168 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
The large amount of material in this table gives the following results:— 
The average length of the trunk (head and body) is 4.42, or slightly less 
than four and a half inches. The minimum, of apparently adult animals, is 
3.50, the maximum is 5.75, and so two inches and a quarter is the gross 
amount of variation deduced from the figures as they stand. “To make 
allowance, however, for probable error, both from inaccuracy of measure- 
ment and from imperfect preparation of the dried skins, from which most of 
the measurements are taken, and thus to keep largely within reasonable 
bounds, we will add 0.25 to the minimum and subtract 0.25 from the maxi- 
mum. With this very liberal allowance, it will be seen that we have proven 
a net variation of one and three-quarters inches to occur in the sixty-three 
specimens measured. 
The tail averages 1.59 in this series, with 1.10 and 2.00 as extremes. 
Making a fair allowance for error, as before, its true variation may safely be 
held at three-quarters of an inch. Its average length relative to the trunk 
is as 4.43 to 1.59 :: 1: 0.36 nearly, or a little over one-third the length of 
the trunk. 
The average hind foot is here 0.80, with 0.72 and 0.92 as extremes. 
Probably little or no allowance is here to be made for error, as the feet are 
never skinned, shrink but little in drying, and can be measured to a nicety. 
‘The hind foot, then, varies ¢wo-tenths of an inch in length. 
We tabulate a résumé of the four preceding series, as far as the three 
principal measurements, of head and body, tail vertebra, and hind foot, are 
concerned. 
a Length BE head |} |... ; 
3 and) beds Tail (vertebre). | Hind foot. 
x“ — = —- 
= 2 = : 5 = 
Series Ur Oe ae cee ise ec lesa | 
2a ep A = ec S =| 4 ‘| = 
2 = oe a S JS =I Ss = & 
Ee 3 oll Sa a 4 a 3 4 2 
s = cs — - aS = > i = 
A <A | = = < = = < =| = 
L | a | E 
Philadelphia series....-. ......-...- 19 | 4.35 | 4.75 | 4.00 | 1.42 | 1.60 | 1.25 | 0.77 | 0.82 | 0.70 
Massachusetts series .-.--......--- 16 | 4.52 | 5.75 | 4.00 | 1.66 | 1.90 | 1.37 | 0.76 | 0.85 | 0.70 
Wlinois;/S¢! series|sesss- se aes ee cee 16 | 4.04 | 4.50 | 3.50 | 1.49 | 1.70 | 1.25 | 0.79 | 0.85 | 0.75 
Generaliseries- <= << 32-222. soos cece 63 | 4,43 5.75 | 3.50 | 1.59 | 2.00 | 1.10 | 0.80 | 0.92 | 0.72 
114 | 4.33 | 5.75 | 3.50 | 1.59 | 2.00 | 1.10 | 0.78 | 0.92 | 0.70 
Combining the results of the 114 specimens, we have an average length 
of trank of exactly four and one-third inches; a length of tail of 1.59, or almost 
