494 ZOOLOGY SECT. 



soft fur, except in one group of Microchiroptera in which the integu- 

 ment is practically naked. The tail is sometimes short, sometimes 

 well developed ; in the latter case it may or may not be involved in 

 the tail-membrane. 



In the Lemurs and their allies (Prosimii) the body is slender, 

 and the limbs adapted for an arboreal existence. The hallux is 

 divergent from the other digits of the foot and opposable to them, 

 and the same holds good, in some cases, of the pollex. In some, all 

 the digits are provided with claws, in others all but the hallux. 

 More commonly all the digits have flat nails, except the second 

 of the pes, which always has a claw. The eyes are very large. 

 The muzzle is sometimes elongated, sometimes short ; the nostrils 

 are slit-like. The tail is sometimes absent or short ; more usually 

 it is greatly elongated, but it is never prehensile. The surface 

 is always covered with soft fur. 



Of the Anthropoidea the Hapalidas or Marmosets are small 

 squirrel-like animals with all the digits except the hallux provided 

 with pointed claws, with the pollex incapable of opposition, the 

 tail non-prehensile, and without cheek-pouches or callous patches 

 over the ischia. The Cebidse resemble the Hapalidae in the negative 

 characters of the absence of ischial callosities and of cheek-pouches, 

 and of the power of opposition in the hallux. But the limbs are 

 much longer, the digits are all provided with flat nails, and the 

 tail is frequently prehensile. The Cercopithecidse all have brightly- 

 coloured, bare, callous patches of skin (callosities) over the ischia, 

 and most of them have cheek-pouches for the storage of food. 

 All the digits are provided with flat nails. The tail may be long, 

 or short, or absent ; when present it is never prehensile. The 

 pollex, when developed, is always opposable to the other digits. 

 In the SimiidaB or Man-like Apes (Fig. 1136) a tail is never developed, 

 and there are no cheek-pouches ; ischial callosities are present only 

 in the Gibbons. The Gibbons can walk in an upright position, 

 without the assistance of the fore-limbs ; in the others, though, in 

 progression on the surface of the ground, the body may be held in 

 a semi-erect position with the weight resting on the hind-limbs, 

 yet the assistance of the long fore-limbs acting as crutches is necessary 

 to enable the animal to swing itself along. 



Endoskeleton. The spinal column of Mammals varies in the 

 number of vertebras which it contains, the differences being mainly 

 due to differences in the length of the tail. The various regions 

 are very definitely marked off. In the cervical region the first two 

 vertebrae are modified to form the atlas and axis. Owing to the 

 absence of distinct cervical ribs, the posterior cervical vertebrae 

 are much more sharply marked off from the anterior thoracic than 

 is the case in Reptiles and Birds. The vertebras of the cervical 

 region have double transverse processes (or a transverse process 

 perforated at the base by a foramen) in all except the last. The 



