748 



MAMMALIA. 



second and third toes are narrow and bound together by skin, 

 the fourth and fifth free. The tail is generally long and pre- 

 hensile. The stomach is simple, the caecum usually large. 

 Average dental formula, 3> T 2 '3> 3^ 



i, o, 0-2, 3-4 



Examples. The grey Cuscus (Phalanger orientalis] ; Tarsipes, a 

 small mouse-like animal which feeds on honey, and is remark- 

 able in having no inflection of the angle of the mandible and 

 no caecum ; the flying phalangers (Petaurus), with a parachute 

 of skin extending from the little finger to 'the ankle ; the Koala, 

 or "native bear" (Phascolarctos cin- 



4 ereus), a relatively large form, about 



2 ft. in length. An extinct form, 

 ThylacoleO) of the late Tertiary period 

 of Australia, is interesting in its extra- 

 ordinary dentition, the functional teeth 

 being reduced to large front incisors and 

 the third premolars, both adapted for 

 sharp cutting. 



4. Family Macropodidse. Kangaroos, herbi- 

 vorous terrestrial Marsupials. Denti- 

 tion, 3> ' I> 2> -*. The incisors are sharp, 



and 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 

 (Potorous) ; the genus Hypsiprymnodon, 

 with a foot approaching that of the 

 Phalangers. 



FIG. 405. Foot of The true ' kangaroos, belonging to the genus 



young kangaroo. Macropus, include the largest living Marsupials ; 



2, 3, Small syndactylous but within the genus there is much difference in 



toes; 4, large fourth size. 



toe ; 5, fifth toe. The gfey kangaroo ( M . gi gan teus} 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 for 

 more than scratching, and are bound together by the skin (syndactylous). 

 'f he length of the hind-limb is due to the tibia and fibula, and to the 



