Mr. F. A. Bather on British Fossil Grinoids. 35 



III. — British Fossil Grinoids. — IV. Thenarocrinus gracilis, 

 sp. nov., Wenlock Limestone, and Note on T. callipygus. 

 By F. A. Bather, M.A., F.G.S. 



[Plate I.] 



A. Note on Thenarocriuus callipygus. 



Some seven weeks after the publication of Paper III,, " On 

 Thenarocrinns callipygus " *, my friend Mr. W. Madeley of 

 Dudley sent me an excellent specimen of that species which 

 he had found in the cabinets of Mr. 0. B. Ketley of Smeth- 

 wick. The collection of the late Mr. Charles Ketley is for 

 the most part in the museum of Mason's Science College at 

 Birmingham, and it may be remembered that three of the 

 finest specimens of T. callipygus are there to be found. 

 Some of the collection is, however, still in the possession of 

 Mr. C. B. Ketley, and it is remarkable that it should contain 

 this other even more instructive specimen of so rare a species. 

 My best thanks are due to its owner for the ready loan of 

 this interesting fossil. 



The specimen appears to come from the same horizon and 

 locality as all the others, viz. the Upper Wenlock Limestone 

 of Dudley. 



The specimen is a complete crown broken away from the 

 stem at the second or third joint. Its interest lies in the 

 fact that it is seen from the posterior, and that the anal plates 

 and lower portion of the ventral sac are very clearly displayed 

 in their natural positions. In no other specimen known to 

 me is the anal area shown so clearly or completely ; hence in 

 the preceding paper it could only be represented by a recon- 

 structed and composite diagram (Diag. I, p. 227). The 

 figure of the present specimen (PI. I. fig. 3) proves the 

 essential truth of this diagram. 



It was stated on p. 228 that slight variations existed, hence 

 we are not surprised to find the present individual departing 

 in one or two minor particulars from the more usual type. 

 Thus, the first plate of both the distichous series is axillary, 

 and not the second as was stated on p. 228 to be generally 

 the case. In the tetrastichous series the first plate on the 

 inner right hand is seen to bear two small plates, but these 

 again support only one. Such variations have no systematic 

 value, but it would be unwise, while we are yet in the dark as 



* < A minis/ 1890, vi. p. 222. 



