118 B. S. Lull — Primitive Pecora in Yale Museum. 



while a third bears the same relation to the heel. Thus 

 there are three internal buttresses separated by valleys. 

 No traces of cingula on premolars. Measurements : 



mm. 



Length, P to M 3 ca. 28* 



Length, M^ to M 3 18.3 



Length, M 3 8 



Width, M 3 3.5 



*Slightly elongated by fracture between P, and P 3 . 



A detached small, slender, two-rooted premolar is 

 present. It probably represents P 2 of the left ramus and 

 is not distinguishable from that already described. 



Relationships. — This is the smallest artiodactyl thus 

 far described from the Lower Miocene. In this respect 

 it is suggestive of the Oligocene Hypisodus, with which 

 it also agrees in hypsodonty and in the absence of the 

 mesostyle. They differ, however, in the absence of a 

 buttress on the posterior external crescent of M 1 - 2 and in 

 the character of the premolar teeth. The inner anterior 

 crescent of M 1 is markedly different. 



The form under discussion differs from Leptomeryx 

 in the absence of mesostyles, character of heel of poste- 

 rior lower molar and of the premolars, and in size. "With 

 Hypertragulus it agrees in the absence of mesostyle and 

 the character of the heel of M 3 , but differs again in its 

 much smaller size and the character of its premolars. 

 Nanotragulus differs markedly from Merycodus in size 

 and geologic level, also morphologically in the absence in 

 the former of the mesostyle, in the convergence of the 

 molar crowns, and in the character of the premolar teeth. 

 They agree mainly in hypsodonty. 



From its contemporary, Stenomylus, the new genus 

 also differs very markedly in size and in the character of 

 the premolars. The two genera agree, however, in 

 hypsodonty, and in the absence of mesostyle, though the 

 latter is indicated on M 1 of Stenomylus. In Stenomylus, 

 moreover, the external face is relatively smooth except 

 for parastyle and metastyle. In the lower dentition of 

 Stenomylus there is greater simplicity, especially in P 4 , 

 which in no way resembles that of Nanotragulus. In 

 other words, Nanotragulus is deer-like, not camel-like as 

 is Stenomylus. 



