166 aiR. J. W. GKEGOEY ON ARCHJEOPNEUSTES ABEUPTUS. 



Franks, to whom the British Museum is indebted for a valuable 

 collection of fossils and rocks from Barbados. The specimen was 

 collected by Mr. Franks in a bed belonging to the Oceanic Series at 

 Bissex Hill. It was obvious that it belonged to the genus Palceo- 

 'pneustes^ but the whole appearance of the abactinal surface was 

 so much like that of A. cubense, Cott., that I was led to ask 

 M. Cotteau for further information about the j)eristome of that 

 species. M. Cotteau's sketch shows that it is on the normal 

 spatangoid type, and that it agrees in all essential respects with 

 the new species from Barbados and with Palcvopneustes liystricc^ 

 A. Ag.^ The new species, the two fossil species from Cuba, and the 

 two recent species also from the West Indies, may all be described as 

 irregular, nodostomatous, adete Echinoids, in which the peristome 

 is anterior and bilabiate, the periproct on the low posterior vertical 

 margin, and the anterior ambulacrum reduced. This definition 

 includes a sufficient series of characters to show that the five 

 species are in very intimate alliance. There are, however, two 

 points of difi^erence : three of the species (cubensis, liystrix^ and 

 abriiptus) have the petals continued to the margin and the mouth 

 very excentric anteriorly ; two others (cristatus and Jimenoi) have 

 the petals short and closed, and the mouth somewhat more central. 

 This latter point is clearly shown in Prof. A. Agassiz's figures of 

 P. cristatus,^ and it may be inferred from the figure of the abactinal 

 side of A. Jimenoi given by M. Cotteau. These characters are asso- 

 ciated with a marked difference in the form of the test, which is 

 elliptical and conical in the first group and more evenly rounded in 

 the second. The difference in the structure of the petals seems 

 fully entitled to generic distinction, especially when accompanied 

 by the concomitant variation in form and the position of the mouth. 

 As the petals in the three first species are on the more primitive 

 type, it is proposed to name the genus proposed for them Archceo- 

 pneustes. 



Duncan's genus Pseudasterostoma has to be abandoned as a 

 synonym of Palceopneustes, and one would be glad if it could be 

 retained for the three species for which a name has to be found. 

 But this unfortunately cannot be done, for the following reasons : — 

 (1) P. Jimenoi (Cott.) is expressly mentioned as the type ; (2) A. 

 £ubense, Cott., is expressly excluded;^ (3) the shortness of the peta- 

 loid portions of the ambulacra is given as one of the characters of 

 that genus. Pseudasterostoma cannot therefore be dissociated from 

 its type species and applied to a form with different characters, 

 which Duncan had rightly excluded from it. 



^ A. Agassiz, ' Eeports on the Eesults of Dredging .... by the ' Blake ': 

 No. IX. Preliminary Report on the Echini,' Bull. Mus. Comp. Zool. vol. viii. 

 no. 2 (1880), p. 82 ; also Mem. Mus. Comp. Zool. vol. x. no, 1 (1883) pp. 

 58-60. pis. xviii., xix. fig. 2. 



2 ' Zoological Eesults of the Hassler Expedition : Parti. Echini,' 111. Cat. 

 Mus. Comp. Zool. no. viii. (1874) pi. iv. fig. 3, and especially Mem. Mus. Comp. 

 Zool. vol. X. no. 1 (1883) pi. xxi. fig. 11. 



8 Duncan, Ojp. su^ra cit, p. 204. 



