416 Dr. J.E.Gray’s Synopsis of the American Squirrels 
of the metatarsus, (3) with a small patch of hair only in the 
centre of the sole.” (Mamm. N. A. 247.) 
It has been observed that in the species which have an exten- 
sive geographical range there is a difference in the average 
size of the species, agreeing with the latitudes which it inha- 
bits. Thus several of the North-American Squirrels become 
smaller as they extend southward, until, on the sea-coast of 
Georgia, Florida, and the Gulf, they reach the minimum size. 
There are some species and some local varieties that appear 
constant, and present very little variation in outer appearance ; 
and I have no doubt the difficulties which we experience in 
studying the specimens in museums would immediately vanish 
if we could study the animals in their native haunts. 
The colour of the back is very liable to vary, especially in the 
larger species. In Sc. vulpinus it varies from pale iron-grey to 
nearly black, and, on the other side, to fulvous brown grey. 
Se. carolinensis varies from pale iron-grey to fulvous; and a 
melanic variety of a nearly uniform black colour is common. 
The colour of the underside is quite as variable in some spe- 
cies. Sc. vulpinus and Sc. carolinensis, which have the under- 
side normally of a pure white colour, sometimes have it deep 
black, and at others reddish or reddish white. Several species, 
especially of the smaller kind, which have the underside of a 
reddish colour, have it sometimes much paler, and at others 
white with a yellow tinge, or nearly white. 
Many species have a ‘tuft of soft hair at the base of the ears : 
this is usually white or yellow, according to the species; but I 
have seen it white on one side and yellow on the other in the 
same specimen. 
The colour of the tail is generally characteristic of the spe- 
cies; but in some kinds it is variable, though the variations are 
confined within certain limits im each species. The size of the 
dark band on the hairs of the tail and the general colour of the 
hairs constitute a pretty permanent specitic character; but it 
sometimes varies: the base-colour changes from grey to deep 
yellow or white ; and the black band is sometimes diffused so as 
to make the tail almost, and sometimes entirely black, or black 
with a minute pale tip. 
It is almost impossible to give a definite .character for the 
species in a few words ; each individual requires to be described. 
2. ScrurRvs. 
Gray, Ann. & Mag. Nat. Hist. 1867, xx. pp. 271, 272, 325. 
Ears tufted. Head broad; muzzle short. Feet hairy at the 
heels. Front upper molar small or often wanting. 
