62 



A hiisal ridge exists at the outer back part of the crown of tlie seconcl pre- 

 molar, and, less produced, exists in the same position in the third. No ridge 

 occupies the inner prominence of tlie inner lobe of the second premolar. 



A specimen of an upper left last premolar, found at Grizzly Buttes by Dr. 

 Corson, is represented in Fig. 12, Plate IV. It is larger than in the entire series 

 of Fig. 10 and is less worn. It exhibits a basal ridge externally interrupted 

 at the middle ; and internally the ridge is also interrupted or nearly obsolete 

 at the middle. The posterior ridge or fold between the inner and postero- 

 external lobes, though smaller, is more defined from the lobes than the ante- 

 rior I'idge. The latter appears rather as a pi'olongation of the inner lobe to 

 the fore jiart of the base of the antero-external lobe. The posterior ridge has 

 the appearance of an introduced piece defined from the lobes by consti'ictions 

 or grooves. The arrangement is badly represented by the artist; nor is it 

 obvious if it existed iii the corresponding more worn tooth of the series (jf 

 Fig. 10. 



In a much mutilated specimen, obtained by Dr. Corson at Grizzly Buttes, 

 containing the remains of the last two premolars and succeeding two premo- 

 lars, the basal ridge is better developed at the inner part of the crown than 

 in any of the preceding. The last premolar exhibits the same condition of 

 the posterior ridge intervening to the internal and postero-external lobes of 

 the crown as that described in the isolated tooth. The same tooth, barely 

 worn, exhibits the summit of the inner lobe of the crown slightly divided into 

 two points, so that it presents a less degree of connation than in the preceding 

 specimens. 



The upper molars and premolars, except the first one, are inserted by three 

 fangs, of which the inner one is a connate pair; the connation being most 

 complete in the premolars. The first premolar has two fangs. The space 

 occupied by the upper molar series is about 3| inches. 



Fig. 13, Plate IV, represents a specimen, found by Dr. Carter, in company 

 with the upper molar teeth of Figs. 9 and 10, and evidently pertaining to the 

 same individual. The specimen consists of the anterior extremity of the 

 lower jaw, retaining the incisive alveoli, the canines, and on one side the four 

 premolars. A view of the triturating surfaces of the latter is given in Fig. 

 14. Figs. 15 and 16 represent a second molar, and Fig. 18 an incisor from 

 (he same individual. 



Fig 25, Plate XX, was drawn from a specimen consisting of the greater 



