lvon] the hares and their allies 35 5 



Leporidre. This is Forsyth Major's view on the relative number 

 of premolars and molars in Ochotona. Xo. 84,064, O. ladaccnsis 

 from Ladak, a young individual bears out this view, for it shows 

 the third maxillary tooth in process of replacement by the permanent 

 premolar. 



The teeth of Ochofoiia are simpler in every way than the teeth of 

 Lcpiis and its allies; they lack the more complicated infolding of 

 enamel and its beautiful crenation. 



Incisors. — The first upper incisors of the Ochotonidse have each 

 a simple groove. Their cutting edge is very sharp ; the portion 

 external to the groove much produced downward, the internal 

 portions slightly so produced. In this manner an unequally sided 

 V-like notch is seen on the front cutting edge of each tooth, with 

 the groove at the point of the V' . 



The second upper incisors are small slender teeth placed behind 

 the first pair as in the case of the Leporid?e. 



The single pair of lower incisors of the Ochotonidse are longer, 

 slenderer, and more pointed than the corresponding teeth in the 

 Leporid;ie. 



Check Teeth. — The first upper premolar is relatively much smaller 

 than the corresponding tooth in the Leporidae. It has a single re- 

 entrant angle, on its anterior face toward the inner edge. 



The second upper premolar has a reentrant angle on its anterior 

 face, extending to the middle of the tooth, and thence toward the 

 outer edge. There is also a broad shallow angle on the internal 

 face of this tooth. 



The third, fourth, and fifth upper cheek teeth possess each a single 

 reentrant angle on the internal face, extending all the distance 

 across the tooth, very much like the reentrant angles of the Leporidse, 

 but lacking the crenation usually seen in that family. The last 

 of these teeth has a projecting loop of enamel from the posterior 

 aspect of the tooth, thus differing from the others. 



The first lower premolar much resembles the anterior half of the 

 first lower premolar of Lcpits. It has two reentrant angles on the 

 external face, and one on the internal. 



The second, third, and fourth mandibular cheek teeth in Ochotona 

 arc much like the corresponding teeth of the Leporidse, but the 

 division into anterior and posterior portions is more marked, and 

 the two portions are subequal. 



The last lower molar is small, irregularly ovate in section, its 

 pointed end being toward the external side. A "posterior portion 

 to this tooth is completely lacking. 



