OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 377 



The question of the relationship of Araeoscelis to Bolosaurus 

 has been raised by Broom in the paper cited. He beHeves that all 

 three genera, Bolosaurus, Ophiodeirus, and Araeoscelis, are closely 

 related members of the Bolosauridae of Cope. The genus Bolo- 

 saurus was originally described by Cope from a fragmentary skull, 

 of which the only distinguishable character is found in the teeth 

 These are remarkable, formed as they are of a low crown, with a 

 sharp principal and a low accessory cusp. The type specimens 

 were later studied by Case who referred them to the Cotylosauria, 

 as had Cope, and as did Huene also later. With these typical 

 specimens Case later associated other imperfect ones discovered 

 by himself, describing them, so far as his material sufficed, as 

 Bolosaurus striatus Cope. With these later skulls Case provi- 

 sionally associated a number of vertebrae and fragments of limb 

 bones, but with no assurance, as he expressly stated, of their actual 

 identity — they were merely found in the same bone-bed and he 

 could refer them to no other known form. Had he followed the 

 more usual rule of paleontologists he would have described them as 

 new and left to others the problem of their identity ! This caution, 

 however, was not imitated by Broom, who referred all these remains 

 to one species without question of possible distinction, notwith- 

 standing Case's warning. 



He distinguishes very properly the skeletal bones from Bolo- 

 saurus, of which nothing is known with certainty, under the name 

 Ophiodeirus casei Broom, but recognized their relationship and 

 possible identity with Araeoscelis. I had hoped that the time was 

 past in vertebrate paleontology when genera and species were 

 named on the mere possibility of validity. There can be scarcely 

 a doubt that, aside from the skull, the bones described by Dr. 

 Broom as of Ophiodeirus casei are those of Araeoscelis gracilis, and 

 in much probability the discrepancy of the skull is due to error. 



VERTEBRAE 



The precise number of cervical vertebrae (Fig. 4, A, C, E) 

 cannot be determined. The probability is seven, though there is 

 the possibility of a larger number. The atlas has not been recog- 

 nized, nor is its loss surprising, since the bones composing it must 



