xii PHYLUM CHORDATA 535 



and may be naked or covered with fur ; but sometimes, as 

 in the Rabbits and Hares, it is very short. A few special 

 modifications, however, have to be noted in certain families 

 of Rodents. The Flying Squirrels have on each side a fold 

 of skin, the patagium^ which serves as a parachute. The 

 African Flying Squirrels (Anomalurus) are remarkable also 

 on account of the presence of a series of overlapping horny 

 scales on the lower surface of the basal part of the tail. 

 The Jerboas (Dipus) and their allies are characterised by the 

 great relative length of the hind- limbs the mode of loco- 

 motion of these remarkable Rodents being by a series of 

 leaps, not unlike those made by the Kangaroo and by 

 the reduction of the number of the toes to three in some 

 of them. The Porcupines (ffystricida) have numerous 

 elongated spines or " quills " among the hairs of the dorsal 

 surface, and some of them have prehensile tails. 



The Insectivora are, in general, small, furry, burrowing 

 Mammals with short limbs and an elongated muzzle. But 

 there is a considerable range of modification within the 

 order in adaptation to different modes of life. The Colugos 

 (Gakopithecus) have a fold of skin extending along each side 

 of the neck and body and continued between the hind legs, 

 enclosing the tail ; the fore and hind feet are both webbed, 

 and the tail is prehensile. The Hedgehog (Erinaceus) has 

 the surface beset with pointed spines. The Moles (Taipei) 

 and their allies, which are active burrowers, have the limbs 

 very short and stout, and provided with extremely strong 

 claws. The Jumping Shrews (Macroscelididce) have slender 

 limbs adapted to progressing by leaps on the surface of the 

 ground. 



The Chiroptera (Fig. 300) are the only Mammals which 

 are capable of active flight. The fore-limbs have the 

 segments greatly elongated, especially the fore-arm and the 



