Cope.] 450 [May 3, 



Their characters are somewhat similar to those of H. speciosum in the 

 plications of the enamel, but the form of the internal columns is entirely 

 distinct, referring the species to ihe group of the JB. calarnarium. The 

 latter species is, however, distinguished by the very short wide form of 

 the anterior teeth, especially of the second premolar. While noting this 

 character in the Report of Lieut. Wheeler, as above cited, I did not regard 

 it as specific. Having obtained anotlier similar specimen, I am now in- 

 clined to attach more importance to it. It indicates that the H. calarnarium 

 exhibited a greater facial concavity at the diastema than any other species 

 known from this country. 



In this species the anterior distinct column has an oval section with an 

 angle directed to the anterior inner crescent. The enamel border connect- 

 ing the crescents sends towards the column two loops. The borders of 

 the lakes are plicate on their inner and adjacent sides. The front of the 

 anterior lake has a deep notch, and three still deeper ones enter from the 

 posterior inner border. There are two others on the posterior outline. 

 The adjacent face of the posterior lake has four inflections, and there are 

 two deep ones on the posterior part of the inner border. The posterior 

 crescent sends an angle backwards, which is sepai-ated from the posterior 

 inner column by a deep notch. The third premolar is narrowed and 

 somewhat produced forwards, and its interior inner column though dis- 

 tinct is reached by the narrow loop of the inner enamel border. The an- 

 terior inner crescent is peculiar in being distinct and isolated, so that the 

 cementum of the anterior lake communicates with that covering the ante- 

 rior inner side of the tooth. In the second and less worn specimen, the 

 two lakes also have a narrow communication. The former character is 

 found in H. calarnarium and R. isonesum, but not in H. speciosum. 



Measurements. 



No. 1. M. 



r longitudinal 018 



Diameters crown third premolar < anteroposterior 025 



(^transverse at column 019 



C longitudinal 015 



Diameters crown left molar J anteroposterior 022 



(^ transverse 021 



No. 2. 



r longitudinal 028 



Diameters crown eecond premolar -j anteroposterior 035 



(^transverse at column. . .014 



r longitudinal 019 



Diameters crown right superior molar ) anteroposterior 022 



(^transverse at column .022 



The specimen No. 1 equals that of H. speciosum in dimensions ; No. 2 

 is a little larger. 



