DIPR TO DO NT I A . 



725 



4. Family Macropodidce. Kangaroos, herbivorous terrestrial Mar- 



supials. Dentition, " ' T> 2> 4 . The incisors are sharp, and 



I, O, 2, 4 



suited for 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 (Potoroiis} \ the genus Hypsiprymnodon^ with a 

 foot approaching that of the Phalangers. 



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

 largest living Marsupials ; but within the genus there is much difference 

 in size. 



The grey kangaroo (J7. giganteus] lives on ^ 



the grassy plains of Eastern Australia and Tas- 

 mania, 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 for more than scratching, and 

 are bound together by the skin (syndactylous). 

 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 tuberculated molars crush. 



As the kangaroos are exclusively herbivorous, 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 

 oecum. 



Numerous fossil forms related to the kangaroos are found in 

 Australia, some considerably larger than the existing forms. The 

 gigantic Diprotodon australis, which was as large as a rhinoceros, is 

 related both to the kangaroos and the phalangers. Except the 



5. American forms already mentioned, Diprotodont marsupials are 

 unknown, either living or fossil, outside the Australian area. Forms 

 related to the Polyprotodonts are, on the other hand, common as fossils 



FIG, 356. --Foot of 

 young kangaroo. 



2, 3, Small syndactylous 

 toes ; 4, large fourth 

 toe ; 5, fifth toe. 



