VERTEBRATES FROM PERMIAN OF TEXAS 



395 



the posterior end is thin and greatly expanded so that it overlaps 



the upper portion of the distal end of the scapula and is closely 



applied to it as a thin scale ; it is convex outwardly. The 



anterior two-thirds of the bone is rounded and rod-like. It lies 



close to the upper edge of the scapula, but is to be described as 



applied to it rather than 



being articulated with 



it, for where the bone is 



broken away the edge 



of the scapula is smooth 



and complete. The 



edges of the rod-like 



portion of thecleithrum 



were evidently extended 



as narrow and very thin 



wings. The anterior edge is sharp and marked with rugosities 



where it joined the clavicle, as indicated in Cope's figure. 



Broken fragments of the clavicle were found with the scapula 



and show that the anterior face of the proximal portion was 



marked with very deep and rugose striations and ridges. The 



evidence of the cleithrum afforded by this specimen makes our 



knowledge of the shoulder-girdle of Eryops complete. 



Fig. I. — Scapula of Eryops sf., showing attach- 

 ment of cleithrum. clt. Left side. 



MEASUREMENTS OF E. LATUS. 



Breadth across epicoracoid region 



Breadth opposite center of face for humerus - 



Width of scapula at middle 



Greatest length scapula - - - - - 



Greatest length of cleithrum 



182 

 079 

 073 

 371 

 237 



In the process of investigating this scapula it becomes very 

 evident that a close similarity existed, superficially, between the 

 scapula of Eryops and that of the Pelycosaurian reptiles, and 

 this led to a search for points that might be used in their separa- 

 tion. Baur says that there is no ossified coracoid in the 

 Stegocephali and that the cleithrum does not occur in the 

 reptiles, Pareiasaunis excepted. Williston mentions the presence 

 of scapula, coracoid and pre[epi]coracoid in Eryops, but says that 

 they are so closely united that the sutures are indistinguishable. 



