xin PHYLUM CHORDATA 471 



live digits in each foot. The upper surface of the head and body, 

 the sides of the latter, and the entire surface of the tail, are covered 

 with an investment of rounded horny epidermal scales. The 

 lower surface is covered with hair, and there are a few coarse hairs 

 between the scales. There are five digits in both manus and pes. 

 In walking the weight rests on the upper and outer side of 

 the fourth and fifth toes of the manus, and on the sole of 

 the pes. 



The Aard-varks (Fig. 1051) have a thick-set body, the head 

 produced into a long muzzle with a small tubular mouth, the 

 pinnae of great length, the tail long and thick. The fore-limbs 

 are short and stout, with four toes, the palmar surfaces of which 



FIG. 1051. Aard Vark (Orycteropus capensis). (Aftei- Vogt and Specht.) 



are placed on the ground in walking. The hind-limb is five-toed. 

 The surface is covered with thick skin with sparse hairs. 



The Cetacea (Fig. 1052), among which are the largest of 

 existing Mammals, are characterised by the possession of a fusi- 

 form, fish-like body, tapering backwards to the tail, which is 

 provided with a horizontally expanded caudal fin divided into 

 two lobes or " flukes," and a relatively large head, not separated 

 from the body by any distinct neck. A dorsal median fin is 

 usually present. The fore-limbs take the form of flippers, with 

 the digits covered over by a common integument, and devoid 

 of claws ; the hind-limbs are absent. The mouth is very wide ; 

 the nostrils are situated on the summit of the head, and the 

 auditory pinna is absent. Hairs are completely absent, or are 



