THE RODENTS 195 



manent pulps and are curved, the concavity of the uppers as 

 usual being- directed outward and that of the lowers inward. 

 Otherwise the description already given of the "Wombat's 

 cheek teeth will suffice for these (page 91) except that the 

 single premolar is completely molariform and does not resem- 

 ble merely half a molar as in the Wombat while the upper 

 molars increase in size from before backward. 



We now take up the study of the teeth of the Duplicidentata 

 but shall examine only a single representative, namely the 



Fit. 71. — Dentition of Northern Cottontail (Lepus floridanus transitionalis, 9.322-1). 

 In this very specialized form the distance between the rows of mandibular teeth is 

 less than that between the maxillary tooth rows. Hence in the Rabbit as in 

 Ruminants, mastication takes place on one side of the mouth only at one time. 



Northern Cotton-tail, Lepus floridanus transitionalis (Fig. 

 71) a grazing animal which is by no means averse to roots, 

 stems and bark also. The dental formula is: 



2 3 3 

 I f'C^,P|,M|. total 28. 



The large anterior upper incisors show a well-marked groove 

 on their labial surface. Behind each of these teeth is the dimin- 

 utive posterior incisor. The cheek teeth are all molariform in 



