39^ SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45. 



any of the rabbits except those of the genus Orycfolagiis. The por- 

 tion of the palate bone that borders the maxilla caudad of the 

 posterior edge of the bony palate is poorly developed in Sylz'ilagiis. 



The posterior palatine foramina are of moderate size and located 

 between the palatine plate of the maxilla and the horizontal plate 

 of the palate bone, at the anterior outer angles of the horizontal 

 plate. 



The zygoma of Sylzilogiis is thin and shallow. The foot-like 

 extremity of zygomatic process of the squamosal is short, the external 

 lateral length of the squamoso-malar suture is contained about two 

 times into the superior border of the malar measured from the 

 anterior end of the squamoso-malar suture to the antero-inferior 

 angle of the orbit. The antero-inferior end of the zygoma is only 

 slightly enlarged. The posterior free extremity of the malar is short. 



The audital bullae, the external auditory meatus and the fenestra- 

 tion of the maxillse in Syk'Hagiis show nothing distinctive and may 

 be said to represent normal degrees of development. 



The angular process of the mandible is rather larger and more 

 rounded, as compared with Lcpiis. The ascending ramus is of 

 moderate development, resembling that of Lepus. 



Teeth (pi. xci, 9; figure 44, 2 and 3). — The following are the char- 

 acters of the teeth of the genus Syh'Uagus, which, with the exception 

 of the front upper incisors and first lower premolar, and smaller size 

 throughout, are not different from those of the teeth of Lepus: First 

 upper incisors with longitudinal groove in anterior face always 

 simple, usually shallow and filled with cement only in a few speci- 

 mens from Mexico. The first upper maxillary tooth has typical fold- 

 ing 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 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. In some of the specimens of Sylvi- 

 lagiis, from Mexico, the anterior face of this tooth is marked by two 

 reentrant angles, instead of the usual one, the tooth in this case 

 resembling the first lower premolar of Limnolagits. The second, 

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

 reentrant angle extending from the internal face about three-quarters 

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

 almost in contact with one another throughout their whole extent. 

 The enamel of the reentrant angle is crenated. In the second, third, 

 and fourth lower molariform teeth the lateral diameter of the pos- 

 terior half of each tooth is about four-fifths of the lateral diameter 



