III. Thenar ocrinus callipygus. 235 



The second point to be noticed is the extension of the 

 tegmen over the arms as far as the end of the distichals. 

 Tliere is really nothing very remarkable in this ; but it is 

 obviously parallel with the extension of the tegmen in Crota- 

 locrinid?e, 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- 

 crinidffi, 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, which I feel 

 it a privilege to introduce to naturalists. For, with its long 

 and finely ringed column, its well-proportioned cup, tlie 

 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 brancli 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. 67478 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 h. 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. 



