IN THE MOKPHOLOGY OF THE CYSTIDEA. 19 



A still closer approacli to the conditioa of tlie Actiuocriuidse 

 is presented by Caryocrinus (PL I. fig. 14). The greater part 

 of the summit is occupied by six oral plates, together with two 

 smaller ones, which bound the anal opening. Immediately in 

 front of this is a heptagonal or hexagonal plate, round which the 

 five others are grouped symmetrically. I have seen one specimen 

 m which this plate is nearly pentagonal ; and the two antero- 

 lateral orals meet above it, pnshing the anterior one away with 

 it, so that the summit looks very much like that of an ordinary 

 pentamerous form. The normal arrangement of these summit- 

 plates in Garyocriniis at once recalls the five orals of the Camerata, 

 viz., a central plate ia front of the anus, with four others round 

 it, the so-called proximals. But why are there five proximals in 

 Caryocrinus^. Simply because the symmetry of this type is 

 hexamerous and not pentamerous. Wachsmuth and Springer 

 must have overlooked this well-known fact when they stated that 

 the eight plates round the central piece of Caryocrinus "are 

 arranged in a totally difi'erent manner from the so-called proximals 

 of the Pal^eocrinoidea " *. The anterior and the postero -lateral 

 orals coincide in position with the primary ambulacra, of which 

 there are only three, and they are therefore considered as radial 

 in position by Wachsmuth and Springer, who remark : — " We 

 think the distribution and arrangement of the surrounding plates 

 in Caryocrinus prove conclusively that these cannot be orals, 

 for the most ingenious speculator would be unable to reconstruct 



have discoTered for themselves that the supposed central plate is really the 

 displaced posterior oral, which is not represented by two small plates separated 

 by the anus, as we formerly supposed, my comparison of it to the dorsocentral 

 of the abactinal system need not be further considered. It is proper for me to 

 state, however, that some months before Messrs. Wachsmuth and Springer's 

 change of opinion had been made public, Professor Beyrich had convinced me, 

 during a visit to Berlin at Easter, 1888; that the supposed central plate in the 

 summit of the Camerata is really the posterior oral homologous with that of 

 Haplocriiius. He had then held this view for some time, and it had been sug- 

 gested as a possible one by Wachsmuth and Springer in 1885. But it was 

 never seriously advocated by them ; and even as late as 1887 they criticized me 

 somewhat severely for still believing in the oral nature of the summit-plates in 

 Allagecrinus, Goccocrinus, Culicocnnus, &c., and of the four anterior proximals 

 in the Camerata generally. These criticisms, however, were altogether with- 

 drawn in the following year, and we are now in complete accordance upon this 

 long-discussed question. 



* " The Summit-Plates in Blastoids, Crinoids, and Cystids, and their Mor- 

 phological Relations," Proc. Acad. Nat. Sci. Philad. 1887 p-. 100. 



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