58 AMERICAN PERMIAN VERTEBRATES 



as a cartilaginous extension throughout life. The scapula mentioned 

 by me in my paper on Cacops {Bull. Geol. Soc. Amer., XXI, 268, 

 near bottom) as having the posterior part unossified I iind really 

 belongs with Seymouria, though resembling in other ways that of 

 Cacops so much as to be practically indistinguishable. The supra- 

 coracoid foramen pierces the bone in its usual place, below the 

 scapula-coracoid suture a little in front of the preglenoid facet, 

 at the bottom of a rather large fossa. Between this foramen and 

 the posterior cartilaginous border the smooth surface shows not 

 the slightest indication of a suture. Inasmuch as the sutures 

 elsewhere are all more or less patent, it is quite impossible that the 

 posterior coracoid should be ossified here, and even if ossified it 

 must be merely vestigial and wholly below the scapula. There 

 cannot be the least doubt but that the posterior bone, the so-called 

 coracoid, is unossified in Seymouria, as in Varanosaurus, and that 

 precisely this same condition with the sutures in the same place 

 I have observed in a scapula-coracoid which I refer provisionally 

 to Aspidosaurus peltatus, described elsewhere in this work. The 

 coracoid of all these forms consists exclusively of the anterior 

 element, the so-called procoracoid. That this bone has entirely 

 disappeared in all later reptiles, giving place in its entirety to 

 another bone, here unossified, with hke attachments, and with it-s 

 perforating supracoracoid foramen in the same position, I cannot 

 believe. On the other hand, Broom has brought arguments to 

 show that the coracoid process of the mammals really represents 

 the posterior element, and that it is the anterior one, the procora- 

 coid, which has disappeared in the mammals. Whether his views, 

 the ones generally accepted for all the later vertebrates, will 

 eventually be proven beyond doubt for the mammaha, I am not 

 competent to predict. That there have been two divergent 

 methods of development of the coracoid in the amniota is not, of 

 course, impossible, nor perhaps at all improbable. The absence 

 of a perforating coracoid foramen in the mammaUa, and its almost 

 universal presence in the reptilia (absent only in the Pterosauria, 

 and I am not sure but even in that order the opening back of the 

 glenoid fossa as I have described it really represents this foramen) 

 may indicate a different mode of ossification. In any event it 



