88 
plates, still I am quite unable to find any trace of an articular surface sucb as 
tliese Authors suggest. It appears to me that Mr. llatte more apropriately 
explained these plates in his “ Second Note on Trihrachiocrinus corrmjatm” 
udicreiu he remarked that the “ Ankylosed hrachials are very much reduced 
in size and thickness, and that if, according to Messrs. "Wachsmuth and 
Springer, ‘ they evidently su})ported two arms, one on each side,’ these arms 
were probably abortive, or at any rate very much reduced, or reduced next 
to nothing, as I do not see any sockets for them, nor any strength to support 
tliem.”^ 
In Trihracldocrinus Olarhei and T. corrugatus, the basal cup of the 
calyx is generally convex ; in T. ornatiis it seems to be somewhat 
flattened, whilst in T. granulatus it presents a semblance of concavity. 
The scar of attachment for the first stem-joint is small in all the species, 
but proportionately largest in T. corrugatus. In the form of the under- 
basals and basals there is a very close resemblance between all the 
species, except in outlines of the heptagonal, and its adjacent posterior 
hexagonal basals. These plates in T. corrugatus and T. granulatus are much 
more transversely-obliquely hexagonal than in T. Clarkei, and the suture 
between tbeni is far shorter than between those of the type species. A 
great similarity exists in the form of all the radials, except that in 
T. corrugatus and T. granulatus the anterior radial is much more transversely 
pentagonal than in cither T, Clarkei or T. ornatus. In both of these species 
the pentagon is decidedly deltoid-triangular. 
The most important jioints of difference Ijetween the species, however, 
lie in the position and form of the azygous and anal plates. In T. corrugatus, 
and, apparently also in T. granulatus, were it not for the small truncated 
apex, the azygous plate would bo quadrangular ; but, in T. Clarkei, it is far 
less of this shape and more irregularly pentagonal in outline ; and, besides, it 
is not thrust upwards between the anal and right posterior radial to anything 
like the same extent as in the species named. A similar difference is 
perceptible between the anal plates of the respective species. In T. corru- 
gatus, the anal plate is roughly triangular, extending upwards a little beyond 
the azygous plate, and supporting with that jdate, on their truncated upper 
edges, either a second anal, or the proximal plate of the ventral tube, which is 
thus interpolated between two of the radials. 
’ Proc. Linn, Soc. N. S. Wales for 188G [1837], I (2), p. 1074. 
