237 



Measurements. 



M. 



Length of the last maxillary tooth 0. 003 



Long diameter of the basis of the last maxillary tooth 0. 004 



Depth of the maxillary bone at the basis of the last maxillary tooth 0.012 



TETHEODUS, Cope. 



Premaxillary bone a petrous mass, without teeth ; the maxillary with 

 teeth in a single row, the anterior much enlarged ; dentary with a single 

 series, one anterior tooth much enlarged. Apices of teeth with trenchant 

 edges. 



A genus chiefly differing from Enchodus in the absence of the large tooth 

 at the extremity of the premaxillary bone. 



Tetiieodus pepiiredo, Cope. 



Both premaxillaiy and portions of the maxillary and dentary bones of one 

 specimen represent this species. They show it to have been a powerful fish, 

 of the size of the Enchodus j)etrosus below mentioned. The premaxillaries are 

 excavated by the usual three oblique fossae above on the inner side. The alve- 

 olar face is a ridge extending obliquely across from a tuberosity on the inner 

 side, behind the apical tuberosity. There is no surface for the attachment 

 of a tooth, and no scar or other trace of the former existence of one. The 

 maxillary underlaps it by an oblique suture, and supports a large tooth simi- 

 lar to that at the end of the premaxillary in Enchodus, behind which are seen 

 the crescentic scars of the previously shed teeth. The outer face of the basal 

 cementum of this tooth is perfectly smooth. The distal portion of the dentary 

 bone is toothless ; its anterior tooth is a fang, with the base excavated in front; 

 and an angle rising from the external side of it becomes a latero-exterior 

 cutting-edge of the crown to the apex. The inner posterior, or more convex, 

 face of the tooth is regularly and closely striate-grooved. On one dentary, 

 there are three or four small denticles in front of it on the outer side. The 

 smaller teeth have two cutting-edges, and the posterior face at the base is 

 grooved striate. This regular grooving, as well as the large size of the first 

 maxillary, distinguishes this fish from the Phctsganodus anceps. 



Measurements. 



sr. 



Length of the premaxillary bone above 0. 075 



Depth of the premaxillary bone above 0. 03£ 



Width of the basis at the first maxillary tooth 0.010 



