288 



Zoological Society 



shelving off on the upper edge to the base of the oblong part of the 

 aperture. The articulating surface of the hinder side is similar ; 

 but the articulating surface is shorter at the sides, and transversely 

 truncated in a line with the middle of the upper, oblong, transverse 

 opening (figs. 1, 2). 



Fig. 2. Fig. 1. 



Fig. ] . Front of atlas of Catodon Krefftii. 

 2. Hinder side of ditto (reduced). 



The second and other cervical vertebrse are all united together into 

 one mass, anchylosed by their bodies, lateral processes, and neural 

 arches. The neural arches form a triangular mass, which is strongly 



Fig. 3. 



Hinder view of cervical vertebrae of Catodon Krefftii. 



keeled on the central line ; and the keel is stronger and produced 

 into an acute point at the hinder end (figs. 3, 4). 



