822 ZOOLOGY 



low state of development and eggs are laid, as in reptiles 

 and birds. There are two principal types, the "Duck- 

 bill " (Fig. 296), with aquatic habits, and the " Spiny 

 Ant-eaters " (Echidna, Fig. 297), inhabiting rocky places. 

 Both types are confined to Australia and neighboring 

 islands. 



The Marsupialia l have a remarkable distribution over 

 the earth to-day. All are confined to Australia and adja- 



FIG. 297. Echidna aculeata, the spiny ant-eater. After Vogt and Specht. 



cent islands, excepting the family of opossums (Fig. 298), 

 found only in the Americas. There is thus a great dis- 

 continuity in the distribution of marsupials. This is 

 accounted for by the evidence that formerly the whole 

 world contained marsupials, so that those living to-day are 

 the separated remnants of that once universal race. The 

 opossums are most numerous in the tropics, but the Vir- 

 ginian opossum ranges north to New York. 

 1 marsiiphim, a pouch. 



