3o6 Bulletin American Museum of Natural History. [Vol. XVI, 



LEPORID^. 



Palseolagus Leidy. 



The genus was based on the division of the anterior lower 

 premolar into two columns, instead of three as in Lepns. The 

 dentition and characters of the front of the skull and of parts 

 of the skeleton were fully figured and described at length by 

 Professor Cope in his 'Tertiary Vertebrata, ' and have been 

 further discussed and revised in recent papers by Dr. Forsyth- 

 Major on the Lagomorpha. We are now enabled to add cer- 

 tain skull characters, not hitherto known. 



PalcEolagvis has a well-developed postfrontal process in all 

 four species, scarcely less than in Lepus ennisianus , but much 

 less than in modern Lepores. The angle between basicranial 

 and basifacial axes varies considerably in the different species, 

 but in none is it as great as in the modern species of Lepus. 

 The brain is relatively smaller than in Lepus. The tooth 

 pattern varies greatly during life; in the young it approxi- 

 mates that of Lepus, especially in such species as L. ennisianus ; 

 in the old animal it becomes much simpler. P. agapetillus is 

 the most advanced in tooth, but least in skull, characters; P. 

 interinedius most nearly approaches the John Day Lepus. 



The pattern of the teeth changes greatly in Palceolagus,'ap- 

 parently from the superposition of a new pattern (that of 

 Lepus) on an older and simpler one. The young individuals 



show an internal inflec- 

 tion on the upper molars, 

 whose depth and persist- 

 ence varies in the differ- 

 ent species ; there is also 

 an external inflection, 

 never deep, but rather 

 persistent, and a median 

 crescent which origin- 

 ates as an anterior mar- 

 Fig. 15. Lepus ennisianus. Cope. Skull and lower . , . _ 

 jaw natural size. Type specimen No. yigo. John Day, gmal mfleCtlOn OH p*, 

 Oregon. Muzzle supplied from another individual. , 



an anteroexternal one 

 on p3 (apparently median-external on p* and m^), a postero- 



