CLASS MAMMALIA 



647 



burrow in the bank, the entrance of which is under water. In 

 this chamber one or two eggs are laid and the young reared. 



Order Marsupialia. MARSUPIALS OR POUCHED MAMMALS. 

 The MARSUPIALS occur mainly in' Australia and neighboring 

 islands, but a few are natives of America. Their method of 

 reproduction is peculiar. The eggs, which are without shells, 

 absorb food from the uterus; they are not laid, as in the mono- 

 tremes, but hatch within 

 the mother's body and the 

 young are born in an im- 

 mature condition. The 

 mother transfers them 

 with her lips to a pouch 

 on the abdomen, where 

 they are fed, by means of 

 teats, upon milk from the 

 mammary glands. 



The opossums (DIDEL- 

 PHIID^E) and kangaroos 

 and wallabies (MACRO- 

 PODID^E) are well-known 

 groups. The opossums 

 are confined to America. 

 There are four genera and 

 about twenty- five species; 

 only one of these is com- 

 mon in the United States, 

 the Virginia opossum, 

 Didelphis mrginiana (Fig. 514). The opossum occurs in the 

 Southern and Middle states. It sleeps during the day, usually 

 in a hollow tree or stump, but is active at night, seeking insects, 

 eggs, young birds and mammals, berries, nuts, etc., which con- 

 stitute its food. When disturbed the opossum frequently feigns 

 death, or " plays possum." Two or three litters of from six to 

 fourteen young each are produced per year. The young remain 



FIG. 514. The opossum, Didelphis mr 

 giniana. (Photographed by the author.) 



