Geological Papers. 241 



Recently, Williston (Journ. Geol., July-August, 1908) has rede- 

 scribed the specimen and has referred it to another species, which 

 he calls Isodectes copei sp. nov. Cope distinctly stated in 1896, 

 and again in 1897, that the form was a true reptile, and as such 

 was the earliest reptile known. His statement seems, however, to 

 have been overlooked, for when Raymond announced the discovery 

 of Carboniferous vertebrates near Pittsburg, Pa., he stated that the 

 forms there discovered were the oldest known reptiles; but Cope's 

 discovery antedated his in two ways — chronologically and geologic- 

 ally. Holland corrected this error in the report of the director of 

 the Carnegie Museum for 1908. 



The specimen as preserved is less than six inches long and con- 

 sists of the entire body of the animal, minus the head and the right 

 fore limb. The absence of the head is to be especially regretted, for 

 it is upon the skull characters that most of our classification is based, 

 and it is to this portion of an animal's anatomy that we refer for 

 the final analysis of the creature's position. The most noteworthy 

 reptilian characters which can be detected on the remains pre- 

 served to us are the osseous carpus and tarsus, two sacral vertebrae, 

 the reptilian phalangeal formula (2, 3, 4, 5, 4) for the hind foot, 

 the inter-central attachment of the ribs (as is the case in the Mi- 

 crosauria), and the well ossified condition of the limb bones, a mat- 

 ter of no slight importance. In some of its characters it is so clos6 

 to the Microsauria that were it not for the two sacral vertebrae and 

 the osseous carpus and tarsus it would undoubtedly find a place 

 among the Amphibia. The absence of ventral ribs is to be espe- 

 cially noted. 



The presence or absence of the ventral ribs seems to be a matter 

 which is little understood, and doubt has been thrown on the use 

 of this character as one of any importance. Among the Micro- 

 sauria there are forms which possesss well-developed ventral ribs, 

 and others, not distantly removed otherwise in structure, which 

 possess no ventral ribs whatever, i. e., the Tuditanidse and the 

 Amphibamidse. What the function of the ventral ribs was is also 

 a little doubtful. To say that they developed merely to protect 

 the abdomen of the animal is merely begging the question, for if 

 they develop for this purpose in one form why should not other 

 forms with similar habits also develop similar structures? The 

 degree of the ossification of the limb bones is a matter to which 

 but slight attention has been paid. In the study of a large series 

 of the Microsauria this is found to be quite variable. Some forms 

 seem to have the limb bones made up of perichondrium alone, 

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