Contributions to Palaeontology, 



129 



straight in front. This specimen and the others are associated with 

 a pygidiuni described below. 



A Pygidium (of this species ?, Plate ii, f. 49) has the 

 axis comparatively narrow and abruptly elevated, marked 

 by six annulations besides the anterior articulating seg- 

 ment. The lateral lobes are marked by about four ribs, 

 besides the anterior segment. 



The anterior margin of the pygidium is extremely 

 curved, and the antero-lateral angles are produced into 

 long curving spines which are as long as the body of the 

 pygidium. The posterior margin between the spines is 

 rounded, and the ribs terminate in a continuous thickened 

 border. 



At least five individuals of this peculiar species have been seen. The 

 figure is twice enlarged, from a cast made in the natural mould in sand- 

 stone, associated with the glabella described above. 



GENUS CONOCEPHALITES (Zenker). 



I have referred to this genus several species heretofore 

 placed under Dikelocephalus and Lonchocephalus by 

 Owen; restricting the former designation to the typical 

 species of that author, which are certainly very distinct 

 from some of the others described nnder that genus. 

 Those species with the more conical and highly arched 

 forms of glabella were in part designated by Dr. Owen as 

 Lonchocephalus, of which one character is the long spine 

 projecting from the base of the glabella. 



The generic description of Lonchocephalus is as follows: 

 " Generic character. In this small and singular genus the 

 " highly arched glabella is either undivided, or has only 

 " two very obscure furrows. A spine of greater or less 

 " length projects backwards from the base of the gla- 

 " bella, in the median line of the body over the thoracic 

 [Trans, v.] 17 



