i62 ANIMAL LIFE PAST AND PRESENT. 



teeth occurs in the second representation of the present 

 group, to be noticed immediately. 



The Duck-bill chiefly frequents the still and open 

 pools, thickly covered with aquatic plants, which are 

 of common occurrence in the Australian rivers. In the 

 banks of these pools the burrows of these creatures 

 are constructed ; the entrance being concealed among 

 the water-plants, and frequently opening some distance 

 below the level of the Water. From the entrance the 

 burrow takes an upward direction in a somewhat ser- 

 pentine course, and may run for a distance of some 

 20 feet before it ends in a chamber situated far above 

 the level of the water, and lined with dry grass. In 

 this chamber, which may have a diameter of some 18 

 inches, the eggs are laid, and the young in due course 

 hatched therefrom. The young when first hatched are 

 entirely naked, and their beak is soft and fleshy, so 

 that it can be readily applied to the milk-glands of the 

 mother, which merely open on the surface of the body, 

 and are not provided with nipples. This feature of the 

 nurturing of the young by milk-glands, in spite of the 

 peculiarities of internal structure to which we shall 

 allude later on, and the oviparous reproduction, at once 

 proclaims that the Duck-bill is a true mammal, although 

 a very lowly representative of the class. 



The second representative of the group includes the 

 Spiny Anteaters (Echidna), of which one species occurs 

 in Australia and New Guinea, and a second and larger 

 one only in New Guinea. A figure of the Australian 

 species is given in Fig. 49. 



