78 AMERICAN PERMIAN VERTEBRATES 



SPHENACODON 



Sphenaco don ferox Marsh, Amer. Jour. Science, XV, 410, May 3, 

 1878. 



In the present genus the anterior teeth are somewhat like those of the 

 reptile described above, but the posterior, or more characteristic ones, are 

 totally different. The crowns are much compressed, and have very sharp cutting 

 edges, without crenulations. In the present species the carnivorous teeth are 

 crowded together, and the crowns placed slightly oblique, and twisted. The 

 jaws were comparatively short and massive. The rami of the lower jaws were 

 apparently united by cartilage only, and the symphysis was short. The 

 vertebrae are deeply biconcave. 



Measurements from the type of this species are as follows : 



Length of dentary bone 150 mm. 



Space occupied by teeth 130 



Extent of four anterior caniniform teeth 25 



Extent of twenty compressed teeth 105 



Height above jaw of second lower tooth 15 



Depth of dentary bone at symphysis 26 



Height of crown of compressed tooth 8 



Transverse diameter 4 



This reptile was about six feet in length, and carnivorous in habit. Its 

 remains are from the same locality in New Mexico that yielded those of 

 Nothodon. 



The type specimen is shown natural size in Plate XXXIV, 

 Fig. i, a left, incomplete dentary. The second tooth, while agree- 

 ing with his measurements, is incomplete; the fracture is evident, 

 yet apparently Marsh did not observe it. The tooth was probably 

 twice the length shown in the figure. There appears also to have 

 been a very small tooth in front, of which only a slight indication 

 of the alveolus remains. That this specimen is the holotype, 

 aside from the general agreement of the measurements, is assured 

 by the fact that it was the only bone in the entire collection which 

 had been mended, by the gluing together of the seven separate 

 pieces of which it was composed. And there is no other specimen 

 in the entire collection which will agree with his description. In 

 immediate association with this dentary, in the same lot and collected 

 with it, are two maxillae, which agree in size, color, and condition of 

 preservation. There can be scarcely a doubt but that they belong 



