128 COMPARATIVE DENTAL ANATOMY 



• 5-5 1-i 3-3 4-4 ro 



L 5^5 C ' E3 P - m - 3^3 m - M = 52 ' 



The incisors are small except the centrals, 

 which are long and separated. The canines are 

 long and sharp (Fig. 42). The premolars are 

 sub-compressed. The upper molars are triangu- 

 lar in outline, and are an interesting survival of 

 the primitive tritubercular type of the Eocene for- 

 mations. The molar series have rather sharp 

 cusps for the crushing of insect coverings. The 



Fig. 42. — Teeth of Opossum (Didelphis virginiana). 



Dasyure of Australia is more carnivorous than 

 the Opossum, the canines being more developed 

 and the molar series of more blade-like form. 

 The "Wombat is a heavy, clumsy Marsupial of 

 Australia, with true rodent incisors. The insec- 

 tivorous Marsupials have a dentition similar to 

 the Insectivora. Other Marsupials are found, 

 both fossils and recent, which are closely related 

 to other orders as to dentition. 



The Insectivora are so named on account of 

 their peculiar diet, — the bodies of insects, — for 



