l^'On] the hares and their allies 



431 



Its general build of skull seems to associate it with Caprolagus and 

 Ncsolagus. But Caprolagus has typical leporine teeth and the upper 

 cheek teeth of Ncsolagus seem to resemble those of Bracliylagus. 

 In the structure of the first lower premolar, Fciifalagus, Ronicrolagus, 

 and Pronologus are very similar. 



The dental formula, the relation between radius and ulna, and 

 the extremely short hind foot associate Pcntalagtis with Oclwfojia, 

 but the general structure of its skull is entirely leporine. 



Family OCHOTONID^ 



Genus OCHOTONA Link 



1778 



Lepus (in part) Pallas, Glires, pp. 1-70. 



1795. Ochotona Link, Beytrage Naturgesch., i, pt. ii, p. 74. 



1800. Lagoniys Cuvier, Legons d'Anat. Comp., i, Table. 



1867. Ogotoma Gray, Ann. Mag. Nat. Hist., xx, 3d sen, p. 220. 



1867. Lagoniys Gray, Ann. Mag. Nat. Hist., xx, 3d sen, p. 220. 



1897. Ochotona Trouessart, Catalogus Mammalinm, i, fasc. ii, p. 645. 



1899. Lagoviys Major, Trans. Linn. Soc. London, 2d sen, vii, Zool., p. 

 435, November, 1899. 



Type. — Ochotona ochotona (Pallas). 



Geographical Distribution. — In the mountain ranges of eastern 

 Europe, central Asia, Siberia, and the Boreal Zone of the mountains 

 of western North America. 



Diagnosis. — Same as for the family Ochotonidas. Duplicidentate 

 rodents without postorbital processes, and the second upper cheek 

 tooth different in structure from the third. See also page 384. 



Skull (pi. xc). — As a whole the skull of Ochotona is small, 

 flat, not arched, brain case not rounded or inflated, rostrum short and 

 moderately slender, the greatest width of the nasals being anterior 

 and not posterior as in the case of the typical Leporidoe. 



Postorbital processes are lacking. 



The interparietal is present as a distinct bone. 



The bony palate is very short, and the incisive foramina in front 

 and the choanse behind are separated only by a very narrow bridge 

 of bone. The sutures of the horizontal plates of the palate bones 

 and of the horizontal plates of the maxilla are obliterated in adult 

 skulls. Young individuals show that more than half of the bony 

 palate is formed by the horizontal plates of the palate bones. The 

 horizontal plate of the palate is largely developed between the dental 

 alveoli and the outer border of the choanse, each such portion of the 

 horizontal plate of the palate bone being approximately equal to the 

 width of the choanse. 



