72 THE VOYAGE OF H.M.S. CHALLENGER. 



Antedon cubensis, which has pinnules on the second and following brachials, does not 

 correspond to the characters of the smaller specimen which he called by this name, as it 

 has a complete basal ring, and there are no pinnules on any of the arm -joints which are 

 preserved; while another reason is that the dredgings of the "Blake" in the years 

 1877-79 have led to the discovery of eight examples of Atelecrinus balanoides, all of 

 them better preserved than the single individual which was referred by Pourtales to 

 Antedon cubensis. 



The first specimen of Atelecrinus balanoides known to science was dredged by the 

 Challenger in 1873 ; but its cirri had disappeared, together with the whole of the arms 

 above the fifth brachials (PL VI. fig. 7). The Pacific species {Atelecrinus wyvillii) was 

 not much better (PL VI. fig. 5), and it was not till I received the " Blake " collection in 

 1880 that I was able fully to reahse the singular peculiarities of the type represented by 

 the two Challenger specimens which are figured on PL VI. 



The distinctive characters of Atelecrinus balanoides are (l) the transversely oblong- 

 shape of the second radials, wdiich are but slightly incised to receive the bluntly angular 

 proximal edges of the axillaries ; and (2) the outline of the lower part of the calyx, which 

 slopes uniformly downwards from the radials on to the centro-dorsal, without the basals 

 being specially prominent at the interradial angles as they are in Atelecrinus cubensis. 



The difference is very much of the same kind as that between the basals of Pentacrinus 

 wyville-ihomsoni and Pentacrinus miilleri respectively. 



The nine individuals of Atelecrinus balanoides which I have examined, all agree 

 very well in their general characters, but differ considerably in the relative proportions 

 of the two outer radials and of the lowest brachials respectively. In all of them which 

 have enough of the arms preserved, the first pinnule is on the twelfth brachial, except in 

 one arm of one individual, in which the tenth joint bears the first pinnule. 



2. Atelecrinus wyvillii, n. sp. (PL VI. figs. 4, 5). 



1882. Atelecrinus wyvillii, P. H. Carpenter, Journ. Linu. Soc. Lond. (Zool.), 1882, voL xvi. p. 492. 



Description of an Individual. — Centro-dorsal acorn-shaped, 4 mm. high by 3 mm. 

 wide. The double rows of cirrus-sockets are well separated from one another by 

 intervening spaces, and do not reach the dorsal pole. Four, or rarely five, sockets in 

 each row, the ends of which stand out prominently and give a serrate appearance to the 

 lateral edge of the plate. The upper portion is uniformly smooth, without any interradial 

 ridges ; but the edge is marked by five slight incisions situated interradially. 



The basals are nearly uniform in height throughout their whole width, but are some- 

 what arched in form. The apex of each arch is interradial, and the interval between it 

 and the notched edge of the centro-dorsal below is only occupied by perisome. Hence 

 the basal ring is really only in contact with the centro-dorsal at its five lowest points, 



