138 TEXT-BOOK OF ZOOLOGY 



particularly molluscs. In closing its mouth, the water (as in the duck) 

 runs out through the " strainers " in the mandibular portion of the beak, 

 while the prey is retained. To prevent water entering the trachea, the 

 food is stored up in the cheek-pouches (see marmot) until the animal 

 comes again to the surface. In the adult animal the beak is toothless 

 (a few small teeth, which soon drop out, are developed in the young) . 

 Seeing that the favourite food of the duck-bill consists of hard-shelled 

 molluscs, the absence of teeth appears an advantage rather than a 

 deficiency. In the cracking of the hard shells of these animals teeth 

 would very soon get worn away ; this is not the case with the thick, 

 horny margins of the jaws. A horny fold at the base of the beak 

 protects the fur against being soiled by the mud whilst rummaging. 



The duck-bill does not bring forth living young, but lays eggs, like 

 birds and reptiles. These are hatched out in the padded chamber of its 

 burrow by the heat of the mother's body. 



Related Species. 



There are only two other well-known species of this order, viz., the 

 Spiny and Long-Haired Ant-eaters (Echidna hystrix and setosa). These 

 animals in external appearance (coat of spines) resemble our hedgehog. 

 In correspondence with their habit of feeding on ants, they possess, like 

 the ant-eater, powerful digging claws, a tubular face with very small 

 mouth, and a long worm-like adhesive tongue. In these species the eggs 

 are hatched in a pouch situated on the abdomen.. They inhabit Tasmania, 

 Australia and New Guinea. 



