AMERICAN OrOSSUMS 



155 



course the chief interest of the genus, which may be " an un- 

 modified survivor from Mesozoic times, and therefore from a 

 time long before the Didelphyidae, Peramelidae, and Dasyuridae 

 were differentiated one from the other." Another ancient feature 



Fig. 82. Banded Aiistraliaii Anteater. Myrmecobius faaciatus. x i. 



(found in Jurassic mammals) is a mylo-hyoid groove upon the 

 lower jaw, which, however, is not always present, and its exist- 

 ence has therefore been denied. The single species, M.fasciatus, 

 is partly arboreal and partly terrestrial in habit, and feeds upon 

 ants. It is a Western and Southern Australian form. 



Fam. 2. Didelphyidae. All the members of this family are 

 pentadactylous. The 

 teeth are fifty in number, 

 arranged thus : I % C 1 

 Pm | M A. The caecum 

 is small ; the pouch is 

 generally absent ; the 

 tail generally long and 

 prehensile. 



The genus Didelphys 

 contains most of the 

 forms belonging to this 

 family, including as it 

 does some twenty -three 

 species. The Opossums 

 are mainly arboreal ani- 

 mals, insectivorous in FIG. 83. Virginian Opossum. Didelphys virginiana. 

 , i / i i , , i i XT- (After Vogt and Specht.) 



their food ; but the larger 



species eat reptiles, birds, and their eggs, 

 species carry their young, when able to 



Several of the small 

 leave the teats, on 



