232 Mr. F. A. Bather on British Fossil Crinoids : 
Messrs. Wachsmuth and Springer have apparently found out 
for themselves * by this time that Angelin’s description of 
Sagenocrinus was, so far as the number and position of the 
plates were concerned, perfectly correct : this is not the place 
to discuss the matter, but the sixth plate in the basal circlet 
does after all appear to be an u anal.” 
That the structure of Carahocrinus was in all essentials 
correctly described by Billings, Messrs. Wachsmuth and 
Springer subsequently admitted f ; but with their pronounced 
views as to the extreme improbability of an anal or a radial 
descending into the basal circlet, they naturally slurred over 
the importance of that structure. This was their explana- 
tion : — u The small plate within the basal ring, which is only 
known in this genus, is, we think, a supplementary azygous 
plate of no fundamental importance, a plate bearing to the 
regular azygous plate similar relations as the small accessory 
interradials in some specimens of Archceocrinus sculptus to the 
regular interradials/’ Now, however, Tkenarocrinus enables 
us to look at Carahocrinus from a different standpoint ; the 
supplementary plate may very naturally be regarded as a 
portion of the radianal, just as the radianal itself is a portion 
of the right posterior radial ; so that, were this supplementary 
plate again united to the radianal, we should have a dispo- 
sition of anal plates very similar to that which obtains in 
Tkenarocrinus. 
It was this similarity in a structure so dissimilar to that of 
all other Fistulata that led me, when discussing the classifi- 
cation of the group, to place Tkenarocrinus alongside of Cara- 
bocrinus. It is no doubt conceivable that this structure, 
peculiar though it is, may have been arrived at along two dif- 
ferent lines of descent. There are, however, yet other points of 
resemblance, in the dichotomous branching of the arms, the 
number of the costals, and the structure of the column. The 
only important difference between the two genera lies in the 
greater breadth and length of the arms in Tkenarocrinus ; but 
this is no great difference for two forms so widely separated 
in time and space. The more globular shape and generally 
radiate ornamentation of the dorsal cup, exhibited by the 
described species of Carahocrinus , go for nothing, for they do 
not obtain in two specimens of that genus kindly lent me for 
examination by Dr. G. J. Hinde. 
Whether these considerations warrant the establishment of 
* W. & S., “Discovery of the Ventral Structure of Taxocrinus &C./’ 
Proc. Acad. Nat. Sci. Philadelphia, 1888, p. 357. 
t Pev. III. (217), Proc. 1886, p. 141. 
