26 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Here the figures are 6.25 to 8.50, or nearly as 75: 100; that is, the tail is 
about three-fourths the length of the head and body, at any rate. But, to be 
fair to ourselves, we will take one other, No. 3806, a typical ‘“occidentalis;” 
here the figures are 5.50 : 9.25, or about 59 : 100; that is, considerably under 
two-thirds the length of the head and body. 
In other words: throughout the whole series, the tail (vertebrae) ranges 
from about half as long to about four-fifths as long as head and body; in the 
series of true cinerea alone, the tail ranges from about one-half to about three- 
’, so called, the tail ranges from 
fourths as long; in the series of ‘occidentalis’ 
less than two-thirds to about four-fifths as long; and the respective ranges 
of the two series overlap each other by about as much as they differ from 
each other. Throughout, the variation is by insensible degrees; there is no 
break in the series. Obviously, therefore, the characters “caudal vertebrae 
about as long as the trunk”, as opposed to “caudal vertebrae considerably 
shorter than the trunk” (Baird, op. cit. 487), fail to be diagnostic of two 
species. ; 
The average tail is about two-thirds as long as the average body. 
Excluding No. 3898, which seems to be an abnormally small individual 
if really adult, as it appears, the hind feet range from 1.40 to 1.85 in length, 
a more customary range being 1.45 to 1.75; and the average settles very nearly 
“at 1.66 inches. The fore feet (not given in the table) are about one-third 
of an inch long. 
The ears, measured from the notch in front, average a little over an inch 
in length, ranging from 0.90 to 115. 
The whiskers are immensely long—the longest ones averaging nearly 4 
inches. An idea of their length will be gained when we say that in one 
specimen the distance between the tips of the outstretched whiskers is over 
eight inches. 
The densely hairy tail of this animal, unique in the genus, early attracted 
attention. The average tail is haired almost exactly as in Myozxus ; the hairs 
increase in length, usually, from base to tip, and likewise, as in Myozus glis, 
are more or less distichous in arrangement, so that the tail is flattened. In 
some of the more heavily-haired tails, the resemblance to Tamas is striking; 
and the hairiest of all even approach the condition of Sciwrus itself, although 
the shape is subterete rather than perfectly distichous. Thus, in No. 8314, 
the hairs, pressed out flat, measure fully three inches across, and the terminal 
