NEW PERMIAN VERTEBRATES. 247 



twenty-four is the number of presacral vertebrae in the rhachitom- 

 ous Trematops as determined by me ; twenty-three or twenty- 

 four was the number ascertained by Thevenin in Saiiravus costci,. 

 a probable reptile from the Upper Carboniferous of France ; and 

 I believe that Isodectes Copci, from the Lower or Middle Missis- 

 sippian of Linton, Ohio, had the same number. This uniformity 

 seems to be more than a coincidence. Of this number the atlas 

 alone can be called, as in the amphibians, a true cervical. All 

 the vetebrae bore ribs, and, inasmuch as there was no sternum in 

 these early forms, a distinction into neck and trunk is impos- 

 sible. The centra of our specimen are rather slender more so 

 than in Labidosaurns each with a marked constriction in the 

 middle. Some of the posterior vertebrae lie partly upon their 

 sides, disclosing the attachment of the ribs. No distinct process, 

 is seen on the centrum for them, differing in this respect from 

 Labidosaurns, though doubtless the lower part of the proximal 

 extremity of the ribs did articulate with the centrum. A small 

 intercentrum is present in one or two of the anterior vertebrae,, 

 and a small space is seen between the lower edges of the centra 

 of all. The sacral vertebrae are of course not visible in the 

 pelvis. There were, in all probability, but two sacral vertebrae,, 

 though this is not certain since another form of Permian 

 reptile, which will be illustrated and described later, has three, 

 while Labidosaurus has but two. If the vertebrae above the 

 pubes and ischia are of the same length as those immediately fol- 

 lowing or preceding, there are six concealed from view, one of 

 which is the first presacral, and three the basal caudals. Behind 

 the pelvis eight caudal vertebrae in a connected, gently curved 

 series are visible. They are somewhat shorter and more slender 

 than the presacral vertebrae, the entire series measuring about 

 forty-six millimeters. Beginning with the second of these there 

 are long, slender chevrons, each reaching to beyond the end of 

 the next succeeding centrum, that is, about fourteen millimeters 

 in length. Just how far back these chevrons continue is not 

 certain, but at least eight centra bore them. The first entire 

 vertebra back of the pelvis bears a long, curved rib on each side, 

 springing from the anterior end of the centrum. The next two 

 vertebrae doubtless have similar, but short ribs, though only the 



