236 S. W. WILLISTON 



with the coracoid of the lacertilia and rhynchocephalia, that is, 

 it is the true coracoid, and not the procoracoid. To assume that 

 the coracoid of these animals has been replaced in toto by another 

 bone, leaving only the supracoracoid foramen, which alone has 

 remained permanent, the bone surrounding it disappearing to give 

 place to another represented by cartilage, in some of the forms at 

 least, and far back of the foramen, is beyond the limits of my 

 credulity, whatever it may be for others. 



In the structure of the skeleton of Seymouria nothing is more 

 conspicuous than the extraordinary development of the arches 

 of the dorsal vertebrae, forming almost a carapacial protection 

 for the body. That the animal was crawling in habit there would 

 seem to be no doubt, notwithstanding the position in which the 

 hind legs were found — a position quite the same as that of the 

 type specimen of Limnoscelis. No indications of ventral ribs are 

 preserved and I think it may be said with absolute certainty that 

 the creature possessed none in life. On the other hand, scattered 

 through the matrix were numerous small flakes of bone, always 

 isolated. They may indicate osseous scutes. The teeth of the 

 creature are long and slender, utterly useless for the seizure and 

 retention of large prey. I think it very probable indeed that its 

 food consisted in large part, probably wholly, of the smaller inver- 

 tebrates, cockroaches, land mollusks, worms, etc., and that in 

 habit Seymouria was not unlike the modern land salamanders, 

 slow and sluggish in movement, hiding under fallen and decaying 

 vegetation in low and damp places. 



The American cotylosaurs, more especially the Diadectidae, 

 Limnoscelidae, and Seymouriidae, show marked resemblances in 

 many ways to the contemporary amphibians, in their short legs, 

 broad feet, enormous humeral entocondyle, digital fossa of the 

 femur, pronounced adductor crest, as well as girdles; but I do 

 not believe that these resemblances were so much the result of 

 phylogeny as of convergent evolution, the adaptation to similar 

 environmental conditions and similar habits. Araeoscelis alone 

 among the known American Permian reptiles had a very slender 

 body and delicate, slender legs, adapted for climbing, or at least 

 for swift-moving upland habits. That there were many other 



