A DESCRIPTION OF THE GENUS DIMETRODON, COPE. 



9 



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 : 



MM. 



Length of dentary bone 150 



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." 

 This is probably one of the Clepsydropidce. 



" Ophiacodon minis, gen. et. sp. nov. 



" A third genus of Reptiles allied to the last described is indicated by various well- 

 preserved remains from the same locality. The teeth are all carnivorous in type, conical 

 in form, and all are similar. Those in the anterior part of the jaws are recurved, and in 

 general shape resemble those of Serpents. The rami of the lower jaws were united only 

 by cartilage. The vertebrae are very deeply biconcave, and even perforate, and the intra- 

 central bones large. In the present species the teeth are nearly smooth, and somewhat 

 compressed. 



" The following measurements indicate the size of this reptile : 



MM. 



Extent of anterior sixteen teeth in dentary 75 



Extent of anterior five lower teeth 20 



Height of crown of fourth lower tooth 10 



Depth of lower jaw at symphysis 15 



Extent of seven anterior maxillary teeth 33 



Height of crown of first maxillary tooth 9 



Antero-posterior diameter of crown 3 



" This species was about as large as those described above, and is from the same 

 geological horizon in New Mexico. 



" Ophiacodon grandis, sp. nov. 



" A second larger species of apparently the same genus is represented by portions of 

 the jaws, and teeth, and various parts of the skeleton. In this species the dentary bone 

 is angular at its anterior extremity, and triangular in section. Its external surface is 



a. p. s. — VOL. XX. B. 



