352 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



The groove is bifurcated internally, deep and filled with cement 

 in Lepiis (Macrotolagits) gaillardi, in Lcpus (Macrotolagus) alleni, 

 in Lcpus (Macrotolagus) uicrriami, in Lcpus ruHcaudatus, in Lcpus 

 sp. from Jumna river, India. The groove is deep, filled with 

 cement, and trifurcated in Lcpus {Macrotolagus) callotis and Lcpus 

 [Macrotolagus) ascllus. 



It is rather difficult to make any general statement about the 

 character of the groove, so far as groups go. In certain members 

 of the genus Lcpus this groove attains the greatest development, 

 but at the same time in the subgenus Poccilolagus the groove is 

 shallower than in any of the specimens at hand, and is not filled 

 with cement. Even in the subgenus Macrotolagus the same ex- 

 tremes are met. 



Check Teeth. — In Brachylagus the anterior surface of the first 

 upper molariform tooth presents a single shallow reentrant angle. 

 In all the other genera the anterior surface of the tooth presents a 

 relatively deep median reentrant angle, and two shallower lateral 

 reentrant angles, one on each side of the main median one. There 

 is more or less individual variation in the depth and form of these 

 folds, and occasionally the median fold itself is slightly crenated. 

 In the genera Pronolagus, Caprolagus, and Pcntalagus these re- 

 entrant angles are deeper than they are in any of the other genera. 

 In Pcntalagus the main reentrant angle of this tooth is much crenated. 



The first lower molariform tooth has the simplest folding of 

 enamel in Brachylagus, there being only a shallow reentrant angle 

 on the outer surface of the anterior half. 



The genera Lcpus, Oryctolagus, and Sylvilagus all have a small 

 reentrant angle on the anterior face of the first lower molariform 

 tooth, and a broader one on the anterior half of the external sur- 

 face. Some skulls of Sylvilagus from Mexico show two reentrant 

 angles on the anterior surface, resembling Limnolagus in this 

 respect. 



In Limnolagus are found two or more reentrant angles which may 

 be somewhat crenate on the anterior surface, and a broad crenated, 

 reentrant angle on the anterior half of the external surface of the 

 tooth. The whole anterior half of the tooth is more solid looking 

 and more quadrilateral than it is in the other genera. 



There are two deep simple reentrant angles in front on the first 

 lower molariform tooth of Pronolagus and a broad shallow one on 

 the external surface of the anterior half of the tooth. Unlike any 

 other genus except Ronicrolagus and Pcntalagus, Pronolagus has 

 a deep reentrant angle on the internal face of the first lower molari- 



