214 PROCEEDINQS OF THE ACADEMY OF ' [1886. 



ring of radials, and next to the dorsocentral ; and it seems there- 

 fore only natural to regard the six proximal interradial plates 

 surrounding the central piece (oro-central) in the vault of a Palaeo- 

 crinoid as representing oral plates." Tliis argument is not quite 

 correct, in so far as the central piece is frequently surrounded not 

 only by the proximals his orals but also by the radials and 

 anal plate (see PI. 7) ; contrary to the basals, which form a ring 

 by themselves. Besides, his argument is based to a large extent, 

 if not altogether, upon the hypothetical plate which he calls 

 "oro-central." 



Taking everything in consideration, is it not reasonable and 

 more natural to regard the five orals of the Neocrinoidea, which 

 in the larva are loosely folded together, and which in some of the 

 Cystidea and also in Stephanocrimis were united by a close suture, 

 as gradually becoming anchylosed in a group in which they were 

 permanently closed, than it is to invoke the existence of a new ele^ 

 ment unknown in Echinoderm morphology, and even then have to 

 assert that six plates take the place of five ? ! But not only that, 

 we also have to admit that these so-called "orals " contain in their 

 midst anal and radial plates contrary to the case of the orals of 

 the Neocrinoidea, Stephanocrinus and the Cystidea, and contrary 

 to the basals, the abactinal representatives of the orals as Car- 

 penter admits. 



As a further proof that the central jiiece is the representative 

 of the orals, we refer to the Cystid genus Caryocrinus^ which 

 has three in place of five groups of arms, and which, according 

 to our interpretation, has no proximals. The central piece which 

 occupies the centre of figure, and which we think represents the 

 oral pyramid, is surrounded by eight plates, b}"^ five, (not four) 

 large ones, and three smaller ones, the latter conforming jointly 

 to one of the other five. Three of the plates have a strictly 

 radial position, the three others, including the compound one 

 which takes the azygous side, are interradial. We doubt if 

 Carpenter will regard these six plates, wholly or partly, as the 

 representatives of our proximals his orals or his theory will 

 have to undergo further modifications, as he will find it difficult 

 to restore five primitive pieces from an assemblage of plates as 

 here exhibited. 



