194 MAMMALIAN DENTITION 



tively. In the lower molars the same four cusps seen in Arc- 

 tomys can again be identified. All the cheek teeth are sub- 

 equal in size and though they are brachyodont and do not 

 possess permanent pulps they begin to show that curvature of 

 root and obliquity of occlusal surface so pronounced in the 

 type next to be considered and indicating Nature's method of 

 protecting the growing root from injury. 



As representing the most advanced type of Rodent denti- 

 tion among the Simplicidentata, we have chosen Dolichotis 



Fig. 70. — Dentition of Patagonian Cavy (Dolichotis patachonica, 9.3213-6). This 

 extreme type of placental Rodent should be compared with the* similarly extreme Mar- 

 supial Phascolomys (Wombat, Fig. 28). 



patachonica, the Patagonian Cavy or Mara (Fig. 70). In habits 

 and general appearance this animal resembles the Hare but its 

 legs are longer and its ears are shorter and broader. It is essen- 

 tially a grass feeder but will also eat roots and stems of such 

 plants as grow near its burrow. Very marked specialization 

 is seen in the greatly restricted palate, the abutting against one 

 another of the upper cheek teeth rows in front, and in the 

 double columnar cheek teeth. These are hypsodont, possess per- 



