34^ SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



The antero-inferior end of the zygoma is much expanded and 

 flared outward in Liinnolagus, Nesolagus, and Rouicrolagus. It 

 is also enlarged, but not quite to the same degree in Oryctolagus. 

 In Pronolagiis is is moderately enlarged. In Lcpns, Syhilagus, 

 Brachylagns, and Pentalagiis the antero-inferior angle of the zygoma 

 is only slightly enlarged. In the last the deep fossa seen just in 

 front of the antero-inferior angle of the zygoma in the other genera 

 except Limnolagns is lacking. In Caprolagiis the antero-inferior 

 angle of the zygoma is apparently not enlarged at all. 



The posterior free projecting extremity of the malar is very large 

 and long in Roincrolagus, and is nearly as large in Limnolagns, 

 OryctolagHS, and Caprolagns. It is moderately enlarged in Pcnta- 

 lagns and in Brachylagns; in the remaining genera, Lcpns, Sylvi- 

 lagns, and PronoJagns the posterior free extremity of the malar is 

 short. 



AUDITAL BULL.E 



Most of the Leporidse have well-developed audital bullae, but the 

 degree of development is subject to some variations. The external 

 auditory meatus is prolonged upward and backward into a tubular 

 or spout-like structure. The bulla and this tvibe combined much 

 resemble a flask, the external auditory meatus being the neck. 



In Brachylagns the audital bulla is very much enlarged, the ex- 

 ternal auditory meatus large and rounded. Pronolagus, Caprolagns, 

 and Pcntalagns have very small audital bullae. The external audi- 

 tory meatus in the last is not at all spout-like ; it has the form of an 

 irregular oval bony ring, rather closely applied to the side of the 

 skull. Romerolagns has the external auditory meatus relatively 

 larger than in any of the other genera, and decidedly oval in 

 outline, instead of simply circular. The rest of the Leporidse 

 present nothing unusual in respect to the audital bullae or the ex- 

 ternal meatus. 



FENESTRATION OF MAXILL,^ 



The sides of the maxilla are fenestrated in nearly all the Leporidae. 

 In certain groups, however, this fenestration is less marked than 

 in others. In Pentalagiis there is practically none. In Limnolagns, 

 Pronolagus, and Romerolagns the degree of fenestration is mvich 

 less than it is in all the other genera, which may be said to have a 

 normal degree of fenestration. In the genera with the least degree 

 of fenestration, the infraorbital foramen is most marked and attains 

 its largest size. 



