412 



METAZOAN PHYLA 



albumen. It is retained in the uterus, the young being nourished through 

 the embryonic membranes, which are in contact with the uterine wall. 

 Rarely a primitive allantoic placenta is developed. The young is born 

 in an exceedingly immature condition and makes its way or is transferred 

 by the mother to a brood pouch, or marsu/pium, on the ventral surface 

 of her abdomen. Here it attaches itself to a teat, remaining so attached 

 until it has become sufficiently developed to move about and resume 

 its attachment when it wishes to feed. 



The marsupials were distributed ages ago over both Europe and 

 North America but now they are confined to Australia and neighboring 

 islands, South America, and the southern portion of North America. 

 In Australia, where they are the only native mammals, the marsupials 



Fig. 281. — The Australian duckbill, Ornithorhynchus anatinus (Shaw). {Drawn from 

 Lydckker, " Wild Life of the. World;' vol. II.) X H. 



have adapted themselves to various modes of living, some of them having 

 become carnivorous, and others molelike, shrewlike, or rodent-like. 

 The phalangers are flying marsupials similar to the flying squirrels. 

 The kangaroo has very large hind legs and a large tail, the former being 

 used for leaping while the small forelegs serve merely for grasping food 

 and handling the young (Fig. 282). 



442. Unguiculata. — Insectivora (in sek tiv' o ra; L., insectum, insect, 

 and vorare, to devour) includes the hedgehogs, moles, and shrews. They 

 are probably the most primitive of placental mammals and are found 

 everywhere except in Australia and a large part of South America. 

 They are all insect eaters and are, generally speaking, beneficial. 



The order Chiroptera (ki rop' ter a; G., cheiros, hand, and pteron, 

 wing) includes the bats. These are the only true flying mammals, the 

 wings being formed by membranes stretched between the greatly elon- 



