20 
GUIDE TO THE 
of burrowing Crustacea, which occur in immense numbers, 
and at low tide the monkeys may be observed wandering 
about searching for the crabs and inserting their arms into 
the burrows even up to the shoulders. 
Macacus silenus is markedly distinct from any of the 
foregoing examples of the genus, as it is jet-black, with 
long grey whiskers and beard, giving rise to the two 
names which are sometimes applied to it of Satyr or Lion 
monkey. Its tail is moderately long and somewhat tufted. 
It is peculiar to the forests of Southern India. 
The Rodent House. 
In close proximity to the Dumraon House, and a little to 
the south of it, is the house devoted to the gnawing animals, 
or Rodentia , a class of animals illustrated by the rabbit, 
rat, and squirrel, and which is distinguished by the 
presence of two front cutting-teeth or incisors in both 
jaws, which unlike the teeth of the majority of Mammals, 
are persistent growers, that is, they are always growing 
outwards as their tips are being worn away ; and as the 
thick enamel which covers the front of the tooth is not 
worn away by attrition so rapidly as the part behind it, their 
incisor teeth have cutting edges like a chisel, and it is the 
hard character of the enamel which enables some rodents 
to eat their way even through wire-cages. Unlike other 
animals, they have no eye-teeth or canines, and the incisor 
teeth which are generally four in number in other Mam¬ 
mals, become in all the Rodentia, reduced to two in 
number, with the exception of the family that includes 
the hares and rabbits, in which another pair of incisors 
exists in the upper jaw. 
The ether teeth of these animals (rodents) present con- 
