466 GEOLOGICAL. SURVEY OF THE TEEEITORIES. 



niform tooth be regarded with F. Ouvier as a premolar, the nnmbers 

 of the latter teeth must be read in these genera f and f respectively. 

 Since it is situated in advance of the foramen mentale and closes in 

 front of the superior canine, it is probably not a premolar, but a true 

 canine, and the number of inferior incisors is correctly stated as four on 

 each side. In the typical species, H. fugax, the superior molars are 

 co'mposed of two.external triangles, and an internal cingulum-like cres- 

 ent, near the base of the crown ; last molar with only one external tri- 

 angle; premolars compressed, simpte ; canines large, simple, subyerti- 

 cal ; inferior incisors slender. 



The homologies of the cusps of the upper molars appear to be that 

 the apices of the external triangles represent a median series of cusps, 

 while the longitudinal ridge forming their bases represents the cusps of 

 the external row. When in an unworn state, their apices are probably 

 more distinct. At present, in the typical specimen, the ridge is not less 

 elevated than the apices of the triangles. This genus differs from the 

 Talpidce and resembles the Isacidce in the fact that the cusps of the pre- 

 molars are homologous with the external one of the true molars, and not 

 with those of the median series, as in the former family. But it agrees 

 with the Talpidce in the presence of two triangles and a well-developed 

 internal lobe. All of the teeth, and especially the canines, are more 

 robust than in Talpa and Sealops. 



The known species differ as follows : 



I. Anterior cusp of molars well separated ; several molars 

 with three cusps on the heel : 



Size, medium H. tricuspis. 



Size, very small H. huntii. 



II. Anterior cusp well separated ; heel (except of the last) 



with two cusps : 

 Heel of M. 4 narrow ; middle cusps moderate : 



Yery small S. stevensonii. 



Large M.fugax. 



Heel of M. 4 narrow ; middle cusps elevated much 

 above heel : 



Medium S. scalare. 



Hbepetotherium: tricuspis. Cope., Synopsis IsTew "Vertebrata GoL, 

 1873, (October 16,) p. 5. 



Eepresented by portions of five mandibular rami. Posterior tubercle 

 low, on the inner side, visible in all the molars. A hiatus between the 

 first and second premolars; foramina below P. m. 1 and M. 1 : canine 

 well developed. 



Measurements, 



M. 



Length of dental series from canine, omitting M. 4 „ 0.0110 



Length of first true molar .* 0020 



Elevation of first true molar 0018 



Depth of ramus at third true molar 0027 



Herpetotherium huntii, Cope, Synopsis, loc. cit., p. 5. 



The least species of the genus, represented by portions of three man- 

 dibular rami with all of the molar teeth. 



All the cusps low, the median unequal, the anterior and posterior 

 divergent, the latter concealed by the former when in place, although 

 well developed. Foramina below P. m. 2 and M. 1. 



