NATURAL HISTORY OF THE KANGAROO. 425 



other classes, birds, reptiles, and fishes together, makes up the back- 

 boned or vertebrate primary division of the Avhole animal kingdom, 



AVhat, then, is the relation of the kangaroo's order the Maesu- 

 piALiA to the other orders of the class Mammalia ? 



Now, these orders are : 



1, The order which contains man and apes, 



2, That of the bats. 



3, That of the mole, shrew, hedgehog, and their allies all insec- 

 tivorous. 



4, That of the dog, cat, weasel, and bear all carnivorous. 



5, That of the gnawing animals, such as tlie rat, squirrel, jei*- 

 boa, and guinea-pig all with cutting-teeth f, with jDermanent pulps. 

 They are called Rodents. 



6, The order containino- the sloths, 



7, That of the grazing, hoofed quadrupeds deer, antelopes, and 

 their allies. 



Besides tln-ee orders of aquatic beasts (seals, whales, and the 

 manatee order), with which we need not be now further concerned. 



FiG. 18. The Yapock (Chironedes). 



Now, in tlie first place, very noticeable is the much greater diver- 

 sity of structure found in the kangaroo's order than in any other order 

 of mammals. While each of the latter is of one predominate type 

 of structure and habit, we have found in the marsupials the greatest 

 diversity in both. 



Some marsupials are, we have seen, arboreal, some are burrowing, 

 some flit through the air, while others range over and graze upon 

 grassy plains. Some feed on vegetable food only, others are as exclu- 



