MAMMALS 



197 



in a fold of the skin until hatched. Since it is pouched 

 it could be classed with the pouched mammals (next order), 

 but it is egg-laying. Suppose the two animals in this 

 order did not nourish their young with milk after hatching, 

 would they most resemble mammals, birds, or reptiles ? 



Write the name of this order. -(See Table, 



p. 193.) Why do you place them in this order ( )? 



See p. 193.) The name of the order comes from two Greek 



FlG. 361. OPOSSUM (Didelphys Virginianus). 



words meaning "one opening," because the ducts from 

 the bladder and egg glands unite with the large intestine 

 and form a cloaca. What other classes of vertebrates 

 are similar in this ? 



Pouched Mammals. These animals, like the last, are 

 numerous in the Australian region, but are also found in 

 South America, thus indicating that a bridge of land once 

 connected the two regions. The opossum is the only 

 species which has penetrated to North America (Fig. 361). 

 Are its jaws slender or short ? What kinship is thus sug- 

 gested ? As shown by its grinning, its lips are not well de- 



