1878.] *)\J i [Cope. 



Char. Specif. The external surface of the crown is marked to the apex 

 with waved grooves of the enamel. The edge of the elevated cusp, which 

 presents posteriorly in the maxillary teeth, constitutes the abrupt termina- 

 tion of the exterior face, and is serrate by the interference of the sulci. 

 The edge of the basal ledge is slightly serrate. The muzzle is rather 

 elongate, and the sides of the maxillary and dentary bones are plane and' 

 smooth. The mandible is rather narrow, and forms a narrow wedge in 

 profile outline. It rises posteriorly behind the dental line. The teeth are 

 separated by intervals as wide as a tooth. 



Measurements. M. 



Long diameter of orbit No. 1 0130 



Depth of upper jaw at orbit 0045 



" lower jaw at front of orbit 0050 



Four teeth in 0080 



Elevation of a crown 0025 



Transverse diameter of inferior molar No. 2 0025 



From the same locality as the Diadectes sideropelicus. 

 A slight modification of character is found in two imperfect crania. 

 The principal character is to be seen in the teeth. The enamel of the ex- 

 ternal surface of the cusp is not sulcate, but is smooth ; and the posterior 

 cutting edge of the cusp is much less distinct. It is, in fact, obtuse, and 

 not serrate. The orbit is large, and the front and muzzle are regularly 

 decurved to the premaxillary border. The angle of the mandible is modr 

 erately prominent, and is massive and obtusely truncate. The interorbital 

 region is flat in the transverse direction. 



Measurements. M. 



Length of skull to mandibular angle 050 



orbit 015 



Long diameter of orbit .018 



Width of interorbital region 009 



Six teeth in 010 



Boi,OSAURUS RAPIDENS. Sp. nOV. 



Established primarily on a tooth from the posterior or middle portion of 

 the series, with which is associated another, probably from an anterior 

 position in the jaw. The size is many times greater than that of the spe- 

 cies of this genus already described, and it is uncertain whether the poste- 

 rior tooth possesses the internal ledge characteristic of them. The anterior 

 tooth does not possess it. The transverse diameter of the crown is consid- 

 erably greater than the antero-posterior, and the convexity of the outer 

 side is without facets. One side of the curve is flatter than the other. 

 The enamel is perfectly smooth. The inner face is occupied by the surface 

 of attrition of the corresponding tooth of the opposite jaw. The supposed 

 anterior tooth is from anothor locality. Its section is similar to that of the 

 present tooth, and the enamel is similarly smooth. The cutting edges are 

 both smooth, and bounded by a little groove next the plane inner face. The 



