VERTEBRATA 



45 



principally of the former, and the same structure is charac- 

 teristic of the remaining Batrachia. In the Reptilia, on 

 the other hand, the intercentra gradually disappear-, being 

 represented in most of the types in the cervical and caudal 

 regions only. In the latter they support the chevron 

 bones. 





I 



Fig. 13 — Trimerorhachis insignia Cope; skull. From the Permian bed of Texas. 

 Original. 



Of the Ganocephali two families are known, the Tri- 

 merorhachidse (Figs. 12-13), without, and the Archego- 

 sauridse with neural spines of the vertebrae. They occur in 

 the Coal Measures and the Permian of Europe and North 

 America. 



