235 
III. Thenarocrinus callipygus . 
The second point to be noticed is the extension of the 
tegmen over the arms as far as the end of the distichals. 
There is really nothing very remarkable in this ; but it is 
obviously parallel with the extension of the tegmen in Crota- 
locrinidse, and leads up to the apparent inclusion of costals an 
distichals in the walls of the dorsal cup, on which Wachsmuth 
and Springer lay so much stress. 
All these resemblances point no doubt to certain conclu- 
sions. But it is not so long since Messrs. Wachsmuth and 
Springer published their elaborate paper on the Crotalo- 
crinidse, in the preparation of which they had the advantage 
of studying a very large number of specimens including those 
figured by Angelin. To traverse their arguments and to 
contradict their conclusions would be presumptuous in one who 
has not examined their evidence. Till that is done let us be 
content with the knowledge of this new genus, w T hich I feel 
it a privilege to introduce to naturalists. For, with its long 
and finely ringed column, its w T ell-proportioned cup, the 
delicacy of its ventral sac, and its more than myriad arms, 
the living Thenarocrinus must have been one of the most 
beautiful and wonderful forms in that paradise of lovely 
marvels, the Wenlock Sea. 
EXPLANATION OF PLATE X. 
Fig. 1. Postpalmars of the left-central branch of the left posterior arm of 
144 Mason College : seen partly sideways. To show lateral 
ridging, (x 2.) 
Fig. 2. 153 Mason College, posterior view. The oldest specimen. (Nat. 
size.) 
Fig. 3. 57478 a , B.M. Chiefly to show the fine branches of the arms. 
(Nat. size.) 
Fig. 4. 48049, B.M. To show general form and stem-characters. 
(Reduced from 9± to 7J inches long.) 
Fig. 5. 57478 b. To show ventral sac and tegminal plates. (Nat. size.) 
Fig. 6. 293 Holcroft. The youngest specimen. (Nat. size.) 
Fig. 7. Part of the stem of the Dudley specimen. Showing ornament ; 
see p. 231. (Nat. size.) 
Fig. 8. 138 Mason College. To show weathered arms and ventral sac. 
(Nat. size.) 
Fig. 9. Part of the Madeley specimen. To show stem crushed along 
suture-lines. (Nat. size.) 
N.B. — To ensure accuracy all the drawings except Figs. 1 and 7 have 
been traced from photographs. 
