MURIDAE—SIGMODONTES—HESPEROMYS LEUCOPUS. ay 
The average length of the trunk (head and body) of this series is a little 
over three and a quarter inches. 
The average length of the tail-vertebre is almost exactly three inches. 
As the usual length of the terminal pencil of hairs is about two-tenths of an 
inch, the tail may be considered as averaging a little less than the length of the 
trunk. 
The distance from nose to eye averages barely over half an inch; that 
from nose to ear, barely over nine-tenths of an inch; the length of the head, 
about one inch and an eighth. 
The palms, with the nails, are barely over one-third of an inch. 
The soles, with the nails, are almost exactly four-fifths of an inch. 
The ears average half an inch and half a tenth of an inch in height, 
measured frem the notch in front. 
With these standard dimensions, we have the following range of vari- 
ation :— 
Of the ears, 0.50 to 0.65—a difference of 0.15. But these wide extremes 
are not often exhibited; the ordinary variation is within 0.10, or about twenty 
per cent. of the mean. 
The soles run from 0.70 to 0.83 
from 0.75 to 0.€0. They do not appear to vary quite as much as some other 
a difference of 0.13, and ordinarily range 
parts; but this may be partly due to the fact that their admeasurement is made 
with great accuracy, and that they do not change much in drying. 
The palms range from 0.30 to 0.40—a difference of 0.10, or nearly thirty- 
three per cent. of the mean. But this is a difficult measurement to make 
with nicety, and probably the real variation is not quite so great. 
The distance from nose to eye ranges (among the alcoholics, alone reli- 
able in this instance) from 0.49 to 0.59 
cent. of the mean, as before. ‘The distances from nose to ear, 0.80 to 1.02, 
a difference of 0.10, or twenty per 
and from nose to occiput, 1.02 to 1.25, appear slightly more variable. 
But the most important point is the determination of the total length of 
trunk and of tail, and of their relations to each other; for several supposed 
species are implicated in this matter. As the figures stand, the shortest speci- 
men has the trunk 2.33 inches, and two others 2.50; but these are not full 
grown, and it will be well to fix the minimum adult length at not less than 
2.75. The maximum length as given is 4.00, but the two or three specimens 
which alone touch this figure are certainly overstufled,* and it will be safe to fix 
* We have ceen specimens stuffed up to 4.50 without obvious distortion. 
