SCIURIDZ—SCIUROPTERUS VOLUCELLA. 657 
Alaska and Louisiana, Nova Scotia and California, and from many interme- 
diate localities. As shown by the subjoined table of measurements, there is 
a gradual decrease in size from the north southward. The average length 
of specimens (exclusive of the tail) from Arctic America is about 7.50; of 
specimens from near the 49th parallel, about 6.85, or a little less, ranging 
from 7.10 to 6.50; of specimens from Northern New England, about 5.75, 
ranging from 6.00 tu 5.35; of specimens from Southern New England, about 
5.25,* ranging from 5.50 (or even 6.00) to 4.50; of specimens from the Gulf 
States, about 4.75, ranging from 5 20 to 4.80, or about one-third less than 
the most northern specimens. 
In respect to color, specimens from the same locality sometimes differ 
in the color of the dorsal surface as much as do the most diverse examples 
from widely separated localities. There are, however, easily recognized local 
differences of coloration, especially in respect to the tail; but even here there 
is a considerable individual (or seasonal!) variation. As a rule, the speci- 
mens from norti of the United States have darker tails than those from south 
of the parallel of 44°, while the average difference in color between northern 
and southern specimens is quite marked. 
A series of five specimens from the Red River of the North nearly 
covers the whole range of variation in color exhibited by the whole series 
No. 3257 (Red River Settlement) is dark fuscous-brown above, with the tail, 
especially the distal half, decidedly blackish, and the under parts faintly 
washed with rusty-fulvous. No. 3717 (same locality, December 10) is soft 
yellowish-brown above, with the tail much less dusky, and the under parts 
white, with merely the faintest tinge of yellow. No. 3718 (same locality 
and date) is quite similar, but shows a variation toward No. 3257. No. 11539 
(Pembina, June 14) is much redder than 3717; the tail is especially brighter, 
with much less dusky. No. 9083 (Selkirk Settlement) is very light-colored 
(as light as any from any locality), being pale yellowish-brown above, with 
only the terminal third of the tail blackish. 
*Many of the New England specimens (mostly measured from alcoholic specimens) are evidently 
immature. In the case of the males, the testes are generally abdominal, and the females show no sign 
of having suckled young. All the males with the testes scrotal and all the females with the teats bearing 
evidence of maternity are of much larger size than the others. All the measurements of northern speci- 
mens have necessarily been taken from skins, some of which are evidently overstuffed. Taking, how- 
ever, only such measurements as are least affected by faulty taxidermy, as the length of the feet and the 
measurements of the head, in cases where the skull is left in the skin (and only from such specimens are 
the measurements of the head given), there is evidently a very striking, as well as very gradual, decreaso 
in size southward. 
42 M 
