20 DE. P. H. CABPENTEE ON CEETIUST POT:NrTS 



five primitive plates from sucli an assemblage of jDieces as we find 

 in Caryocrinus and in Von Koenen's new genus Juglandocrinus. 

 "What those plates may be, whether actinal or abactinal structures, 

 we will not pretend to decide ; but we do undertake to say that 

 they are not orals, otherwise the rule that there are always five 

 primitive orals meets with a very serious exception " *. I am not 

 aware of the absolute rule to which they refer, for where there 

 are six basals, a point which Wachsmuth and Springer have 

 overlooked, one would certainly expect to find six orals. They 

 have also forgotten the fact that, besides the ordinary pentamerous 

 form of Rliizocrinus, Sars t described individuals with 4, 6, and 7 

 rays, and a corresponding number of " valvules orales." 



In this same communication, published in 1887, before their 

 change of opinion, Wachsmuth and Springer say " Caryocrinus 

 has a large central piece, and this is surrounded usually by eight 

 plates, which are arranged in a totally different manner from the 

 so-called proximals of the Palgeocrinoidea. Three of them are 

 radial, the others are interradial. The interradial pieces alternate 

 with the radial ones, one to each side, excej)t at the anal inter- 

 radius, where three smaller pieces take the place of the single one 

 at the two other sides." At that time the American authors 

 regarded the central piece as a composite oral plate, like that of 

 the Camerata; but they have since recognized that the latter is 

 really the posterior oral displaced forwards %, and that the smaller 

 plates between it and the anus are not members of the proximal 

 series at all, but anal plates. On the same principle Caryocrinus 

 would have to be regarded as having six orals, a central one and 

 five others round it (fig. II., and PL I. fig. 14). But Wachsmuth 

 and Springer have given no hint that they now take this view of 

 its structure, and I conclude, therefore, that they regard the 

 summit of Caryocrinus as composed of three orals, a central and 

 two antero-laterals, with three alternating radial jjlates which 

 cover the ambulacra. This would mean, of course, that the 

 actinal plates of Caryocrinus are trimerous and not hexaraerous, 

 as those of the dorsal cup are ; and the fact that three of them 

 cover the primary ambulacra seems, at first sight, to be a strong 

 * Ibid. p. 107. 



i" ' Memou-es pour servir a la Conuaissauce des Oriiioides vivants,' Ckristiania, 

 1S63, pp. 18, 19. 



\ "Discovery of the Ventral Structure of Taxocrinus and Haplocrinus, and 

 consequent modifications in the Classification of the Criuoidea," Proc. Acad, 

 Nat. Sci. Philad. 1888, pp. 342, 348. 



