66 S. W. WILLISTON 



that are known, is represented by Seymouria (Fig. 8). It reached 

 a length of not more than two feet, and had the shortest and broad- 

 est feet of all. Its skull is so nearly like that of the contemporary 

 amphibians, especially that of some of the armadillo forms, not 

 only in appearance, but also in actual structure, that close observa- 

 tion is necessary to distinguish them. The teeth are all slender and 

 small, indicating insectivorous habits like those of the amphibians. 

 Doubtless this too was a littoral inhabitant of more or less aquatic 

 habit. 



Still another group, one of the most peculiar of all, is unfortu- 

 nately known only from the skull, of which the best specimens are 



Fig. 8. — Seymoiiria baylorensis, a cotylosaur reptile about two feet in length. 

 From Texas. 



in the Chicago museum, and known as Pantylus. In size this 

 animal was probably no longer than Seymouria. It is pecuhar in 

 having a broad, flat, and firm skull with the mouth filled every- 

 where, on jaws and palate, with low, stumpy teeth, suitable only for 

 crushing shellfish. 



Remarkable as is the diversity of structure and habit of these 

 primitive cotylosaurs, that of the next group, commonly called 

 the Pelycosauria, is vastly more so. The reptiles of this group or 

 order, which I prefer to call the Theromorpha, after Cope, are all 

 of a distinctly higher type, especially characterized by the lightened 

 skull, which has one or more holes in its roof behind the eyes, and 



