100 



AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



and lower edges of the blade are nearly parallel. The lower edge is con- 

 tinued forward on the bone, forming a sharp prominence just over the cotylus 

 for the humerus. There are two foramina perforating this part of the 

 bone; a deep triangular pit lies just beneath the prominence and above the 

 cotylus; a foramen penetrates the bone in this pit and opens on the posterior 

 side in a deep, crescent-shaped pit. Another foramen lies just anterior to 

 the prominence, and, perforating the bone, opens in the same crescentic pit 

 on the posterior surface. 



The cleithrum is a slender rod anteriorly, lying on the upper side of the 

 scapula and outside of the distal end of the clavicle. The distal end is 

 expanded into a thin, fan-shaped plate, which is closely pressed to the outer 

 surface of the scapula and is even fused with it in old specimens. This is 

 especially well shown in specimens No. 4037 Am. Mus. and No. 182 Uni- 

 versity of Chicago, the latter the type of Eryops latus Case. 



Fig. 31. — E. migacephalus. No. 4255 Am. Mus 



A. Posterior edge of right humerus. 



B. Anterior view. 



Fig. 32. — E. migacephalus. No. 4183 Am. Mus. 



A. Posterior view of left femur. 



B. Lateral view of same. 



The humerus (No. 4186 Am. Mus.): The proximal and distal ends are 

 almost at right angles. The articular face on the proximal end is carried 

 around the end somewhat obliquely, as in the Pelycosaurs. The short shaft 

 between the two ends is nearly quadrangular in section, due to strong ridges 

 from the edges of the distal and proximal ends. On the upper part of the 

 anterior edge there is a strong, thick process expanded at right angles to 

 the main axis of the bone; this is one of the most characteristic features of 

 the Eryops humerus; it is not developed in any reptilian bone except a 

 humerus. No. 6541 University of Chicago, from Vermilion County, Illinois, 

 described by Williston as Desmospondylus anomalus. On the outer side of 



