PERMOCARBONIFEROUS AMPHIBIANS AND REPTILES 63 



Varied as were the amphibians, they were not nearly so numer- 

 ous or so diverse in habit and structure as were the contemporary 

 reptiles. While it is comparatively easy to classify the amphib- 

 ians, the problems which the reptiles present are vastly greater. 

 Hitherto they have been generally classed in two main groups or 

 orders, the Cotylosauria and Pelycosauria, but the many discov- 

 eries of recent years have broken all boundaries and opened up 

 most compHcated problems of relationships, problems which will 

 probably not be wholly solved in many years to come. It may be 

 twenty-five years hence before we shall have a tolerably good 

 bird's-eye view of the complete fauna. Especially are the smaller 

 animals, those very difficult to collect and to study, for the most 

 part yet awaiting laborious research. 



Fig. 5. — Dlasparactus xetios, a cotylosaur reptile of about seven feet in length. 

 From New Mexico. 



But there are about one dozen of these reptiles of which we 

 know nearly all that we may ever hope to know, forms of which 

 complete or nearly complete skeletons have been assembled and 

 mounted. And it is of some of these that I have attempted 

 restorations, and will briefly discuss here. 



The order Cotylosauria, whose ultimate distinctions from other 

 reptiles consist solely of the roofed-over skull, without holes in the 

 sides behind, and a short neck, comprises a large group of the most 

 primitive reptiles that we know. All that are known have prac- 

 tically no neck, short and stout limbs, a rather thick-set body, 

 and for the most part not. very long tails. They belong to three or 

 four groups, that have been called suborders, and six or more 

 strongly differentiated families. The first of these is represented 

 by Diasparadus (Fig. 5), so nearly related to Diadectes that one 

 restoration will do for both. It is a reptile of seven or more feet in 



