43 



thickened basis. Tbey are rather remote in a fauctional condition, each 

 interspace being entirely occupied by the alveolar fossa of the shed 

 tooth. These bases are very stout and composed of dense bone 5 their 

 apices rise a little above the edge of the external alveolar border. The 

 bases of the crowns are oval, and they display an anterior cutting edge, 

 which descends from the apex, thus differing materially from those of 

 the P. caninus. The teeth diminish in size from the middle of the den- 

 tary bone to the symphysis ; beside the latter are two teeth of reduced 

 size. The outer face of the dentary is smooth, except some small im- 

 pressed fossse. The mental foramina are small and do not issue in a 

 groove. Below them, on the outer face, is a fossa, with level floor to 

 the inferior margin. 



Measurements. 



M. 



Length of margin bearing four teeth 0.050 



Depth of ramus at third tooth 025 



Elevation of tooth basis 008 



Long diameter base of crown of ditto 006 



Niobrara epoch of Phillips County, Kansas. 

 Pachyrhizodus SHEARERi Cope, Proceed. Amer. Philos. Society, 1872, 

 p. 347. 



Mobrara epoch of the Smoky Hill Eiver. 



PHASGANODUS, Leidy. 



Phasganodus dirus, Leidy, Proceed. Acad. ITat. Sciences, Philada., 

 1857, 167 ; Keport Geolog. Survey Terrs. 1873, I, 289; tab. xvii, figs. 

 23, 24. 



From Cannon Ball Eiver, Dakota. 



Phasganodus (?) G-LADiOLUS, Cope ; ClmoUchthys gladiolus^ Cope, Pro- 

 ceed. Amer. Philos. Soc, 1872, 353. 



Niobrara epoch of the Smoky Hill Eiver. 



TETHEODUS, Cope, ge>i. nov. 



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 trench- 

 ant edges. 



A genus chiefly differing from Encliodus in the absence of the large 

 tooth at the extremity of the premaxillary bone. 



Tetheodus pephredo, sp. nov. 



Both premaxillary and portions of the maxillary and dentary bones 

 ot one specimen represent this species. They show it to have been a pow- 

 erful fish of the size of the Encliodus petrosus below mentioned. The 

 premaxillaries are excavated by the usual three oblique fossse above to 

 the inner side. The alveolar 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 ob- 

 lique suture, and supports a large tooth similar to that at the end of the 

 premaxillary in _E//ic/iOcZMS, behind which are seen the crescentic scars of the 

 previously-shed teeth. The outer face of the basal cementum of this tooth 



