Dr. F. A. Bather on Protoechinus, Austin. 17 



scattered plates, P. anceps differs in the less regular shape 

 and Less width, both relatively and absolutely, of its inter- 

 ambulacra! plates ; also in the less height, relatively and 

 absolutely, of its ambulacrals. It is worth noting here that 

 Jackson has referred to P. tenuis a specimen from Coplaw, 

 Clitheroe (Mus. Pract. Geol., 10,304). 



Pholidocidaris aeuaria (Whidbornc) is so imperfectly 

 known that no comparison is possible ; but since it comes 

 from the Upper Devonian (Piltou Beds) it is unlikely to be 

 the same species as P. anceps. 



Pholidocidaris gaudryi Julien is also known only from 

 fragmentary imprints of plates and radioles, which cannot 

 be compared. The possession of six ambulacral columns 

 seems, however, to constitute a difference. 



Conclusion. 



Protoechinus anceps may therefore be referred to the family 

 Lepidesthidae, genus Pholidocidaris. 



Since Austin's description has proved to be quite unre- 

 cognizable, the name Protoechinus, though of earlier date, 

 cannot possiblv supplant Pholidocidaris Meek & Worthen, 

 1869. 



If the specimen could be proved to belong to any species 

 of Pholidocidaris hitherto described, the name anceps also 

 would have to give way. Since, however, it appears to he 

 specifically distinct I propose to retain the name, denoting 

 the species as 



Pholidocidaris anceps. 



Diagnosis. — A Pholidocidaris with 4 columns to the ambu- 

 lacral area; adoral ambulacrals of both the double and the 

 quadruple series more than twice as wide as high, fairly stout, 

 with pore-pairs outside the median meridional line and orad of 

 the median transverse line, sloping from the perradial end in 

 an adapical direction, with 5 (? 6) columns to the inter- 

 ambulacral area; adoral ambulacrals thin, irregular in 

 outline, but width not more than 2/3 height, except in the 

 primordial plate, which is about as wide as high. 



This diagnosis, being based only on the internal surface 

 of the adoral region, is of course incomplete. The real 

 interest of the specimen lies in its structural features. 



EXPLANATION OF PLATE II. 



The Holotype of Pholidocidaris anceps, from a photograph by Herbert 

 G. Herring, enlarged t" two diameters. The unnatural appear- 

 ance of the shadow below the specimen is nut due to Mr. 

 Herring's excellent photograph. 



