SURVEY OF VERTEBRATES 



127 



1. Monotremes 



The primitive egg-laying Mammals living to-day, known as 

 Monotremes, quite evidently point to a Reptilian ancestry for 

 the class. Although they are oviparous, the young when hatched 



A B 



Fig. 87. — Monotremes. A, Duckbill, Ornithorhynchus anatinus; B, Echidna, 



Echidna aculeata. (From Newman.) 



are nourished by milk. There are only three species, each about 

 the size of a Rabbit: the Duckbill (Ornithorhynchus) and the 

 Spiny Anteaters (Praechidna and Echidna) found in Australia, 

 Tasmania, and New Guinea. (Fig. 87.) 



2. Marsupials 



The pouched Mammals, or Marsupials, occur chiefly in Aus- 

 tralia and neighboring islands where they are the characteristic 





Sim 



-JS, 



%>% 



Fig. 88. — Marsupials. A, Virginia Opossum, Didelphys virginiana; B, Wal- 

 laby, Petrogale xanthopus; C, Koala, Phascolarctos cinereus. B and C carrying 

 young. (From Newman, after Vogt and Specht, and Brehm.) 



Mammalian fauna: a primitive one that has flourished there 

 isolated from keen competition, but is now rapidly dying out since 

 Man has imported the higher Mammals. The Kangaroos and 



