oh fy Shape eae PEE acca ¥ Far shaicten) Wy ayom ay ewe Myatt ’ rah ays attend OL aE South reel: Wad ere 8M) ; 4 } ate re i on oth ay ie arate ay wae ete we : i onan \s Ratt x " acta wit ain fhe Ve! any verse ye teen } are y athe © Sse hes ay Be ae oh be T) peters Saat aie, ated, i i f Milt Pie it ee if ae ‘esti "i Maude att ‘i raha the SAM Po aren it i ath ip an can nie Mi Paisay My Lette he ie siti at teen ‘ea one tt Fe he bate Haars HORT : oh pee rt ie et Acie Heit Viasat aka ” \' yay pA bes ree 4 vig tyes Mp re, thane ai Tt Via ae na ieee tity aah Neat ty ett é iets nase ' os cians habit ith ' iit nite Ahh tee KID ATER. * ruited tar ay pennde it wee Le eyo he 7 * : . ro : ‘ ve t " : 73 9 ie ; . alee: | Met Sy ‘ 7 ‘ “ i | | Vlewahe . ine biuret ' hoy ‘ f ame ‘6 | ei jew . 7 Perebe whye Whee oPely | sian i et f ; ie meni . vt Thee. : sree i ib won sae ' a 7 “ Oe, aR ot haat feage syste 7 4 wow a 3 ot won c i ‘ ; ; re oh ‘ feet sis ‘ ‘ : vy : re: : Bs au 4 (82% , moos “ vy rch Pitoerest CCE CS ar (EKG COLE (Cai @ Cae (Cad C @ GLE (a «se CoE T C CE «ae @,¢ (Ca EC ce ( ce. €C Ss (Ch OCG «cae Ca Ca Ca 4 Ca Ca ‘Ce (Cc CE c a qa Cia LG (aq (CG ce / y 7 ., \ \ \ ana Ae AAARARAARARE lA'AA\ ates VV) \ } ARARA \ aan \/ \VWAYA a i. ae i i\ \’ N lala) \/ \ \I7 | y \ (aN aN ANI \y NA Y La I/ L-VE A ant fN Ve Ar AAR SAAN \ \ | lax ANAS TAWe A VAN AMAA Aa A \ em \ \ KC «4 ra CL « am = AAA AR a AANAAA a |e 5 Py ea j Nf | AAA / A - } / WY \ gm \f | 4 EA /Zal AAT i~ltalal aa. A nial! A 7 AP | i; Va $i " a } | 5) > | . A : | | \ | | . i ! . : | Naa Aiea!) yy \ nn fy \ ) a» I/ ip! : | . : YY ~ d } ] | VY, a Sa & “y | . i> , ) QD \f > . ry \ le lal, -Yy WV Ce TCE EK CC CC KCaC C @ C& NN ~ AAA THE 10 Wien fi OF THE LINNEAN SOCIETY ZOOLOGY. VOL. XXIII. 169322 LONDON: SOLD AT THE SOCIETY’S APARTMENTS, BURLINGTON HOUSE, PICCADILLY, W., AND BY LONGMANS, GREEN, AND CO., AND WILLIAMS AND NORGATE. 1891, > O1Y Dates of Publication of the several Numbers included in this Volume, No. 141, | , 142, | . ie f pp. 1-811, published December 31, 1889. » 144) Pe 2s ers | best 0 4 July 31, 1890. » 146, ,, 3881-432, 7 October 18, 1890. » Ue, . 4ep-sBil. A January 24, 1891. >» 1S , eae a August 12, 1891. PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. LIST OF PAPERS. Duncan, Prof. P. Martin, M.B. (Lond.), F.R.S., F.L.S., &e. A Revision of the Genera and great Groups of the Echinoidea. 1 Gutick, Rey. Joun THomas. Intensive Segregation,or Divergence through Independent Trans- Hrrpman, W. A., D.Sec., F.L.S., Professor of Natural History in University College, Liverpool. A Revised Classification of the Tunicata, with Definitions of the Orders, Suborders, Families, Subfamilies, and Genera, and Analytical Keys to thei Spectess oe. 6. ee venice so eee a 4 _~ Howes, G. B., F.LS., F.Z.S., Assistant Professor of Zoology, Normal : School of Science and Royal School of Mines, S. Kensington. o On the Intestinal Canal of the Ichthyopsida, with especial reference to its Arterial Supply and the Appendix Digiti- Honetini snus Celeterele de I) srccraiic lied its Sage cce va dloe oekeaeiens On some Hermaphrodite Genitalia of the Codfish (Gadus mor- rhua), with Remarks upon the Morphology and Phylogeny of the Vertebrate Reproductive System. (Plate XIV.) .... Jennines, A. Vaucuan, F.LS., F.G.S., Lecturer on Comparative Anatomy to the Birkbeck Institute. On a Variety of Alectona Millar, Carter. (Plate XIII.)...... Page 1 formation. (Communicated by W. Percy Sladen, Sec. L.S.). 312 381 539 531 iv \ Page _ Kirpy, W. F., F.LS., F.E.S., of the British Museum (Nat. Hist.). A Revision of the Forficulide, with Descriptions of New Species inthe British Museum, «(Plate XU)... o.2 n-ne eee 502 Pocock, R. L., of the British Museum (Nat. Hist.). On some Old-World Species of Scorpions belonging to the Genus Tsometrus. (Communicated by W. Percy Sladen, Sec.L.58.) (Bigite NOES) fis. salt eta meter nee eee eee ee 433 SAUNDERS, Epwarp, F.L.S., F.E.S. On the Tongues of the British Hymenoptera Anthophila. (Plates ILT=X..) niviieci mein eretet eee se ee tore eee 410 Winpit, Bertram C. A., M.A., M.D., Professor of Anatomy in the Queen’s College, Birmingham. Teratological Evidence as to the Heredity of Acquired Condi- tions. (Communicated by E. B. Poulton, M.A., F.RS., 1 Dice Bee SRI Dn ania POROUS oo aamalad 6066 6 448 EXPLANATION OF THE PLATES. PLATE I. | Illustrating Prof. G. B. Howes’s paper on the Inrusrinan Canat II- and ARTERIES oF IcHTHYOPSIDA. HOI) TV. Vv. Vili: je iueioune Mr. H. Saunders’s paper on the British HymEno- VII. { prera ANTHOPHIDA. VIII. Ix. XI. New anp Rare Scorrions. Illustrating Mr. R. I. Pocock’s paper on some Old-World Scorpions of the Genus Jsometrus. XII. Illustrating Mr. W. F. Kirby’s paper on Forricunipsz. XIII. Auzcrona in Lima excavata. Illustrating Mr. A. Vaughan Jennings’s paper. XIV. Genrrauia or Hermaruropite Coprisa. Illustrating Prof. G. B. Howes’s paper on this subject. THE JOURNAL THE LINNEAN SOCIETY. A Revision of the Genera and great Groups of the Echinoidea. By P. Martin Duncan, M.B. (Lond.), F.R.S., F.L.S., &e. [Read 7th February, 1889.] I. Introduction :—the necessity for a Revision of the Fossil and Recent Genera of the Class Echinoidea and for a reconsideration of the arrangement of the great groups.—Definition of the Class Echinoidea and of its Subclasses the Palechinoidea and the Euechinoidea. Remarks upon the Palzechinoidea, their Classification.—Definitions of the Orders and Genera. Tre last work of L. Agassiz and Desor, “ Le Catalogue Raisonné des Familles, Genres, et des Espéces de la Classe des Echinides,” was published in the ‘ Annales des Sciences Naturelles’ during 1846-7, and was a magnificent conspectus of all their previous labours in the classification of both the fossil and the recent Echinoidea. The work formed the foundation of a vast super- structure, which, however, soon separated into studies of the fossil species and genera apart from those of the recent fauna. -Desor gathered together all the information regarding the fossil forms up to 1858, when he published his ‘ Synopsis des Echinides fossiles.’ This standard work has been of great value to paleon- tologists. The history of the Zoology of the recent Echinoidea, subsequently to the date of the ‘ Catalogue Raisonné’ and up to 1883, and also a previous ‘ Revision of the Hchini’ (1872-4) were the contributions of Alexander Agassiz. The Reports on the Echini of the ‘ Hassler,’ 1874, ‘ Challenger,’ 1881, and ‘ Blake, LINN. JOURN.— ZOOLOGY, VOL. XXIII. i 2 PROF. P. M. DUNCAN’S REVISION OF THE 1883, Expeditions, by this author, contain nearly the whole of the systematic and much of the morphological knowledge of the recent fauna. The work of Desor, and those of A. Agassiz, the one on the fossil, and the others mainly on the recent genera and species, are invaluable and have formed the basis of all subsequent research. But no book has appeared which has been written by any naturalist who has personally laboured in the classification and morphology of the Class, which has treated of both the fossil and the recent genera. Palzontologists have published great numbers of genera and species since the days of Desor, and have not invariably paid attention to the progress of their fellow workers who have described recent forms. And, on the other hand, much that was written a few years since by some naturalists, dealing with recent forms, would not have seen the light had careful descriptions of fossil genera, such, for instance, as have been published by Cotteau, de Loriol, and Sven Lovén, been available in a standard work of reference. The results of this division of labour and of the independent researches of Palzeon- tologists and Zoologists have been the adoption of too many genera and the production of much confusion in the nomen- clature ; and the recognition of genera and species, both fossil and recent, has been rendered difficult by the publication of their diagnoses in the Journals of learned Societies, and in the works of Geological Surveys of nearly every civilized country. The progress of the morphology of the recent HEchinoidea has been great, and it chiefly dates from the time of J. Miller (1854) and the subsequent publication of 8. Lovén’s ‘Etudes sur les Echinoidées’ in 1874; it was maintained by the author of the * Revision of the Echini,’ and much valuable new matter is to be found in the ‘Chalienger’ and ‘Blake’ Reports. Lovén’s wonderful work on Pourtalesia and his later contributions, together with the results of the work of Sir Wy. Thomson, and of Messrs. Norman, Stewart, Ludwig, H. Carpenter, Sladen, Hamann, Sarasin, and Bell, and of some publications in the Journals of the Linnean and Geological Societies of London, have rendered some modifications in the terminology and of the taxonomic value of certain structures absolutely necessary. It is the belief of all practical Echinologists that a work which would collect the generic descriptions of both the fossil and recent faunas, and which would revise and -eliminate when necessary, by the light of modern morphology, is very GENERA AND GROUPS OF THE ECHINOIDEA. 3 urgeitly required. Hence in this “ Revision of the Genera and great Groups of the Fossil and Recent Hchinoidea,” the Author has endeavoured to remedy anurgent want. He has had unusual advantages and opportunities for studying fossil and recent Echinoidea ; and in this endeavour to utilize them he is under great obligations to his friend A. Agassiz and to the able natu- ralists and paleontologists connected with the British Museum, the Museum of Practical Geology, the Woodwardian Museum at Cambridge, to his colleague in the description of the Sindian Fauna, Mr. Percy Sladen, and last, but by no means least, to his kind and generous friend Sven Lovén. Nore.—It will be noticed that many genera no longer find a place in the classification, but are either removed entirely or placed as subgenera, and, as the intention was to limit the genera rigidly, very few new ones are introduced. In describing every genus, the name which comes imme diately after the generic term is that of the founder, and when it is in roman type it may be as sumed that the original definition was improved by the naturalist whose name stands next. The names placed after the first one, even when this is not in roman type, are those of subsequent investigators and describers of species who have added to the value or have modified the original diagnosis of the genus. When any anatomical details have been described relating to a genus, the name of the investigator has been added. The references, as a general rule, refer to the date, volume, and page of works in which there are illustrations; but, to save space, the number of the plate is not given, especially as it will be found upon the page referred to. The distribution of the genera has, of necessity, been considered, but the great geological formations alone are noticed in dealing with the fossil forms. A description of the terms employed in the classi- fication will be found at the end of the Essay. The synonymy adopted by A. Agassiz in his ‘ Revision of the Echini,’ 1872-1874, is accepted. The classification of Dujardin et Hupé, in ‘ Les Suites a Buffon,’ was a useful but not critical literary work, beg a compilation. M. Pomel’s “Théses,” Algiers, 1883, contain a classification which is not followed in this communication, for the fundamental methods employed do not com- mend themselves, it being impossible to admit genera which are not differ- entiated by characters which have a decided and important physiological value. 1* + PROF. P. M. DUNCAN’S REVISION OF THE Subkingdom ECHINODERMATA. Class ECHINOIDEA. Echinodermata with a solid or slightly flexible test covering the viscera, variable in shape from spheroidal to flat, composed of numerous, closely placed, more or less geometrical plates of car- bonate of lime, covered with soft structures and carrying spines. Most of the plates arranged in several vertical series, reaching from the mouth to the dorso-central or apical system, constituting five ambulacral and five interradial areas. Other plates in the dorso-central system—the basal and radial and anal plates. With a mouth on the under or actinal surface, rarely in front of the test, and an internal gullet and intestinal tract ending externally in an anus, which is either placed in the dorgo-central system or somewhere in the posterior interradium. A madreporite body placed in the dorso-central system and in relation with a renal organ and with the water-system, which is partly within the test and partly external, in the form of branchiw and branchial tentacles. With or without five teeth in jaw-pieces, which are moved by muscles connected with a connected or disconnected perignathic girdle. Unisexual or bisexual ; the genital glands with ducts perforating the basal plates or opening beyond them; the young, either under- going metamorphoses and being free-swimmers, or found perfect upon the parent’s test. Marine: fossil and recent. I. Subclass. The PanmEontnorpEs, Zittel (amended). Echinoidea with only one, or with more than two, vertical rows of plates in each of the five interradia, and with either two or many vertical rows of simple or compound plates in each of the five ambulacra; plates of the areas overlapping or not. Peristome actinal. Jaws present. Periproct within the dorso-central system or in the posterior interradium beyond. IT. Subclass. The Evrcutnorpga, Bronn. Echinoidea with two vertical rows of plates in each of the five interradia, and a similar number of vertical rows of simple or of compound plates in each of the five ambulacra. Peristome aciinal., GENERA AND GROUPS OF THE ECHINOIDEA. 5 rarely anterior; jaws and teeth present or absent. Periproct either within the dorso-central system or in the posterior inter- radium. I. Subclass PALAEHCHINOIDEA. The Paleechinoidea have gradually become a great group which is readily separable from all the other divisions of the Eechinoidea. The first careful descriptions of its genera and species were given by McCoy in his “ Description of the Carboniferous Fossils of Ireland;” subsequently Baily, Meek and Worthen, Hall, and J. Miller added greatly to-the knowledge of the anatomy and taxonomy. In ‘Les Etudes,’ Sven Lovén summarized the information which had been obtained up to 1874 and mainly followed McCoy’s classification. About the same time A. Agassiz gave some important notices of the Perischoechinide, McCoy, then the only group of Paleechinoidea, in the ‘ Revision of the Kchini’ (p. 644). In the course of his observations A. Agassiz criticised the classifications of previous authors, and very pro- perly drew especial attention to the discovery of J. Miiller regarding the overlapping of the coronal plates of some genera, and he compared this phenomenon with the imbrication of the peristomial plates of Cidaris and of the coronal plates of the Echinothuride. It became evident that a new taxonomy of the group was necessary, and Messrs. R. Etheridge, Junr., and W. Keeping contributed papers (1874-6) to the Geological Society of London, in which the limits of the new classification were fairly stated. _ Discoveries of some remarkable forms, such as Bothriocidaris, Schmidt, 1874, Tiarechinus, Neumayr, 1881, and the reconsideration of Echinocystites, Wy. Thomson, 1861, necessitated the intro- duction of groups which could not be placed as Perischoechinide. Zittel gave an admirable classification in his ‘ Palzontologie,’ 1876-80; and finally A. Agassiz introduced some pages in his Report on the ‘ Challenger’ Echini, 1881, which are full of most valuable matter. He had the opportunity of studying the rare species described by American palzontologists, of which plates and figures alone have been noticed by EKuropean geologists, and he brought to bear on their consideration a vast amount of knowledge about the recent Echini and especially of the Echion- 6 PROF. P. M. DUNCAN'S REVISION OF THE thuride. The descriptions of some genera by Meek and Worthen and McCoy require additions, in consequence of this work of A. Agassiz. The foundation of a classification upon the presence or absence of primary tubercles upon tests was due to McCoy, and it served its time; but it was too artificial and permitted genera to be closely associated which had structural differences of great phy- siological importance. For instance, some genera with two and with more than two vertical rows of ambulacral plates were associated closely ; moreover, genera which had bevelled plate- edges, and where there was overlap, were associated with forms which had rigid tests and no overlap of plates. It must be admitted that too much has been made of the presumed and real imbrication of plates in classification. Whilst it is undeniable that our knowledge of the genera of Paleechinoidea has increased, it is still necessary to remember that any classification must be open to exception. It is not possible to place some of the genera in the same groups upon the admitted principle of the preponderating taxonomic value of the structure of the ambulacra, and, indeed, there must be some anomalous genera; but the following grouping is suggested as the best at the present time. All genera founded in reference to sitet plates or spines are not considered, and Hocidaris, Keyserl., is omitted, for it isa true Cidarid. Palgocidaris, Beyr.,is synonymous with Lepidocentrus, J. Miller. Perischocidaris, Neum., is the same as Perischodomus, McCoy. Hchinocrinus, Ag., and Palcocidaris, Desor, are synonymous with Archéocidaris, McCoy. Protoechinus, Aust., is the same as Paleechinus, Scoul. Melechinus is Melonites, Norw. & Owen. Cystocidaris, Zitt., is Echinocystites, Wy. Th. Paleodiscus, Salter, which was intended for an Asterid genus, really contains some Echinoidean types closely resembling Hehz- nocystites ; but the position of the periproct is not known. The genera remaining after these removals and absorptions are classified under four orders of the subclass Paleechinoidea. Bothriocidaris, a remarkable form from the Lower Silurian formation, requires, as Zittel has shown, a special group, and an order is established for it. The Perischoechinoida group them- selves with as little friction as possible into two families, the Archeocidaride, with narrow ambulacra, and the Melonitide, with more than two vertical rows of poriferous plates in an GENERA AND GROUPS OF THE ECHINOIDEA. 7 ambulacrum. Tiarechinus, so ably described by Lovén after Neumayr, is unique and must enter an order of its own. And, finally, the exocyclic E'chinocystites comes into the order Cysto- cidaroida. It is certainly supremely interesting to find jaws and teeth in these old forms and to be able to classify, thanks to Sir Wy. Thomson, an exocyclic gnathostome amongst the Paleozoic Kechinoidea. Classification. Supcrass PALAMECHINOIDEA. (Page 5.) OrveErR I. BOTHRIOCIDAROIDA. Genus Bothriocidaris, Schmidt. OrpER IJ. PERISCHOECHINOIDA. Family ARCH HOCIDARID &. Genus Lepidocentrus, J. Miiller. Koninckocidaris, Dollo & Buisseret. Perischodomus, McCoy. Archeocidaris, McCoy. Lepidocidaris, Meek & Worthen. Lepidechinus, Hall. Paleechinus (Scouler), McCoy (pars). Rhoechinus, W. Keeping. Family MELONITID2. Genus Melonites, Norwood and Owen. Oltigoporus, Meek & Worthen. Lepidesthes, Meek & Worthen. Hybochinus, Worthen & Miller. Pholidocidaris, Meek & Worthen. Orver III. PLESIOCIDAROIDA. Genus Tiarechinus, Neumayr. Orpver IV. CYSTOCIDAROIDA. Genus Echinocystites, Wy. Thomson, 1861. Order I. BOTHRIOCIDAROIDA, F. Schmidt, 1874; Zittel, 1876-80. Test regular, more or less spherical, solid; interradia with only one vertical row of plates which do not imbricate; ambulacra with two vertical rows of plates; plates united at their edges. Periproct in the central apical system. Jaws ? Peristome actinal, central. 8 PROF. P. M. DUNCAN'S REVISION OF THE Genus Boturiocrpartis, Hichwald, 1860, Lethea Rossica, p. 654. Fr. Schmidt, 1874, Mém. Acad. St. Pétersb. sér. 7, vol. xxi. no. x1. pp. 86-38. Zittel, 1876-80, Palgont. Bd. i. p. 481. Lovén, 1883, Pourtalesia, p. 57. (Slightly altered.) Test small, hemispherical or conico-hemispherical. Apical system central dorsal, with five large broad radial plates limiting the periproct, each with two pores surrounded by a raised rim, with five small, imperforate, triangular basal plates inter- vening between the radial plates, entering or not the periproct. Six or eight ovoid, acuminate anal plates, each with a spiniferous tubercle. Ambulacra wider than the interradia, straight, with two rows of plates, large, hexagonal at the ambitus, and smaller above and below; each plate with a central circular pit, with a pair of pores on its floor, and with 2-4 small, perforate, wart-like tubercles, carrying finely longitudinally-striated small spines; around is some granulation. The ambulacra end dorsally at the large radial plates and actinally at the peristomial margin, where they are moderately broad and exclude, by their contact, the interradial plates. ’ Tentacles long and cylindrical. (Lovén.) Interradia five in number, narrow, composed each of one row of plates subequal to the ambulacral, but smaller dorsally and actinally, excluded from the peristomial margin. Plates may have small tubercles and granules. Peristome subcircular, margin formed by the ambulacra; five narrow triangular buccal plates project inwards. Fossil. Lower Silurian: Europe. Order IJ. PERISCHOECHINOIDA, McCoy, 1849, Ann. § Mag. Nat. Hist. vol. iii. (Amended.) | Tests regular, with more than two vertical rows of interradial plates which are dissimilar ; with two or many vertical rows of ambulacral plates, each with a pair of pores. Test thick and rigid, or thinner and with the plates overlapping more or less. Ornamentation variable. Jaws present. Family ARCH HOCIDARIDZ. Perischoechinoida with narrow ambulacra, each with only two rows of poriferous plates. GENERA AND GROUPS OF THE ECHINOIDEA. 9 Genus Leprpocentrus, J. Miller, 1856, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 258. L. Schultze, 1867, Denks. d. k. Akad. Wiss. Wien, vol. xxvi. p. 128. Lovén, 1874, Htudes, p. 39. Zittel, 1879, Paleont. Bd. i. pt. iii. p. 482. A. Agassiz, 1881, ‘ Challenger’ Report, p. 79. (Amended.) Syn. Pale@ocidaris, Beyr. Interradial areas with from five to nine vertical rows of plates at the ambitus; plates hexagonal, except close to the ambulacra, where they are quadrangular ; imbrication aboral and also laterally from the median row ; some projection at and over the interradio- ambulacral sutures. Ambulacra very narrow, two vertical rows of plates, low and broad, each with a pair of pores. Beyond the peristomial margin the plates are continued to the true mouth, no distinction being possible between coronal and peristomial plates. Tubercles of the interradia distant, there being two or three upon a plate near the ambulacra ; the other plates carry only one or two. Spines subulate and small, but articulated upon tubercles. Jaws exist. Fossil. Devonian-: Europe. Lower Carboniferous: U. States. Genus Konincxociparts, Dollo § Buisseret, 1888, Compt. Rend. del Acad. des Sct. Nat., 26 Mars. Shape, apical disk, and jaws unknown. Ambulacra broad, with two vertical rows of imbricating plates ; a pair of pores to a plate near the interradial edge; the pores of the pair oblique, the adoral internal and separated from the other by an oblique ridge; interporiferous area projecting, carrying numerous secondary tubercles similar to those of the interradial plates. Interradia with seven vertical rows of polygonal plates at the ambitus, the median row the smallest ; plates only twice as high as those of the ambulacra, imbricating, carrying rather distant secondary tubercles; the adambulacral plates carry a larger primary, perforated tubercle near their margin. Spines, some stouter than the others and doubtless belonging to the larger tubercles ; some very delicate and slender, striated longitudinally and more or less cylindrical. Fossil. Carboniferous Limestone: Europe (Belgium). 10 PROF. P. M. DUNCAN’S REVISION OF THE Genus Prriscnopomus, McCoy, 1849, Ann. & Mag. Nat. Hist. ser. 2, vol. ili. p. 251. W. Keeping, 1875, Quart. Journ. Geol. Soc. 1876, vol. xxxii. p. 35, pl. 11. figs. 1-5. Worthen & Miller, 1883, Geol. § Pal. Lilinois, vol. vii. p. 833. (Amended.) Syn. Perischocidaris, Neum. Test spheroidal, depressed, subpentagonal in outline. Apical system central, with five broadly pentagonal basal plates surrounding a small periproct, each with from 6-8 genital per- forations ; radial plates small; anal plates exist. Ambulacra narrow, straight, sunken, overlapped on either side by the interradia; plates in two vertical series, numerous, small, low, broad, and either regular in shape, elongate pentagonal, or wedge-shaped, the small end of one plate in contact with the large part of its neighbour; plates overlap from the apex actinally, each with a pair of pores in simple vertical series or slightly al- ternating ; surface minutely granular. Interradia broad, with five vertical rows of large scale-like plates at the ambitus, diminishing in number to two or three at the apex. Plates variable in thickness, thick or thin, convex and irregular in outline, those of the middle rows the most symmetrical, trapezoidal or depressed hexagonal ; plates of the middle row overlap those of the row on either side and these the other rows to the ambu- lacra ; each plate also overlaps, with its aboral edge, the plate situated apically to it; the highest plates overlap the basal plates of the apical system. Ornamentation granular, homogeneous, and of small and alsoa few large, perforate, non-crenulate tubercles with a low, depressed, broad, conical boss, placed upon a circular scrobicule. A larger tubercle upon some interradial plates close to, or in the second | row from the ambulacra, or more than one, often with a circle of the smaller kind near the edge of a plate. Jaws large; teeth large and grooved. Spines, some small, aciculate, and striated ; others larger but still short, smooth and cylindrical, tapering, broadest inferiorly, without a ring or collar, striated. Fossil. Carboniferous: Wexford, Ireland, and Clitheroe, Eng- land ; Scotland ; Europe. (The diagram given by Keeping, op. cit. fig. 3, should be reversed. ) The type specimen of P. biserialis, McCoy, in the Wood- wardian Museum, Cambridge, has a great adoral underlap of the interradial plates. GENERA AND GROUPS OF THE ECHINOIDEA. 11 Genus ArcumocrpaRts, McCoy, 1844, Synop. Carb. Foss. Irel. p. 173. Trawtschold, 1868, Bull. Moscow, vol. xli. p. 467. J. Young, 1873, Geol. Mag. vol. x. p. 8302; Proc. Nat. Hist. Soc. Glasq. vol. ii. pt. 2, p. 325. R. Etheridge, Junr., 1874, Quart. Journ. Geol. Soc. vol. xxx. p. 811. Lovén, 1874, Etudes, p. 43. W. Keeping, 1875, Quart. Journ. Geol. Soc. vol, xxxii. p. 89. A. Agassiz, 1881, ‘ Challenger’ Report, p. 77. (With additions.) Syn. Hehinocrinus, Ag.; Paleocidaris, Desor. Test large. Shape and apical system unknown. Ambulacra narrow, straight, reaching beyond the peristome to the true mouth; plates irregular, imbricating adorally, each perforated by two pores ; plates in two vertical rows. Interradia with from three to five vertical rows of large, thin plates, the median hexagonal and those of the rows nearest the ambulacra more or less pentagonal, diminishing in number towards the poles, and continued beyond the peristome as small plates.. The median plates are bevelled over those on either side slightly, and these over others to the ambulacral edge, which may be raised ; the adoral edge of each plate with a broad groove for the reception of the corresponding aboral process of the next plate situated adorally ; the plates within the peristome overlap towards the apex. Slits at the peristome for the external branchie. Jaws with long, broad, grooved teeth, the pyramids rather short, upper foramen small, cheeks deeply cut. A large primary tubercle upon each interradial plate, having a low, conical truncated boss, supporting a narrower subconical per- forated mamelon, surrounded by a wide groove ; scrobicule large, almost flat ; plate beyond with a circlet of secondary tubercles and large granules, with concentric striations or crenulations. Spines of the large tubercles large, long, slender, bluntly serrated on the longitudinal ribs, some spines smooth, and beyond the lower third striated and with rows of oblique spinules. The annular ridge of a spine may be crenulated. Fossil. Carboniferous Limestone : Ireland, Scotland, England, Wales, Hurope, and N. America (Upper Coal-measures, Illinois). Permian: England. 12 PROF. P. M. DUNCAN’S REVISION OF THE Genus Lerrpocipaxtis, Meek § Worthen, 1869, Proc. Acad. Nat. Set. Philad. p. 79; 1873, Geol. Illinois, vol. v. p. 478, pl. ix. fig. 15. Syn. Hocidaris, sensu, Meek & Worthen. A fragment of a very large test, spheroidal, depressed. Am- bulacra narrow, slightly convex; plates in two vertical rows feebly imbricated adorally, compound; the primaries alternate with demi-plates, which are pointed towards the median suture. Interradia very broad, with eight or nine vertical rows of plates or even more, hexagonal towards the median line and pentagonal close to the ambulacra, all imbricated aborally and laterally ; but the lateral overlap is from the ambulacral edge to the central plates, which are overlapped on either side. A large central tubercle on each interradial plate, with a small, perforated, central projection for the spine; the base of the tubercle surrounded by a circular smooth depression, bordered with granular mamelons. Primary spines long, cylindrical, slender, finely striated ; articular end perforated and swollen so as to form a distinct ring. Dental apparatus with the teeth grooved. Fossil. Lower Carboniferous Limestone: N. America. Genus Lerrpecuinus, Hall, 1861, Descr. new sp. Crinoidea, Prelim. note, Albany, p. 18; 1867, Twentieth Report State Cabinet New York, p. 295. Meek & Worthen, 1866, Geol. Surv. (Pal.) Illinois, vol. u. p. 294 (reference to Hail). Meek & Worthen, 1868, Geol. Illinois, vol. 11. p. 522 (note). Lovén, 1874, Ltudes, p. 44. RB. Etheridge, Junr., 1874, Quart. Journ. Geol. Soc. vol. xxx. p. 812. Keeping, 1875, Quart. Journ. Geol. Soc. 1876, vol. xxxii. p. 36. Test large, spheroidal. Apical system pentagonal, made up of several ornamented plates, also a circle of small plates within the periproctal ring. Ambulacra narrow, straight, with two vertical rows of small, low, broad plates imbricating, the adoral edge of one plate over- lapping the aboral edge of the plate below it. A pair of pores to each plate. Interradia very broad, composed of from nine to eleven vertical rows of plates, diminishing considerably in number apically, the plates nearest the ambulacra smallest; the plates imbricating laterally from the median series and from pole to pole, the GENERA AND GROUPS OF THE ECHINOIDEA. 13 median plate overlapping at its sides its neighbours, and the aboral edge of each plate overlapping the adoral edge of the plate above. Tubercles on each of the plates of the numerous rows above the ambitus, and absent below, except upon the plates nearest the ambulacra, where they are solitary. Dental apparatus unknown. Fossil. Upper Devonian and Lower Carboniferous: N. America. Carboniferous: Europe (Belgium). Genus PatzEcuinvs, Scouler, MSS. 1839. McCoy, 1844, Synop. Carb. Foss. Ireland, p. 171 (pars). Baily, 1864, Journ. Roy. Geol. Soc. Irel. vol. i. pp. 63-65; 1865, Geol. Mag. vol. i. p. 42. Meek & Worthen, 1866, Pal. Illinois, vol. ui. p. 229. De Koninck, 1869, Bull. Acad. Bruax. vol. xxviul. p. 554. R. Etheridge, Junr., 1874, Quart. Journ. Geol. Soc. vol. xxx. p- 311, pl. xx. Lovén, 1874, Etudes, p- 40. W. Keeping, 1875, Quart. Journ. Geol. Soc. vol. xxxii. (1876), p. 37- Duncan, 1889, Ann. §& Mag. Nat. Hist. ser. 6, vol. iii. p- 196. (Amended.) Syn. Protoechinus, Aust.; Typhlechinus, Neum. Test moderate to very large, prolate or oblate spheroidal, rigid, thick. Apical system central, with a pentagonal periproct sur- rounded by five large basal plates, each perforated by three canals, or one plate may have but one perforation ; five small, doubly perforated radial plates, placed either within the periproctal ring or not separating the basal plates; the anal membrane with concentric plates, largest externally. Ambulacra narrow, straight, convex along the median line and sunken in the poriferous zones, composed of two vertical rows of very numerous low, thick plates of different shapes; these are either primaries, all of which reach the ambulacro-interradial suture as well as the median ambulacral suture, or alternate plates which are more or less blocked out from the inter- radial suture, by the increased dimensions of the outer parts of the plates above and below; or there may be demi-plates and more or less perfect primaries in the same ambulacrum, the demi- plates being large at the interradial suture and short and pointed towards the median ambulacral line, the primaries being long and may not reach the interradial suture; compound plates rare. Pairs of pores, in two vertical rows, on each side of an ambu- 14 PROF. P. M. DUNCAN’S REVISION OF THE lacrum; the outer pairs either in demi-plates or in primaries, the inner pairs always in primaries, which may, however, be short ; the outer row is associated with the plates, which form decided salient angles at the ambulacro-interradial sutures; pores of pairs separated by distinct septa and without peripodia, always distant from sutures. Ornamentation of ambulacra of small granules and one or more transverse rows of a few very small tubercles consisting of a flat scrobicule and a small boss. Interradia broad, convex, with from five to eight vertical rows of thick tumid plates diminishing in number towards the poles; middle plates hexagonal, the adambulacral pentagonal and with the ambulacral edge with salient and reentering angles to fit the corresponding structures of the ambulacral plates ; some obliquity of the edges of all the plates, but no true overlap. Ornamentation of numerous small, close tubercles with a flat scrobicule and a boss; there may be a linear ornamentation also; spines small, acicular, short. Jaws and teeth with a groove. Fossil. Upper Silurian: England. Carboniferous Lined England, Ireland, Scotland, Europe; N. America. The reasons for restricting the species of Palg@echinus to those with two vertical rows of pairs of pores on each side of an ambu- lacrum and for insisting upon the presence of radial plates have been considered in a late publication (Ann. & Mag. Nat. Hist. ser. 6, vol. iii. p. 196, 1889), and the necessity for enlarging the interesting genus Lhoechinus, W. Keeping, has been shown in the same place. The genus Rhoechinus now admits the forms of Paleechini with only a single vertical row of pairs of pores on each side of an ambulacrum, such as P. elegans, McCoy. Genus Ruorcuinus, W. Keeping, 1875, Quart. Journ. Geol. Soc. vol. xxxii. (for 1876), p. 37. Duncan, 1889, Ann. & Mag. Nat. Hist. ser. 6, vol. ui. p. 205. (Amended.) Test small or moderate, spheroidal. Apical system with five basal plates with several perforations ; radial plates with more than one perforation; periproctal ring formed by both radial and basal plates or only by the basal plates. Ambulacra narrow, straight, composed of a vertical row of plates on either side of the median line; plates low, broad, thick, primaries only; a vertical row of pairs of pores on each side of an ambulacrum, a pair to each plate. Interradia with from four to five rows of plates diminishing at GENERA AND GROUPS OF THE ECHINOIDEA. 15 the poles, irregular in shape or hexagonal in the median line and polygonal at the ambulacral edge. Ornamentation of small granules with occasional small bosses surrounded by a flat scrobicule ; plates obliquely bevelled at the edges, admitting of slight overlap. Fossil. Carboniferous Limestone: England and Ireland. Family MELonirip#. Perischoechinoida with broad ambulacra composed of many vertical rows of poriferous plates. Genus Metonites, Norwood & Owen, 1846, Amer. Journ. 2 ser. vol. ii. p. 225. Meek & Worthen, 1866, Pal. Lilinois, vol. ii. p. 227. Quenstedt, 1872-75, Petr. Deutsch. Abth. i. vol. iii. p- 881, pl. Ixxv. figs. 44-50. Lovén, Etudes, 1874, p. 41. R. Etheridge, Junr., 1874, Quart. Journ. Geol. Soc. vol. xxx. p: 318. W. Keeping, 1876, Quart. Journ. Geol. Soc. vol. XXXL. p. 395. Syn. Melechinus, Quenst. Test very large, ellipsoidal, grooved longitudinally ; plates thick. Apical system central, with five equal, pentagonal, tall basal plates with a corresponding number of intervening radial plates ; genital perforations of the basal plates varying in number from three to five, a single pore to a radial plate. Periproct circular. Ambulacra broad, concave on both sides of a median ridge, with ten or more vertical rows of rather geometrical or of small, low, broad plates, thin or thick, each perforated near its centre by a pair of pores, median rows the largest; some slight imbrica- tion of the plates. Interradia with seven or eight or nine vertical rows of plates, diminishing in number towards the poles, thick, small, hexagonal near the median lines, pentagonal next to the ambulacra and the edges festooned there for the zigzag of the ambulacral suture. Some obliquity of the edges of the plates, especially when thick. Ornamentation of very small, distant, mamillate, imperforate tubercles ; on the ambulacra they are close, and upon scrobicular circles. Spines minute, acicular. Peristome central. Jaws large, and with stout pyramids, teeth large, grooved, and long, pointed. 16 PROF. P. M. DUNCAN’S REVISION OF THE The obliquity of the edges of the interradial plates is slight, and its direction and amount are insufficient for imbrication ; the ambulacral plates, when thin, have some imbrication adorally and laterally. Fossil. Carboniferous: England, Europe; N. America. Genus Oxicororus, Meek g Worthen, 1860, Proc. Acad. Nat. Sci. Philad. vol. xii. p. 474; 1866, Pal. Illinois, vol. u. p. 247. Test with the same general shape as Melonites, and the apical system also. Ambulacra with four vertical rows of plates, each plate per- forated by a pair of pores, some demi-plates amongst the pri- maries. . Interradia large, convex, with from five to nine vertical rows of plates at the ambitus, diminishing in number towards the poles. Fossil. Lower Carboniferous: N. America. Genus Leprpestues, Meek & Worthen, Pal. Illinois, vol. iii. p. 522. Test ellipsoidal ? Ambulacra very broad, consisting of ten vertical series of plates at the ambitus; the plates overlap adorally, and they are broad, small, low, and each has a pair of pores. Interradia comparatively narrow, with five or six vertical rows of plates, which overlap aborally and at the sides. Tubercles very small, equal. Fossil. Carboniferous: N. America. The next genus requires careful consideration, for it was founded partly by Worthen, whose name is so familiar to students of the Paleechinoidea, and yet contains characters which appear to be due to the same cause which led some excel- lent observers into error with regard to the nature of the imbri- cation of the Echinothuride. it appears that it is quite possible that the distinguished American paleontologist may have seen the plates of his type from within, and, if so, it accounts for the character which he has — given the type, of the plates overlapping in a direction contrary to all other Paleechinoidea. Worthen and Miller, after noticing | GENERA AND GROUPS OF THE ECHINOIDEA. a7) this anomaly, observe that the direction of the overlap is the same as that seen in Hchinothuride. Now there is no doubt that this mistake about the direction of the overlap of the ambu- lacral and interradial plates in Echinothuride originated with the late Sx Wyville Thomson, who wrote in ‘The Depths of the Sea,’ 1873, p. 158, that the overlap was of “the plates of the interambulacral ares from the apical pole towards the mouth, those of the ambulacral areze from the mouth towards the apical disk.” He referred, for the purpose of illustration, to his figure 28 (on p. 157). Unfortunately this figure is of part of the inside of the test of Calveria (Asthenosoma) hystrix, Wy. Th. The direction of overlap is always considered in relation to the out- side of tests. In 1874 Mr. R. Etheridge, Junr. (Quart. Journ. Geol. Soc. vol. xxx. p. 307), quoted Sir Wyville Thomson’s words, and it became generally believed that the overlap of the plates of the Echinothuride was in the opposite direction to that of the Perischoechinoidea. But Sir Wyville Thomson also wrote in 1874 (Phil. Trans. Roy. Soc. p. 730), after the publication of Mr. Etheridge’s paper, as follows :—“ The plates of the interambulacral areas overlap from the mouth towards the apex, and the am- bulacral plates in the opposite direction.” A. Agassiz also pointed out that the overlap is normal. Again, the most striking character of Worthen and Miller’s genus is the projection in the form of humps of the ambulacra near the apex. But that con- dition is so anomalous that one is tempted, especially after the explanation of the abnormal overlap, to believe that the reverse condition should be seen from outside, and that the humps are really marsupia seen from within the test. The genus as defined by its authors is given, but the remarks just made should have their weight. Genus Hyzocuinus, Worthen § Miller, 1883, Geol. §& Pal. of Lilinois, vol. vii. p. 331. Test flexible, subspheroidal, consisting of 5 ambulacral and the same number of interradial areas; protuberances at the apical ends of the ambulacra (possibly marsupial cavities). Ambulacra composed of numerous (10) ranges of alternating and overlapping plates, and even more at the ambitus; each plate perforated in the central part by a single pair of pores. The plates imbricate from below upwards (probably from above downwards). LINN. JOURN.—ZOOLOGY, VOL. XXIII. 2 18 PROF. P. M. DUNCAN'S REVISION OF THE Interradia one half as broad as the ambulacra, with five or more vertical rows of overlapping plates, which diminish in number towards the poles; the plates imbricate from above down- wards (probably the reverse) and from the central range outward. Surface covered with small granules for the articulation ef minute spines. Jaws consisting of large subtriangular, truncated, conical pieces deeply furrowed towards the ends and perforated in the central part. Genital plates probably with four pores. The spines minute and acicular. Fossil. Carboniferous: N. America. Genus Paorroctrparis, Meek 5 Worthen, 1869, Proc. Acad. Sei. Philad. p. 78 (under Lepidocentrus) ; 1873, Geol. Illinois (Pale@ont.), vol. v. p. 510, pl. xv. fig. 9. Loven, Etudes, 1874, p. 40. Zittel, 1879, Paleont. Bd. i. p. 482. Fragments belonging to individuals of from 90 to 100 milli- metres in diameter. Interradia with five or more rows of plates imbricated aborally and laterally, granular, thin, rounded, convex, unequal, those nearest the ambulacra three or four times the size of the others, elliptical, higher than broad, projecting. On one surface (ventral?) there are primary tubercles one to a plate, placed centrally, and perforated, and surrounded by two smooth rings; similar tubercles on the opposite surface of the test only on the ambulacral plates. Spines subulate, finely striated longitudinally. Ambulacra broad, with six vertical rows of small plates, variably shaped, oval, rhomboidal, or with the angles rounded; plates imbricating adorally ; with a moderate-sized mamelon, and the pores in single or sometimes double pairs, in a depression. There are also small spines and small buccal scales present. Fossil. Inferior Carboniferous: N. America. Type P. irre- gularis, Meek and Worthen. There is a singular question about the zoological position of Paleodiscus, Salter, for the late Sir Wyville Thomson placed it ax a synonym of Hchinocystites. There are specimens in the Museum of Practical Geology, Jermyn St., and in the British Museum; and it is tolerably evident that there are forms there which simulate the typical Palgodiscus, which Salter decided to be an Asteroid. Two of these forms in the British Museum are associated, and properly so, with the Palechinoidea, but are flattened, badly preserved semicasts. The interradial parts have GENERA AND GROUPS OF THE ECHINOIDEA. 19 several vertical rows of plates and the ambulacra are narrow, and with a multitude of small, low plates each perforated minutely by a pair of pores; as there are two pairs of pores on each side of the median line and placed nearly horizontally, the presence of two vertical rows of ambulacral plates on either side of the median line must be admitted. The peristome presents some appearance of jaws. There is not enough to define a new genus from, and certainly the reason for placing the forms in Hehino- cystites is not apparent. The alliance is with Oligoporus, but it is necessary to wait for better specimens. (See Hchinocystites.) Order III. PLESIOCIDAROIDA. Test small, subhemispherical, solid, with a large apical system, having large united basal plates and a central periproct. Ambu- lacra narrow, and with two vertical rows of poriferous plates. Interradia with a single peristomial plate, followed by three plates separated by vertical sutures. Large tubercles on the actinal surface. Genus Trarecutnus, Vewmayr, 1881, Sttzwngsb. d. kais. Akad. d. Wiss. Wien, 1882, Bd. 84, Heft i. p. 69. Lovén, Pourta- lesia, 1883, Kongl. Svenska Vetensk.-Akad. Handl. Bd. xix. pp. 11, 64, pl. xi. Test small, flat actinally and slightly elliptical in marginal outline, subhemispherical dorsally. Apical system very large, extending nearly halfway to the ambitus ; periproctal space small, pentagonal; basals very large, the posterior the smallest, hexagonal, forming a very broad ring; — genital pores two in number, one in the basals 1 and 3; radial plates pentagonal, notching the union of the basals slightly ; pores absent. Ambulacra band-like, equal, but the posterior pair are closer together than the others; straight, broadest at the peristome, made up of two vertical rows of numerous low, broad primary plates, each with a pair of pores and a small plain tubercle, Interradia broad, actinally composed of a single peristomial plate, above which are three tall plates only, one median and the others at its sides. Ornamentation, a plain primary tubercle to each plate at the ambitus and actinally ; elsewhere the test is coarsely granular, including the apical system. ‘Sutures very 2% 20 PROF. P. M. DUNCAN'S REVISION OF THE invisible; test solid-looking. Peristome large, oval-elliptical, without branchial incisions. Fossil. St. Cassian-Trias: Europe. It is to be observed that the single species of this genus, T. princeps, Laube sp., was diagnosed from specimens 3°8 millim. in height, 5:2 millim in length, and 4°9 millim. in breadth. Order IV. CYSTOCIDAROIDA, Zittel, 1876-81. Test irregular (exocyclic), globular or ovoid, thin, flexible (?) ; madreporite central and dorsal. Ambulacra narrow, and with two vertical rows of poriferous plates. Iuterradia broad, with numerous vertical rows of scale-like moveable plates ; periproct in the posterior interradium above the ambitus. There has been a difficulty made about the name of the principal, if not the only, genus of this family. Wyville Thomson defined the genus very well in 1861, and employed the term Echinocystites, which was a good one. In 1864 Hall ealled a genus of Cystidea by the name already occupied by Wy. Thomson’s genus. In 1876-80 Zittel, in his ‘ Palzontologie,’ p. 480, altered Wy. Thomson’s term to Cystocidaris, and noticed the fact about Hall’s using the name Hehinocystites, although it was preoccupied. Certainly Wy. Thomson’s name must continue, and Hall’s Cystidean will have to be called by something else, and Cysto- cidaris must lapse according to the ordinary rules of nomen- clature. Genus Ecurnocystitss, Wy. Thomson, 1861, Hdinb. New Phil. Journ. n. ser. vol. xiii. p. 108, pls. iii., iv. (on Echinocystites, Hall, 1864). Syn. Cystocidaris, Zitt.; Paleodiscus, Salt. in Wy. Thoms. op. Citaps LG, Test large, spheroidal or ovoid, thin, flexible. Apical system central and dorsal, apparently consisting of a large madreporite only. Ambulacra narrow, straight; plates numerous, small, low, in four vertical rows, a central pair of pores in each plate, and * The genus Paleodiscus, Salter, 1857, Ann. & Mag. Nat. Hist. ser. 2, vol. xx. p. 332, was considered by Wy. Thomson in the same essay as that which contained the description of Hchinocystites, and the solitary species was stated to be flexible and the teeth were as chisels. GENERA AND GROUPS OF THE ECHINOIDEA. 21 therefore four vertical rows of pores two on each side of a median groove. Interradia with numerous, 6-8, vertical rows of scale-like lozenge-shaped or irregular plates, each with a small primary tubercle surrounded by a scrobicule; granules present, and the Spines short, sharp, striated, and serrate. The areas appear to unite apically. Peristome central, actinal, small, pentagonal or stellate, sur- rounded by marginal ambulacral and interradial plates; dense sheaves of short spines at the edge. Jaws highly developed, five pyramids; the inner, oral surface of the pyramids with strong spines* or with striated chisel-shaped teeth. Periproct large, on a low pyramidal protuberance in an interradium, at about one third of the diameter of the test from the peristome. Fossil. Upper Silurian: Scotland. II. Remarks upon the Subclass Huechinoidea, the five Orders, definitions, and of the Suborders of the second Order. Order I., the Cidaroida; the Family Cidaridz. Section I. Genus Cidaris (note on the classification), The seven divisions of the genus; definitions ; Subgenus Goniocidaris. Other genera. Section II. Order II., the Diadematoida. The Suborder Streptosomata; con- siderations regarding the anatomy and classification. The Family Hchinothu- ridze, and Subfamilies Pelanechinine and Kchinothurine ; the description of the genera. Il. Subclass HUHCHINOIDEA. The classification of the Huechinoidea, like that of many of the great groups of Invertebrata, can be generally natural and definite ; but an artificial method seems to be necessary, occa- sionally. Some of the “ Orders” are well defined by characters of considerable anatomical and physiological value, but others are of unequal relative value, are perhaps too comprehensive, and Suborders have to be founded. The Orders Cidaroida and Clypeastroida, amongst the Gnatho- stomes, are well defined, but the discovery of the Drs. Sarasin * The spines at the oral surface of the pyramids are accidental, and the result of crushing. 2D PROF. P. M. DUNCAN’S REVISION OF THE regarding the internal branchie of the HEchinothuride and Ludwig’s remarks concerning the rudimentary nature of these organs in some Diadematide, coupled with the knowledge that in some genera of this great family the internal branchiz are not seen, renders it impossible to classify upon the old grounds- The difficulty is where to place the Echinothuride, and the Tem- | nopleuride, Echinometride, and Hchinide in reference to the Diadematide and close allies, and the Saleniide. Itis the opinion of A. Agassiz that the Hchinothuride should be placed close to the Diadematide and not with the Paleechinoidea; and it ap- pears to be justified by facts. But the flexible forms with the ambulacral plates continued to the mouth are, as a group, not of the same taxonomic value, in reference to the Diadematida, as the other families just mentioned. The Hehinothuride have sub- ordinal characters. On the other hand, it is not possible to separate the Hchinide, Echinometride, and Temnopleuride from the Diadematide ; and they all belong to a suborder. There is at present no other method possible than to separate the Gnathostomes which are endocyclic, and which have continuous perignathic girdles and external branchiew, into two Suborders. In one the test is flexible and the branchiz are both external and internal; and in the other the test is rigid, and the internal branchie are either small, rudimentary, or absent. A difficulty occurs amongst the Exocyclic genera, and there is, at present, no satisfactory classification possible of some of the Exocyclica without teeth. It appears to be straining a point to separate such a genus as Discoidea from tke Order which contains Holectypus, but the perignathic girdle of the last-named and its jaws and teeth differ from those of the first-nawed genus. In Discoidea thereis a perignathic collar with possibly the relics of ambulacral pro- cesses; but it is the opinion of Mr. Percy Sladen and the author of this Revision that no jaws were present. lLovén is of a dif- ferent opinion, but still no jaws have been found. It is not possible to place Hehinoconus with either of these genera, for the ambulacra and the peristome differ, it has most rudimentary auricles, and the perignathic girdle is reduced to more or less defined interradial ridges, and the genus was jawless. Discoidea was a transition form, between the Gnathostomes and the Suborder of Cassiduloidea, and part of the dental apparatus was abolished, and degeneration of the perignathie girdle occurred. To place GENERA AND GROUPS OF THE ECHINOIDEA. 23 the genus in a separate Suborder is not advisable; and it is perhaps best to enlarge the definition of the Order, which con- tains Holectypus as a type, so as also to include the genera with perignathic girdles of more or less continuous collar-shape, without jaws. At present our knowledge of the genera Galeropygus and Pachyclypeus is so defective that they must remain zncerte sedis. The abolition of the toothless Irregulares (Exocyclica) as a group assists the definition of the Cassiduloidea, for Phyilo- clypeus, Conolampas, and even Echinoconus can enter it, only the latter genus being, possibly, somewhat artificially placed. The separation, made many years since by Desor, between the Cassiduloids with a floscelle and without that important peristomial character, holds good, and the only difficulty in the taxonomy is to place the few genera which have, besides some Cassiduloid characters, the dissimilarity of the ambulacra charac- teristic of the Spatangoida, and variable apical systems, such as Holampas, Archiacia, Claviaster, Asterostoma, &c. These genera are aberrant, yet they link the Cassiduloidea with the Spatan- goidea in an Order. They form a new Family, the Plesio- spatangide. ; The classification of the great group of Spatangoidea—a Sub- order—has been rendered difficult in consequence of the discovery ofthe abyssal forms. Under the hands of Lovén* and A. Agassiz t the suborder has become manageable, and its Families are those of the Ananchytide, Spatangide, Leskiide, and Pourtalesiide. The Spatangide contain four well-marked types, but they do not appear to be worthy of subfamily distinction, for their separating characters are rather artificial and are of unequal value. The divisions are those insisted upon by Loven, namely, the genera without fascioles, those without a subanal fasciole, those with a subanal fasciole, and those which are apetaloid. These are the divisions of Adetes, Prymnadetes, Prymnodesmia, and Apetala. The attempt is made, in this revision, not to overvalue the characters of perforation and crenulation or of the plain and imperforate nature of primary tubercles. The physiological value of crenulation is very slight, it often occurs or is absent in the * ‘Etudes’ and ‘ Pourtalesia.’ + Report on the ‘ Challenger’ Echini. 24 PROF. P. M. DUNCAN’S REVISION OF THE same species and specimen, and it and the opposite condition will not-distinguish genera for the future *. The nature of the ambulacral plates, the arrangement of the pairs of pores, and the shape and functions of the tentacles are, how- ever, considered to be of great. taxonomic importance. The great importance of the radial plates, formerly erroneously considered to have a reference to an optic organ instead of a primary tentacle, is not admitted ; and M. Pomel is not followed when he endeavours to establish genera and subgenera upon the entrance or not of one or more of the radial plates within the periproctal ring. Following A. Agassiz, the structure and shape of the spines are considered of secondary importance in classification, and genera are not separated on account of dissimilarities in the spines, nearly or quite all other structures being the same. These remarks will account for a proceeding which may take some paleontologists by surprise, namely, the absorption of Pseudo- diadema into the previously diagnosed genus Diadema, and the union with this last of many subgenera which were formerly - considered to be genera. Il. Subclass HUHCHINOIDEA. I. Order.—Euechinoidea with an actinal, central peristome and an abactinal DeDeaet situated within the dorso-central system ; with internal, branchiz only, and having jaws and more or less vertically placed teeth, and a discontinuous perignathic girdle; the interradial as well as ambulacral plates continued beyond the peristome to the true mouth. Spheridia absent. Endocyelic, anectobranchiate, Gnathostomes. an GH CIDAROIDA. II. Order.—Huechinoidea with an actinal, central peristome and an abactinal periproct situated within the dorso-central system; with perfect or rudimentary or absent internal branchiz, with external branchiz and incisions in the peri- stome ; with jaws and teeth and a continuous perignathic girdle; ambulacral plates alone continued beyond the peri- stome or as separate buccal plates. Spheridia present. Endocyclic, ectobranchiate, Gnathostomes. . pice DIADEMATOIDA. * Ann, & Mag. Nat. Hist. 1888, pp. 120-122. GENERA AND GROUPS OF THE ECHINOIDEHA. 25 1. Suborder SrreProsomata.—Test more or iess flexible, with external and internal branchie. Ambulacral plates alone continued beyond the peristome to the stoma. 2. Suborder SrerEosomata.—Test rigid, with external bran- chiz and rudimentary or absent internal branchie ; with isolated buccal ambulacral plates. Perit. Order.—Huechinoidea with an actinal, central peristome, IV. and the periproct situated beyond the dorso-central system in the posterior interradium ; with external branchie ; with a pair of pores or only one pore to an ambulacral plate ; with feeble jaws and vertical teeth, or without these structures ; with a variably constructed perignathic girdle. Spheridia present. Exocyelic, oligoporous, Eetobranchiata. HOLECTYPOIDA. Order.—Euechinoidea with an actinal peristome, a peri- proct situated beyond the dorso-central system, in the pos- terior interradium ; with external branchie ; with tentacular | pores in the interradia, and more than a pair to an am- bulaeral plate ; tentacles heteropodous in arrangement; with more or less horizontal and rarely vertical teeth, and with jaws situated superiorly to the disconnected perignathic girdle. Spheridia present. Hxocyclic, petalo- branchiate, polyporous, Gnathostomes. CLYPEASTROIDA. V. Order.—Huechinoidea with an actinal or afrontal peristome, and a periproct situated beyond the dorso-central system, in the posterior interradium ; without external branchiz, jaws, teeth, and perignathic eirdle. Spheridia present. Exocyclic, anectobranchiate, Nodostomata. SPATANGOIDA. 1. Suborder CassIDULOIDEA. 2. Suborder SPATANGOIDEA. 26 PROF. P. M. DUNCAN'S REVISION OF THE Subclass Il. HOUHCHINOIDEA. Order I. CIDAROIDA (p. 24). Family Crparipa, Agassiz & Desor, 1846, Catal. Rais., Ann. Scr. Nat. vol. vi. p. 325 (pars). Joh. Miller, 1854, Abh. d. k, Akad. d. Wiss. Berlin, p. 128. Desor, 1858, Synopsis, p- 2 (pars). Wyv. Thomson, 1874, Phil. Trans. vol. elxiv. p: 720. A. Agassiz, 1874, Revision, pp. 251 & 384 (pars)*. Test spheroidal; the ambulacra narrow, with two vertical rows of very numerous low plates, which are primaries, and rarely become compound, united by their edges, each with a pair of pores arranged in single and rarely in double series; other plates continued from the peristome to the true mouth and imbricating, besides being perforated; interporiferous areas with large and small granules only. Interradia broad, with few plates in two vertical series, most with a large primary, scrobiculate tubercle, carrying a large — spine, secondary tubercles and granules with smaller spines ; plates united at their edges; some broad and low plates con- tinued from the peristomial margin to the true mouth, and imbricating. Apical system large, with five basal plates and five radial plates, each with a perforation; periproct in the midst, covered with plates. A madreporite in the right anterior basal plate. Jaws with the foramen of the pyramid small, and not closed in by epiphyses; teeth grooved; perignathic girdle discontinuous, with a bifid process on each interradium only. Branchie in- ternal; tentacles subheteropodous t. Peristomial branchial inci- sions and external branchie absent. Spines variable. Spheridia absent. * A, Agassiz pointed out in the ‘ Revision’ that the anatomical researches of Johan. Miller rendered a correct definition of the family Cidaridze possible. But nearly all the definitions which have been recorded have been too synthetic. Since A. Agassiz gave such a mine of information regarding the recent genus Cidaris and its subdivisions, there has been a general movement towards simpli- fication. The old subfamily “ Salentde” has been eliminated and the fossil and recent Cidaride form a tolerably homogeneous group. In the Report on the ‘Challenger’ Hchini, 1881, A. Agassiz remarks concerning the branchial slits at the true mouth of recent specimens of Cidaris (p. 53) :—‘“‘ Whether it is these organs (gills) which find their way through the cuts or not, in our Florida species, I am unable to state; and a renewed examination of living specimens will be necessary before we can settle this interesting question.” + The definition of terms is given at the end of this Essay. GENERA AND GROUPS OF THE ECHINOIDEA. 27 Order CIDAROIDA. Family CrpaRID&. Section I. Ambulacral pairs of pores uniserial. Genus Cidaris. Subgenus Goniocidaris. Genus Orthocidaris. Temnocidaris. Polycidaris. Section 11. Ambulacral pairs of pores biserial. Genus Diplocidaris. Tetracidaris. Section I. The first genus of the Cidaride is Cidaris, Agassiz and Desor, 1846; and it is a very large one. Nevertheless it is well dif- ferentiated from any other genus; and it would be easily de- fined had nota series of artificial divisions, raised to the dignity of subgenera and even of genera, been employed to group the species. It is best to give the amended generic definition, and then to consider the grouping of the species. Genus Crparis, Klein, 1734 (pars); Lamarck, 1816 (pars) ; Gray, 1825 (pars). Agassiz § Desor, 1846, Cat. Rais., Ann. Sci. Nat. vol. vi. p. 325. J. Muller, 1853, Bau. d. Ech., Abhi. d. k. Akad. d. Wiss. Berlin, pub. 1854, p. 128. Desor, 1858, Synopsis, p.3. A. Agassiz, 1872-74, Revision of the EKchini, p. 252; and 1881, ‘Challenger’ Report, p. 33. C. Stewart, 1871, Quart. Journ. Mier. Sct. n.s. vol. xi. p. 54; and 1879, Trans. Linn. Soc. vol. i. p. 569. Lovén, 1887, Ech. descr. by Linneus, pp. 1388, 146. Syn. :—Hocidaris, Desor, 1858 * ; Anaulocidaris, Zittel, 1884 ; Discocidaris, Doderlein, 1885; Schleinitzia, Studer §. Syn., when employed as genera and not as artificial divisions :— Stephanocidaris, A. Agassiz ||; Rhabdocidaris, Desor 4; Leio- * Synopsis, p. 155. t N. Jahrb. f. Min. Bad. ii. p. 182. t Archiy f. Naturg. Wiegm. 1885, Heft i. p. 82. § Monatsb. d. k. Akad. d. Wiss. Berlin, 1877, p. 463. || Revision, p. 393. {| Synopsis, p. 39; and de Loriol, 1883, Cat. Rais. d. Ech. réc. 4 V’Ile Maurice, p. 7. 28 PROF. P. M. DUNCAN'S REVISION OF THE cidaris, Desor*; Phyllacanthus, Brandt +; Dorocidaris, A. Agassiz t. Test variable in size and thickness, spheroidal, depressed or tall. Apical system large, either flat, and with the large geometrical basal plates weakly united, or solidly sutured ; the radial plates large, separating the basals or not, and in the first case often touching the outer periproctal plates which may intrude. Basal pores large; the madreporite in the right anterior basal plate; the periproct pentagonal, variable in size, numerously plated. Ambulacra narrow, undulating or nearly straight, composed of very numerous broad low primaries, which are perforated by single pairs of pores, the pores being variable in their distance, and may or may not be united by a groove; poriferous zones broad ; interporiferous areas with vertical rows of distinct granules which are small, and may have rudimentary mamelons. The plates are continued beyond the peristomial margin to the edge of the mouth, and are low, broad, imbricating, and each is pierced by a pair of pores. Interradia broad ; coronal plates few, from 5 to 11, in each of - the two vertical rows, each with a primary tubercle, scrobiculate, and perforate, may be crenulated or not. Scrobicule large, often sunken, its margin with small secondary tubercles and large eranules ; the space beyond the scrobicules with large miliary granules. Peristome large, without branchial incisions; the interradial plates continued beyond the peristome to the mouth, small, low, imbricating, in double series. Spheridia absent. Perignathic girdle discontinuous; auricular processes upon the interradia. Pyramids of jaws unclosed above by epiphyses ; teeth grooved. Spines of the ambulacra, the scrobicular circle, the miliary zones, and of the plates beyond the peristome very similar, small, straight, blade-of-oar-shaped, very close; and those of the scro- bicules cling around the primary spines. Primary spines very variable, even in the same species, with a calcareous network internally and solid outside, lamellary, or fluted externally, and variously spinuled, granulate, laminated, some whorled; long, with a cylindrical or angular section, pointed or blunt; or very short, * Synopsis, p. 48. + Prodr. d. Act. d. Acad. St. Pétersb. 1834 (Additions), p. 267. { Revision, p. 254. GENERA AND GROUPS OF THE ECHINOIDEA. 29 clubbed, and large at the blunt end; fusiform, sharp, or blunt ; cylindrical and blunt, with spinules, thorns, and granules or disk-shaped expansions, or cup-shaped at the end, with spines radiating ; or long, flat, expanding, furrowed and spined. Tentacles disciferous actinally, and gradually becoming non- prehensile and branchial. Pedicellarie large, tridactyle, gemmi- form, and small and blunt-headed. Sexes separate or not; young usually undergoing metamor- phoses, rarely not, and then found upon the parent. Fossil. Permian: Europe. Trias: Europe, Asia *. Jurassic to Post-pliocene: England and Europe, N. Africa, Asia. Cretaceous to Tertiary: N. America, Egypt, and W. Africa. Tertiary : Australia. Recent. World-wide. Every writer upon the classification of the Echinoidea since Desor has complained of the unsatisfactory attempts of some of the most distin- guished authorities to subdivide the genus Cidaris. The subdivisions gradually became subgenera; and of late these have received generic importance. The divisions were made upon very unimportant external characters ; and subsequent research has proved that these structures, the _ yariations of which led them to be considered of good diagnostic value, are of no physiological importancet. The presence or absence of perfo- ration and crenulation of the primary tubercles, and the connection of the pores of pairs by a groove, or their disconnection by a granule or swelling, have really been the main features relied upon to establish divisions, sub- genera, and finally genera. Common observation will satisfy anybody that crenulation is not invariable upon the same test in many instances ; and itis a mistake to believe that it is a structure which relates to the strength of the spme-muscles. These are attached to the edge of the scrobicule, and are inserted just below the milled ring of the spine; and they have nothing to do with the crenulation. This appears to add to the attach- ment surface of the membrane of connective tissue which closes the ball- and-socket joint of the spine and tubercle. The grooving, or the reverse condition, between the pores of a pair is of no physiological importance whatever; and it is frequently impossible to decide whether the pores are connected by a groove or not. Any classification in which these characters are used is artificial. The number of interradial coronal plates is of physiological importance ; * HKocidaris = Cidaris has been found in the Salt Range, British India. t+ Duncan, 1888, Ann. & Mag. Nat. Hist. vol. i, p. 124. 30 PROF. P. M. DUNCAN’S REVISION OF THE and there is a great temptation to consider typical Cidarids as having but a few, say not more than seven, in a vertical row. But all the other structures, or the varieties of structures, are to be noticed in combination with few or many plates. The spines of some species are apparently so peculiar that they have been used as classiiicatory data of primary importance; and one subgenus has been founded upon them. But A. Agassiz very properly now lays down the law that Cidarids cannot be classified by their spines alone. The nature of the apical disk is very different in some Cretaceous and recent species: in the former it is solid, and with a tall basal ring and_a small pentagonal periproct in some well- known forms ; and in the latter it is large, flat, with feebly united plates, the radial plates sometimes separating (with or without the assistance of some periproctal plates) the basals. But there is every link in the inter- mediate chain of structures to be seen, and even in the same species there are variations in relation in the position of the basals and radials, entry or not of the latter taking place within the ring. The size of the miliaries and the occasional want of perfection of the tubercles of the interradial plates close to the apex cannot be of any great importance. Both Lamarck and Agassiz, and subsequently Desor, insisted upon the subdivision of Cidaris, in reference to the condition of the primary tubercles and the grooved or not nature of the test between the pores of pairs. Desor thus established Rhabdocidaris and Leiocidaris; Brandt established the subgenus Phyllacanthus from the nature of the spines and straightness of theambulacra. A. Agassiz decides against Leiocidaris, and adds to the diagnosis of Phyllacunthus; and he introduces Dorocidaris, which is a true Cidaris with non-crenulate tubercles. De Loriol and M. Cotteau have both altered the range of diagnosis in Rhabdocidaris and Leiocidaris; and the first-named naturalist decides against Leiocidaris and Phyllacanthus. It appears, after having given the subject careful consideration, that none of these divisions is worthy of a true subgenerie position, but that Rhabdocidaris, Leiocidaris, Dorocidaris, Stephanocidaris, Phyllacanthus (Brandt), A. Ag., and Porocidaris are fairly useful artificial divisions. They are synonyms of Cidaris, however. Goniocidaris is a good subgenus. I. Diviston. Typical Cidaris. Ifthe system of subdividing the genus artificially is adopted, the typical species will be those with a small number of inter- radial coronal plates (5-8), and with the ambulacra more or less undulating, the pores of pairs rather close and separated by a nodule or ridge, and the primary tubercles perforated and crenulated. The other divisions will be as follows :— GENERA AND GROUPS OF THE ECHINOIDEA. 31 IJ. Division. Syn. Genus Rhabdocidaris, Desor, 1848, Synopsis, p. 39. Large swollen tests, often as high as broad; remarkable on account of the particular structure of the poriferous zones, which are broader than in true Cidaris, the two pores of a pair being distant, and linked by a groove which is small and hori- zontal. Ambulacra in general straight or slightly flexuous. Tubercles large, always strongly crenulated (at least in the fossil species), and proportionally more numerous than in true Cidaris. Scrobicules large, often elliptical. Miliary zone broad. Spines very stout, some cylindrical or prismatic, and furnished with dentations or spines, and others in the shape of oars, either simple or with spines at the base. Articular facette very large and strongly crenulated. Neck little or not constricted.—(Type, Cidaris copeoides, Cott., and C. guttata, Cott.) III. Dirviston. Syn. Genus Leiocidaris, Desor, op. cit. p. 48. Large tests, with smooth tubercles; but they differ from Cidaris because the pores of a pair are linked by a small groove, as in Ehabdocidaris. Miliary zones very broad. Spines as large smooth cylinders, resembling those of Heterocentrotus. Desor defines Leiocidaris as Rhabdocidaris with uncrenulated tubercles.—(Cidaris canaliculata, Dune. & Sladen, Foss. Ech. Sind, Pal. Ind. ser. xiv. p. 109, 1884, is a good type.) TV. Diviston. Syn. Subgenus Dorocidaris, A. Agassiz, 1872, Revision, p. 254. - Ambulacral median area narrow; a small number of inter- radial plates; scrobicules sunken, and median space also. Tubercles without crenulations, and the pores of a pair without an intermediate groove. It will be observed that the spines are very variable in this division. Dorocidaris is a true Cidaris, with no crenulation on the tubercles.—(Cidaris papillata, Leske, is the type.) V. Division. Syn. Genus Stephanocidaris, A. Agassiz, 1872, Revision, p. 393. Test thin. Apical system larger than the peristome, the plates feebly united, and the whole flexible; the polygonal basal plates separated by large radial plates.—(Cidaris bispi- _nosa, Link., is the type.) ; 32 PROF. P. M. DUNCAN’S REVISION OF THE VI. Drviston. Syn. Subgenus Phyllacanthus, Brandt, 1834, Rec. d. Actes de l’Acad. Imp. d. Sci. de St. Pétersb., pub. 1835, Additions, p. 267; A. Agassiz, Revision, 1873, p. 387. (Amended.) Test large, swollen, comparatively thin, and with the maximum of coronal plates, 8-11. Apical system large ; the basal plates in contact, or separated by radial and anal plates. Ambulacra almost straight or very slightly undulating, broad; the pores in a broad zone, and united by a groove. Primary tubercles of the interradia large, perforate, non-crenulated, scrobicular circle large, areola sunken, mamelon small. Miliary area wide. Spines mostly solid, the primaries varying greatly in shape and size, cylindrical, triangular, flattened in section, elongate or club-shaped, blunt or pointed; flutings strong, either as simple striation, or as continuous or broken lamell variously projecting, sometimes forming secondary spinules.—_(P. dubia, Brandt. See Lovén’s remarks upon the subgenus in ‘ Echin. described by Linneus,’ 1887, p. 148.) VII. Diviston. Syn. Genus Porocidaris, Desor, Synopsis, pp. 46, 47. Wy. Thomson, 1874, Phil. Trans. p. 726. Ambvlacra broad and straight ; pores wide apart, united by a groove. Primary interradial tubercles with small perforate and crenulated mamelons; the scrobicules more or less transversely oval, with shallow grooves more or less defined, radiating from the periphery towards the centre, along the flank of the tubercles, with or without pores or depressions at the outer extremity of the grooves. Some spines flattened, with strongly serrated edges, resembling the smaller peristomial spines of Cidaris papillata.—(Cidaris purpurata, Wyv. Thoms., the type.) Subgenus Gon10crIDaRIs (genus), Desor, 1846, Agassiz & Desor, Cat. Rais. d’ Ech., Ann. d. Sct. Nat. vol. vi. p. 887. Lutken, 1864, Ved. Med. f. Nat. Kjobenh. p. 187. A. Agassiz, 1873, Revision, p. 395. Test high ; coronal plates numerous ; ambulacra narrow; the median sutural regions of interradia and ambulacra sunken, forming with the horizontal sutures a zigzag, culminating in pit-like depressions at the angles of junction of the sutures. GENERA AND GROUPS OF THE ECHINOIDEA. 33 Spines variable, either long, cylindrical, and pointed, the sur- face having thorns, pointing irregularly outwards, or short, stout, eylindrical or flat in outline, with enlarged cup-like tops with a fringe of strong radiating spinules; spinules in vertical series along the stems or restricted to the edge, in the flat specimens. Viviparous, unisexual. Fossil. Tertiary: Sind, Asia. Recent. Philippines ; Indian Archipelago; Hast Indies; Aus- tralia, N. South Wales; Tasmania; Falkland, Marion, and Ker- euelen Islands ; Patagonia; Antarctic Ocean; Natal; Zanzibar. Wy. Thomson and Studer discovered about the same time, in 1876, that Goniocidaris was viviparous, and that the young were carried upon the apical system, protected by the upper spines of the test, until their full development took place. Studer, 1876, Berl. Akad. Monatsb. p. 455, noticed the large genital openings covered by athin membrane; and Thomson described the method of carrying the young, and that the female genital openings notch the edge of the basal plates (Journ. Linn. Soe. vol. xiii. 1876; and Voyage of the ‘Challenger,’ vol. 1. p. 228). It is necessary to admit the unisexual nature of the species*. Genus OrrHoctpaRris, Cotteau, 1862, Pal. Frang., Terr. Crét. vol. vu. p. 364. Syn. Hypodiadema, Desor (pars). Test moderate and subspherical. Apical system flush, pentagonal, small. Ambulacra narrow, straight ; interporiferous area with small sranules, which may have mamelons, placed in several rows and without order ; pairs of pores in simple straight series, the pores separated by a granule, in low primary plates. Interradia very broad, plates numerous; primary tubercles very small, perforate and plain, distant, occupying a small portion of their plates ; the scrobicules small and circular; the miliary areas large, and the granules with mamelons. Peristome small, narrow, without branchial incisions; the interradial lips the largest. Fossil. Lower Cretaceous: Europe. * Genus Discocidaris, Doderlein, from Japan, has large outer anal plates and disciform ends to the primary spines; and it isa Cidaris. Anaulocidaris, Zittel, is too close to Czdaris to be considered otherwise than a species. Schleinitzia, Studer, is a Cidaris. Eocidaris, Keyserl., now appears to have all the requisite structures to classify it with Cidaris, and thus the genus is carried back in time to the Permian age. LINN. JOURN.—ZOOLOGY, VOL. XXIII. 3 34: PROF. P. M. DUNCAN’S REVISION OF THE The next three genera are not satisfactory. Genus Tremnocrparis, Cotteau, 1863, Pal. Franc., Terr. Crét. vol. vil. p. 855. Test large, spheroidal. Apical system large, flush, wider than the peristome. Ambulacra subflexuous, narrow; poriferous zones broad, the pairs of pores in simple series ; interporiferous areas with small granules placed without order, except a larger row near the poriferous zone. Interradia large; tubercles numerous and large, plain and scrobiculate ; miliary areas large and minutely granular, marked with linear depressions. Peristome moderate, subcircular. Numerous small shallow circular pits in the miliary areas and in the interporiferous areas, but scattered without order, and not in relation with the sutures or their angles of junction. Fossil. Cretaceous : Europe. The pits do not resemble those of the Temnopleuride ; and there is a suspicion of their post-mortem origin. Certainly the test, apart from the pits, is that of a Cidaris. Genus Ponycrparis, Quenstedt, 1858, Der Jura, p. 644, tab. 79. _ fig. 69; 1874, Petr. Deutschl. p. 216, tab. 69. figs. 10-12. Zittel, 1879, Palgont. Bd. i. Lief. iii. p. 496. Coronal plates low, broad, numerous in the broad interradia (9-15), two vertical rows of primary tubercles which are per- forate and crenulate, and with scrobicules which run the one into the other vertically. Median interradial area smooth, between broad angular zones. Ambulacra very narrow, straight; pairs of pores in simple series; pores separated by a nodule; interporiferous areas with two vertical rows of very small and numerous tubercles or granules. Fossil. Oolite : Europe.* * Leptocidaris, Quenst., 1858, pl. 90. fig. 10; 1874, Petr. Deutschl. p. 282, tab. 69. figs. 71-7ly. This name was given to a fragment in which the coronal plates are numerous and low, and the pairs of pores are in simple series. In Quenstedt’s last work, 1874, the anatomy of an ambulacral plate is given, and it is not that of a Cidarid. The genus is placed after the Hemicidarida, p. 55. GENERA AND GROUPS OF THE ECHINOIDEA. 35 Family CIDARIDS. Section II. The ambulacral pairs of pores biserial. Genus Drenocrparis, Desor, 1854-58, Synopsis, pp. 45 & 439. Cotteau, 1862, Rev. et Mag. Zool. vol. xiv. p. 185, pl. 10. Test large, spheroidal, wider than high. Apical system large, solid, pentagonal, flush. Ambulacra narrow, straight; poriferous zone as broad as the interporiferous area ; pairs of pores very numerous, close, biserial, alternating more or less, placed in low primary plates which are single actinally, and which form compound plates elsewhere, these being double or triple combinations of low primary plates. Interporiferous area narrow, with two vertical rows of large granules with mamelons and a narrow, bare median space. Interradia broad ; plates few, high, 7-8 ; two vertical rows of large, perforate, scrobiculate, primary tubercles, which may or may not be crenulated, in each area; miliary zones large, with scattered granules. Peristome narrow, with narrow ambulacral lips; branchial incisions absent. Jawsstrong; the foramen of the pyramid small or absent. Perignathic girdle with interradial ridges only, and they are notched and bilobed. Spines long, thick, cylindrical, granular, and pustulate in longi- tudinal ridges. Fossil. Oolite: England? ; Europe; N. Africa. The next genus is placed here provisionally ; it has four coronal interradial plates in each interradium, but not in every part of the areas; and the nature of the peristome is unknown in the species. The shape and the construction of the ambulacra are very remarkable; and it must be remembered that A. Agassiz found divisions in the interradial plates of Astropyga radiata (‘ Challenger’ Echini, pl. x a. fig. 9, 1881). Genus TrTRacipDaRIs, Cotteau, 1872, Rev. et Mag. de Zool. sér. 2, vol. xxiii. p. 445, pl. 29. Test large, circular in equatorial outline, tumid, broader than high, depressed, spheroidal. 3% 36 PROF. P. M. DUNCAN’S REVISION OF THE Apical system central, large. Ambulacra straight, moderately broad; poriferous zones de- pressed, pairs incompletely biserial; plates low, primaries nu- merous. Interporiferous area narrow, granular, and with a vertical row of small plain tubercles, placed near each poriferous zone. Interradia with numerous very large crenulate and perforate primary tubercles, in scrobicules, separated by a narrow median zone with few miliaries ; there are four vertical rows of tubercle- bearing plates as far as the ambitus, diminishing thence to the apex by two. The plates are numerous, in vertical suc- cession (16). Peristome ? Spines narrow, elongate, subcylindrical, keeled. Fossil. Cretaceous : Hurope. This is a very suggestive, but at the same time, on account of the defective anatomical details, a most unsatisfactory genus. The resemblance to Astropyga and the very non-Cidaridean characters of the ambulacra render the classification merely provisional. (See Astropyga, p. 78.) Order IT. DIADEMATOIDA (p. 24). It is impossible to proceed with the classification of the next important group of genera of this Order without some remarks concerning the anatomical characters of the Streptosomata and the method of classifying the Family Diadematide of the Stereo- somata. The late Dr. 8S. P. Woodward described a flexible KEchinoid from the Chalk in 1863, and the knowledge regarding the recent forms commenced with Grube, who described Asthenosoma in 1868. Then the dredgings of H.M.S. ‘ Porcupine’ revealed to the late Sir Wy. Thomson the extraordinary spectacle of a panting, plate-moving form, which he called Calveria. The descriptions of the species, which turned out to belong to Asthenosoma, were published in the Phil. Trans. 1874, and illustrated. The impor- tance of the “imbrication”’ of the plates was inculcated, and the bearing of this structure upon the classification of the Family, and upon the possible alliances with the Perischoechinide, was rather overstrained. Unfortunately the very arduous life and necessary GENERA AND GROUPS OF THE ECHINOIDEA. 37 absence from England of Sir Wy. Thomson prevented him from giving more time to the study of the specimens, so that some errors were published. It is evident, however, that the mistake made about the direction of the imbrication of the plates in ‘ The Depths of the Sea’ was corrected in the Phil. Trans. 1874. But the description and drawing of the continuation of interradial overlapping plates beyond the peristome to the true mouth were unfortunate and so was the failure to recognize the external branchiw. Some of the internal structures were described, such as the series of longitudinal muscles running up the sides of the ambulacra, and having to do with the positive motions of the plates one over the other; but, incomprehensibly enough, the huge internal branchize were not recognized, and their dis- covery has fallen to the Drs. Sarasin in 1888! A. Agassiz, in his Report on the Challenger Echini, 1881, considered the question of the amount of the imbrication of the plates of the Echino- thuride—its cause, nature, and its relation to bevelling in thicker Palzechinoidea. These phenomena were exhaustively and most judiciously explained. Nothing can be more definite than the description of A. Agassiz of the construction of the test of Asthenosoma pellucidum, A. Ag. He remarks that the test is remarkably thin, and that even in a test of the diameter of 64 millim. the plates do not give the test any degree of solidity. The examination of a specimen of Phormo- soma luculentum, A. Ag., in the British Museum proves the com- paratively large size of some of the interradial plates, but they are excessively thin, consist of very open reticulate carbonate of lime, and they thin off at the edges, the calcareous structure being lost in the membranous part of the plate. This membranous part is continuous between plates, and the soft edge of one plate merges into the corresponding membranous part of the neighbouring plate. In Asthenosoma coriacewm, A. Ag. (‘ Challenger’ Report, pl. xvii. a. figs. 5-7), the amount of soft interplate tissue is con- siderable; in some places the plates show an extremely small calcareous part, and the excess of soft tissue is great. The semi- transparency of some species, when kept in alcohol, is remarkable, and the calcareous part of the plates is seen to be surrounded by a greater or less amount of soft movable, but probably not extensible, connective tissue—that is, of uncalcified plate-area. The flexibility of such tests is considerable in large parts of them, 38 PROF. P. M. DUNCAN’S REVISION OF THE and it is of course less when the pressure is localized ; they may be bent inwards and swell out elsewhere correspondingly. During life, movements of the test occur, and it is doubtless due to the contraction and dilatation of the internal longitudinal muscles, noticed and drawn by Wy. Thomson, and so well described and drawn by the Drs. Sarasin, as well as to gravitation. During this contraction and also after death the edges of the plates, especially the transverse edges, are approximated and slip over or under each other as the case may be. Nothing can be clearer than the drawings of A. Agassiz in regard to Phormosoma tenue (‘ Challenger’ Report, p. 93, pl. xviii. a. figs. 1-18). The whole of the transverse edge of a plate overlaps that of its fellow im suc- cession. The fig. 4 hag no overlap of edge, fig. 5 has it slightly, but not figs. 2, 7,8. The amount of overriding is small, and is assisted to a small degree by the thinning of the edges of all the plates, but there is no such thing as a bevelled thick edge. In the drawing given by Sir Wy. Thomson (op. cit. 1874, pl. Ixv. fig. 2), which shows the inner part of a test of Asthenosoma below the ambitus, the pairs of pores situated in the transverse sutural spaces are not forced out of their direction ; hence the overriding must be very slightthere. There is, on the other hand, definite but limited overlap of the interradial plates. The amount of interplate membrane varies in the species of Phormosoma, and it is less on the whole than in those of Asthenosoma, and yet the amount of overlap is only partial in this genus. The species Phormosoma rigidum, A. Ag., has a significant name, and it is evident that the interplate membranes are reduced to their utmost ; there is no appreciable space between the plates in the drawing (Report on the ‘ Challenger’ Echini, pl. xii. a. figs. 1-4, p. 104); all the other generic characters are present, but this is not a flexible and “‘ panting” form, and has most significant alliances with the Diadematide. The pistol-shaped outlined plates of Asthenosoma do not imbri- cate on most of their transverse edges, but the overlap is perfect at the median line of both areas,‘and a flap of plate must be more or less permanently overlapped or underlapped by another there. The ambulacral plates within the peristome, clearly overlap, and in order that the movement shall be uncontrolled there, the tentacles are associated with pores which are seen upon the plates themselves, and they are not upon the interplate structure. In both genera of recent Echinothuride a special character GENERA AND GROUPS OF THE ECHINOIDEA. 39 is the imperfect calcification of plate areas; the plates are therefore surrounded by soft tissue, and that of one plate is con- tinuous with those of its neighbours, without close suturing. It must be admitted that the overlap in Astropyga is rather an overstrained analogue of that which occurs in Asthenosoma; it is slight and persistent in Astropyga, and there is no movable soft tissue between the plates. The interesting work of the Drs. Sarasin upon swollen to subconical dorsally, depressed, flat or re-entering actimally. Apical system small, ornamented; the periproct circular or somewhat elongate, and even unsymmetrical; basal plates narrow; radial plates small, equal or unequal, and some may enter the periproctal rmg; the pore close to the adoral edge; madreporite distinct and in the right anterior basal plate. Ambulacra much narrower than the interradia; plates as single low primaries near the apex and soon becoming compound, the central com- ponent with the tubercle, a primary, and the adoral and aboral constituents also primaries, their sutures curved, convexity towards the tubercle ; some- times a demi-plate near the peristome. Pairs of pores in simple straight series near the apex and in the same towards the ambitus, or in slight ares 62 PROF, P. M. DUNCAN’S REVISION OF THE of triplets slightly crowded near the peristome; primary tubercles in two rows, perforate and crenulate, fairly developed. Interradia wide, with two or more vertical rows of primary tubercles, larger than those of the ambulacra, and otherwise similar; secondary tubercles may exist with or without a distinct and often crowded granu- lation. Some diminution in the size of the tubercles and of the number of vertical rows may occur dorsally. Peristome moderate, nearly flush or incurved, decagonal, with large branchial incisions, having a raised edge. Jaws well developed, with a large foramen, without epiphyses ; teeth grooved ; perignathic girdle conti- nuous. Spines variable in size, short, or longer than the diameter of the test, striated longitudinally, finely tapering, cylindrical pointed (solid, and this condition is due to fossilization). Fossil. Lias, Oolites, Cretaceous: England, Europe, N. Africa, Egypt, Asia, N. America; probably Eocene, Europe (Hebertia). The alliance of Microdiadema, Diademopsis, Hemipedina, and Echino- diadema (Cott.) with the old genus Pseudodiadema is evident. The im- perforation and non-crenulation, or the reverse conditions, of primary tubercles are insufficient to define and limit genera. Now all these “genera”’ are placed as subgenera with Pseudodiadema, which is synonymous with Diadema. Subgenus MicropiapEMa, Cotteau, 1863 (genus), Rev. et Mag. de Zool. sér. 2, vol. xv. p. 225. Test small, swollen and hemispherical abactinally, re-entering actinally. Apical system solid, narrow, projecting, granular. Ambulacra with the pairs of pores in simple vertical series ; arrangement of plates “diadematoid.” Interporiferous areas with small, almost uniform, perforate and crenulate, scrobiculate primary tubercles in several vertical rows. Interradia with primary tubercles resembling those of the ambulacra in several vertical rows. Peristome large, subcircular or decagonal, with well-developed branchial incisions. Fossil. Lias: Europe. Subgenus DrapEemopsis, Desor, 1858 (genus), Synopsis, p. 79. Cotteau, 1864, Rev. et Mag. de Zool. sér. 2, vol. xvi. p. 212. Test moderate and small, depressed, but subconical above the tumid ambital outline. Coronal plates low and numerous. Apical system large ; madreporite and the basals large; radial plates between the basals, but excluded from the periproct. GENERA AND GROUPS OF THE ECHINOIDEA. 63 Ambulacra narrow, with very small perforate and plain primary tubercles in two rows ; pairs of pores in simple vertical series, rarely, but sometimes, crowded at the peristome; plates low, simple primaries near the apical system, and compound elsewhere ; the adoral constituent a small primary with its aboral suture convex ; the median plate a large primary, and the aboral plate a low primary with the adoral suture convex (diadematoid). Interradia with four vertical rows of small perforate, plain, primary tubercles, without scrobicules, rather larger than those of the ambulacra; the outer vertical rows reach up furthest ab- actinally, and hence a granular median area. Peristome large, branchial grooves moderate. Spines longer than the diameter of the test, very delicate and slender, sharp, striated longitudinally, solid. Fossil. Infra-Lias and Lias: England and Europe. Etallon remarked long since upon the slight value of the genus Hemipedina and noticed that crenulation of the tubercles is sometimes visible on some portions of a test. Hence the plain condition is in this, as in other groups of forms, not of generic value. It is not possible to separate Hemipedina from Diadema generically, but the species formerly associated with it form a somewhat natural series, and may enter a subgenus. Subgenus Hemipepina, Wright, 1855 (genus), Pal. Soc. Monogr, Eich. Foss. Oolit. Form. p. 148. A. Agassiz, 1872-74, Re- vision, p. 291. Duncan, 1885, Quart. Journ. Geol. Soc. vol. xli. p.42. Déderlein, 1886, Wiegm. Archiv, Hefti. p. 96. Test moderate in size or small, circular or slightly pentagonal at the tumid ambitus, flat actinally, depressed, tumid, or sub- conical dorsally. Coronal plates numerous. Apical disk large, with large united basal plates. Ambulacra narrow, straight ; pairs of pores in straight series or in ares of three; simple primary plates near the apex, compound plates elsewhere as in Diadema; tubercles in two vertical rows perforate and not crenulate; secondary tubercles exist and granules. Interradia large, and with from two to six vertical rows of small primary tubercles, but larger than those of the ambulacra, only the outer rows reach the apex, perforate, and some may be crenulated. Median area often bare or granular near the apex ; secondary tubercles form rows near the ambulacra. 64 PROF. P. M. DUNCAN'S REVISION OF THE Peristome moderate, decagonal, and with rather deep branchial incisions; ten buccal plates upon the peristomial membrane. Spines long and slender, needle-shaped, longitudinally striated. Fossil. Lias and Oolites: England, Europe. Cretaceous: Europe. Recent. Caribbean Sea, 188-270 fms.; Sigambai, Japan. Subgenus EcutnoprapEeMa, Coftteau, 1869 (genus), Rev. et Mag. de Zool. sér. 2, vol. xxi. p. 238, pl. xl. (non Verrill). Test small, subconical. Ambulacra with undulating or straight poriferous zones ; three pairs of pores directly superimposed to a compound plate, forming arcs actinally; arrangement “ diade- matoid.”” Ambulacral and interradial tubercles nearly equal, plain, most numerous and largest actinally; each interradial tubercle corresponding to a swelling of a plate. Granulation distinct and distant, considerable. Peristome large, subcircular, with branchial incisions. Fossil. Oolite: Europe. Genus PracopiaDEMA, Duncan. Syn. Plesiodiadema, Dunc. (non Pomel), 1885, Quart. Journ. Geol. Soe. vol. xli. p. 433, fig. viii. De Loriol, 1887, Faune Crét. du Portugal, Ech. fase. i. p. 31. Test of moderate size, depressed, circular in marginal outline, tumid dorsally and flatter actinally. Apical system small, compact, the five basal plates and five radial plates all perforated. Ambulacra moderately broad, the poriferous zones with nu- merous pairs of pores in simple vertical series or somewhat arched; plates high, compound, made up of from four to six component primary plates, the sutures curved, with their con- vexities towards the centres of the plates, the second component from the adoral suture of the compound plate being the largest primary component; a pair of pores to a component plate. Interporiferous areas with two vertical rows of small primary tubercles, perforate and crenulate. Interradia wider than the ambulacra, with two or more rows of primary tubercles, resembling those of the ambulacra. Peri- stome decagonal, moderate, and with branchial incisions. Spines striated, moderately long, hollow (see specimen in Brit. Mus.). Fossil. Oolite: Europe. Cretaceous: England and Europe. GENERA AND GROUPS OF THE ECHINOIDEA. 65 Genus Hurrroprapema, Cotteau, 1862, Rev. et Mag. de Zool. sér. 2, vol. xiv. p. 200. De Loriol, 1887, Faune Orét. du Portug., Ech. fase. i. p- 44. (See Pseudodiadema (Hetero- diadema) Pseudo-Bourgeti, Cott. Pal. Frang., Terr. Crét. vol. vil. pl. 1097.) (Amended.) Syn. Loriolia, Neumayr, 1881, Zeits. d. deutsch. geol. Gesellsch. Bd. xxxi. p. 571; Colpotiara, Pomel. Test moderate, circular in tumid ambital outline, subconical, swollen but depressed abactinally, convex and rarely flat actinally. Apical system long, and when absent leaving a large scar which intrudes a considerable distance into the depressed posterior interradium. When present, the madreporite is large and passes from the right anterior basal plate to the centre of the system and pushes backwards the periproct, which is bounded by the postero-lateral basal plates and the postero-lateral radial plates and one or two interradial plates. Moreover, the antero- lateral radial plates separate the pairs of basal plates, and either touch the madreporite, or come into the periproctal ring; fifth basal plate absent. Ambulacra with straight, narrow poriferous zones; ie purs of pores in simple series, except actinally, where there is some doubling; plates compound (diadematoid). Tubercles of both areas in vertical rows, moderate in size, very equal, perforate and cre- nulated. Peristome flush, decagonal, with branchial incisions. Fossil. Cretaceons: Europe, N. Africa, Asia (Syria). Genus Coptopsis, Agassiz, 1840, Cat. Syst. Ectyp. Ech. Foss. p. 19. Desor, 1858, , Synopsis, p- 112. De Loriol, 1887, Faune Cret. du Portug., Ech. fase. i. p- 57, pl. ix. (Amended.) Test moderate, swollen, high, often nearly globular, circular or pentagonal in marginal outline; coronal plates numerous, high. Apical system small, solid. Ambulacra straight, narrow; pairs of pores wuiserial, in very slight arcs; the plates low primaries, but near the peristome they are compound, the middle component a large primary, and the aboral and adoral components demi-plates. Primary tubercles of both areas small, smooth, nearly equal in size, and only occurring actinally and for a short distance towards the ambitus, a granu- lation being elsewhere. Peristome pentagonal, small, with slight branchial incisions. Desor states that the primary tubercles are perforate, but they are not so in available specimens. Fossil. Cretaceous: Europe, N. Africa, Expt. LINN. JOURN. —ZOOLOGY, VOL. XXIIT. 5 66 PROF. P. M. DUNCAN’S REVISION OF THE Genus PrevroprapEemaA, De Loriol, 1870, Ech. Helv. Jura, p. 196; and 1885, Mém. Soc. Pal. Suisse, Genéve, p. 18. Test of moderate size, more or less swollen above and flat below. Apical system well developed, flush, compact. Ambulacra narrow at the apex, with some projecting, imper- forate, smooth or slightly crenulate tubercles on the actinal sur- face only, the rest granular. Poriferous zones straight; pairs of pores in simple series, directly superimposed and separated by small horizontal coste, which are raised, distinct and stout, especially actinally, and are prolonged to the interradial tu- bercles. Interradia actinally and at the ambitus with two rows of wide- apart, projecting tubercles with large mamelons, without scrobi- cules, and imperforate, slightly crenulate. Very small tubercles abactinally, secondary tubercles absent. Peristome decagonal, with everted edges; branchial cuts small. Fossil. Jurassic: Europe. Genus Maenosta, Michelin, 1853, Rev. et Mag. de Zool. sér. 2, vol. v. p. 84. Desor, 1858, Synopsis, p. 115. De Loriol, 1887, Fawne Crét. du Portug., Ech. fase. i. p. 59. Test small or moderate, circular at the tumid ambital outline, subhemispherical dorsally, or depressed, concave actinally. Co- ronal plates numerous, low. Apical system small; periproct small. Ambulacra narrow except actinally, where they are broad ; pairs of pores in simple straight series, barely in slight ares of triplets, but near the peristome they become close and polyserial. Plates compound. Interporiferous areas with from two to six or more oblique rows of very small plain primary tubercles. Interradia with a median depression, abactinally, which is smooth; from four to nine horizontal or oblique rows of very small tubercles resembling those of the ambulacra, diminishing in number abactinally. Peristome very large, pentagonal, well incised, the ambulacral lips the largest. Fossil. Oolite: England and Europe. Cretaceous: Europe and N. Africa. The Liassic species described by M. Cotteau cannot well enter, and, as he suggests, should be removed. GENERA AND GROUPS OF THE ECHINOIDEA. 67 Genus Cortarpta, Desor, 1858, Synopsis, p. 113. Test thin, small or moderate in size, tumid, subhemispherical or subconical, slightly depressed, circular or subpolygonal in ambital outline, flat and slightly tumid actinally. Apical system small, one or both of the posterior radial plates may enter the periproctal ring. Coronal interradial plates very numerous, low and broad. Ambulacra narrow; the poriferous zones narrow, slightly sunken, straight, the pairs of pores in simple vertical succession, slightly in ares actinally ; plates compound, there being three low primaries in each, with almost straight sutures. Interporiferous areas slightly tumid, crowded with very small perforate non- erenulate tubercles in horizontal rows, with or without order, and large granules. Interradia wide, the low plates with very numerous tubercles resembling those of the ambulacra, placed in a horizontal row on each plate, and with granules nearer the transverse sutures. Peristome sunken, small; the branchial incisions small; the interradial lips the largest. Fossil. Cretaceous: England, Europe, and N. Africa. Recent. a A. Agassiz admits his Cottaldia Forbesiana (‘ Challenger’ Report, p. 182) into the genus with much reservation; and I agree with him that the generic position is doubtful. Cottaldia Oarteri, Dune., from the Cretaceous of Ras Fartak, Arabia, must enter the genus Orthopsis. II. Subfamily Diplopodiine (p. 59). Genus Dietoropia, McCoy, 1848, Ann. § Mag. Nat. Hist. ser. 2, vol. ii. p. 412. Desor, 1858, Synopsis, p.75. Duncan, 1885, Quart. Journ. Geol. Soc. vol. xli. p. 443. De Loriol, 1887, Faune Orét. du Portug., Ech. fase. i. p- 33. Test moderate, depressed, circular in tumid ambital outline. Ambulacra narrow, with two vertical rows of primary tubercles, perforate and crenulate, smaller or nearly equal in size to the interradial tubercles ; pairs of pores in double vertical series near the apex and peristome, and uniserial at the ambitus; there is much crowding out of the poriferous plates in the biserial parts ; at the ambitus there are four primary components to a compound plate, or the lowest component may be a demi-plate, the second 5x 68 PROF. P. M. DUNCAN’S REVISION OF THE primary from the adoral suture of the compound plate is the largest component. Interradia with two or more vertical rows of primary tubercles, which are large and otherwise similar to those of the ambulacra. Peristome with well-marked branchial incisions. Fossil. Oolite: Europe. Cretaceous: England, Europe, Asia, N. Africa. Diplopodia is very interesting in the construction of the ambu- lacral plates, which, when compound, are “ diadematoid ;” on the other hand, Pedinopsis, according to De Loriol, has the middle plates of its compounds formed upon the ““Hchinus”’ type first described by J. Miiller. Genus Preptnopsts, Cottfeau, 1863, Ech. Foss. de Pyrén., Extr. de Congr. Sct. de France, 28 Sess. Bordeaux, p. 16; 1879, Ech. Foss. del Algér. fase. 5, p. 207 (P. Desori). De Loriol, 1887, Faune Orét. du Port., Ech. fase. i. p. 53, pl. x. figs. 7, a, 0. Test moderate, thin, tumid, subconical, flat actinally. Ambulacra moderately wide ; pairs of pores biserial throughout, or polyserial at the peristome, or uniserial at the ambitus ; inter- poriferous area with two or more vertical rows of small perforate and crenulate primary tubercles; the compound plates high, numerous, and the middle plate of each arranged with the others — upon the “Echinus”’ type. Interradial areas with numerous plates not much higher than the compound ambulacral plates, with several or numerous rows of small distant primary tubercles, resembling those of the am- bulacra and diminishing in number abactinally. Peristome with feeble branchial incisions. Fossil. Cretaceous: England, Europe, N. Africa. Genus Acantuecuinus, Duncan & Sladen, 1882, Pal. Ind. ser. xiv., Hoss. Ech. W. Sind, pt. 1i. p. 34, pl. viii. Test turban-shaped, flat actinally. Ambulacra convex from side to side, one half of the breadth of the interradia, with two vertical rows of primary tubercles ; pores im numerous pairs, diplopodous apically, in single series actinally, very numerous, close, from five to eight pairs to a compound plate ; zone narrowest actinally, slanting from the interporiferous GENERA AND GROUPS OF THE ECHINOIDEA. 69 areas. Every compound plate has not a tubercle, for smaller wedge-shaped compound plates intervene between those with tubercles. Interradia with sunken median areas ; plates distinctly sutured and high. Primary tubercles of both areas well developed, some on raised areolz, all with a broad-based conical boss, largely cre- nulated, with ridges passing down their tall flanks, and a small imperforate mamelon. Secondary tubercles and granules sharply pointed and spiny. The apical system and peristome of the species of this inter- esting group are lost. Fossil. Eocene: Asia, W. Sind. The place of this genus must be provisionally with the Dia- dematide. Genus Paymecuinus, Desor, 1858, Synopsis, p. 133, pl. xvii. bis. Test rather large, tumid in marginal outline, subhemisphe- rical, and depressed abactinally, broad, flat, and slightly tumid actinally. Coronal plates numerous. Apical system small; madreporite large; basals unequal, some radial plates entering the periproctal ring. Ambulacra straight, rather broad, especially actinally ; pairs of pores diplopodous, close vertically, crowded at the peristome ; plates compound, with at least five pairs of pores. Interpori- ferous areas with two vertical rows of large, projecting, plain, imperforate primary tubercles, with many surrounding granules, extending from the peristome to the apex. Interradia broad, with two very prominent vertical rows of primary tubercles, resembling in structure those of the am- bulacra, but larger, with four rows of small secondary tubercles, extending nearly to the peristome and diminishing above the ambitus. Peristome very large, decagonal, with very decided branchial incisions ; interradial lips small. Fossil. Oolite : Europe. Genus Astpropsis, Cotteau, 1883, Bull. Soc. Zool. de France, sér. 2, vol. vill. p. 450. Test of moderate size, circular in ambital outline, swollen 70 PROF. P. M. DUNCAN'S REVISION OF THE above, depressed and subpulvinate actinally. Apical system wanting, large. Ambulacra with two vertical rows of small, imperforate, cre- nulate, primary tubercles; poriferous zones straight, the pairs biserial to below the ambitus, in barely oblique triple combina- tions, not increasing near the peristome. Interradia with abactinal bare median areas, broad, with two vertical rows of small distant primary tubercles resembling the ambulacral, with large bosses and small mamelons, all diminishing abactinally, scrobiculate ; small crenulated secondaries between the primaries and the poriferous zones; granules abundant around the tubercles. Peristome sunken, subcircular. Spines slender, elongate, cylindrical, marked throughout with granular coste, which are regularly placed; the ring is crenulated. Fossil. Upper Cretaceous: Europe. Genus Diptotaema, Schliter, 1871, Zeitsch. f. d. ges. Naturw. (Giebel), n. F., Bd. iv. p. 339. Zittel, 1879, Paleontol. Bd. 1. Lief. ii1. p. 509. Test thick, high, conical, spheroidal. Apical system small, with a narrow ring. Ambulacra broad; pairs of pores biserial, and with from five to eight pairs to each tubercle-bearing plate ; plates compound. Tubercles similar in both areas, plain, numerous. Peristome small, central ; branchial incisions small. Fossil. Cretaceous: Europe. Genus Micropréa, A. Agassiz, 1879, Proc. Amer. Acad. vol. xiv. p- 200; Report on ‘Challenger’ Echini, 1881, p.67. Duncan, 1885, Journ. Linn. Soc. (Zool.), vol. xix. p.110, pl. 5. fig. 11. Test large, thin, flat actinally, with a rather sharp circular or subpentagonal ambitus, arched upwards towards the low flattened abactinal surface, broader than high. Apical system central, with a small periproct, its membrane with small plates, with miliaries ; anal opening minute. Basals uniform, largely perforate, angular towards the interradia. Madre- porite in the usual basal. Radial plates all entering the narrow periprectal ring, concave at the distal edge where the pore is situate. GENERA AND GROUPS OF THE ECHINOIDEA. id Ambulacra narrow, with two vertical rows of perforate, plain, primary tubercles; the poriferous zones with diplopodous pairs, which are numerous, close vertically, distant horizontally, and regular. Plates numerous, low, broad, composed above the ambitus, as elsewhere, of three small plates; the adoral and aboral are low broad demi-plates and the middle plate is a primary which carries the tubercle and occupies the median suture. Pairs of pores of a compound plate really in low broad triplets ; only every alternate compound plate has the adoral pair of pores nearest to the ambulacral median line. Interradia with many low broad plates, with many vertical rows of perforate primaries slightly larger than those of the ambulacra, ceasing at the ambitus, and largest there ; and two rows extend vertically to the apex. Peristome moderate, star-shaped, with broad projecting ambu- lacral ends, having a well-marked branchial incision and a tag on either side, the interradial margins being more pointed and narrower than those of the ambulacra. Peristomial membrane with imbricating plates. Jaws and teeth “diadematoid.” Spines short, slender, and stri- ated above the ambitus, slender and blunt club-shaped actinally. Recent. Philippines, Fiji Islands; 100-600 fathoms. Genus PristopHyma, Péron ff Cauthier, 1881, Ech. Foss. de P Algér. fasc. 8, p. 176, pl. xx. Test moderate, circular at the tumid ambitus, very depressed, nearly three times as broad as high. Apical system large and subpentagonal. Ambulacra narrow, straight, with two vertical rows of imper- forate plain primary tubercles. Poriferous zones with the pairs of pores biserial, actinally and dorsally, and in simple series at the ambitus. Interradia broad at the ambitus, the median area distinct and bare abactinally ; four or five vertical rows of primary tubercles im each (or more); tubercles resembling those of the ambulacra, those next to the median suture the largest and passing up to the apex, rows oblique; plates numerous, low, broad, and oblique, especially at the ambitus. Peristome large, pentagonal; branchial mcisions small. Fossil. Cretaceous: Europe and N. Africa, 72 PROF. P. M. DUNCAN'S REVISION OF THE Cotteau, 1882, Bull. Soc. Géol. de France, sér. 3, vol. x. p. 346, considers the genus to be close to Magnosia, and that there is a species at Martigues; but the structure of the apical system and of the poriferous zones forms a decided distinction. III. Subfamily Pedinine (p. 59). Genus Prptna, Agassiz, 1840, Ech. Foss. de la Suisse, p- 33. Wright, 1855, Pal. Soc., Ech. Ool. Form. p. 171. Duncan, 1885, Quart. Journ. Geol. Soe. vol. xli. p. 433. Test large and moderate, thin, circular orslightiy pentangular in tumid ambital outline, depressed. Apical system small, with nearly equal basal plates and small excluded radial plates ; periproct moderate. Ambulacra narrow; poriferous zones wide; pairs of pores in oblique triserial ranks, really in exceedingly arched triplets. Plates low, crowded, and consisting of three components, each with a pair of pores, the pair nearest the median ambulacral line being in the adoral plate, which is either a long low primary plate ora demi-plate, with its aboral suture convex towards the middle component ; the middle plate of the three is the largest, is a pri- mary, and its pair of pores is nearest the interradio-ambulacral suture ; the aboral plate is either a low primary or a demi-plate, and its adoral suture is convex towards the middle plate, its pair of pores is further from the suture between the interradium and ambulacrum than the pair of the middle plate. Tubercles in two vertical rows; aud they are small perforate primaries. Interradia broad, and with two vertical rows of small primary tubercles resembling those of the ambulacra, extending from peristome to apex, and two or four rows of secondary tubercles, which cease at or above the ambitus. Peristome small and with branchial incisions. Fossil. Oolite: England ; Europe. Subgenus PseupopEpiNa (genus), Cotteaw, 1858, Rev. et Mag. de Zool. sér. 2, vol. x. p. 221; 1884, Pal. Frang., Jura, livr. 66, p- 661, pl. 439. Test subcircular in marginal outline, depressed or subhemi- spherical. GENERA AND GROUPS OF THE ECHINOIDEA. 73 Apical system large, granular, flush; basals large, high, ex- tending into the interradia somewhat; radials small; periproct small, pentagonal. Ambulacra narrow, straight, having distant, large, perforate, non-crenulate primary tubercles on the flat actinal surface and near the ambitus only. Pairs of pores in oblique triplets, the aboral pair being nearest the interradium, and the adoral nearest the median ambulacral line. Plates low, compound, the three components being “ diadematoid” primaries. Interradia with large perforate non-crenulate tubercles dimin- ishing abactinally ; plates high and granular. Peristome large, decagonal; branchial incisions large. Fossil. Oolite: Hurope. The size of the primary tubercles characterizes this subgenus of Pedina. Genus Ecuinorrpina, Cotteau, 1866, Rev. et Mag. de Zool. sér. 2, vol. xviii. p. 362. Syn. Hchinopsis (pars). Test moderate, spheroidal or subspheroidal, flattened above and actinally. Apical system with a narrow ring and a large madreporite ; the posterior radials entering the periproctal ring. Ambulacra broad and straight, with broad poriferous zones, the pairs in decided arcs of triplets, more or less biserial or tri- serial ; a vertical row of perforated, non-crenulate small primary tubercles close to each poriferous zone; small secondaries or large granules nearer the median line. Interradia with two vertical rows of small primary tubercles resembling those of the interradia, the broad median space being occupied by rows of granules or small secondaries. Peristome small, and with branchial incisions fairly developed. Fossil. Hocene: England and Europe; America, Cuba. The arched nature of the triplets of the ambulacra distinguishes Echinopedina from Echinopsis. Echinopedina Gacheti of the French Hocene is the type. Cotteau has described Hchinopedina cubensis from the Eocene of Cuba (Ann. de la Soe. Géol. de Belg. t. ix. Mémoires, 1881, p. 9, pl. 1. figs. 1-6) ; and it only departs from the generic character by having a second vertical row of small primary and some secondary tubercles. The figure 3 of Cotteau’s plate i. shows 74 PROF. P. M. DUNCAN'S REVISION OF THE ambulacral plates near the ambitus, and fig. 4 above the ambitus ; the difference is remarkable. The adoral pair of pores (fig. 4) is nearer the ambulacral median line than the others, as in Lchinothriz. Genus Stomecuinus, Desor, 1858, Synopsis, p. 124. Duncan, 1885, Quart. Journ. Geol. Soc. vol. xli. p. 485. De Loriol, 1887, Fuune Crét. du Port., Ech. fase. i. p- 65, pl. x. Test moderate and large, circular in tumid ambital outline, subconical or subhemispherical dorsally, more or less depressed. Coronal plates numerous. Apical system with large angular basals forming the peri- proctal ring, and projecting into the interradia; radial plates small. Ambulacra moderately wide; at a short distance from the apical system the pairs of pores are in close, oblique, triple series ; three pairs to a compound plate, the adoral pair nearest the inter- poriferous area. A compound plate consists of an adoral and aboral low primary component, the sutures being convex towards the tubercle, and a large median primary carrying the greater part of the tubercle and forming the median sutural angle (diade- matoid). Interporiferous areas with non-crenulate imperforate primary tubercles arranged in two vertical rows, with or without additional rows in the median part. Interradia with a primary tubercle on each coronal plate, similar to, or larger than, the ambulacral tubercles, imperforate and non-crenulate, thus forming two main vertical rows; a varying number of small secondary tubercles and granules on either side of the primary tubercles ; median area may be bare hear the apex. Peristome large, pentagonal; branchial grooves large, with raised rims; ambulacral margins much larger than the interradial. Spines small, short, blunt, striated longitudinally. Fossil. Oolite: England and Europe; America, South. Cretaceous: Europe. ‘s M. de Loriol’s species 8. camarensis (op. cit. p. 65)1s abnormal ; for nothing can be clearer than the “ diadematoid” nature of the ambulacral plates of the British types. The narrowness of the ambulacra of the peristome, the small branchial incisions, and the demi-plates of the ambulacra characterize M. de Loriol’s species, but do not bring it within our idea of Stomechinus. GENERA AND GROUPS OF THE ECHINOIDEA. 75 Genus Microprpina, Cotteaw, 1866, Pal. Frang., Terr. Crét. vol. vii. p. 822, pl. 1197. fig. 8. Stoliczka, 1873, Cret. Fauna of S. India, vol. iv. 3 ser. vii. 3. Eehin. p. 41, pl. vi. De Loriol, 1887, Faune Orét. dw Port., Ech. fase. i. jo> GIL, jolls xe, Test of moderate size, circular in tumid ambital outline, sphe- roidal, depressed actinally, or generally depressed. Apical system small. Ambulacra straight, slightly prominent ; pairs of pores flush, in a narrow zone, either in straight or oblique series of triplets, the adoral pair being remotest from the interradium, and the aboral close to it. Plates low, composed of alow, broad, median primary component, and of adoral and aboral demi-plates, or the adoral may be a primary, the sutures convex towards the tubercles. Interporiferous area with several vertical rows of very small perforate, smooth, primary tubercles, most not reaching the apex. Interradia with numerous low, broad, coronal plates, with very numerous vertical rows of primaries resembling those of the am- bulacra, some of the plates with oblique rows. Rarely more than two vertical rows reach the apex. Peristome small, circular ; branchial incisions small. Fossil. Cretaceous: Europe, N. Africa, 8. India, Asia. The next genus is represented by a very fine species in the Inferior Oolite of France, Heterocidaris Trigeri, Cotteau, and by a small fragment of a probably second species, H. wickense, Wright, from the Inferior Oolite of Yorkshire. But although Cotteau had the advantage of examining a fine specimen which was admirably drawn by Humbert, Wright, under unfavourable circumstances, placed the species in their proper family, and noted the affinities with Astropyga of the recent fauna. Follow- ing Wright, I am able to confirm his judgment in some poiuts, after an examination of the structures of the ambulacra and peristome, Cotteau placed the genus amongst the Cidaride, and distinguished it from any of the Diadematide. TVhiy ig to be regretted because really so much of our knowledge about the form is derived from his excellent work and Humbert’s masterly drawing. Wright missed the points which I would press upon the distinguished French Hchinodermatist, and con- sidered that the narrowness of the ambulacra and width of the 76 PROF. P. M. DUNCAN’S REVISION OF THE interradia and their numerous tubercles allied the forms suffi- ciently with Diadematide and removed them from Cidaride. , I would point out that in Humbert’s figure (Cotteau, Ech. de la Sarthe, Suppl. p. 338, pl. lvi. figs. 1-4) the outline of the margin of the peristome is decagonal, the ambulacral borders bemg very narrow and it is clear that there is a decided branchial cut on either side of the peristomial end of the best preserved ambulacrum. Moreover, there are indications, in the drawing of the peristome, that the perignathic girdle is not after the simple Cidaroid type, The statement of M. Cotteau that the pairs of pores form ares near the peristome is strictly true, aud the figure given by Hum- bert of the component plates of three compound poriferous plates and parts of an upper and lower one on fig. 4 are conclusive in respect of Cotteau’s exactitude. Ifthe upper pair of pores of the fig. 4, pl. lvi. (Cott. op. cit.), be removed and the lowest also (they belong to defective compound plates), it will be evi- dent that three sets of triplets remain, and that each set is in a compound plate made up of three smaller plates, and that the middle one of each carries the tubercle. The thin lines indicate the sutures between the component plates of each com- pound plate; and it will be observed that the middle plate of each is the largest, occupies much of the plate at the tubercle end, which is near the median suture of the ambulacrum, and that its pair of pores is nearer the ambulacro-interradial suture than the other pairs of pores. Then it can be noticed that the adoral suture of the upper pore-bearing plate, in every compound plate, is slightly curved convexity adorally, and that it reaches the median ambulacral sutural line just above the base of the tubercle. The component plate is thus a low pri- mary, and its pair of pores is placed remote from the ambulacro- interradial suture. On the other hand, the aboral suture of the lowest of the pore-bearing plates of each series has its con- vexity directed aborally, and it may noticed that the end of the suture is either at the median line or falls short. In this last instance the plate is a demi-plate; but in either case the pair of pores is situated normally, that is, remote from the ambulacro- interradial suture. Now this arrangement of the plates com- posing a component ambulacral tubercle-bearing plate is essen- tially “diadematoid,’ and is most distinct from that of any Cidaroid. (Duncan, Anat. Amb. Recent Diadematide, Journ. Linn. Soc. (Zool.), vol. xix. p. 96, 1885.) GENERA AND GROUPS OF THE ECHINOIDEA. VLTh The arrangement is represented in the recent forms of Hehi- nothria, to which genus the alliance is greater than to Astropyga. But other distinctions of structure between the genera are evident. The fossil form has not the ambulacra with the width and con- vexity of those of Hchinothrix, and the median interradial area near the apical system is tuberculate in Heterocidaris. Genus Heterocrparts, Cotteau, 1860, Bull. Soc. Géol. de France, sér. 2, vol. xvi. p. 378 ; Ech. Foss. de la Sarthe, Suppl. p. 338, pl. lvi. Wright, 1860, Pal. Soc., Ech. Ool. Form. p. 456. (Amended.) Test large, circular in outline at the tumid ambitus, broader than high, flat actinally, subconvex abactinally. Apical system absent in the specimens. Ambulacra very narrow, straight, not projecting, with two vertical rows of very small perforate and crenulate tubercles. Poriferouszones slightly depressed, narrow; pairs of poresin almost straight series at and above the ambitus, although in triple com- pound plates; near the peristome the pairs of pores are in arcs and oblique ; the tubercle of a compound plate is on the middle com- ponent plate, and the sutures of the adoral and aboral component plates and the middle plate are curved more or less, their con- vexities directed towards the middle plate. Usually the com- ponents are low, broad primaries; but a demi-plate may occur near the actinosome. Interradia very broad and tumid; the plates low and broad, carrying several rows of large, perforate, crenulate and scrobi- culate primary tubercles separated by a rich granulation. The vertical rows diminish above the ambitus; but at least four reach close to the apical system, especially the pair close to the ambulacra, so that the median vacant space is very small and insignificant. Peristome small, decagonal ; ambulacral ends small, with branchial incisions on their flanks. Spines long, cylindrical, striated longitudinally. Fossil. Inferior Oolite: England, Europe. M. Cotteau states that the auricular processes must have been strong. 78 PROF. P. M. DUNCAN'S REVISION OF THE Genus Ecurnorurix, Peters, 1853, Abh. k. Akad. Wiss. Berlin, (1854), p.114. A. Agassiz, 1872-4, Revision, p.418. Dun- can, 1885, Journ. Linn. Soe. (Zool.), vol. xix. pp. 101 and 202. Lovén, 1887, Ech. dese. by Linneus, p.137. (Amended.) “Syn. Garelia, Gray ; Savignia, Desor. Test large, thin, tumid, moderately high, depressed, broad. Apical system large, more or less sunken; basals large and projecting into the interradial spaces ; radials small and entering the ring; the periproct large, with a close pavement of plates. Coronal plates numerous. Ambulacra tumid, narrow, with several vertical rows of very small tubercles, which are crenulate and perforated, diminishing in number actinally ; plates numerous, low, broad, composed of three primaries, with the sutures convex tewards the tubercle ; near the peristome the adoral component is small and excluded from the interradial suture. Pairs of pores large, in close ares, the adoral pair nearest the ambulacral median line, forming, with others, a vertical series. Interradia with a bare median space, sunken, elsewhere several vertical rows of large primary tubercles, crenulated and perfo- rated, scrobiculate, diminishing in number abactinally. Peristome large, with deep branchial incisions and tags ; mem- brane with small plates. Perignathic girdle with very broad, low ridges; processes expanded above, opening large. Jaws with the foramen of the pyramid an open arch, the teeth grooved. Spives slender, long, striated, verticillate, more or less solid. Recent. E. coast of Africa, Pacific Islands, Japan, Philippines, E. Indian Islands, Red Sea. Genus AstropyGa, Gray, 1825, Ann. Phil. vol. xxvi. p. 246. Peters, 1853, Abh. k. Akad. Wiss. Berlin (1854), p. 110. A. Agassiz, 1872-4, Revision, p.417 ; 1881, Report on ‘Chal- lenger’ Echini, p. 72, pl. x. a. fig. 9. Duncan, 1885, Journ. Linn. Soc. (Zool.), vol. xix. p. 106, pl. v. (Amended.) Test large, tumid at the ambitus, depressed, thin, more or less flexible; ambulacra bulging. Apical system large; basals large, triangular, elongate ; radials much smaller, narrow, and entering the periproctal rmg. Mem- brane with circular rows of plates. Ambulacra narrow, convex, with two vertical rows of large, GENERA AND GROUPS OF THE ECHINOIDEA. 79 crenulate and perforate primary tubercles; poriferous zones broad ; plates compound, large, high, composed at the ambitus and actinally of two sets of triplets, each consisting of low, broad primaries, sometimes with a demi-plate, with their sutures curved, convexity towards the tubercles; pairs of pores in oblique sets of three pairs, really in close triplets, the adoral pair of a compound plate being nearest the ambulacral median line and the aboral the most remote. Interradia with a broad median area abactinally, elsewhere with several rows of crenulate and perforate primaries, slightly larger than those of the ambulacra, each with a large flat scrobicule. Coronal plates rather numerous, low and broad, overlapping more or less, pitted inside and some split longitudinally or not. Peristome variable in size; branchial cuts large; membrane with pilates, the largest carrying spines. Jaws small; teeth grooved. Larger spines about one half of the diameter of the test, striated, verticillate. Recent. Panama, Gulf of California, Zanzibar, Philippines, East-Indian Islands. Genus Potycypuus, Agassiz, 1846, Cat. Rais. des Ech., Ann. d. Sci. Nat. sér. 8, vol. vi. p. 361. Desor, 1858, Synopsis, p. 117. Cotteau, 1863, Rev. et Mag. de Zool. sér. 2, vol. xv. p. 261. Test small, subconical or hemispherical dorsally, tumid at the circular ambitus, rather flat actinally. Apical system small; basal plates large and united ; periproct oblique or not. Ambulacra straight, rather wide, with rather broad poriferous zones, which may be sunken; pairs of pores in close and very oblique triplets, triserial abactinally and polyserial actinally ; plates low, compound, “ diadematoid.” Tubercles of the inter- poriferous areas small, plain, in four or more vertical rows, the outer the larger. Tnterradia with numerous low broad plates, each with two horizontal rows of numerous plain tubercles, resembling those of the ambulacra; but one row has small tubercles; usually the tubercles increase in size actinaily ; vertical rows five or more in number. Peristome large, decagonal ; ambulacral lips large; branchial incisions well developed. Fossil. Oolite: England and Europe. 80 PROF. P. M. DUNCAN’S REVISION OF THE Genus Coprcutnvs, Desor, 1858, Synopsis, p.111. Cotteau, Pal. Frang., Terr. Crét. vol. vii. pl. 1198. fig. 6. Test small, tumid, spheroidal, flattish actinally. Coronal plates high. Ambulacra broad; poriferous zones broad; pairs of pores triserial, close, in nearly horizontal triplets: plates compound, low, some of three low: primaries, ‘‘ diadematoid”’; others with a large middle primary, alow aboral demi-plate, which is broad, and an adoral demi-plate which is excluded from the interradial suture. The middle pair of pores is nearest the interradium. Tubercles very small, plain, distributed irregularly, most nume- rous and closest actinally, but few elsewhere. Interradia with the median sutural area rather depressed ; tubercles resembling those of the ambulacra, limited to parts of plates remote from the median line of the area, which is naked. A minute granulation separating the tubercles of both areas. Peristome small, central, diagonal. Fossil. Cretaceous: Europe, N. Africa. IV. Subfamily Orthopsine (p. 59). Genus Ortuopsts, Cotteau, 1863, Pal. Franc., Terr. Crét. vol. vi. p- 550. Stoliczka, 1873, Pal. Ind., Cret. Fauna 8S. India, vol. iv. 3. vil. ser. 3, Hchin. p. 45, pl. vu.. De Loriol, 1887, Fawne Crét. du Port., Ech. fase. i. p. 46, pl. viii. Test moderate in size or small, depressed, circular or slightly pentagonal in ambital cutline, tumid dorsally, flat actinally. Apical system with five perforated basals; madreporite well developed; radial plates, all or some entering the anal ring, which is variable in outline. Ambulacra much narrower than the interradia, straight ; pairs of pores numerous, in straight series; poriferous zone narrow; plates simple, low, primaries dorsally, but near the ambitus and _ actinally two primaries may combine, and the suture passes transversely through the interporiferous tubercle. Tubercles of the ambulacra small, perforate, and smooth; two vertical LOWS. Interradia with several vertical rows of small primaries re- sembling those of the ambulaera, or slightly larger, some reaching up dorsally. ! Peristome moderate, with well-developed branchial incisions ; GENERA AND GROUPS OF THE ECHINOIDEA. 81 perignathic girdle with ridges and processes which unite and form a small arch. Fossil. Oolite: England, Europe. Cretaceous: Europe, N. Africa, Hindustan. Eocene: Egypt. De Loriol has shown that Hemipedina Semanni, Wright, 1855, is an Orthopsis. Genus HopIADEMA, gen. nov. Test small, thin, circular intumid marginal outline, subconical dorsally, tumid and re-entering actinally, broader than high. Apical system moderate in size, ovoid or elliptical in the out- line of the periproct ; five large basal plates, four in contact and the fifth or posterior separated from its fellows, on either side, by a radial plate. Ambulacra narrow, ‘straight, wider than the interradia at the peristomial margin, narrower elsewhere ; poriferous zones narrow ; the pairs of pores numerous, in simple vertical series, barely any crowding near the peristome ; plates all low, broad primaries ; interporiferous areas rather broad, crowded with blunt granules dorsally, some larger granules near the poriferous zones, and giving place at the ambitus to some very small crenulate and perforate tubercles which diminish actinally. Interradia broad; plates not numerous, broader than high ; two vertical rows of perforate, crenulate and scrobiculate pri- mary tubercles in each area, a few large at the ambitus and becoming rapidly very small dorsally, or replaced by distinct, large, crowded granulation, diminishing also actinally. Scro- bicules large at the ambitus, and usually coalescing. A large, blunt, very marked granulation occurs beyond the scrobicules on each plate, and also on all the plates up to the apex, except at an aneular space contiguous with each basal plate, and extending downwards, variously, along each median line, where there are no granules, but a plain surface. Peristomial edge small and pointed. Peristome sunken, decagonal, small, and with well-marked branchial incisions. Fossil. Middle Lias: England. This is a most interesting genus; and the species Hodiadema granulata was discovered by H. Wilson, Esq., F.G.S., of the Bristol Museum. The alliance is very close to the Orthopside, although LINN. JOURN.—ZOOLOGY, VOL. XXIII. 6 82 PROF. P. M. DUNCAN'S REVISION OF THE they have smooth tubercles as a rule. It is the single primary plates of the ambulacra without any compound ones, coupled with the small tubercles of the ambulacra and the few large primaries near the ambitus, all the rest of the test being granular, that sepa- rate the type from Hypodiadema and Hemicidaris and Diadema. It is very interesting to find such a simple form so low down in the Mesozoic series, and it may well have been the precursor of the genera just mentioned. The similarity of the genus to Aero- salenia is striking ; but there is evidence that the sur-anal plates were not present. If more was known about Hypodiadema, the alliance of the new genus with the oldest Mesozoic forms would be very defi- nite; but the good drawings of Desor and other describers show that the interradia of the genera differ considerably. MM. Péron and Gauthier have described Cyphosoma Heinz, and notice its abnormal nature; and they consider that had it been placed in Psewdodiadema it would have been equally erratic. Probably the classificatory position is near Orthopsis, for the pairs of pores are in simple, low, primary plates. I have diagnosed a new genus for the form, and dedicate it to M. Péron. Genus PERONIA, gen. nov. Syn. Cyphosoma, Cotteau, Péron et Gauthier, 1884, Ech. Foss. de P Algérie (2nd edit. of fase. 2), p. 96, pl. ix. Test small, circular in tumid ambital outline, very depressed. Apical system annular, pentagonal, symmetrical; periproct large, circular ; basal plates equal, broad, low, perforated largely ; radial plates small, all entering the ring and reaching the peri- proct, the margin of which is slightly raised. Ambulacra narrow, with narrow poriferous zones, the pairs not numerous, and in simple vertical series throughout, each in a low primary plate. Interporiferous areas with small granules only. Interradia broad, with only seven coronal plates on a side, with as many crenulate, imperforate and scrobiculate tubercles, largest at the ambitus, the rest of the plate granular ; secondary tubercles absent. Peristome large, decagonal, the branchial incisions with everted edges. Fossil. Cretaceous (Neocomian) : Algeria. GENERA AND GROUPS OF THE ECHINOIDEA. 83 Cyphosoma Heinzi thus becomes Peronia Heinzi, Péron et Gauthier, sp. Genus Ecurnopsts, Agassiz, 1840, Catal. Syst. Hctyp. Ech. p. 18. Desor, 1854, Synopsis, p. 98 (pars). De Loriol, 1881, Koc. Ech. aus Aigypt. uv. d. Lib. Wiiste, Paleontographica, nu. F. ods (09%) opal: Test thin, small or moderate in size, hemispherical, or sub- conical and tumid abactinally, rather flat actinally. Apical system narrow, the basals unequal; the radials small and close to the periproct, but not forming its ring. Periproct large. Ambulacra large, straight, flush with the test; pairs of pores in simple straight series ; plates compound, triple, or quadruple, made up of low broad primaries; tubercles very small, close, perforate and non-crenulate, extending the whole length of the ambulacrum in two vertical rows placed near to the poriferous zones. Interradia with two vertical rows of small primary tubercles, slightly larger than, but otherwise similar to, those of the ambu- lacra; minute granules surrounding the non-sunken scrobicules. Sutures of the plates distinctly seen. Peristome small, slightly depressed ; branchial incisions slight. Fossil. Hocene: Europe, Egypt. Hichinopsis Edwardsi, Forbes, of the London Clay, is an EHchinopedina. Genus Gymwnopiapema, De Loriol, 1884, Recueil Zool. Suisse, vol. i. No. 4, p. 606. Test thin, tall, swollen, moderate. Apical system flush ; the madreporite triangular, slightly deve- loped; radial plates small. Ambulacra narrow; poriferous zones straight, with regularly superimposed pairs of pores in simple series; the plates very numerous, low, narrow primaries; interporiferous areas very narrow, have abactinally very small granules, which are barely visible to the naked eye, yet forming vertical series; they are replaced actinally by very small tubercles with perforate mamelons. Interradia very broad, covered with granules like shagreen; 6* 84. PROF. P. M. DUNCAN’S REVISION OF THE near the peristome there are some small tubercles, which are perforate and scrobiculate ; they are more developed than those of the ambulacra. Peristome (wanting) probably small. Fossil. Oolitic: Europe. The drawing of the solitary species given by De Loriol shows a globose test longer than broad, and very minutely granular ; the increased size of the ornamentation actinally is very charac- teristic. Genus incerté sedis. Genus Progonecuinus, Duncan and Sladen, Pal. Ind. sev. xiv., Foss. Ech. W. Sind, p. 438, pl. x. figs. 1-4. Test small, moderately high, subhemispherical, concave acti- nally ; margin circular and tumid. Apical system absent. Ambulacra narrow, with straight poriferous zones having numerous pairs of pores directly superposed and close. The plates compound, the adoral component a low broad demi-plate, the middle a large primary plate carrying two small tubercles, and the aboral component a low broad primary ; sutures grooved and distinct; tubercles plain, in two vertical series on each side of the median line, others near the ambitus; low granules often forming ridges. Interradia broad; plates low; two persistent vertical rows of plain scrobiculate primaries larger than those of the ambulacra ; at the ambitus two or more vertical rows occur besides, but are lost actinally and dorsally. Large granules with mamelons oceur, and a row near each poriferous zone has coste passing towards the pairs of pores and also to the scrobicules of the neighbouring primary tubercles. Grooves along the upper and lower sutures of the interradial plates near the median line. Peristome circular; branchial incisions well developed, with thick everted margins. Fossil. Hocene: Asia. This is a very synthetic genus, and links the Diadematide and the Temnopleuride. GENERA AND GROUPS OF THE ECHINOIDEA. 85 V. Family CyPHoSoMATIDA. Test moderate in size, circular or subpentagonal in tumid marginal outline, depressed, rarely subconical, highly orna- mented ; plates moderate in number or numerous. Apical system very variable in size, shape, and structure, com- pact, or with some or all radials intervening between the basgals, and the posterior basal intruding upon the posterior inter- radium; with the periproct posterior, and its plates either few or numerous and hexagonal ; arms posterior; the madreporite in the right anterior basal. Ambulacra with high compound plates, with from three to seven pairs of pores in an arc; near the apical system, and ex- tending variously actinally, a biserial arrangement of the pairs, or not; pairs crowded or not at the peristome. The adoral and supra-adoral components are primaries, and the others demi- plates. Two vertical rows of primary tubercles. (Duncan, 1885, Amb. Foss. Ech., Quart. Journ. Geol. Soe. p. 447.) Interradia usually depressed dorsally, with bare median spaces ; rows of tubercles variable in number, larger than those of the ambulacra. Peristome moderate and large, with branchial incisions. Spines long and short, solid, some as needles; striated longitudinally. This family subdivides with difficulty; and the two groups of it are not of subfamily value. Division I. Genus Cyphosoma. Subgenus Leiosoma. Genus Coptosoma. Gauthieria. Thylechinus. Division II. Genus Micropsis. Subgenus Gagaria. Division I. Species with and without a diplopodous poriferous arrange- ment cannot be placed in the same genus; and therefore only the diplopodous species remain in the genus Cyphosoma as now constituted. Moreover, the genus now includes the species with the apical system encroaching upon the posterior inter- radium. Cotteau has-found the details of the apical system ; and 86 PROF. P. M. DUNCAN’S REVISION OF THE the typical arrangement is seen in C. Delmarrei, Pal. Frang., Terr. Crét. vol. vii. pl. 1140; see also C. Foukanense, Péron & Gauth. Foss. de l Algér. fase. 7, pl. vi. fig. 8. Genus CyrpHosoma, Agassiz, 1840, Catal. Syst. Ectyp. Ech. p. 19. Desor, 1858, Synopsis, p. 86. Wright, 1869, Pal. Soc., Foss. Cret. Ech. vol. i. p. 128. A. Agassiz, 1873, Revision, p. 487. Duncan & Sladen, 1882, Pal. Ind. ser. xiv., Foss. Ech. W. Sind, p. 31. Duncan, 1885, Quart. Journ. Geol. Soc. vol. xli. p- 447. J. Lambert, 1888, Bull. Soc. d. Sci. Nat. de ? Yonne, 1 Semestre. Syn. Phymosoma, Haime. Test moderate in size, tumid at the circular or slightly poly- gonal ambitus, swollen but depressed dorsally and actinally, broader than high. Coronal plates few, their sutures distinct superficially. Apical system large, with five basal plates; the madreporite in the usual plate, and all or some of the radial plates entering the periproctal ring, the posterior basal thrown more or less back- wards and intruding upon the posterior interradium. Ambulacra with well-developed poriferous zones, undulating ; pairs of pores diplopodous abactinally, and in ares of from four to six or more pairs, and more crowded still at the peristome ; plates compound, high, formed of an adoral, a supra-adoral, and an aboral primary component, the other plates of the compound being demi-plates ; the direction of the sutures of the primary plates of the compound is convex towards and on the boss of a large tubercle, the sutures usually being visible on its flanks. Two vertical rows of primary tubercles. Interradia large, with two or more vertical rows of primary tubercles equal to or larger than those of the ambulacra and similar in their constitution, being imperforate and crenulate. Secondary tubercles exist, and small tubercles or granules in large numbers, the median areas often bare for some distance from the apical system. Peristome small or moderate ; branchial incisions well marked. Spines solid, long, subcylindrieal, aciculate, or spathiform, straight or bent spoon-shaped, striated or smooth; milled head and acetabular cuts distinct. Fossil. Oolite: Europe. Cretaceous: England, Europe, N. Africa, Asia. Eocene: Asia. GENERA AND GROUPS OF THE ECHINOIDEA. 87 Subgenus Lriosoma, Cotteaw & Triger, 1859 (genus), Ech. du Dépt. de la Sarthe, p. 271 ?, pl. xlv.; 1881, with Péron et Gauthier, Ech. Foss. de lV Algér. pt. 2 of fase. 8, p. 141, figs. 7-11. Syn. Gomphechinus, Pom.; Micropeltis, Pom. The primary tubercles are plain, and neither crenulate nor perforate. Pairs of pores biserial throughout, or not so at the ambitus ; several rows of interradial primary tubercles, or two only. . Fossil. Oolitic: Europe. Cretaceous: Europe and N. Africa. Genus Coprtosoma, Desor, 1858, Synopsis, p. 91. Duncan & Sladen, 1882-86, Pal. Ind. ser. xiv., Foss. Ech. W. Sind, pp. 116-117, pl. xx. Duncan, 1885, Quart. Journ. Geol. Soe. vol. xli. p. 447. Lambert, 1888, Bull. Soc. d. Sct. Nat. de V Yonne (extrait), p. 7. Syn. Cyphosoma (pars). Test moderate, subconical, or depressed dorsally, tumid at the ambitus. Coronal plates few in number. Apical system flush, intruding somewhat upon the posterior interradial spaces ; one or more radial plates may enter the sub- circular or deformed periproctal ring ; periproct somewhat thrown back. Ambulacra with uniserial pairs of pores, and in ares throughout ; plates formed of more than three components, uniting after the Cyphosomatoid type. Interradia with two vertical rows of primary tubercles, crenu- lated, and with several small secondaries upon each broad and comparatively low plate, larger than or of the same size as the primaries of the ambulacra; sutures may be visible, and the tubercles may be deficient dorsally. Peristome moderate to large, with branchial incisions. Fossil. Cretaceous: Europe, N. Africa, N. America. Eocene: Europe and Asia. Recent. Japan. The genus differs from Cyphosoma,; for it is not diplopodous, and the poriferous plates have more than three components. It appears that very probably the recent Phymosoma=Cyphosoma crenulare, A. Ag., and also De Loriol’s C. Mortoni, should come 88 PROF. P. M. DUNCAN'S REVISION OF THE in here. Unfortunately the name of the genus refers to cuts or sutural impressions upon the tubercles; and these are not cha- racters of any importance. The fine Sindian forms of Cyphosoma macrostoma, Dunc. & Slad., and C. undatum, Dune. & Slad., are now species of Coptosoma. C. Joudi, Péron et Gauth., should enter. The genus Microsoma, Cotteau, 1886, Bull. Soc. Zool. de France, vol. xi. p. 715, is so doubtful on account of the bad condition of its specific type, that it is simply recorded. Genus Gauruterta, Lambert, 1888, Bull. Soc. d. Sci. Nat. de lV Yonne, 1 Semestre (extrait), p. 7. Syn. Cyphosoma (pars). Test moderate, subcircular or subpentagonal, moderately tumid. Apical system largely developed, pentagonal, with the posterior angle extending well into the corresponding interradium; the basal plates unequal ; the madreporite in the largest and anterior lateral basal; the other lateral basals more or less hexagonal, and at the angles of the system the posterior basal forming a narrow rim to the posterior angle, and limiting the posteriorly excentric anus; radial plates large, all entering and separating the basals. Periproctal area large, and occupied by seven or more hexagonal plates, forming a closed area anterior to the circular anus. Spines long, cylindrical, finely striated longitudinally. Fossil. Cretaceous: England and Europe. In one solitary instance this remarkable apical system has been preserved and described, thanks to M. Lambert; in all others there is only a large vacant space. The genus includes the former Cyphosoma radiatum, Sorginet (subradiatum), 1850, and its synonyms C. simplex and C. spatulifera, Forbes, and C. perfectum, Cotteau. M. Lambert has founded a genus, or rather suggests the recog- nition of a genus of M. Pomel for Cyphosoma pe and C. Said and many others. In agreeing with M. Lambert’s intelligent scheme, fo 1s neces- sary to draw attention to M. Pomel’s definition, which contains the statement that the upper part of the “interambulacrales ” is more or less depressed “ en gouttiere ”’ in the males, and hollowed GENERA AND GROUPS OF THE ECHINOIDEA. 89 “en marsupium ” in the females. This is not quite capable of veri- fication ; but it has nevertheless originated the name of a genus, Thylechinus. Genus THytecuinus, Pomel, 1888, Théses, Class. Méth. p. 91. Lambert, 1888, Extr. Bull. Soc. d. Sci. Nat. de? Yonne, p. 11. (Amended.) Syn. Cyphosoma (pars), Cott., Pér. et Gauth. 1881, Ech. Foss. de PAlgér. fasc. 8, p. 172, pl. xix. figs. 8-10 (Cyphosoma Said). Test with a compact symmetrical apical system ; radial plates excluded. Ambulacral plates having three components and three pairs of pores in simple series only. Pairs of pores uniserial throughout ; the interporiferous areas with two vertical rows of crenulated tubercles smaller than those of the interradia. Interradia with two vertical rows of large primary tubercles crenulated. ‘The median areas more or less depressed dorsally. Peristome large ; lips unequal ; branchial incisions slight. Fossil. Cretaceous: Europe, N. Africa. For the generic position of Cyphosoma Heinzi, Pér. et Gauth., see p. 83. Division II. The genus Micropsis, Cotteau, 1855-56, was diagnosed so as to include WZ. Desori, which has four vertical rows of ambulacral tubercles, and the pairs of pores in arcs of four; the interradial plates very wide and rather low, with a primary tubercle and three small primaries on one side, and two on the other on each plate. There is no doubling of pairs, and the branchial incisions are small; but the number of coronal plates is great. It is like a Coptosoma with a considerable number of coronal plates. A species, Micropsis microstoma, has three vertical rows of tubercles and five or six pairs of pores in ares, toa plate. Again, MW. Leymerii has only two pairs of vertical rows of tubercles and three pairs of pores to a plate. All the radial plates enter the apical ring. We do not understand how I. globosa, Cott., and M. leridensis, Cott., can be associated with the type species in the same genus. The Mcropsis we described from the Nummu- litic of Sind has many of the characters of, but the structure of the ambulacra differs from, M. Cotteau’s type. 90 PROF. P. M. DUNCAN’S REVISION OF THE M. de Loriol (Ours. Tert. de la Suisse, Pal. Soc. Suisse, 1875, vol. ii. p. 16) considers Micropsis to be synonymous with the Cyphosomatoids with uniserial pairs of pores (Coptosoma); but the height of so many of the tests of Micropsis, the considerable number of the coronal plates, and the small size of the primary tubercles are distinctive. Nevertheless it is evident that not only are there species of Coptosoma in Cotteau’s list of Micro- psides, for instance I. leridensis, but some require elimination from the family, for instance WZ. Vidali, Cott., which is alto- gether aberrant. The ambulacra of the species with four pairs of pores to a compound plate, such as the type species JZ. Desori, have not the component plates of their symmetrical compound plates arranged as in the genera Cyphosoma and Coptosoma; on the contrary, the arrangement resembles that of the species of Placodiadema (p. 64), which have numerous components to an ambulacral plate. The compound plate is high, and is composed of a small, low, broad adoral primary, very low at the median suture of the compound plate; or it may be a demi-plate ; next comes a large primary, comprising most of the tubercles and the angle of the median suture; then succeed aborally, two low broad primaries, their adoral sutures beg rather curved, convexity adorally. (See Quart. Journ. Geol. Soc. vol. xl. p. 431, fig. 8.) This arrange- ment may also occur when there are five pairs of pores toa com- pound plate; and then the last pair of pores is in a low broad primary, which resembles the aboral primaries of the other plate. This kind of arrangement is not seen in any species of Cyphosoma; and therefore there is a good physiological difference between the species with numerous pairs of pores and those with few which have been included in MMicropsis and Cyphosoma or Coptosoma. The species with three pairs of pores in an ambulacral plate may be grouped around Micropsis venustula, Dunc. & Sladen, 1884, Pal. Ind. ser. xiv., Foss. Ech. Sind, p. 119, pl. xxii. figs. 1-7. The apical system has large basal plates ; a radial enters the ring, and the periproct is large and deformed ; the amulacra are narrow, and have two vertical rows of small perforate and crenulate pri- mary tubercles and two vertical rows of secondary tubercles ; the plates are high and compound; the adoral plate is a large primary carrying the bulk of a tubercle, and the other plates, placed aborally to it, are low broad primaries. The difference GENERA AND GROUPS OF THE ECHINOIDEA. 91 between this arrangement and that already noticed is that in the instance of the plates with more than three pairs of pores the adoral primary is added, as it were, to the compound. The interradia have only two vertical rows of primary tubercles, very slightly larger than those of the ambulacra; and there are two vertical rows of small secondary tubercles. Micropsis Leymerii, Cott., and IL. d’ Orbignit, Cott., appear to be associated with this Sindian species in a little group which is hardly worthy of more than a subgeneric title (see Gagaria). A new genus or subgenus is required for MZ. Vidalz, Cott. ; for as we define the species it is a Psammechinus with crenulate tubercles. Having made these necessary remarks, we proceed to give the diagnosis of MMicropsis, which is transitional between the Cyphosomatide and the Diadematide. Genus Microprsts, Cotteau, 1855, Ech. Foss. des Pyrén., Bull. Soe. Géol. de France, sér. 2, vol. xiii. p. 826; 1882, Bull. Soc. Zool. de France, vol. vii. p. 411. Duncan and Sladen, 1884, Pal. Ind. ser. xiv., Foss. Heh. of Sind, p. 119. (Amended.) Test of variable size, circular or slightly polygonal in tumid marginal outline, tumid dorsally, subconical, subhemispherical or depressed, concave actinally. Apical system flush, with a large periproct, large basals, and one or more of the radial plates may or may not enter the ring. Coronal plates rather numerous. Ambulacra with small primary tubercles, perforated and cre- nulated, in two or more vertical rows ; pairs of pores from three to five in number ; plates compound ; the aboral components low and broad, with adoral sutures convex adorally, and the adoral component a large primary carrying the tubercle ; alow primary or a demi-plate may or may not form the lowest part of the com- bination. Interradia with many or few vertical rows of primary tubercles and secondaries. Peristome small; branchial incisions well developed. Spines slender, long, subcylindrical, striated longitudinally, sharp. Fossil. Cretaceous: Europe. Eocene: Europe, Asia, Egypt. Subgenus Gagaria, Duncan. Syn. Micropsis (pars). Tests with two vertical rows of primary tubercles in each area, 92 PROF. P. M. DUNCAN’S REVISION OF THE and with only three pairs of pores in each compound ambulacral plate. Fossil. Cretaceous: Europe. Eocene: Asia (Sind). The specific type is Gagaria (Micropsis) venustula, Dune. & Sladen, 1884, Pal. Ind. ser. xiv., Foss. Ech. W. Sind, pt. ui. p- 119, pl. xxii. figs. 1-7, from the Nummulitic. M. Lambert, 1888, Bull. Soc. d.Sci. Nat. de Yonne (extrait), contains some excellent remarks bearing upon M. Pomel’s sub- division of Cyphosoma. VI. Family ARBAcIIDz, Gray. (Amended.*) Test moderate in size, subhemispherical or subconical, depressed dorsally, flat actinally; epistroma with granules, projecting ridges, grooves, sessile glassy knobs, elongate or rugose, and tall, especially on the bare dorsal interradial median areas. Apical system large; the periproct oval and oblique; the periproctal plates four, rarely more, triangular; the radial pores adoral, double. Ambulacra straight, narrow, expanding near the peristome ; pairs of pores simple or in large arcs, or crowded actinally ; the plates compound near the ambitus, the middle component a large primary ; the adoral and aboral being demi-plates with very curved sutures, their direction being nearly vertical towards the ambulacral median line ; or the primary is adoral and the demi- plates are aboral to it. Interradial plates with several or few vertical series of primary imperforate, non-crenulated tubercles, usually larger than those of the two rows of the ambulacra; with expanded bosses. Ten- tacles heteropodous. Spheridia solitary or numerous. Peristome large, incurved at the sides of the ambulacra, and with branchial tags. Teeth keeled. Jaws with the pyramidal foramen open above. Plates united along the vertical sutures by dowelling, some of the projections may be large and lamellar. Genus Arbacia. Echinocidaris (gen. noy., non auct.). Ceelopleurus. Podccidaris. * For the structures noticed in this definition, see Duncan and Sladen, Journ. Linn. Soe. vol. xix. 1885, pp. 25 e¢ seg.; and Lovén, 1887, Ech. deser. by Linnzus, pp. 80 eé seg. GENERA AND GROUPS OF THE ECHINOIDEA. 93 Genus Arpacta, Gray, 1835, Proc. Zool. Soc. p. 58. Troschel, 1872, Arch. f. Naturg. vol. xxxvill. p. 298; 1872, vol. xxxix. p. 808.