274 MAMMALIA OF INDIA. 
The J/schyromyide is founded on a single North American fossil genus 
(Ischyromys typus), which is nearly allied to the Sciuridz, but also shows 
some affinity to the beavers. 
The Haplodontide is also an American family, founded on one genus, 
but an existing and not a fossil animal. The Aaplodon rufus is a small 
burrowing rodent, valued by the Indians both for its flesh and its skin, 
of which from twenty to thirty are sewn together to form a robe; the 
teeth are rootless, simple, and prismatic, the surface of each being 
surrounded by a mere border of enamel. 
The Castoride is the beaver family, which is also unknown in India. 
Unlike as this animal is externally to the squirrels, its anatomy warrants 
its position in the Sciuromorpha, otherwise one would feel inclined to 
include it in the next section. 
We see that of the five families, of which this section is composed, 
only the second has its representatives in India. 
SCIURIDA—THE SQUIRRELS. 
This family contains the true squirrels, including the flying ones, and 
the marmots. The distinctive characteristics of the former are as 
follows: The gnawing teeth are smooth, compressed. The grinding 
teeth are = or oe in the former case the first upper premolar is 
small, and sometimes deciduous ; they are tubercular, at least in youth, 
and rooted. Skull with distinct post-orbital processes; infra-orbital 
opening small, usually placed in front of the maxillary zygomatic 
process; palate broad and flat; twelve or thirteen pairs of ribs; tail 
cylindrical and bushy ; feet either pentadactylous or with a tubercle in 
place of a thumb on the fore-feet. Mostly quite arboreal. 
GENUS SCIURUS. 
2—2 3-3 : 
73, molars, 333 gnawing teeth smooth, orange- 
coloured, or brown ; no cheek pouches ; mamme three or four pairs ; first 
upper pre-molar soon lost in many cases; limbs free ; form agile ; tail 
long and very bushy. 
Jerdon states that “there are three well marked groups in India 
distinguished by size, coloration and habits,” by which he means the 
large forest squirrels, the medium size grizzled ones, and the little 
striped squirrels, to which however I must add one more form, which 
is found out of the geographical limits assigned to his work—the 
Pre-molars, 
