64 Mr. F. A. Bather—Suqgested 
a view which in recent times has been advocated by M. Neu- 
mayr (‘Stiimme des Thierreichs’). Most recent writers, 
however, among whom P. H. Carpenter may be mentioned, 
have considered them as Interradials, though whether homo- 
logous with Interbrachials or with Interambulacrals was left 
a little uncertain. ‘The most recent and most original view 
is that of Wachsmuth and Springer *, who treat them as 
partly, if not altogether, Subambulacral, a view which can 
hardly be defended ft. The latter authors have, however, 
suggested that these plates correspond to the deltoids of the 
Blastoidea (ibid.).. P. H. Carpenter, in a letter to me, dated 
25th 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, 
interradially situated plates of the tegmen, in Huspirocrinus 
and the Cyathocrinide, 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 term deltoid to 
any plate or plates in the posterior interradius. 
Interradial 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,” I. 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 2 was primitively 
derived from a brachial, affect the main contentions of the 
paper referred to. 1 still believe, for reasons given in that 
* Op. cit. pp. 858-360. Ex 
+ See review of this paper in Geol. Mag. dec. iii, vol. vili. p. 222, May 
1891. 
