Mr. P. EL Carpenter on Democrinus Parfaiti. 335 



I have the strongest conviction that M. Perrier's Crinoid is 

 not only not a new genus at all, but that it is identical with 

 Rhizocrinus Rawsoni^ which I have long known to occur on 

 this side of the Atlantic. It was first dredged by Pourtalfcs 

 off Barbadoes ; and he described its cup as " composed of 

 five rather long basals and the rather short first radials." * 

 The u sillon circulaire " described by M. Perrier in Demo- 

 crinus is the constriction of the calyx at the basiradial suture, 

 to which I have referred as one of the characters distinguishing 

 R. Rawsoni from R. lofotensis f. But I cannot agree with 

 Prof. Perrier in regarding the calyx as formed by the basals 

 only. Although the radials are quite small externally, they 

 have large distal faces for the attachment of muscles and 

 ligaments, the inner surfaces of which form the funnel lodging 

 the lower part of the coelom. On the same principle one 

 would have to describe the cup of those species of Antedon in 

 which the first radials do not appear externally as formed by 

 the centrodorsal only ! 



The fragmentary condition of the arms in M. Perrier's 

 specimens is nothing unusual. The arms of Rhizocrinus very 

 frequently break off" at one of the numerous syzygies, so that 

 their more or less complete absence is no proof of their being 

 u extremement pen developpees " as M. Perrier infers is the 

 case in Democrinus. In fact R. Rawsoni may have as many 

 as one hundred single joints, or, rather, fifty syzygial pairs, 

 with pinnules on all but the first five. But as the first 

 brachial consists of two parts which are united by a syzygy %, 

 it not unfrequently happens that the whole of the arms break 

 away at this syzygy, carrying with them the visceral mass to 

 which the rest of the lower brachials are attached. I strongly 

 suspect that this loss may occur and be made good during life ; 

 for I have seen specimens in which the epizygal and the fol- 

 lowing brachials are much smaller than the hypozygal of the 

 first joint. This is exactly what happens when the arm of a 

 Comatula is broken at a syzygy and subsequently repaired. 

 The new epizygal and the following joints are for a while 

 much smaller than the old hypozygal and the brachials below 

 it ; and I imagine that Prof. Perrier's specimens with the 



• 111. Cat. Mus. Oomp. Zool. viii. p. 28. 



t " The Stalked Crinoids of the Caribbean Sea/' Bull. Mus. Comp. 



Zool. vol. x. no. 4, p. 174. 



\ These two parts are described as the second and third radials by Sars 



and Ludwig, and as the radial axillary and first brachial by M. Perrier. 

 The latter author also speaks of them* as united by an " articulation/' If 

 this were the case, however, and muscles and ligaments were present, he 

 would most assuredly not have found that the arms hr^ak u ties fariie- 

 ment " at this point. 



