174 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
But since several nominal species are represented in the list, which might 
collectively strike a general average without being severally on an average, it 
becomes necessary to discuss the series in detail. On running the eye over 
the column of lengths of ¢runk of the adults, it will be seen that they are 
imperceptibly graduated from 3.50 to 4.75, and that this graduation is inde- 
pendent of geographical or other considerations. We have only, then, to 
discuss the relative length of tail and feet as compared with the body. 
Now, the specimens from Nebraska, Utah, and the upper and mountain- 
ous parts of California do not differ in any way from the eastern in size or 
shape (as will be seen by making a calculation from the figures). ‘Those 
from the lower parts of California and the Pacific Coast itself (representing 
“edax”, “californicus”, and “occidentalis”) average a little less (3.92 ; that is, 
0.16 less) than the average of the whole; while the tails average a little 
more (1.33; that is, 0.15 more), giving a relative length of body and tail as 
3.92: 1.68 :: 1.00 : 0.43; while that of the whole eastern series is only 
1.00 : 0.87. The feet are correspondingly enlarged, averaging 0.84 instead 
of 0.79. We may say, therefore, that these specimens are a little smaller 
than usual, with tail and feet both absolutely and relatively a little longer. 
But we must remember that this is only one end of a very long series of 
145 specimens, a great many of which shade up to this extreme, and some 
of which overlap it, and that the utmost of variation in these 39 specimens 
is fairly within the normal limits of variability we demonstrated for the 
eastern series. We now propose to match several individual specimens out 
of this series, as nearly as may prove possible, with eastern ones. 
No. 4318 (Nebraska) is 4.50 1.60 0.78, and No. 8325 (North 
Carolina) is 4.75 1.60 0.79; differing less than two specimens from 
Nebraska. No. 3551, from Utah, is 4.75 & 2.10 0.78, -and No. &57, 
from New York- City, is 4.75 & 2.00 & 0.80; difference much less than 
that between the several Utah specimens. No. 3867 (Fort Crook) is 
42514083; No. 4723, from Pennsylvania, is 4.00 1.40 X 0.82; 
the type of “longirostris” (No. 1268) is 4.50 & 1.50 & 0.73; a Philadelphia 
skin is 4.25 1.40 0.70 (precisely the same proportions). A typical 
specimen of “montana” is 4.50 & 1.55 & 0.81; a Philadelphia skin is 4.60 x 
1.55 X 0.82. The type of “edax” is 4.00 X 1.55 <‘0.90; No. 903, from 
Nantucket, is 4.20 < 1.40 & 0.85; and No. 901 (type of rufidorsum) is 4.20 X 
1.55 X 0.82. The type of ‘californicus” is 4.00 X 1.75 & 0.80; No. 1578, 
