286 EGG-LAVING MAMMALS. 
till they are eventually shed. That the ancestors of the duckbill were provided 
with a full series of persistent teeth is thus evident. 
Distribution. The duckbill is restricted to Southern and Eastern Australia and 
and Habits. Tasmania, where it is fairly common in places suited to its habits. 
Thoroughly aquatic in their habits, and exclusively frequenting fresh waters, 
duckbills are remarkably shy creatures, and rarely seen, except at evening, when 
they come up to the top of the water, and look like so many black bottles floating 
on the surface,—sinking down immediately if alarmed. By quietly watching the 
stream in the evening they may be easily shot, and they will readily take a bait 
ona hook. Although gregarious when in the water, these animals live in pairs 
in the burrows constructed in the banks; their favourite haunts being where the 
streams expand into wide, still pools. In the banks of such sequestered spots 
are constructed their burrows; each of which usually has one entrance opening 
beneath the water, and another above the water-level, hidden among the herbage 
growing on the bank. The burrow runs obliquely upwards from the water to 
a great distance—sometimes as much as fifty feet—into the bank; and ends in a 
chamber, lined with grass and other substances, where the young are produced. 
Two eggs are laid at a time, enclosed in a strong, flexible, white shell, measuring 
about three-quarters of an inch in length, and two-thirds of that in diameter. 
They resemble the eggs of birds in the large size of their yolk, of which 
only a small portion goes to the formation of the embryo, while the remainder 
serves for its food. When first hatched, the young are blind and naked, with 
the beak very short, and its margins smooth and fleshy, thus forming a nearly 
circular mouth, well fitted to receive the milk ejected from the glands of the 
mother. The duckbill feeds on various small aquatic animals, such as insects, 
crustaceans, and worms, which it obtains by probing with its beak in the mud 
and sand near the banks; the food being first stored in the capacious cheek- 
pouches, and afterwards devoured at leisure. The large front paws are the 
chief agents in swimming and diving. On land these creatures move somewhat 
awkwardly, in a shuffling manner; and when reposing in their nests curl them- 
selves up in a ball-like fashion. The aborigines capture the duckbill, by digging 
holes with sticks into the burrow from the ground above at distances from one 
another, until they light upon the terminal chamber. 
THE ECHIDNAS. 
Family EcHIDNIDZ. 
The echidnas, or spiny anteaters, of which there are two species, representing 
as many genera, are widely different in appearance and structure from the duckbill, 
and have a more extensive distribution. Instead of mole-like fur, the echidnas 
have the upper surface of the head and body covered with a mixture of stiff 
hairs and short thick spines. The head is rather small and rounded, and has a 
long, slender, beak-like snout, covered with skin, at the extremity of which are 
situated the small nostrils. There are no external conchs to the ears; but the eyes 
are of fair size. The opening of the mouth is very small; and the extensile tongue 
