CLASS MAMMALIA. MAMMALS 



481 



Egg-laying mammals 



These most primitive mammals are con- 

 fined to the Austrahan region, that is Aus- 

 tralia, Tasmania, and New Guinea. The 

 young, before hatching, live on the yolk 



contained in the egg. After hatching, the 

 young are for a time nourished by milk 

 from the mother's mammary glands. The 

 best-known species are the spiny anteater 

 echidna (Fig. 353), and the duck-billed 

 platypus (Fig. 352A). The platypus is a 



-% — r- 



i ioLKt. 353. bp.iiv duteater (Echidna). One of the egg-laying mammals. Like the duck-billed 

 plat\pus, its egg shell is not limy, but leathery. The egg is incubated in a pouch where the 

 newly hatched young are kept for a time. The echidna has numerous hard sharp quills and an 

 underfur of coarse hair. It possesses amazing digging powers which enable it to disappear quickly. 

 These animals are typical anteatcrs with a long and slender bony tongue, adapted to catching 

 ants and other insects. Australia has a strange assortment of animal life, due largely to its 

 geographic isolation. (Courtesy of Harold C. Reynolds.) 



beaverlike animal; it is aquatic and con- 

 structs burrows. It feeds chiefly on fresh- 

 water invertebrates. The female, after lay- 

 ing her eggs, curls around them and remains 

 inactive for about two weeks. At the end of 

 this time, the young are hatched. The male 

 has a claw on its heel which is connected 

 with a poison gland. 



Pouched mammals 



Pouched mammals (marsupials) occur 

 mainly in Australia and neighboring islands, 

 but a few are natives of the America.s. Th*" 



voung are born in an embryonic condition, 

 having no hair for protection, no eyes, and 

 no ears, but having good olfactor}' organs 

 and usually wcll-dcvelopcd front feet. At 

 first they live in a pouch on the abdomen, 

 where they feed on milk by means of teats. 

 The young of the American opossum (Figs. 

 337 and 351A) remain in the mother's 

 external pouch until they complete their 

 natal development. Many species of marsu- 

 pials, such as kangaroos (Fig. 354) and 

 koalas (Fig. 355) are distributed over the 

 Australian region. 



