Contributions to Palaeontology. 



131 



importance, while the caudal spines in one species may 

 perhaps be admitted as unobjectionable in Conocephal- 

 ites. At the same time many of the thoracic segments 

 associated with the cephalic shields having the characters 

 noticed, are not like those of Conocephalites. On the 

 other hand, instead of terminating abruptly at the extremi- 

 ties, they are suddenly bent backwards in an elongated 

 spiniform extension very similar to the segments in Para- 

 doxides. Other forms, both of the head and of the 

 thoracic segments, bear some characters in common with 

 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 0. emmerichi 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 compa- 

 rison with this European species. This feature of the thoracic 

 segments would demand an extension of the characters of Conoce- 

 phalites, or the admission of a separate genus j in which case, to 

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

 the names proposed by Dr. Owen be adopted. 



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

 cephalities, because the material, being all fragmentary and in 

 the condition of moulds or casts, may not carry with it the convic- 

 tion to the minds of naturalists, that it otherwise might do. The 

 glabella, moreover, with the fixed cheeks, being referable to forms 

 of similar character to C. emmerichi, offer, in these parts, the 

 greatest analogy with Conocephalites. 



