30 
ZOOLOGICAL GARDENS. 
in each jaw, in addition to the two incisors common to 
nearly the whole Order, three molar teeth on each side, 
fixed by distinct roots, and each surmounted by several 
rounded tubercles varying in number and position in 
the different teeth. The structure of the teeth suffi- 
ciently indicates that the chief subsistence of these 
animals is derived from the vegetable kingdom, but at 
the same time shows that they have no repugnance 
to animal food, especially when it has reached a certain 
state of decomposition. Indeed they have been fre- 
quently known, in times of scarcity, to carry their 
carnivorous propensity so far as to destroy and feed 
upon each other. Even without the stimulus of famine 
they will sometimes exhibit a similar tendency; for 
one of the individuals in the Society's collection having 
died, was found on examination to have been partly 
devoured by the survivors. Their tails are long, round, 
tapering to a point, and furnished only with a few 
scattered hairs or short bristles, emerging at intervals 
from beneath rings of scales formed by the epidermis 
or outer covering of the skin. They have generally 
four distinct toes on the fore feet, besides the rudiment 
of a thumb which is scarcely perceptible ; and uniformly 
possess five on the hind feet, neither connected by a 
membrane nor fringed with stiff hairs as in some of the 
neighbouring genera. Many of the species are never- 
theless excellent swimmers. 
The animals of this group are all of small size, none of 
them exceeding a foot in total length, and some scarcely 
weighing more than a drachm, or the eighth part of an 
ounce. Their habits are subterraneous : living together 
in extensive colonies, they form superficial burrows in 
the earth, and swarm around the habitations and the 
labours of man, rendering themselves equally obnoxious 
to the good housewife and the industrious farmer. They 
