xii PHYLUM CHORDATA 537 



with claws, or 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 is never prehensile.- 

 The surface is always covered with soft fur. 



Of the remaining groups of Primates the Hapalidae 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 Cebidae, or American monkeys, 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 Cercopithecidae, or Baboons and Macaques, 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, short, or absent ; when present it is 

 never prehensile. The pollex when developed is always 

 opposable to the other digits. In the Simiidae or Man-like 

 Apes, a tail is never developed, and there are no cheek- 

 pouches ; ischial callosities are only present in the Gibbons. 

 The Gibbons can walk in an upright position without the 

 assistance of the fore-limbs ; in the others, though in pro- 

 gression 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. 



