842 



PHYLUM CHORDATA : CLASS MAMMALIA 



cropping herbage. The hind-legs are usually larger than the 

 fore-legs, and the animals move by leaps. 

 Examples. — The true kangaroos, e.g. Macropus ; the rat -kangaroos 

 or potoroos [Potorous) ; the genus Hypsiprymnodon, with a 

 foot approaching that of the Phalangers. 

 The true kangaroos, belonging to the genus Macropus, include the 

 largest living Marsupials ; but within the genus there is much differ- 

 ence in size. 



The grey kangaroo (M. giganteus) lives on the grassy plains of Eastern 

 Australia and Tasmania, and is as tall as a man ; the Wallabies, at 

 home in the bush, are smaller, and some are no bigger than rabbits. 



The hind-limbs seem disproportionately long, 

 ^ and are well suited for rapid bounding. The 



long tail, carried horizontally, helps to balance 

 the stooping body as the animal leaps, and it 

 gives additional stability to the erect pose. 

 The fore-limbs sometimes come to the ground 

 when the animal is feeding, and in the largest 

 species they are strong enough to throttle a 

 man. 



The fore-limbs bear five clawed digits ; the 

 hind-feet have only four. The hallux is absent ; 

 the fourth toe is very long ; the fifth is about 

 half as large ; the third and second are too 

 slender to be useful lor more than scratching, 

 and are bound together by the skin (syndacty- 

 lous). The length of the hind-limb is due to 

 the tibia and fibula, and to the foot. The 

 clavicles and fore -arm are well developed. The 

 epipubic or marsupial bones are large. 



The kangaroos feed on herbage, and are 

 often hunted down on account of the damage 

 which they do to pastures and crops. The 

 sharp incisors are suited for cropping the grass 

 and herbs, which the ridged and tub3rculated 

 molars crush. 



As the kangaroos are exclusively herbi- 

 vorous, it is not surprising to find that the 

 stomach is large and complex, with numerous saccules on its walls. 

 The whole gut is long, and there is a well -developed caecum. 



Numerous fossil forms related to the kangaroos are found in Australia, 

 some considerably larger than the existing forms. The gigantic Dipro- 

 todon australis, which was as large as a rhinoceros, is related both to 

 the kangaroos and the phalangers. Except the S. American forms 

 already mentioned, Uiprotodont marsupials are unknown, either living 

 or fossil, outside the Australian area. Forms related to the Polypro- 

 todonts are, on the other hand, common as fossils in both Europe and 

 America. In S. America, further, fossil marsupials related to the 

 Dasyuridae occur ; and as these are not known elsewhere, their presence 

 affords a further confirmation of the view that Australia and Patagonia 

 were once connected. 



Fig. 502. — Foot of 

 young kangaroo. 



2, 3, Small syndactylous 

 toes ; 4, large fourth 

 toe ; 5, fifth toe. 



