342 COMPARATIVE ZOOLOGY. 



1. Monotrernata. This order includes two singular 



O 



forms, the Duck-mole (Ornithorhynchus} and Spiny Ant- 

 eater (Echidna), both confined to the Australian conti- 

 nent and New Guinea. The former has a covering of 

 fur, a bill like that of a Duck, and webbed feet. The lat- 

 ter is covered with spines, has a long, toothless snout, like 

 the Ant-eater's, and the feet are not webbed. Both bur- 



Fio. 331. Ornithorhyuchus. 



row, and feed upon Insects. The brain is smooth in the 

 Ornithorhynchus, and folded in the Echidna. In both, 

 the cerebral hemispheres are loosely united by transverse 

 fibres, and do not cover the cerebellum and olfactory 



lobes. 176 



SUBCLASS II. Didelphia. 



In these implacental Mammals the uterus is divided 

 into two parts. 



2. Marsupialia are distinguished by the fact that the 

 young, always born premature, are transferred by the 

 mother to a pouch on the abdomen, where they are at- 

 tached to the nipples, and the milk is forced into their 

 mouths by special muscles. 178 They have " marsupial 



