c 



283 



:oluinns issue on the grinding-face along the outer border, and are not parallel 

 in their courses, but divergent from nearer origins. The inner face behind 

 the posterior exit of the apical column is excavated as if for the application 

 of another bone ; hence, I have suspected that the piece described might be 

 premaxillary. The grinding-face is convex at the middle, but divided into 

 two planes posteriorly : the outer narrow and elevated ; the inner oblique, 

 and separated by an obtuse angle from the excavation of the inner side. 



Measurements. 



M. 

 Length of the fragment 0. 042 



Length of the fragment to the posterior exposure of the apical column 0. 020 



Depth at the end of the apical angular ridge 0." 018 



Width opposite the end of the apical angular ridge 0. (JIG 



Width of the fragment hebind 0.009 



This species is associated in my collection with specimens of Ischyodus 



smochii, but cannot be the premaxillary of that species, since that element 



occurs in the same series, and is similar to that observed in other species 



of the genus. 



DIPHR1SSA, Cope, genus novum. 



Established on peculiarities exhibited by the mandibular dentition 

 There is a large inner area of dentinal tubules, and a terminal one issuing 

 near the apex. There is but a single small external area In Ischyodus, 

 there are two such areas ; but, in other respects, the mandibles of the two 

 genera are similar. 



DlPHEISSA SOLIDULA. 



Ischyodus solidulus, Cope, Proceedings of the American Philosophical Society, 1869, p. 244. 



Greensand of New Jersey, No. 5, at Hornerstown ; from John G. 

 Miers. 



DlPHRISSA LATIDENS, Cope. 



Indicated by a mandibular ramus, derived from the same locality and 

 donor as the last species. Anterior portion or beak narrowed; the apical 

 area flat, or crescent-like. Inner area very wide, leaving but a narrow border 

 on the outer side of it. This band is but little oblique, the edge being 

 slightly elevated, and does not exhibit any dentinal area. The single outer 

 column issues near the border; its posterior edge in transverse line with the 

 anterior edge of the inner area, its anterior extremity extending a short dis- 

 tance bevon<l. The anterior border of the inner area is broad and obtuse. 



