NATURAL HISTORY. 
127 
ROOM III.] 
process; they are peculiar among the Glires for having no caecum, as 
the genera Glaphirus, Eleomys , and Glis, which have a depressed hairy 
tail, and Myoxus, which has a roundish one. The tribe of Squirrels 
( Sciurina, Case ) have much the habit of the former, but there is 
generally a small additional grinder in the front of the other in the 
upper jaw, and the frontal bone is dilated into a post-orbital process. 
Some of these have the skin of the sides of the body dilated and 
spread out between the limbs, as the Pteromys , which have a short 
wide depressed tail and very complicated crown to the grinders, and 
the Sciuropterus, which has a long roundish tail, and the grinders 
with simple crowms like the rest of the squirrels. The remaining 
genera of this tribe have the skin of the body simple, as the Squirrels, 
which have a large broad depressed tail, and live in trees. The 
Ground Squirrels ( Xerus ), which live in holes in the ground, have 
short rather rigid hair. The Tamias have cheek pouches opening- 
into the mouth. The Souslick ( Spermopkilus) have much the ap¬ 
pearance of squirrels, but the front claws are elongated, and they always 
live in holes on the ground, sitting on their haunches ; and the Marmots 
( Arctomys ) are known from the former by their shorter tails and heavier 
bodies; the front claws are compressed and elongated, and the ears ob¬ 
solete. In the two latter genera the front upper fifth grinder is rather 
larger and more like the others ; they generally sleep during the winter. 
The Aye-Aye ( Cheiromys ) of Madagascar, has many characters of 
the squirrel, but it has only four grinding teeth above and three below, 
and it has very long fingers to the fore feet, which are also furnished 
with an opposable thumb. In the size of the cerebral cavity and the 
form of the skull it has many relations to the Lemurs. 
The family of Mole-Rats ( Aspalacid^e) have very small eyes and 
ears; they have a large blunt head, thick cylindrical bodies without any 
or only a very short hairy tail; they have five toes on each foot, rather 
strong hinder limbs, and the low T er cutting teeth are large, broad, 
truncated, and often much exposed. Some have a very short or no tail, 
and three grinders in each jaw, as the Zemni (Spalax ), w 7 hich have 
rooted simple teeth, and short front claws; and Zoker ( Siphneus ), 
which have elongated front claws and compound laminar teeth. The 
Suckerkan ( Chtonoergus , Case ) of North Asia, w 7 hich has four 
rooted grinders, and short truncated hairy tail and moderate claw s. The 
Rat Moles of the Cape have similar grinders, and short depressed hairy 
tail, as the Georhychus with short, and the Batliyergus , which have very 
long front claws. Others have a short nakedish tail, as the Pouched 
Rat ( Saccophorus ) of America, which have large cheek pouches 
opening on the outside of the cheek; the front claws are very long and 
straight. They are said to use the pouch to carry the earth out of their 
burrows. The Sew 7 ellel ( Apludontia ) of North America have five 
grinders in the upper jaw, and the front one small like the Marmots, 
but the eyes are very small and the tail short, and the fore claws long. 
The Ctenomys of Central America has only four rooted grinders in 
each jaw 7 , the tail thick, and the front claws curved. The Bamboo-Rats 
( Rhizomys ) of Malacca have cylindrical complicated grinders, the front 
claws moderately curved, and the cutting teeth very large and exposed. 
The following Table shews the arrangement of the genera at one 
view. 
