THE SQUIRREL-MONKEYS. 153 
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.” 
(Mfiivart.) 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 centrale—being present as in the majority of 
Monkeys. In Chrysothrix and in JVyctipithecus also, the 
thumb is proportionately shorter than in any other genus, 
except among the Spider-Monkeys (47ée/es), and the Old World 
