ME. J. ^y. GREGOET Ol^r AECHJEOPNETTSTES ABETJPTT7S. 165 



1847 L. Agassiz^ founded a genus Astei^ostoma for a species (of what 

 he regarded as the same as Lamarck's Chjpeasier excentriciis)^ which 

 combined the reduced anterior ambulacrum of the Spatangoidea 

 Avith the central mouth of the Cassiduloidea. With the exception 

 of various expressions of opinion as to the proper systematic position 

 of the genus, nothing material was added till in 1871 M. Cotteau 

 described two species of large Echinoidea which he assigned to the 

 same genus, owing to the great resemblance in the structure of the 

 abactinal surface, and the fact that they came from the same 

 locality/ Unfortunately no figures were given of the peristome, 

 and some palaeontologists subsequently concluded that it was on 

 the same plan as in the typical species, in spite of M. Cotteau's 

 statement that the mouth was bilabiate and anterior. Thus Prof. 

 A. Agassiz* seems to have been greatly impressed with the resem- 

 blance of M. Cotteau's species to an Echinoid dredged off Barbados, 

 which served as the type of his genus Palceopneustes ; he remarked 

 that these differ " only in the absence of actinal ambulacral furrows 

 and in having a labiate actinostome instead of the pentagonal 

 sunken mouth represented in the poorly preserved specimens of 

 Asterosto7na" As in the type of this genus the mouth is central 

 and non-labiate, Prof. A. Agassiz's genus is valid, but he left the 

 two species described by M. Cotteau, to which his own are closely 

 aUied, in the old genus. ^ The first recognition of the importance 

 of the difference of the mouth was by P. Martin Duncan^ in his 

 Revision, where he made a new genus, Pseudasterostoma, for 

 the larger of M. Cotteau's species (A. Jimenoi) ; the other species 

 {A. cuhense) was still left in Asterostoma, but as M. Cotteau has 

 kindly given me a sketch of the peristome of that species (repro- 

 duced in PI. lY. fig. 6) it must also be separated from the genus. 

 Both Asterostoma and Pseudasterostoma were left by Martin Duncan 

 in very close alliance, and associated with some remarkable extinct 

 genera in a new family — the Plesiospatangidoe ; this was included 

 in the order Cassiduloidea, though forming a connecting link with 

 the Spatangidce; the two genera were thus separated far from 

 Pcdceopneustes. Duncan does not seem to have compared them 

 closely with the living genus. 



A short time ago an Echinoid was received from Mr. G. Eirth 



^ In Agassiz and Desor,/ Catalogue Haisonne des families, des genres, at des 

 especes de la classe des Echinodermes.' Ann. Sci. Nat., Zool. ser. 3, t. vii. 

 p. 168. 



^ ' Histoire naturelle des Aniniaux sans Yertebres,' t. iii. (1816) p. 15. 



3 ' Notice sur le genre Asterostoma.' Mem. Soc. geol. Fi-ance, ser. 2, t. ix. 

 (1871) pp. 177-184, pis. xvi. and xvii. For preliminary notice of these, see Bull. 

 Soc. geol. France, ser. 2, t. xxiv. (1867) pp. 826, 827 ; and also ' Sur le genre 

 Asterostoma. de la lamille des Echinocorydees,' Compt. Kend. toI. Ixx. (1870) 

 pp. 271-273. 



4 'The Echini collected on the Hassler Expedition,' Bull. Mus. Comp. 

 Zool. vol. iii. no. 8 (1873) pp. 188, 189. 



^ 'Eeport on the Echini,' Keports, Expedition of the 'Blake,' no, xxir. 

 pt. 1. Mem. Mus. Comp. Zool. vol. x. no. 1 (1883) p. 91. 



^ ' A Revision of the Genera and great Groups of the Echinoidea,' Journ. 

 Linn. Soc, Zool. vol. xxiii. (1889) pp. 201-204. 



