THE SQUIRREL- MONKEYS. I 53 



The Saimiris, or Squirrel-Monkeys, are very beautiful and 

 active little animals, characterised by their soft, close, and 

 erect fur, and especially in having the head produced 

 posteriorly. The face is relatively small and has a high facial 

 angle. The eyes are large, directed forwards, and set very 

 close together. The ears are large ; and the nose has a very 

 broad partition between its nostrils. The tail is long, round, 

 and covered with short hair ; but tufted at the extremity and 

 non-prehensile. 



As regards the skeleton, the skull is elongated, and the arched 

 cranial portion prolonged backwards, the length of the base of 

 the skull being shorter than the cerebral cavity. The facial 

 portion of the skull is relatively smaller and the cranial larger 

 even than in Man ; this character being, however, common to 

 all the smaller representatives of particular groups, and obviously 

 necessary to provide the requisite amount of brain-space." 

 {Mivart.) The angle of the lower jaw is narrow behind. The 

 bony partition between the nostrils is very thin and mem- 

 branaceous ; and that between the large orbits is also thin and 

 imperfect. The lower incisor teeth are vertical, and in regular 

 series with the canines, and the latter are well developed. No 

 Primate has the teeth placed in one uninterrupted series except 

 Man ; but there is always a small interval between each upper 

 canine and the adjacent incisor, and between each lower canine 

 and the adjacent pre-molar. 



The skeleton of the hand is one-fifth of the length of the 

 spinal column. The wrist-bones are nine in number, the 

 central — os cejifrale — being present as in the majority of 

 Monkeys. In Chrysothrix and in Nydipithecus also, the 

 thumb is proportionately shorter than in any other genus, 

 pxcept among the Spider-Monkeys {Ateles)^ and the Old WorlcJ 



