456 ZOOLOGY. 
small, and placed behind the principal pair, and these latter are grooved in 
front. The upper incisors are double ; both the upper and under ones are 
shorter, that is, less deeply implanted in the jaw than in other rodents, and 
they are always white. The molar teeth are always rootless, five above 
and five below, or six above and five below, on both sides of the jaws. 
Only two living genera compose this family ; a third-is extinct. 
The genus Lagomys has no visible tail, short and rounded ears, short 
hind legs, and the molars twenty in number, five above and five below on 
each side. The ‘species are generally of small size. One is American 
(L. princeps),-and inhabits the Rocky Mountains. Other species occur in 
Siberia and Central Asia, as L. alpinus (pl. 118, fig. 2). The pikas,:as 
the Lagomys are commonly called, although found in considerable number, 
are not, strictly speaking, gregarious; they occur only in alpine or sub- 
alpine districts, where they form burrows in the ground, or sometimes take 
shelter amongst the loose stones. Occasionally, when the weather is cloudy, 
they will quit these retreats in quest of food during the day, but the night 
is their ordinary time of feeding. Their food consists of various-kinds of 
grass, and as in the high and cold regions which they inhabit the herbage 
is covered with snow during the winter months, their instincts lead them 
to lay up a stock for this season. Large quantities of dried grass and other 
vegetable matters are collected by the pikas for their winter's consumption ; 
these they pile up in the autumn, like small haystacks, which gradually 
disappear as the spring approaches, unless, as not unfrequently happens, 
these stores are robbed by the-sable hunters to feed their horses. The 
species of this-genus seem to have been more numerous during the tertiary 
epoch than in our days, and inhabited the southern part of Kurope. Some 
of the species have been made the type of the genus Anema.of some Ger- 
man. paleontologists. 
The genus Titanomys is extinct, of which several fragments of jaws with 
prismatical teeth have been found in Germany. The upper molars are 
provided only at the inner side with a very superficial furrow, and the 
under ones, especially the. posterior, exhibit characters wanting in Lagomys. 
Only one species is known. 
The genus Lepus (the hares and rabbits) is characterized by the presence 
of six molars above and only five below. The ears are large and elongated, 
sometimes longer than the head itself; the tail short and very bushy ; the 
hind legs powerful and much leptons aan the fore legs. Under this genus 
come both the hares and rabbits, for no structural difference as yet has 
been discovered between them; the rabbits burrow, whilst the hares make 
a kind of nest, called a form, on the surface of the ground, on which they 
lie. The young of the rabbits, at least such is the case in the common 
kind, are blind and naked when born; those of the hares are clothed with 
hair and have the eyes open. By far the greater number of the species of 
this genus agree with the hare in the habits noticed, and that animal may 
therefore be regarded as the type of the genus. Destitute of means of 
defence, the hares are timid, have remarkable power of flight, and to warn 
them of danger, their senses of hearing, seeing, and smelling are usually 
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