452. RODENTIA 
temporary assumption during the breeding season of a distinctly 
ornamental coat, corresponding to the breeding-plumage of birds. 
For the greater part of the year the animal is of a uniform gray 
colour ; but about December its back becomes a brilliant orange- 
yellow, which lasts until about March, when it is again replaced by 
gray. The Squirrel shown in Fig. 200 is a native of Burma and 
Tenasserim, and is closely allied to S. caniceps, but goes through no 
seasonal change of colour. 
“The number of species in the genus is about 75, of which 3 
belong to the Palearctic, 15 to the Ethiopian, about 40 to the 
Oriental, and 16 to the combined Nearctic and Neotropical regions ” 
(Thomas). 
Fossil species referred to Sctwrus are found in the European 
Tertiaries down to the Phosphorites of Central France, while others 
occur in the White River Miocene of the United States. 
ELhithrosciwrus.i—A very striking Squirrel, confined to Borneo, 
and as yet only known from three or four examples, bas been 
separated generically under this name. The general shape of its 
skull is very different from that of other Squirrels; but its most 
peculiar characteristic is the presence of from seven to ten minute 
parallel vertical grooves running down the front face of its incisors ; 
no other Squirrel having really grooved incisors, and no other 
member of the whole order incisive grooves resembling these. 
Its premolars number 3, and its molars are simpler and less ridged 
than in the other genera. This Squirrel (2. macrotis) is far larger 
than the English, with an enormously long bushy tail, long tufted 
ears, and black and white bands down its sides. 
Xerus.2—Fur coarse and spiny. Claws long and comparatively 
straight. Ear-conchs minute or absent. Skull with the postorbital 
processes short and directed backwards, the bony palate prolonged 
considerably behind the tooth-row, and the external ridge on the 
front face of the anterior zygomatic root more developed, and 
continued much farther upwards than in Sciurus. Premolars 2; 
molars as in Sciurus. Mammztwo. This genus contains four well- 
marked species, known as Spiny Squirrels, all natives of Africa. 
They are terrestrial in their habits, living in burrows which they 
dig for themselves. X. getulus, a striped species of North Africa, 
has much the size and appearance of the Indian Palm-Squirrel ; 
all the others are a little larger than the English Squirrel. 
Tamias.*—All the members of this genus are characterised by 
the possession of internal cheek-pouches, and by their style of colora- 
tion ; being ornamented on the back with alternate light and dark 
bands. Their skulls are slenderer and lighter than those of the 
1 Gray, Ann. Mag. Nat, Hist. ser. 3, vol. xx. p- 272 (1867). 
? Hemprich and Ehrenberg, Symbol. Phys. Mam. vol. i. (1882). 
3 Illiger, Prodromus Syst. Mam. p. 83 (1811). 
