SCIURIDAX—GEOGRAPHICAL DISTRIBUTION AND VARIATION. 645 
have reluctantly come to the conclusion that very many of the species borne 
on the scientific records must be dropped, or reduced to the position of tem- 
porary or local varieties. I hope to be relieved from the imputation of wanton 
and unnecessary reduction in the number of species when I state that the spe- 
cies already published as new by myself have in nearly every case shared the 
fate of others of older date. The nominal species have usually been based on 
varying size or different colors of different specimens. The dusky varieties 
and those with the hairs of the under parts annulated have in nearly every 
instance been raised to the rank of a distinct species. 
“Tn the following pages it will be seen that I recognize only twelve 
species of Squirrels [Sciur7] as satisfactorily proved to belong to the United 
States, and should S. dimitis and castanonotus prove to be nominal ones, as it 
is not at all unlikely [and as has been found to be the case], the number will 
be reduced to ten from the twenty-four given by Audubon and Bachman.”* 
As already stated, a great increase of material has shown that not only 
was the reduction in the number of species of North American Sctwrz, made 
by Professor Baird in 1857, made with good reason, but that a still further 
reduction was necessary. In 1874, in a preliminary paper on the North 
American Sciuride,t I felt authorized in reducing the number of Sciuri from 
the twelve recognized by Professor Baird to five distinct and definable species 
and about seven additional subspecies or intergrading geographical varieties. 
Owing to the large amount of variation with locality, obviously resulting from 
climatic and geographical causes, the number of properly recognizable or 
namable varieties is in a measure a matter of opinion or individual prefer- 
ence; and, though aware that others might deem a larger number of nam- 
able varieties admissible, I do not judge it necessary to depart much from 
the number adopted in my synopsis of the group published three years ago. 
From that paper, in which I referred somewhat at length to the general sub- 
ject of geographical variation among the North American Sciuride, I quote 
the following, with some slight verbal alteration :— 
“Among the Squirrels, this increase [in intensity of color from the north 
southward] is finely illustrated in Sciurus hudsonius and in Tamias striatus, 
representatives of which from the southern parts of New York and Pennsyl- 
vania are much more highly colored than are those from Northern New Eng- 
* Mammals of North America, pp. 244, 245. 
t Proc. Bost, Soc. Nat. Hist. vol. xvi, pp. 276-294, Feb. 1874. By inadvertence, the list of species was 
said to include all the species found “north of the Isthmus of Panama”, instead of north of Mexico. 
