KEY TO GENERA 91 



characters not highly modified for fossorial 

 hfe; ears moderately or well developed; 

 plantar tubercles 6 ; fore-claws not noticeably 

 lengthened ; fur never highly modified. 

 a. Mammse 0—2=4. 



*. ml usually with four, m^ usually with three 

 well-developed salient angles on the 

 inner side; m^ with three or four salient 

 angles on each side, its first outer infold 

 usually deep. 



Skull relatively broad, the temporal 

 ridges feeble and widely separated in the 

 mterorbital region; palate without con- 

 spicuous spinous process behind. 



** 1 J o , , Eothenomys. 



*'. m' and m- normal, the former with three, 

 the latter with two well-developed inner 

 saUent angles; m^ very complex, with 

 five or six salient angles on each side, its 

 first outer infold usually shallow, leaving 

 the anterior loop and first outer triancle 

 broadly confluent. ° 



Skull long and narrow; temporal ridges * 

 stronger, tending to approach in the inter- 

 orbital region ; palate with well-developed, 

 horizontal, median spine behind. Antelio'mvs 

 p. Mammae 2—2 = 8. 



Cheek-teeth with characteristic long-drawn- 

 out appearance; ml and 7?j2 normal ; ?«» 

 variable, sometimes complex, sometimes 

 simplified, with from three to six outer and 

 from two to five inner salient angles, its 

 first outer infold usually shallow and its 

 posterior loop very long and narrow in the 

 more reduced forms of the tooth. 



Skull with the temporal ridges weak and 

 widely separated in the interorbital region. 



* oi II , , Alticola. 



. OkuU normal, not conspicuously depressed. 



** o, „ ,, , Subgenus Alticola. 



**. Skull greatly depressed. 



,,, „ .^, ^, , , Subgenus Platycranius. 



bkuil with the temporal ridges fused in the inter- 

 orbital region ; post-orbital crests of squamosals 

 noticeably lengthened, extending backwards 

 towards the glenoid region; anterior palatal 

 foramina small. Auditory bullae very small. 

 Re-entrant folds of cheek-teeth without 

 cement; m^ and m^ normal; m^ simpfified, 

 with three outer and two inner salient angles. 

 Its posterior loop short and broad, its first 

 outer infold shallow. 



External characters more or less evidently 

 modified for fossorial habits; fur short and 

 dense, sometimes mole-like; ears small- tail 

 short. Mamma; 1-2 = 6. . . Hyperacrius. 



