314, VERTEBRATE ANIMALS. 
CHAPTER XXXII. 
ORDERS OF MAMMALIA. 
ORDER I, MONOTREMATA.—The first and lowest order of the 
Mammals—that of the /onotremaia—comprises only two very 
remarkable animals, both of which are exclusively confined to 
New Holland. These are the Duck-mole (Oruzthorhynchus) 
and the Porcupine Ant-eater (Echidna). The Monotremata 
are essentially characterised by the fact that, as in Birds, the 
termination of the intestine opens into a common chamber or 
cloaca, which receives also the ducts of the urinary and repro- 
ductive organs. The jaws are destitute of true teeth; but the 
Orutthorhynchus has a_kind of beak, like the bill af a duck, 
furnished with small horny plates, which act as teeth. The 
pectoral arch, which supports the fore-limbs, resembles that of 
Birds in ceteeal 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 conver- 
sion 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 df a 
placenta. 
The Duck-mole (fig. 170) is one of the most extraordinary of 
Mammals, and is found inhabiting the rivers and lakes of Aus- 
tralia 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 forma 
flattened beak, very like the bill of a duck. The legs are short, 
furnished with five toes each, and webbed, so that the animal 
