13 



Three scaphoid bones of graduated sizes are contained in the Cypress Hills collection, 

 and there are two magnums which correspond in size to the middle-sized scaphoid and to 

 one between that size and the largest. These may be referred, comparing them with the 

 other bones already described, as follows : — Scaphoid No. 1, M. americanus ; magnum, No. 

 1, M. proutii ; scaphoid and magnum No. 2, M. angustigenis ; scaphoid No. 3, M. (?) sy 

 ceras. Comparisons will be made under the head of M. angustigenis. 



Teeth of the large species of Menodus are rare in the collection, a last inferior molar and 

 premolar representing them. Most of the teeth preserved belong to the size appropriate 

 to the M. angustigenis. 



Menodtjs angustigenis, Cope. 



Annual Report Geol. and Nat. Hist. Survey of Canada, 1885, C, p. 81 ; Haplacodon angustigenis, Cope, Amer- 

 ican Naturalist, 1889, p. 153. 



This large Mammal is represented by numerous specimens. I select for present 

 description two maxillary bones from the same skull, each of which contains the first 

 premolar and the true molars ; and two lower jaws from second and third individuals. 

 One of these consists of little more than the symphysis. The other includes part of the 

 symphysis and part of the left ramus, which contains all the molar teeth except the first 

 and last. 



I refer the species to Menodus, because both lower jaws have, like the Menodus 

 proutii, Leidy, two incisor teeth on each side. The specimen in which the ramus is 

 present has a small alveolus for the first premolar on each side ; the side of the other 

 specimen, where this part is preserved, has no such alveolus. These specimens show the 

 identity of the supposed genus Brontotherium with Menodus. In the contracted shape of 

 its mandibular symphysis this species resembles the species of Symborodon rather than 

 the Menodus proutii, and it resembles the smaller species of Symborodon in its inferior 

 dimensions. It resembles the species of Menodus in the wide internal cingulum of the 

 superior premolars. The species of Symborodon which present this character are the S. 

 trigonoceras and the S. heloceras, Cope. Its measurements are inferior to those of the S. 

 trigonoceras, and the superior molars are of different form. In the species just named their 

 outline is oblong, the anteroposterior diameter exceeding the transverse in all three of 

 them. In the M. angustigenis the molars are nearly square in outline. 



The superior molars of the S. trigonoceras are characterized by the flatness of the 

 middle portion of the external face of the external Vs. This surface is neither excavated, 

 nor is it keeled, excepting a slight convexity on the middle of the anterior Y of the first 

 molar. The middle lines of the external faces of the Vs of the fourth premolar are slightly 

 convex. There is a prominent vertical angle descending from the apex of each external A , 

 and no lateral ones, so that there are no lateral pits at the internal base of the V on each 

 side of the apex, as is seen in the Symborodon trigonoceras. The internal cones of the 

 first superior premolar are not well distinguished. The only traces of cingula on the 

 true molars are just in front of the median external vertical rib. 



