502 GEOLOGICAL SUEVEY OF THE TEERITOEIES. 



are short ; enamel smooth. The valleys of the anterior lower molars 

 disappear with use more readily than in some of the allies. The second 

 inferior premolar is one-rooted. 



The symphysis is spatulate, and emarginate distally, very convex be- 

 low, shallowly concave above. The diastemata are occupied by sharp 

 borders, which are slightly approximated at the posterior part. The 

 teeth are directed anteriorly, and are subequal. The mental foramen is 

 just in front of the bounding angle of the symphysis. 



Measurements. 



M. 



Length of symphysis 0.0090 



Width, (least) 0035 



Width at L5 0042 



Width at L 3.. 0046 



Length of three molars above, (No. 1) .0120 



Length of last molar 0050 



Width of last molar 0030 



Length of three inferior posterior molars, (No. 2) 0130 



Length of inferior last molar 0058 



Width of inferior last molar 0025 



Probably the least-known species of Artiodactyle. This exceedingly 

 small ruminant was very abundant during the period of the oreodons, 

 &c. 



HTPEETEAGULUS, Cope. 



Bulletin U. S. Geol. Survey, No. 1, 1874, p. 26. 



This genus is allied to Bremotlierium^ Geoff. , and Leptomeryx, Leidy. 

 The diagnosis may be thus compared ; that of the first I derive from 

 Pomel : 



ffypertragulus, Cope : Molars, 6-6 ; first superior premolar without 

 internal lobe ; inferior premolars differing in form, the first one lobed, 

 situated at a distance from the second, which is not three-lobed. 



DreynotJierium, Geoff. : Molars, 6-6 ; first superior premolar without 

 interior lobe ; inferior premolars similar, three-lobed, and contiguous. 



Leptomeryx, Leidy : Molars, 6-6 ; first and second superior premolars 

 three-lobed, and with an internal lobe ; third with an inner and an outer 

 crescent ; inferior premolars similar, three-lobed, and contiguous. 



In Hypertragulus, the third upper premolar exhibits an internal as 

 well as an external crescent. The canine of the inferior series stands 

 in the middle of a considerable diastema, which is preceded by three 

 incisors. 



Hypertragulus calcaratus, Cope, Bull. U. S. Geol. Surv., p. 26 ; 



Leptauchenia calcarata, Cope, Pal. Bull., No. 16, p. 7. 



The second superior premolar is quite short, and its inner lobe small. 

 The last premolar has a strong cingulum on the anterior, and especially 

 on the posterior faces of the last premolar. The su^Derior molars have 

 no rib or column opposite the interval between the crescents ; the last 

 molar exhibits four ribs on the outer side. The second (third) inferior 

 premolar is compressed and elevated and much shorter than the third, 

 which is three-lobed. The posterior crescents of the last inferior molar 

 are opposite, and not separated posteriorly by a fissure. 



This very abundant species of musk is a little smaller than the Lepto- 

 meryx evansii. 



