1458 EGG-LAVING MAMMALS, OR MONOTREMES 



with two cusps on one side, separated by a hollow from a longitudinal crenulated 

 ridge on the other. As these teeth are gradually worn away by the sand taken into 

 the mouth with the food, the horny plates grow up beneath and around them, till 

 they are eventually shed. That the ancestors of the duckbill were provided with a 

 full series of persistent teeth is thus evident. 



The duckbill is restricted to Southern and Eastern Australia and 



Tasmania, where it is fairly common in places suited to its habits. 

 and Habits 



Thoroughly aquatic in their habits, and exclusively frequenting fresh 



water, 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 watch- 

 ing the stream in the evening they may be easily shot, and they will readily take a 

 bait on a hook. Although gregarious when in the water, these animals live in pairs 

 in the burrows constructed in the banks; their favorite 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 upward 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, inclosed 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 prob- 

 ing 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 themselves 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 ECHIDNID^E 



The echidnas, or spiny ant-eaters, 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 hair and 

 short thick spines. The head is rather small and rounded, and has a long, slender, 



