lvon] the hares and their allies 39^ 



in most of the other genera. The external lateral length of the 

 squamoso-malar suture is contained about twice in the superior 

 border of the zygoma, measured from the anterior end of the 

 squamoso-malar suture to the antero-inferior angle of the orbit. The 

 antero-inferior angle of the zygoma is only slightly enlarged in 

 Lcpns. The posterior free projecting extreniity of the malar is 

 short. 



The audital bullae, the fenestration of the maxillae, and the shape 

 of the mandible throughout the genus show nothing distinctive and 

 may be said to represent normal degrees of development. 



Teeth (pi. xci, 6).— The following are the dental characters 

 of the genus Lepus: Front upper incisor with longitudinal groove 

 in anterior face, more or less deep, simple or branched inter- 

 nally, filled or unfilled with cement. First upper maxillary tooth 

 has typical folding of enamel on the anterior surface, a deep median 

 reentrant angle, on either side of which is a smaller reentrant angle. 

 The first lower molariform tooth, divided into two portions by a 

 single reentrant angle from the external face, has a small reentrant 

 angle on its anterior surface, and a shallow broader reentrant angle on 

 the external surface of the anterior half of the tooth. The second, 

 third, fourth, and fifth upper molariform teeth show each a deep re- 

 entrant angle extending from the internal face about three-quarters 

 the distance across the tooth ; the adjacent edges of this angle are al- 

 most in contact with one another throughout their whole extent. The 

 enamel of the reentrant angles is beautifully crenated. The lateral 

 diameter of the posterior half of each of the second, third, and fourth 

 lower molariform teeth is about four-fifths the lateral diameter of 

 the anterior half of the tooth. The last upper molar is a small 

 elliptic cylinder; the last lower molar is a small double cylinder in 

 form, the anterior half of which is larger and elliptical, the posterior 

 half terete. 



Vertebral Colunin. — The cervical vertebrae (pi. xcii, 7-9) of 

 Lepus have a form characteristic for the genus and are uniformly 

 lengthened as compared with the same series of vertebras in the other 

 genera. The costo-transverse process does not project laterally from 

 the centrum to a marked extent, and the anterior and posterior spines 

 of the same are more elongated. 



The thoracic vertebrae show practically nothing characteristic of 

 Lepus. The neural spines in the anterior part of the series equal 

 about two and a half to three times the length of their centra. The 

 anticlinal vertebra is usually the eleventh, but it may be the tenth. 

 A well-developed metapophysis is found on the ninth thoracic. 



