HISTOEICAL. 27 



elusion that by far the majority of the Neocrinoidea are built on the dicyclic 

 plan, and either have small infrabasals, or had them in their larval state. 

 We continued to use the term ^Wault " as opposed to disk, believing that 

 the tegmen of Palaeozoic Crinoids differed morphologically from the disk of 

 later ones. Eespecting the oral question our views had undergone consid- 

 erable changes, owing to the discovery that the two smaller plates, which 

 we supposed represented together the posterior oral, are radially disposed 

 instead of interradially, and w^e inferred that the central plate alone repre- 

 sented the oral pyramid of other Crinoids, a view^ afterwards strongly con- 

 tested by Dr. P. H. Carpenter. 



In 1884 Carpenter's Challenger Eeport on Stalked Crinoids came out, 

 and in 1888 that on Comatula3. In the former the author discussed among 

 other things the morphological relations between Palaeozoic and Mesozoic 

 forms, and replied to some points w^hich w^e had brought out in the Revision. 

 With regard to the structure of the tegmen he argued that some Platycri- 

 nidae had a "vault" ; but that the ventral covering of others did not differ 

 essentially from the disk of the Neocrinoidea. He believed that the Pal- 

 aeozoic Crinoids differed essentially from the later ones by means of their 

 irregular symmetry, caused by the introduction of anal plates ; and upon 

 this and other grounds, to which we allude in another place, he made the 

 Palaeozoic and later Crinoids independent orders. In his classification he 

 fell back upon Leuckart's almost forgotten name ^'Pelmatozoa," which he 

 made a branch of the Echinodermata, with Crinoidea, Blastoidea, and Cys- 

 tidea as classes, and the Palaeocrinoidea and Neocrinoidea as orders. He 

 also discussed the oral question, adopting the view which we had brought 

 out in 1881, but abandoned in the following year. He assumed that the 

 so-called central plate represents the dorso-central at the abactinal side, 

 the six proximals (his orals) the basals, and that the latter are homologous 

 with the genitals of the Urchins. In the second Challenger Eeport, that 

 on the Comatulae, we w^ere criticised very severely for asserting that prob- 

 ably the Comatulae had infrabasals in the larva, which were actually dis- 

 covered by Bury before the Eeport was published. 



Among the many interesting papers written by Dr. P. II. Carpenter, 

 none attracted more attention than the one in which he discussed the rela- 

 tions of the basals in monocyclic and dicyclic Crinoids."^ He proved that 



* On the '■' Oral" and Apical Systems of Eclimoderms (Quart. Journ. of Microsc. Sci., 1878, pp. 351- 

 383). 



