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148 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



It is difficult and perhaps impracticable to sustain these genera, 

 or either of them, upon the characters here given ; though it must 

 be admitted that there is some difficulty in referring all these 

 species to Conocephalites, when we restrict the signification to 

 such forms as the C. sulzeri and C. striatus. 



In several of our species the glabella is very depressed convex, 

 and the oblique farrows are wanting or very obscure. It must be 

 stated, however, that we are always dealing with the casts of the 

 interior, and therefore these markings are necessarily obscure. 

 The presence of spines from the occipital ring cannot of course 

 be regarded as of generic importance, while the caudal spines in 

 one species may perhaps be admitted as unobjectionable in Cono- 

 cephalites. At the same time many of the thoracic segments as- 

 sociated with the cephalic shields having the characters noticed, 

 are not like those of Conocephalites. On the other hand, instead 

 of terminating abruptly at the extremities, they are suddenly 

 bent backwards in an elongated spiniform extension, very similar 

 to the segments in Paradoxides. Other forms, both of the head 

 and of the separated thoracic segments, bear some characters in 

 common w^ith Olenus. 



When we look at the course of the facial suture, the form and 

 proportion of the eyes, we find them varying from the characters 

 of Conocephalites as exhibited in the species cited above. 



In the last named characteristics, many of our western species correspond 

 more nearly with the G. emmernchi 'of Barrande, which likewise has a 

 node on the occipital ring. Were it not for the extension of the pleura, we 

 would find no difficulty in the comparison with this European species. This 

 feature of the thoracic segments would demand an extension of the charac- 

 ters of Conocephalites, or the admission of a separate genus ; in which 

 case, to avoid the multiplication of synonymy, I would suggest that one of 

 the names proposed hy Dr. Owen be adopted. 



I hesitate at the present time to separate these forms from Conocepha- 

 lites, because the material, being all fragmentary and in the condition of 

 moulds or casts, may not carry with it the conviction to the minds of na- 

 turalists, that it otherwise might do. The glahella, moreover, with the fixed 

 cheeks, being referable to forms of similar character to C. emmerichi, offer, 

 in these parts, the greatest analogy with Conocephalites. 



