CHAPTER XXXII. 

 ORDERS OF MAMMALIA. 



ORDER I. MONOTREMATA (Gr. monos, single ; trema, aper- 

 ture). The first and lowest order of the Mammals that of 

 the Monotremata comprises only two very remarkable ani- 

 mals, both of which are exclusively confined to New Holland. 

 These are the Duck-mole ( Ornithorhynchus) and the Porcupine 

 Ant-eater (Echidna). The Monotremata are essentially charac- 

 terized by the fact that, as in Birds, the termination of the in- 

 testine opens into a common chamber or cloaca, which receives 

 also the ducts of the urinary and reproductive organs. The 

 jaws are destitute of true teeth ; but the Ornithorhynchus 

 has a kind of beak, like the bill of a duck, furnished with 

 small horny plates, which act as teeth. The pectoral arch, 

 which supports the fore-limbs, resembles that of Birds in 

 several respects, but especially in the fact that the coracoid 

 bones are distinct, and are not amalgamated with the shoulder- 

 blade. There is no pouch developed on the abdomen of the 

 females, but there are the so-called " marsupial bones." These 

 are two small bones which arise from the front of the pelvis. 

 They are really to be regarded as formed by a conversion into 

 bone of the tendons of one of the muscles of the abdomen. 

 There are no external ears. The mammary glands have no 

 nipples, and the young are said to be devoid of a placenta. 



The Duck-mole (Fig. 142) is one of the most extraordinary 

 of Mammals, and is found inhabiting the rivers and lakes of 

 Australia and Tasmania. The body resembles that of a small 

 otter, and is covered with a short brown fur. The tail is 

 broad and flattened, and the jaws are sheathed with horn, so 

 as to form a flattened beak, very like the bill of a duck. The 

 legs are short, furnished with five toes each, and webbed, so 

 that the animal swims with great facility. Their food consists 



