70 RODENTS. 
which a third is occupied by the tail; its colour is bright tawny orange, with a 
white spot between the ears, and another on each side of the muzzle. On the 
other hand, in the pigmy African flying squirrel—the mboma of the natives—the 
length of the head and body is only 11 inches, and that of the tail 54 inches; the 
colour of the upper-parts being dark grizzled grey, while beneath it is yellowish 
white, with the tail uniform pale brown. 
The habits of these animals appear to be very similar to those of 
their Asiatic allies. In climbing tree-stems, preparatory to taking 
their flying leaps, it is said that they use the scales at the root of the tail to aid in 
obtaining a hold on the bark. 
Habits. 
THE SQUIRREL FAMILY 
Family SCIURIDZ. 
The Squirrel family, which includes the true flying squirrels, ordinary squirrels, 
marmots, and susliks, is distinguished from the last by the absence of scales on the 
tail, and the presence of distinct bony (postorbital) processes defining the hinder 
border of the upper half of the socket of the eye. Moreover, when a parachute- 
like membrane is present, it is supported by a rod of cartilage arising from the 
wrist. The palate is broad; and there are generally two pairs of premolar teeth 
in the upper, and one in the lower jaw; but the first upper premolar is small, and 
may be shed or wanting. The molars have roots, and in the young state at least 
have their crowns surmounted by tubercles, but in the adult they often have 
deep wavy enamel-folds, forming transverse plates extending partially across 
the crown. 
Till quite recently the members of the family were divided into two groups, 
or subfamilies, according as to whether they are arboreal or terrestrial in their 
habits; the first group including the true squirrels and flying squirrels, and the 
second comprising the susliks and marmots. From a careful study of their 
dentition, Dr. Forsyth-Major has, however, come to the conclusion that this 
arrangement is an artificial one; he accordingly classes them under three groups, 
of which the first includes the true squirrels, susliks, and marmots, the second the 
flying squirrels, and the third the Oriental pigmy squirrels. 
THE GROOVE-TOOTHED SQUIRREL. 
Genus Rhithrosciwrus. 
According to the above-mentioned scheme, the first representative of the family 
is the Bornean groove-toothed squirrel (Rhithrosciwrus macrotis), which is the sole 
member of a genus easily characterised by the presence of a number of vertical 
grooves on the front of the incisor teeth. Much larger than the common squirrel, 
this species has an enormous bushy tail, long tufted ears, and black and white bands 
along the flanks. The molar teeth are of a simpler type than in any other member 
of this family. 
