VERTEBRATA 



61 



North America and Europe; the PariotichidtB, with several 

 rows of, teeth in the jaws, from North America; and the Elgi- 

 niidse with very thin ossifications and light structure, from 

 the Trias of Scotland. This order is prohably ancestral to all 



4^ ^tt< - -^ ' 



V»..J ' 



Fig. 17. — Empedlas motaris Cope ; inferior view of sliull, one-third natural size. 

 A Cotylosaurian from the I^ermian of Texas. 



other orders of Reptilia. The oldest reptile known is the 

 Isodectes punctulatus Cope from the Coal Measures of 

 Ohio. The South African forms Gorgonops and Proco- 

 ilophum probably belong here, and are supposed to be types 

 of distinct families. 



The Chelydosauria is an order of limited extent, with 



