MOEPHOLOGICAL PAET. 53 



has been substituted, at the suggestion of Prof. Zittel. But Zittel,* and the 

 German Palaeontologists generally, while admitting the homology, and the 

 name " infrabasalia," adopted the term " parabasalia " for the upper ring of 

 plates in the dicyclic base, claiming that the word '' basals," if applied to 

 the dicyclic base as well, might lead to confusion. 



The practice of giving different names to sets of plates which are ad- 

 mitted to be homologous was justly criticised by Carpenter,! and serious 

 difficulties arise as to which term should be applied in certain groups, where 

 infrabasals exist in some species and are wanting in others. Such a case is 

 presented by the Apiocrinidae, among which de Loriol discovered rudimen- 

 tary infrabasals in two species of Millericrinus. t This family was previously 

 supposed to be monocyclic, and the base is described by Zittel as consisting 

 of five basak, whereas in the two species above mentioned, the five corre- 

 sponding plates would be parabasals. There is a similar case among the Penta- 

 crinidae, in which infrabasals are represented in one genus, — Extracrinns. 

 In the Comatulae, in which, according to Bury, § small infrabasals occur in 

 the ciliated larva, but disappear in the Pentacrinoid stages, the very same 

 plates would be " parabasals " in the earher stage, and basals in the later. 

 Carpenter is clearly right when he says that this terminology, instead of 

 making it easier to students, as claimed by the German Palseontologists, 

 would be the source of endless confusion. 



A different interpretation of the basal plates was given by Dr. J. Wal- 

 ther.|| He accepts Zittel's terms for descriptive purposes, but homologizes 

 the infrabasals with the basals of the Monocyclica, the " parabasalia " with 

 the monocyclic radials ; and he takes the radials of the Dicyclica to repre- 

 sent an entirely new element in crinoid morphology. This recalls the idea 

 of Lyon,*"^ who took the basals of the Blastoids for '^ primary radials," and 

 the forked plates for '^ secondary radials." As Walther's views are alto- 

 gether out of keeping with the facts of Palaeontology, and also, as we now 

 know, with those of the embryology of recent Crinoids, any further discus- 

 sion of the subject is unnecessary. 



The Comatul^ have basals only in their earlier stages ; during the later 



* Handbuch d. Palaeontologie, Vol. I., p. 327. 

 t Ann. and Mag, of Nat. Hist, July 1890, pp. 5-11. 

 |- Paleontologie Pranpaise, Tome XI., Part T., pp. 553, 566. 



§ " The Early Stages in the Development of Antedon rosacea." Report of the Pifty-seyenth. Meeting of 

 the Britisli Association at Manchester, 1887, p. 735. 



II IJntersnchimgen iiber den Ban der Crinoideen, Palseontographica, 1886, Bd. XXXII. , p. 189. 

 ** Geol. Pep. Kentucky, Yol. III. p. 469. 



