SCIURIDA—GEOGRAPHICAL DISTRIBUTION AND VARIATION. 643 
Owing to the great tendency to variation exhibited by the Squirrels 
everywhere, both individually and geographically, especially among the Sciuri, 
it is difficult, with our present inexact knowledge of the subject, to compare 
satisfactorily one geographical region with another in respect to the number 
of species actually existing in different parts of the world. The species 
occurring in North America north of Mexico have been studied more care- 
fully, and with far better facilities in the way of material, than those of any 
other equal area, with the result of greatly reducing the number of species 
formerly recognized. During the last twenty-five years, the number of sup- 
posed North American Sciurt has heen reduced from twenty-seven species to 
six, with six or seven additional geographical races, or subspecies. It is but 
fair to suppose that those of Mexico, of Asia, and of Africa, when equally 
well known, will be similarly reduced, especially those of Asia, where authors 
have evidently excessively multiplied synonyms.* Professor Baird, in 1857, in 
elaborating the large amount of material then at his disposal, found it neces- 
sary to reduce the number of North American Sciwrt (exclusive of those of 
Mexico), from the twenty-seven previously supposed to exist to twelve,t 
while the subsequent great increase of available material now renders it appa- 
rent that the number of non-intergrading forms is one-half less than he felt 
authorized in retaining. 
In respect to the subject of individual and geographical variation among 
our Squirrels, I cannot refrain from quoting Professor Baird’s judicious observa- 
tions, especially since he was the first to call attention to the great variability 
of the North American Sciuri.. In his great work on the Mammals of North 
America, published in 1857, he says :— 
“The determination of the species of Squirrels of North America has 
always been a matter of great difficulty, owing to many different reasons. 
The species themselves exhibit an unusual tendency to run into varieties of 
color, among which red, gray, and black are the predominating ones, with all 
*Dr. Gray, in 1867 (see Ann. and Mag. Nat. Hist. 3d ser. vol. xx), recognized forty-three species 
of Sciuri (= Macroxi and Sciuri Gray) from Asia, ten from Africa, and forty from America, nearly half of 
the latter being described by him (in a single paper) as new (besides many “‘ varieties”), all from the 
warmer parts of the two Americas, while a large proportion of the names previously given by other 
authors to the Sciuri of Mexico and Central and South America were left unidentified. A single species 
(Sciurus vulgaris), quite variable in color, he properly allowed to represent the genusin Europe; while, in 
respect to the species of North America, he wisely accepted the reductions made by Professor Baird. 
With a large amount of material before me, I am unable to recognize more than fourteen species, with a few 
additional varieties, and believe that this number will have to be still further reduced as additional 
material becomes accessible. 
tT wo of these were doubtfully admitted. 
