THE MONKEYS AND APES. 12 7 



they have received the name of Catarrhine Monkeys {Catar- 

 rhini)* The New World Monkeys, on the other hand, have the 

 nose flat and the opening of their nostrils directed outwards, 

 and the one nostril widely separated from the other by a broad 

 cartilaginous septum, and they are therefore designated Platyr- 

 rhine Monkeys {^Platy?'rhini).\ 



The dental formula of the Old World forms is If, C|, Pf, 

 M|, making a total of thirty-two teeth in all ; but those of the 

 Western Hemisphere differ in having invariably three pre- 

 molars, and sometimes two molars, instead of three, so that 

 they possess either thirty-two or thirty-six teeth altogether. 

 There is always a gap, or diastema^ in the series of the teeth in 

 front of the upper and behind the lower canines ; the lat- 

 ter teeth being taller than the rest. Many of the Catarrhine 

 Apes have large cheek-pouches as well as bare patches, or 

 callosities, often brightly coloured, on the part they apply to 

 the ground when sitting. None of the Platyrrhine group have 

 cheek-pouches or callosities, but in many of them the tail is 

 marvellously prehensile, which is not the case in any of the 

 Old World species. Again, in the Apes of the Eastern Hemi- 

 sphere, the ear-capsules of the skull have an external bony 

 channel (or meatus) for conveying the sound vibrations into 

 the ear, which is absent in the American species. 



As a rule the Platyrrhine Monkeys have the fore-limbs shorter 

 than the hind-, and are more quadrupedal than those of the 

 Old World. Their thumb is also more like a finger than the 

 same digit in their Eastern brethren. 



Of the New World Monkeys, the Hapalidcc^ or Marmosets, 

 have thirty-two teeth, and the Cebida^^ with several sub- 



* KoTct, down ; /^)s, piv6s, nose. 

 t TtXarl's, flat ; p\s, piv6s, nose. 



