278 ZOOLOGY. 



423. The division of the mammalia called didelphian, 

 is rliarartrn/cd l>y physiological distinctions of great impor- 

 tance. In p'nrral, the young are born prematurely 

 \\rn-, and exceedingly imperfect, and they seem, whilst in the 

 womb, not to be nourished by a placenta, as is the case with 

 all the monodelphs. The brain is comparatively smooth, 

 and without a corpus callosum ; and marsupial bones attached 

 to the pelvis (Fig. 183), give a peculiar character to the 

 skeleton. 



This group is composed of two orders the marsupial and 

 monotremes, 



424. The order marsupialia is chiefly characterized by 

 the presence of a sort of pouch, destined to hold the young 

 whilst attached to the nipple, and during the early period of 

 their growth. A description of this pouch, with a drawing 

 of the form of the marsupial bones, will be found in Fig. 171. 

 The food of the marsupialia is various, some being insectivo- 

 rous, others herbivorous, others carnivorous, whilst some 

 strongly resemble the class rodents. They nearly all belong to 



Fig. 219. Kangaroo. 



Australia and Tasmania. The sarigues (Fig. 171), the phalan- 

 gers, and the kangaroos (Fig. 219), chiefly represent the group. 

 425. Finally, the order called monotremes seems to 

 connect the mammal with the oviparous vertebrata. The 

 intestine terminates, as in birds, in a cloaca, and the repro- 



