates about 1'2 mm. in average breadth. The more distal plates are croAvded, smaller, and polygonal in appearance. Traces of a fine granulation are visible. The adambulacrals are a series of small oblong prominent plates. The largest are about l'6mm. in length and 1P2 mm. in breadth. Remains of their armature are still present. The mouth-angle plates are small and but slightly prominent. They also bear traces of armature. Valvate pedicellariae are scattered apparently irregularly over all these various plates. Locality and Straf {graphical Position. — Upper Greensand of Blackdown. Remarks. — Forbes considered this species was equivalent to Asterias Schultzii, Roemer.1 In this latter species, however, the superomarginalia meet across the dorsal surface of the ray, which would disprove Forbes' statement. 1 Eoemer, ' Versteinerungen des Norddeutschen Kreidegebirges,' pi. vi, fig. 21. COMPTONIA ELEGANS. 71 2. COMPTONIA ELEGANS, Gray. PI. XVII, figs 4 and 4 a. COMPTONIA ELEGANS, Gray, 1840. Ann. & Mag. Nat. Hist., vol. vi, p. 278. STELLASTER ELEGANS, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 476. Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, London, p. 336, pi. xxii, fig. 9. COMPTONIA ELEGANS, Morris, 1854. Catalogue of British Fossils, 2nd ed., p. 50. Dujardin et Hupi', 1862. Hist. Nat. Zooph. Echiu. (Suites a. Buffon), p. 408. STELLASTEB ELEGANS, Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 369, 370, pi. xxii, fig, 9. Specific Characters. — Disc strongly convex, covered with small polygonal plates. Actinal interradial areas large. Arms well produced, the major radius being at least three times as long as the minor radius. Interbrachial arcs paraboloid. Material. — The specimen figured by Dixon, at that time in the Bowerbank Collection, is now preserved in the British Museum of Natural History (E. 2567). Both dorsal and ventral aspects are exposed. Another specimen showing an impression of the ventral surface exists in the Oxford University Museum. Dixon's specimen, however, can hardly be the type, since Gray (1840) stated that the specimens described by him were in the British Museum or in the collection of the Zoological Society. Forbes (1848) refers only to specimens in the British Museum and the collection of the Marquess of Northampton. No part of the Bowerbank Collection is known to have come to the British Museum before 1865. The type specimen therefore must be either lost or still unrecognised in the national collection. Since it was never figured it could never be identified with certainty. It is therefore advisable to take the specimen E. 2567 as type. Description. — The disc is high in the central and radial regions. In the inter- radial areas, however, post-mortem changes have caused a collapse of the test and the consequent production of deep triangular depressions. The plates covering the disc are minute, polygonal, and closely fitting. The centrale is the 72 FOSSIL ASTBROIDEA. only plate of the dorsal surface which is larger or more conspicuous than the remainder; all are covered with a minute uniform granulation of a quite charac- teristic appearance. The anus is almost central in position. It is surrounded by a circlet of plates, amongst which is the centrale. The madreporite is, as usual, situated in the next (clockwise) interradius, almost halfway between the centrale and the margin. It is a triangular plate, the apex of the triangle being a markedly acute angle. The arms are well produced. R : r : : 30 mm. -j- : 9 mm. Their breadth at the base is 9 mm. Radialia, adradialia, and dor so -later alia extend into the base of the arms. The dorso-lateralia soon disappear, but the adradialia persist as far as the seventh or eighth supero-marginal plate. When the adradials disappear the radialia become larger. They are at this point 1 mm. broad and I'l mm. long and therefore appear almost square. The supero-marginalia are oblong plates of curiously uniform size in the portions of the specimen preserved. They are 1*6 mm. long and from l'2mm. to 1'3 mm. broad. The infero-marginalia are of the same length and are opposite to the supero-marginalia. In lateral view the supero-marginalia appear higher than the inferior series. Both series are ornamented with a number of small, fine granules which are uniformly distributed over their surfaces. The ventral surface is concave. The ventro-lateral plates are rhomboidal in the region of the mouth. They become polygonal and croAvded as they approach the margin. Some of these plates extend into the base of the arms. Around the edges of the plates spinelets are visible. The spines of the adambulacral plates are still present. Unfortunately, it is not possible to make out their exact distribution. The mouth-angle plates are not prominent. There is no trace in this species of such valvate pedicellarise as characterise G. Gomptoni. Remarks. — Gray compared this species with Cadaster, Agassiz.1 The rather vague diagnosis of Ccelaster given by Agassiz renders exact identification impossible. Locality and Stratigrapldcal Position. — Upper Greensand of Blackdown. Also in the Upper Greensand at Folkestone (observed by Forbes). 1 Agassiz, ' Annales des Sciences Naturelles,' 1837. Translated in ' Annals and Magazine of Natural History,' vol. i, 1838. PENTAGONASTER EOBUSTHS. 73 Genus— NYMPHASTER, Sladen, 1885. (See p. 14.) 4. NYMPHASTER RADIATUS, n. sp. PI. XXV, figs. 1, 1 a, I b. Specific Characters. — Arms very much produced. R : r : : 150 mm. : 10 mm. Supero-marginalia in contact almost the whole length of arm. Mt it. i' r I i'il.— The only specimen of this species, formerly in the collection of Mr. J. Starkie Gardner, is preserved in the British Museum of Natiiral History (E. 375). The plates have, unfortunately, disappeared from the disc. Practically all that remains is the greater portion of one arm. Description. — At the base of the arm the supero-marginalia are oblong. Each measures 2'8 mm. in breadth, 2 mm. in length, and 3 mm. in height. Distally these plates become almost square. They are ornamented by small granules which tend to run together transversally to the length of the arm (PI. XXV, fig. 1), and articulations for spines and deep depressions for pedicellarige are also present. They are about twenty-five in number. The infero-marginalia equal in number and size and oppose the supero-marginalia. Further they are about the same height in marginal view. The breadth of the arm at the fourth supero-marginal is 6 mm. Stratigraphical Position. — Lower Chalk. Locality uncertain. Genus— PENTAGONASTER, Linck. (See p. 24.) 3. PENTAGONASTER ROBUSTUS, n. sp. PL XXI, figs. 2, 2 a. Specific Characters. — Disc covered with small rounded plates. Margin high. Rays short, high and robust. R : r : : 21'5 mm. : 9'9 mm. The supero-marginal plates meet along the median line throughout almost the whole length of the arm, and form a broad border to the disc. Interbrachial arcs paraboloid. Material. — The only specimen of this species is the one here described, formerly in the Mantell collection and now preserved in the British Museum of Natural History (48085). The locality from which it was derived is stated rather 74 FOSSIL ASTBROIDEA. vaguely as Upper Chalk, Sussex. The specimen is somewhat imperfect, consisting only of the dorsal view of three arms and a portion of the disc. Description. — The disc appears to have been covered on its dorsal surface by a large number of small, rounded, closely-fitting plates. Mostly they are subequal in size and have an approximate diameter of 2 mm. An uncertain number of even smaller granule-like plates exist scattered between these. Both radialia and adradialia extend into the base of the arms, but only as far as the third supero-marginal plate, counting from the median interradial line. The arms themselves are short and high. The height of the specimen in the interradius is 9'2 mm. From this point the height gradually diminishes to the extremity of the ray, where it is 5 mm. The supero-marginalia are about twelve in number. They form a broad margin to the disc and rays. Bach supero-marginal plate is high, and is very convex dorsally. Hence every plate is very distinct. The six proximal supero- marginals diminish only slightly in size distalward along the ray. The next six, however, diminish much more rapidly. The supero-marginal nearest the inter- radius has the following measurements: height, 5'75 mm.; breadth, 4'5 mm.; length, 3 mm. The ocular plate has broken away, and there is no trace of a madreporite. The infero-marginalia alternate with the supero-marginal series. They are not so high and much squarer in appearance. They decrease in size much more rapidly than the upper series (see PI. XXI, fig. 2 a). The infero-marginal plates, nearest the interradius, measure 4'5 mm. high and 3'2 mm. in length. Any orna- ment that may have existed has disappeared from all parts. Locality and Stratigraphical Position. — Upper Chalk, Sussex. 4. PENTAGONASTEE OBTUSUS, Forbes, sp. PL XXII, figs. 1, 1 a, lb,2,2a, 3 a, 3 b, 3Q 7 Q tj O Uj O i OBEASTEE OBTUSUS, Forbes, 1848. Mein. Geol. Surv. Gt. Brit., vol. ii, p. 468. — Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, London, p. 330, pi. xxi, fig. 12. Dujardin et Hupc, 1862. Hist, Nat, Zooph. Echin. (Suites a Buffon), p. 389. Forbes, 1878. In Dixoii's Geology of Sussex (new edition, Jones), pi. xxi, fig. 12, pp. 364, 370. PENTAGONASTER OBTUSUS. 75 Specific Characters. — Disc slightly convex. Majority of the plates covering the disc of subequal size and closely set. R : r : : 25 mm. : 12 mm. Extremities of arms obtuse. Interbrachial arcs only slightly rounded, giving the disc a distinctly pentagonal appearance. Material. — The two extremities of the arms from which Forbes originally described the species when in the Dixon collection, are now preserved in the British Museum (Natural History). They are not on the same slab of chalk as represented by Forbes, but are and probably always have been two independent specimens, E. 5038 (PI. XXII, figs. 3 b, c, d), and E. 5039 (fig. 3 a). More complete specimens have since been added to the collection (40400, PI. XXII, fig. 1 ex J. Simmons' Coll., and 35481, PL XXII, fig. 2, ex H. W. Taylor's Coll.). Two extremities of arms are also preserved in the Brighton Museum. Description. — The disc is high and distinctly pentagonal. At the edge of the disc the dorsal covering plates are crowded and polygonal in appearance. Towards the centre they become slightly smaller and rounded. The average diameter of these plates is 1'7 mm. The madreporite is subcentral in position. It is about the same size as the other plates of the disc and is pentagonal in shape (PI. XXII, fig. la). The arms are stoutly built. A triple row of polygonal plates enters their bases. The adradial series soon disappears, leaving the single radial series, which appears to persist until it reaches that part of the ray which is obtuse. From this point the supero-marginal plates may or may not be adjunct up to the end of the ray. Considerable variation appears to exist as to this point in the single specimen examined. The arms are distinctly obtuse in their distal half. This has given the species its name. The supero-marginalia form a rather broad border to the disc. There are nine supero-marginals from the median interradius to the extremity of the ray. Towards the end of the 'ray the plates of this series become narrower, more oblong in appearance, and distinctly convex. The infero-marginalia are equal in number and situated generally alternating with the supero-marginal series. They are distinctly square in shape, especially at the obtuse extremities of the ray. Their ornament is in some specimens not so coarse as that of the supero-marginals. The actinal interradial areas are very distinct and are occupied by four series of ventro-lateral plates. As usual, the actinal plates near the mouth are larger and more rhoinboidal than the distal plates. Ventro-lateral plates only extend throughout about a quarter of the length of the arm. 12 76 FOSSIL ASTBROIDEA. The mouth-angle plates are not prominent. The adambulacral plates possess a triple row of spines. Dimensions. — Specimens 35,481 and 40,400. — The greatest width of the ray varies from 8'3 to 6'5 mm., and the least width from 7'2 to 5'7 mm. The supero- marginal plates are 3'2 mm. broad near the interradii. Specimen E. 5038. — Greatest width of ray 10'5 mm. Specimen in Brighton Museum. — Greatest width of ray 9'2 mm. Locality and Stratigraphical Position. — Upper Chalk, Lancing, Sussex, and also from the Upper Chalk of Kent. Family— PENT ACE ROTID.E (Gray) emend. Perrier, 1884. Phanerozonate Asteroids with unequally developed marginal plates, the superior series being frequently masked or hidden in membrane. Abactinal skeleton reticulate. Plates with large isolated tubercles, or spinelets, or granulose, or covered with membrane. Actinal interradial areas with large pavement-like plates which bear unequal-sized granules. Genus— PENTACEROS, Schidze, 1760. PENTACEEOS, Schulze, 1760. Betrachtung der versteinerten Seesterne und ihrer Theile, Warschau u. Dresden, p. 50. GONIASTEE (pars), Agassiz, 1835. Mem. Soc. Sci. Nat. Neuchatel, t. i, p. 191. PENTACEROS, Gray, 1840. Ann. and Mag. Nat. Hist., vol. vi, p. 276. OEEASTEB, Miiller and Troschel, 1842. System der Asteriden, p. 44. Generic Characters. — Form stellate, marginal plates conspicuous, denning the ambitus. Abactinal plates regular, with more or less definite intermediate papular areas. Prominent localised mammillated tubercles or spines present. All the fossil species of this genus possess intermarginalia, but do not other- wise approach Sladens' genus Pentaceropsis which possesses this character. In view of the fact that intermarginalia may occur as a variation in unmistakable recent species of Pentaceros this character cannot invalidate the admission to the present genus of the species about to be described. PENTACEROS BULBIFERUS. 77 1. PENTACEBOS BULBIFERUS, Forbes, sp. PI. XX, figs. 1, 1 a, 1 b, and 1 c; figs. 2, 2 a, and 2 6 ; PI. XXI, figs. 1, 1 a, I b, 3, 3 a, 4, 4 a ; PI. XXIII, figs. 2, 2 a. OBEASTER BULBIFEKTTS, Forbes, 1848. Mem. Geol. Surv. G-t. Brit., vol. ii, p. 468. Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, pp. 328, 329, pi. xxiv, fig. 7. Dujardin et Hupe, 1862. Hist. Nat. Zooph. fichin. (Suites ii Buffon), p. 389. Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 363, 370, pi. xxiv, fig. 7. P. H. Carpenter, 1882. Geol. Mag., p. 12. Specific Characters. — Disc and arms very convex. The centrale and primary interradialia large and tuberculiform. The major radius approximately twice the minor radius. Radialia of the arm conspicuous. Extremities of the arms swollen. Material. — The specimens figured and described are all preserved in the British Museum (Natural History). E. 5040 (PL XXI, fig. 1), 40175 (PI. XX, fig. 1), 48748 (PI. XX, fig. 2), and E. 5041 (PI. XXI, fig. 3), which were bought from J. Simmons, and 40399 (PI. XXI, fig. 4), from the collection of E. Charlesworth, are all labelled as coming from the Upper Chalk of Bromley, Kent, which, however, seems to be an inexact dealer's locality, probably intentionally mis- leading. E. 5042 (PL XXIII, fig. 2), also bought of J. Simmons, is labelled "Upper Chalk, Charlton, Kent." Other specimens are known in the Sedgwick Museum, Cambridge, Northamp- ton Museum, and Brighton Museum. Specimens have also been described by Valette from the South of France. This seems to be much the commonest as well as the most graceful of the Chalk Pentacerotidae. Description. — The general aspect of the plates of the disc gives this species a very characteristic appearance, for the five primary interradialia and the centrale are very prominent. They have a lobed widely-spreading base, and are swollen on the upper surface into an almost spherical form. Their weathered surfaces are pitted in a very regular manner, the pits indicating the former presence of 78 FOSSIL ASTEROIDEA. granules. Sometimes the granules are still present in situ. The pits are separated in the example figured PI. XXI, fig. 1, on an average rather less than their own diameter apart. There may or may not be a slight margin to the plate. The centrale in a specimen R : r : : 40 : 20 measures 8'5 mm. in diameter. The primary interradialia are rather smaller, being 6'7 mm. in diameter. Radially the most conspicuous plates of the disc are the proximal radialia. They have a very characteristic appearance, their general shape reminding one of a breastplate. The remainder of the plates of the disc are of very various sizes and distributed in a fairly regular manner. The general arrangement of these plates is given in the general account at the conclusion of these volumes. The madreporite is a conspicuous plate lying at the distal end of a primary interradial. The two neighbouring adradialia are notched for its reception. The arms are moderately produced, the major radius being about twice the minor radius. Measurements of five specimens give the following : R r 40 miu. 20mm. 35 mm. 17 mm. 50 mm. 25 mm. 50 mm. 25 mm. 50 mm. 20 mm. At the base of each arm there are five series of plates visible on the dorsal surface — the radialia, adradialia, and supramarginalia. All the plates at the base of the arm overlap. They are of a type which may be derived from the breast- plate shape mentioned above. They gradually become narrowed in length and increased in breadth until they are shaped somewhat like an inverted T (PI. XX, fig. 2 V). The granulation is generally confined to the central region of each plate. The arm about halfway along its length becomes swollen and the plates no longer overlap but are contiguous. They lose their J_-shaped form, become almost oblong, and at the same time rather tumid. This is especially noticeable in the case of the radialia. The form of the plates is, however, rarely absolutely regular, but one which is generally derivable from the breastplate shape. If we examine a cross-section of the arm, we see that the base of the plates of the dorsal intermediate series is prolonged inwards (and ventralward), so that a single isolated plate appears club-shaped. All the plates are pitted for granules except at the extreme margin. The supero-marginal plates are from twelve to thirteen in number, the infero- marginals from thirteen to fourteen in number. The arm is very high and both PENTACEROS BULBIFERUS. 79 infero- and supero-marginal plates appear in dorsal view. In fact, the infero- marginal plates do not take any part in the formation of the actinal surface. This is parallelled in modern species of Pentaceros, e. g. P. clavatus. In marginal view the supero- and infero-marginals at the extremity of the ray very distinctly alternate. This alternation persists at the base of the arms, but here it is not always so obvious. The supero-marginals are much higher than the infero-marginals, and also more oblong in shape. Both supero- and infero-marginal plates are regularly but coarsely pitted for granules. In specimen figured on PI. XX, fig. 1, we obtain the following measurements : Breadth of fifth infero-marginal from the extremity of ray . 5'8 mm. Length „ „ „ „ „ .4 Breadth ,, supero-marginal „ „ ,, . 9'2 „ Length „ „ „ „ „ . 3'9 „ Breadth „ radialia „ „ „ . 5'8 „ Length „ „ „ „ „ . 4'4 „ Width of ambulacral groove . . . . 1'2 „ The ocular is visible in this specimen. It is about 1'6 mm. in length and breadth. The extremity is slightly pointed, and its ventral surface is hollowed out. A ventral view is figured on PI. XXI, fig. 1. Ventro-lateral plates extend almost to the extremity of the arms. These are, as usual, rather greater in breadth than in length. The adambulacral plates appear to be about half the length of the bordering actinal plates. Their armature consists of several rows of spinelets arranged in pairs. A few intermarginalia are present in the interradii. They, as usual, press the supero- and infero-marginalia on to the abactinal and actinal surfaces of the disc respectively. Locality and Stratigraphical Position. — Upper Chalk, Bromley, Kent; according to Dr. Rowe, probably from the Chislehurst caves near that locality. Variations. — Variations occur amongst all the specimens, especially with regard to the ornamentation of the plates and the madreporite. The British Museum specimens, 48748, which occur together in a slab, are especially note- worthy, inasmuch as the lowest situated individual possesses on the disc no plate, which is bulbiform or raised conspicuously above the remainder. 80 FOSSIL ASTEROIDEA. 2. PENTACEEOS BOYSII, Forbes, sp. PL XXII, figs. 4, 4 a, 41, 4 c ; PL XXIII, figs. 1, 1 a, 1 b ; PL XXVI, figs. 2, 2 a, 2 6. OEEASTER BOYSII, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 468. — Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, p. 328, pi. xxi, fig. 6. — Dujardin et Hupf, 1862. Hist. Nat. Zooph. Echin. (Suites a Buffon), p. 389. — Forbes, 1878. la Dixon's Geology of Sussex (new edition, Jones), pp. 362, 370, pi. xxi, fig. 6. Specific Characters. — The primary radialia and interradialia are large hemi- spheroid punctate tubercles. R : r : : 80 mm. : 18'mm. Rays well produced, steep- sided, almost square in section, and tapering gradually to the extremity. Only a few of the plates of the disc enter the base of the arm. Supero- and infero- marginal plates adjunct, the intermarginalia being represented only by a few scattered granules. Material. — The type specimen was said by Forbes (1848) to be in the collection of the Marquess of Northampton. The specimen figured and described in Dixon's ' Geology of Sussex ' (see reference) was said by Forbes to have been " discovered by Major Boys and formed part of his interesting collection." This statement does not preclude the hypothesis that the specimen figured was also the type specimen. Neither specimen (if there were two) can now be traced. The following description is based chiefly on a specimen in the Sedgwick Museum, Cambridge (PL XXVI, fig. 2), which shows the actinal surface of the arms and a portion of the disc. It is supplemented by reference to a less nearly perfect specimen preserved in the British Museum of Natural History (J. Simmons' Coll., 46600), which presents views of isolated rays (PL XXII, fig. 4), and an isolated ray seen from the dorsal surface (PL XXIII, fig. 1) in the same museum (Dixon Coll., 48083). Description. — The disc is covered with a number of rounded or irregularly- shaped plates. A circlet of large tubercles is very distinct and characteristic of the species. These tiibercles are hemispherical and not so swollen as those of P. bulbiferiis. They are smooth, and possess a fine distinct ornament, thus distinguishing them from the circlet of P. coronatus. Their diameter is about 81 5 mm., and they seem to be arranged radially and in terra dially, making a total of ten. The madreporite was figured by Forbes. It is roughly triangular in shape. PENTACEROS BOYSII. 81 The arms are -well produced. R = 80 mm. and r = 18 mm., the major radius being thus about four and a half times the minor radius. They taper gradually to the extremity. The breadth of the ray about the fourth supra-marginal plate is 6'8 mm. The height of the ray at the same spot is almost exactly the same. The rays are steep-sided, and consequently appear almost square in cross section. The supero-marginalia are adjunct throughout almost the whole length of the ray, for only one or two single radialia enter the base of the ray. At the base of the ray they are flat and slightly rhomboidal. They possess an anterior indenta- tion on their inner surface and are about 3'5 mm. in breadth. They gradually diminish in size distally and at the same time become distinctly swollen. They number about twenty-eight. The infero-marginal plates are approximately of the same size and number as the supero-marginals. Both series imbricate slightly. The ornament of these plates consists of a number of fine granules in the centre, while there is a distinct margin without granulations. Between the supero- and infero-marginal plates a few scattered granules repre- sent a slight development of the intermarginalia. The adambulacrals are a series of small oblong plates. They border the infero- marginals from about the eleventh supra-marginal onward. They are much worn, and but slight traces of their armature remain. About five adambulacrals occupy the same length as two infero-marginal plates. Proximally there is a single row of small plates which separate the two series. Only a few scattered ossicles of the actinal surface of the disc remain. Locality and Stratigraphical Position. — Upper Chalk, Kent. Remarks. — Valette (' Bull. Soc. Yonne,' 1902) has described a number of species of starfishes from the Senonian of the South of France. The remains are found as scattered ossicles. Some of these are grouped by Valette as a new species which he calls P. senonensis. They are noticed by the author to resemble P. Boysii except that they are smooth and therefore do not have the ornament possessed by P. Boi/sii. Valette regards this absence of ornament as rendering them specifically distinct from P. Boysii, as other ossicles found in close proximity still possess the ornament. In view of the vagaries of the way in which solution may occur, I cannot admit this contention and consider that it is much more probable that the ossicles at one time possessed ornament and were identical with P. Boi/sii. All the other ossicles except those of the so-called Arthraster senonensis (vide infra, p. 92) were identified with English Cretaceous genera, which would support this contention. 82 FOSSIL ASTEROIDEA. 3. PENTACEEOS COEONATUS, Forbes, sp. PI. XIX, figs. 1, la; PI. XXIV, figs. 2, 2 a, 2 6, 2 c ; PL XXV, fig. 9. OREASTER CORONATTJS, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 467. Forbes, 1850. In Dixon's Geology and Fossils of the Ter- tiary and Cretaceous Formations of Sussex, pp. 327, 328, pi. xxi, fig. 7 a— d. Dujardin et Hupf, 1862. Hist. Nat. Zooph. Echin. (Suites a Buffon), p. 389. Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 362, 370, pi. xxi, figs. 7, 7 a— d. Specific Characters. — Disc large, with conspicuous nodiilar primary radialia and interradialia. The major radius is about five times the length of the minor radius. Sides of arms very steep, so that the arm appears to be square in cross section. A triple row of intermarginalia present in the interbrachial areas. Material. — The type specimen of this species is preserved in the British Museum of Natural History (Dixon's Coll., 35480). Unfortunately, only one arm and a portion of the disc are preserved. A further specimen, registered E. 2562, from the cabinet of Mrs. Smith, of Tunbridge Wells, is preserved in the same museum, and another example is to be seen in the Museum of Practical Geology, Jermyn Street. Description. — The most conspicuous feature of the disc is the circlet of ten "large, more or less polygonal nodose pyramidal tubercles." These are the primary radialia and interradialia. The interradial tubercles are rather larger than the radial tubercles, the former measuring 9'2 mm., the latter 7'7 mm. in diameter. The remainder of the disc is covered by irregularly shaped plates. The madreporite has been broken away from the disc of the specimen no. 35480. It is figured Plate XXV, fig. 9. II : r : : 58 mm. : 19 -f- mm. in the type specimen where the single arm is broken short. In specimen no. E. 2562 R : r : : 100 mm. : 20 mm. The arms are 30 mm. broad at the base. Their surface is flat, and the sides slope away at right angles, so that a cross section of the arm is square. Both radial and adradial plates are present in the base of the ray. The adradials are irregular in shape and soon disappear. The radials are roughly oblong in appearance, and exist throughout that portion of the arm preserved. They diminish in size, however, distally. The supero-marginal plates are indented on their anterior median surface. 1 Forbes, in Dixou's ' Geology of Sussex,' p. 327. PEKTACEROS SQUAMATUS. 83 They appear to imbricate slightly at their margins. The breadth of the fourth supero-marginal is 7 mm., the length 4 mm., and the height 3'5 mm. The height of the ray at this point is 12' 2 mm. The infero -marginal plates are opposite to the supero-marginals. They are approximately about the same size and number. Between the supero- and infero- marginal series a triple series of intermarginalia occurs in the interradial areas. The inner and larger intermarginals persist throughout the greater part of the length of the arm. It is this intercalated series which gives to the arm its great proportionate depth. The outer and smaller series disappear at about the seventh and ninth infero-marginal plates. The ornamentation of the plates appears to have been worn away, although upon many of the plates a distinct marginal area may be seen. Upon most of the plates there occur small entrenched pedicellarise which are very characteristic of this species of Pentaceros. They consist of a small pit from which radiate two fine entrenchments (see PI. XXIV, fig. 2 a). One of the rows of specimen no. B. 2562 is distorted so as to bring the ventral surface into view. This shows that the ventro-lateral plates extend well towards, and perhaps all the way to, the extremities of the arm. Locality and Stmtigraphical Position. — The locality of the type specimen is given as Lower Chalk, Washington, Sussex. The specimen registered E. 2562 is from the Lower Chalk, Burham, Kent, and the specimen in the Museum of Practical Geology is from the Lower Chalk, Dover. Remarks. — The specimen registered E. 2562 presents only one or two pedi- cellaria?, which are so characteristic and numerous on the other two specimens. 4. PENTACEROS SQUAMATUS, Forbes, sp. PI. XXV, figs. 3, 3 a, 3 b, 3 c. OREASTEK SQTJAMATUS, Forbes, 1848. Mem. Geol. Surv. Gt. Brit., vol. ii, p. 468. — Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, p. 328, pi. xxiii, fig. 7. — Dujardin et HupS, 1862. Hist. Nat. Zooph. Echin. (Suites. k Buff on), p. 389. _ _ Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 363, 370, pi. xxiii, fig. 7. Specific Characters. — Disc high, with conspicuous primary radialia, inter- 13 84 FOSSIL ASTEROIDEA. radialia and centrale. Major radius about four times the length of the minor radius. Only radialia enter the base of the arm. Dorsal surfaces of arms flat, sides slope away at an obtuse angle from this. Ossicles distinctly imbricating. A few intermarginalia present. Material. — The only specimen of this species is preserved in the Brighton Museum. The specimen consists of the disc and a portion of three arms. On the whole little displacement of the ossicles has taken place. Description. — The disc is strongly convex, and is covered with the circlet of primary radialia and interradialia which are disposed around the centrale. All these ossicles appear shaped like a breast-plate. The centrale has a diameter of 4'2 mm. The primary interradialia are larger, possessing a diameter of 5'3 mm., whilst the primary radialia are the smallest of the series, measuring only 3'7 mm. across. Between the centrale and the primary interradialia a number of irregularly distributed plates appear. In the next right-hand interradius to the madreporite a number of these appear to have surrounded an anal opening. The primary interradialia almost touch one another, and the radialia consequently rest on the bases of pairs of ossicles. A few adradialia are present, but they are confined to the disc. A pair of them help to enclose the madreporite, which is a polygonal plate 9 mm. in greatest diameter. The ornamentation of the ossicles is rather coarse when present, but usually it is very much worn away. The arms are well produced. R : r : : 30 -f- mm. : 7'8 mm. They are 1'3 mm. in breadth at the base. After the fourth or fifth radiale the remainder become minute but persist throughout the length of the arm preserved. The supero-marginalia are finger-shaped ; they, as also the infero-marginalia, distinctly imbricate. The dimensions of the third supero-marginal, reckoning from the median interradial line, are as follows : length 2'3 mm., breadth 3*1 mm. The long axes of the supero-marginal plates slope away distally, thus causing pairs of plates to assume the shape of arms of a V. They are at least thirteen in number. The infero-marginal plates are similar in size and number to the supero- marginal series. In the interradii a few intermarginalia are present. These force the supero-marginal series to the surface of the disc. Nothing is known of the ventral surface. Locality and Stratigraphical Position. — Upper Chalk, "Woolwich. PENTACEROS OCELLATUS. 85 5. PENTACEROS OCELLATUS, Forbes, sp. PI. XXV, figs. 4, 4 a. OBEASTER OCELLATUS, Forbes, 1848. Mem. Geol. Surv. Great Brit., vol. ii, p. 468. Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, p. 329, pi. xxi, fig. 13. Diijardin et Hupt, 1862. Hist, Nat. Zooph. Echiii. (Suites u Buffon), p. 389. Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 364, 370, pi. xxi, fig. 3. PENTACEROS McPherson, W., 1902. Eep. Brighton Nat. Hist. Soc. Specific Characters. — Ventro-lateral plates (as probably also the dorsal plates) depressed and finely striated on their truncated surface so as to simulate the surface of a madreporite, with sides rugged and ocellato-punctate. Between these plates smaller ossicles of a similar character are interspersed. Material. — But one specimen of this species was known to Forbes. This is preserved in the British Museum of Natural History (Dixon Coll., E. 2571). It is a mass of ossicles which look as if they were derived from the dorsal surface of the disc. They are more spheroidal and somewhat larger than the ossicles of the ventral surface of the more nearly perfect example discovered by Mr. William McPherson in the Senonian Marsupites band at Brighton. This he presented to the British Museum (Natural History) in 1901 (E. 5012). Description. — The disc and arms are unknown. The specimen no. E. 5012 shows a well-preserved portion of the ventral surface. The mouth-angles were occupied by single initial rhomboidal ossicles. To these succeed the ventro-lateral ossicles which border the ambulacral groove. These are pentagonal ossicles of very uniform size. The length of the exposed sides of the ossicles bordering the groove is 4'4 mm. and the greatest breadth of an ossicle 4'2 mm. The remaining ventro-lateral plates are hexagonal, but of almost the same dimensions, although the plates appear to become a little larger distally. The plates overlap one another considerably, rendering precise measurement difficult. Between the larger plates are interspersed large numbers of smaller and more irregular ossicles which fill up the angles between their sides. The whole test would be thus very strongly built. Both larger and smaller plates are curiously similar in appearance. The 86 FOSSIL ASTEROIDEA. madreporiform striations on the truncated summits and the ocellato-punctate sides give a most characteristic appearance and render the species unmistakably distinct from all known species of Pentaceros. The ambulacral groove is 3'5mm. wide. The adambulacrals are difficult of recognition and have probably for the most part been lost, but a large number of the hour-glass shaped ambulacrals may be seen. Locality ami Stratigraphical Horizon. — Upper Chalk, Kent; Upper Senonian, Brighton. 6. PENTACEROS ABBREVIATUS, n. sp. PI. XXIV, figs. 1, 1 a, 1 b, 1 c. Specific Characters. — Body of medium size. Arms moderately produced, but their breadth making them appear stumpy, rounded at the extremities, and hemi- spherical in cross section. Five series of dorsal ossicles enter their base. Of these the radialia and adradialia persist throughout the length of the arm. A few small intermarginalia are present. Material. — There is only one specimen known of this species, and of this practically all that remains are two arms. It is preserved in the British Museum of Natural History (J. Tennant's Coll., 57538). Description. — These arms are characteristically wide, the width of the arm at the base being 31 mm. They narrow veiy gradually towards the extremity. Throughout the ray the ossicles, except for the differences noted below, are very similar in appearance. At the base of the ray, where dorso-lateralia also enter into the composition of the dorsal skeleton, they are rounded and possess interspaces of considerable extent. These interspaces are often filled by smaller granules arranged irregularly. At times, however, between two radialia or adradialia one of the smaller ossicles is arranged in a very regular and alternating manner. Both large and small ossicles are finely granulated, and the large ossicles alone are perforated for pedicellarise. The average size of the larger ossicles at the base of the arms is about 6 mm. Towards the extremity of the ray the radialia, adradialia, aud marginalia become hexagonal, and fit very closely so as to make a compact skeleton. The terminal ocular plate is hexagonal and conspicuous. It has a flattened articulation which undoubtedly was originally occupied by a spine. Several of the other dorsal plates in the distal portion of the ray also possess similar articulation. PENTACEROS BISPINOSUS. 87 The supero-marginalia and infero-marginalia are equal in number. There were probably thirteen of each in the space between an interradius and an extremity of an arm. In the interbrachial arc there is a series of minute granular intermarginalia. The traces of the disc which are present suggest that the ossicles of this region were oval in shape and minute in size. I exposed a portion of the ventral surface of the arm, but, unfortunately, little trace of structure was shown. The ventro- lateralia extended to the extremity of the ray. The ridges of the adambulacral armature are lost. Locality and Stratigraphioal Position. — Upper Chalk, Charlton, Kent. 7. PENTACEROS BISPINOSUS, n. sp. PI. XXIII, figs. 3, 3 a, 3 b, 3 c. Specific Characters. — Disc large. Arms moderately produced. Single isolated marginal ossicles vertebra-shaped with biconcave extremities. Ventro-lateral plates with strongly marked sockets for two or more spines. Material.— The only specimen of this species is that preserved in the British Museum of Natural History (H. W. Taylor's Coll., 35482). Only the ventral surface is exposed, and this is very much distorted. Description. — The disc appears to have been large. Its actinal surface is covered with a number of sub-equal oblong or polygonal plates, which possessed sockets in which fitted spines (PI. XXIII, fig. 3c). These plates are 4*8 mm. long, and 3'1 mm. wide. The arms are moderately broad, and at least four series of ventro-lateral plates enter at the base. R : r : : 60 mm. : 20 mm. (approximately), the major radius therefore measuring about three times the minor radius. The marginal ossicles are shaped very much like the centrum of a vertebra, and are biconcave. They possess a distinct granulation in their central region, which is surrounded by a wide margin. The infero-marginals at the base of the ray are about 3'2 mm. wide and 2'1 mm. long. There were probably sixteen of them from the interradius to the extremity of the ray. The specimen is otherwise so distorted that little can be made of its structure. Locality and Stratigrapliical Position. — Upper Chalk, Sittingbourne, Kent. 88 FOSSIL ASTEROIDEA. The following are placed provisionally in the genus Pentaceros : 8. PENTACEROS PUNCTATUS, n. sp. PL XXVI, figs. 1, 1 a, 1 b. Specific Characters. — Body of large size. Marginal series of plates possessing well-developed foraminate pedicellarias. Intermarginalia present. Material. — The only example of this species is a fragmentary portion of an arm preserved in the British Museum (Natural History) and bearing the registered number B. 2561. Description. — The body of the starfish must have been of large size. The supero-marginals are in contact in the extremity of the arm, although interspersed granular plates occur. Proximally, at least, radial plates were present. The largest supero-marginal present is 11'2 mm. high and 6'5 mm. long in its widest point. It is of rather irregular shape and possesses two foraminate pedicellariaB. The infero-marginal plates alternate with the supero-marginals. They are of the same height as the supero-marginals but only 5 mm. broad. They are oblong in shape ; the two interior corners of the oblong, however, are cut away, making the ossicles six-sided. The foramina once occupied by the pedicellaria3 are deep and often situated in a depression. From the foramen itself ridges may run out, which probably served for the attachment of muscles. The infero-marginal series border only the side of the arm and take but little part in the formation of the ventral surface. An intermarginal series of rounded granular plates occurs. Locality and Stratigraphical Position. — Upper Chalk. 9. PENTACEROS PISTILLIFERUS, Forbes sp. PI. XXV, fig. 5. OBEASTEK PISTILLIFERUS, Forbes, 1848. Mem. Geol. Surv. Great Brit., vol. ii, p. 467. Forbes, 1850. In Dixon's Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, p. 329, pi. xxi, fig. 15. PISTILLIFORMIS, Dujardin et Hupt', 1862. Hist. Nat. Zooph. flchin. (Suites a Buff on), p. 389. PISTILLIFERUS, Forbes, 1878. In Dixon's Geology of Sussex (new edition, Jones), pp. 363, 370, pi. xxi, fig. 15. PENTACEROS. 89 Specific Characters. — Primary radialia (or interradialia) large with a dilated summit which possesses no ornament and is excavated into pits. " Ossicles of the arm are narrow, shuttle-shaped, tumid in the centre and slightly impressed towards each extremity" (Forbes). Material. — Several fragmentary remains of this species are known. The most nearly perfect remains are those in the Museum of Practical Geology, Jermyn Street. Other specimens are in the British Museum (Natural History), registered E. 5037, 57624, E. 2564 (all PI. XXV, fig. 5), 7600, E. 25637, E. 2565. Description. — Nothing is known further than the description given in the diagnosis. Forbes' description reads as if he had described the species from the specimen in the Museum of Practical Geology. This originally was in the collec- tion of the Marquis of Northampton. Forbes seems to have described the large ossicles upside down. He also says they were in a circlet of five, which is not apparent in any specimen known. The roughened and pitted surface recalls in some respects the primary radialia and interradialia of P. coronatus. Locality and Stratigmphical Position. — Upper Chalk, Kent and Sussex. 10. PENTACEROS, sp. PL XXV, fig. 7. This specimen is preserved in the British Museum of Natural History (no. 5514). It consists of five marginal plates which are 12'3 mm. high, and have an average length of 5'5 mm. The plates are rugged in appearance and the orna- ment is worn away. A cirral of a crinoid (probably Bourgitetiocrinus) has become fixed between two of these plates. 11. PENTACKROS, sp. PL XXV, fig. 8. The only specimen is preserved in the Brighton Museum. It consists of a few marginal plates. The supero-marginals are rather irregular in shape, some being almost wedge-shaped. On an average they are 4 mm. high and 3'2 mm. long. The infero-marginals are opposite and equal in length to the supero-marginals. They are only 2'9 mm. high. The plates possess a distinct margin, but the 90 FOSSIL ASTEROIDBA. ornament otherwise is worn away. There are a few small granular inter- marginalia. With these plates is associated a large plate which appears to be a worn radial or interradial of P. Boy.rii. Family— ASTROPECTINID.E (Gray, 1840), emend. Sladen, 1886. Phanerozonate Asteroids with large marginal plates bearing spines or spiniform papillae. Abactinal skeleton with true columnar papilla?. Actinal interradial areas small, interradial plates when present spinose. Ambulacral plates short and more or less compressed. Superambulacral plates present. Aproctuchous. Pedicellarias rarely present. Genus— ASTROPECTEN, C. F. Sclmhe, 1760. Adambulacral plates touching the infero-marginal plates along the ray. Marginal and adambulacral plate not correspondent in length and number. Supero- marginal plates more or less well developed. ^ Marginal plates long and more or less quadrate. Superior and inferior series subequal. ASTKOL'ECTEN, Sp. PI. XXV, figS. 2, 2 a. Material. — There is one specimen in the Sedgwick Museum at Cambridge, which looks like an Astropeden. It is figured on PI. XXV, figs. 2 and 2 a. Practically only the marginal plates are preserved. Description. — R : r : : 45 mm. : 15 mm. The interbrachial arcs are well rounded. The supero-marginalia are remarkably uniform in size throughout the greater portion of the ray. Their breadth is 4 mm. and length 1'7 mm. About thirty of these are present from the interradius to the extremity. At the apex of the ray these plates are adjunct. The upper surface of each plate is rounded. The infero-marginalia are equal in size, opposite to, and, as far as one can judge, similar in appearance to, the superior series. There is a distinct groove between the two series. Locality and Stratigraphical Position. — Upper Greensand, Blackdown (?). PLATE XVII. METOPASTER MANTELLI, Forbes, sp. (Page 38.) From the Upper Chalk. FIG. 1. Actinal aspect; natural size. (Coll. Brit. Mus., 40402.) a. Infero-marginal plate ; magnified 4 diameters. MITRASTER COMPACTUS, Furbps, sp. (Page 67.) From the Upper Chalk. 2. Actinal aspect ; copied from Forbes in Dixon's ' Geology of Sussex,' pi. xxu, %. 3. COMPTONIA COMPTONI, Forbes, sp. (Page 69.) From the Upper Greensand. 3. Actinal aspect; natural size. (Coll. Brit. Mus., 34311.) a. Infero-marginal plate; magnified 3 diameters. b. Lateral view of interbrachial arc ; natural size. COMPTONIA ELEGANS, Gray. (Page 71.) From the Upper Greensand. 4. Abactinal view ; natural size. (Coll. Brit. Mus., E. 2567.) a. Actinal view of same specimen ; natural size. PL. XVII. la. A.H.So6Lrle del. et.il*.. CRETACEOUS ASTEROIDEA Pitcher L^ imp. PLATE XVIII. ARTHRASTER DIXONI, Forbes. (Page 91.) From the Lmver Chalk. FIG. 1. Actinal aspect ; natural size. (Coll. Brit. Mus., 47000.) a. Supero-marginal plate ; magnified 3 diameters. COMPTONIA COMPTONI, Forbes, sp. (Page 69.) From the Upper Greensand. 2. Abactinal view ; natural size. (Coll. Northampton Mus.) a. Isolated plate of interradial portion of disc; magnified G diameters. b. Isolated radial; magnified 6 diameters. c. Lateral view of interbrachial arc ; natural size. d. Supero-marginal plate ; magnified 3 diameters. PL.XV1II la. 2a Hjri'Ws'S •w i 2c CRETACEOUS ASTEROIDEA Pitcher L*4 imp. PLATE XIX. PENTACEROS CORONATUS, Forbes, sp. (Page 82). From the Loioer Challc. FIG. 1. Abactinal aspect; natural size. (Coll. Brit. Mus., E. 2562.) a. Lateral view of arm ; natural size. METOPASTER PARKINSONI, Forbes, sp. (Page 31.) From the Upper Chalk. 2. Actinal aspect; natural size. (Coll. Brit. Mus., E. 5027.) a. Lateral view ; natural size. b. Ventro-lateral plate ; magnified 5 diameters, showing entrenched pedicellaria. c. Supero-marginal plate ; magnified 3 diameters. NYMPHASTER COOMBII, Forbes, sp. (Page 15.) From the Upper Greensand. 3. Actinal aspect ; natural size. (Coll. Brit. Mus., 48620.) PL . XIX . let A.H.Searle del . Pitcher Ltd imp. CRETACEOUS ASTEROIDEA . PLATE XX. PENTACEEOS BULBIFERUS, Forbes, sp. (Page 77.) From the Upper Chalk. FIG. 1. Abactinal view; natural size. (Coll. Brit. Mus., 40175.) a. Plate from dorsal part of disc ; magnified 3 diameters. b. Supero-rnarginal plate ; magnified 3 diameters. c. Plate from dorsal part of disc ; magnified 2 diameters. 2. Abactinal view of two specimens ; natural size. (Coll. Brit. Mus., 48748.) a. Madreporite ; magnified G diameters. b. Proximal supero-marginal plate ; magnified 4 diameters. 2b. la/. 2. A.H.Searle del.etlith. CRETACEOUS ASTEROIDEA Pitcher Ltd- imp. PLATE XXI. PENTACEHOS BULBIFERUS, Forbes, sp. (Page 77.) From the Upper Chalk. FIG. 1. View of the extremities of three arms and portion of disc; natural size. (Coll. Brit. Mus., E. 5040.) a. Ventro-lateral plate ; magnified 6 diameters. 1. Actinal view of the extremities of two of the above arms ; natural size. PENTAGONASTER ROBUSTUS, n. sp. (Page 73.) From the Upper Clialk. 2. Abactinal aspect ; natural size. (Coll. Brit. Mus., 48085.) a. Lateral view of an arm ; natural size. PENTACEROS BULBIFERUS, Forbes, sp. (Page 77.) From the Upper Chalk. o. Abactinal aspect; natural size. (Coll. Brit. Mus., E. 5041.) a. Madreporite ; magnified 6 diameters. 4. Abactinal aspect ; natural size. (Coll. Brit. Mus., 40399.) ft. Madreporite ; magnified 6 diameters. PL. XXI leu ««''**« * •?••-* 1 .