64 Mr. F. A. Bather — Siu^gested 



a view wliicli in recent times has been advocated by M. Neu- 

 mayr (' Stjimme des Thierreichs '), Most recent writers, 

 liowever, among whom P. H. Carpenter may be mentioned, 

 liave considered them as Interradials, though whether homo- 

 logous witli Interbrachials or v/itli Interambulacrals was left 

 a little uncertain. The most recent and most original view 

 is tliat of Wachsmuth and Springer *, who treat them as 

 partly, if not altogether, Subambulacral, a view which can 

 hardly be defended f. The latter authors have, however, 

 suggested that these plates correspond to the deltoids of the 

 Blastoidea [ihid.]. P. H. Carpenter, in a letter to me, dated 

 2oth September, 1891, said: "They are unquestionably 

 homologous with the deltoids of Stephanocrinus and the 

 Blastoids." It is not likely that any one will disagree with 

 this statement, however much opinions may differ as to the 

 homologies of the Blastoid deltoids themselves. Conse- 

 quently we may temporarily extend to the four cordiform, 

 interiadially situated plates of the tegmen, in Euspirocrinus 

 and the Cyathocrinida, the term " Deltoids," which may be 

 fittingly symbolized by the Greek delta, A. 



We can hardly doubt that a homologue of the deltoids 

 exists in the posterior interradius ; but whether this be repre- 

 sented by the madreporite or by two of the small plates at 

 the base of the anal tube is a question not yet settled. It is 

 therefore inadvisable at present to extend the terra deltoid to 

 any plate or plates in the posterior interradius. 



Inter radial Plates. — Anals x and t. 



It may be as well to take this opportunity of stating that 

 the term " anal x " will be applied for the present in my 

 papers to the single anal plate that enters into the compo- 

 sition of the dorsal cup in such genera as Cyathocrinus, and 

 to the homologue of that plate in other genera. This is the 

 plate for which the term " Brachianal " was proposed in 

 " British Fossil Crinoids," II. p. 330 ; that term, however, 

 lays too much stress on an inference that has not met with 

 general acceptance. 



Once more, however, it is necessary to point out that 

 neither the rejection of the term Brachianal, nor even the 

 rejection of the inference that the anal x was primitively 

 derived from a brachial, atfect the main contentions of the 

 paper referred to. 1 still believe, for reasons given in that 



• Op. cit. pp. 3o8-n60. 



t See review of this paper in Geol. Ma;r. dec. iii, vol. viii. p. l'l>i\ Mav 

 1891. 



