162 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
TABLE XXXIX.— Measurements of ninetcen specimens of A. rrparrus from Philadelphia. 
Bolg ls 
p\\ Bl Be ibs 
z Locality. Date. Colleeted by— Prepared by— F = 5 bs 
2 Eilelélea 
2 ee hegre Wee 
Philadelphia, Pa ------ .| Nov. —, 1860 | J. Kvider -.-....----.. E. Coues 4,75 | 1.50 | 0.36 | 0.76 
sido es: 4.60 | 1.55 | 0.37! 0.22 
2:00}25-6 4.30 | 1.45 | 0.35 | 0.80 
tetudoeee 4.25 | 1.40 | 0.36 | 0.70 
S00 2a. 4.40 | 1.55 | 0.38 | 0.£0 
Bee (Es See ene ea 4.50 | 1.60 |-0.35 | 0.75 
a Sedotses sea ss 4.00 } 1.30 | 0.36 | 0,80 
EOE ALE 4.60 | 1.45 | 0.36 | 0.20 
pa.-do 4.50 | 1.30 | 0.35 | 0.80 
...do 4.30 | 1.55 | 0.34 | 0.20 
so) UO Fic 4.40 | 1.60 | 0.25 | 0.75 
_.do 4.25 | 1.45 | 0.56 | 0.78 | 
dose ees 4.30 | 1.35 | 0.36 | 0.77 | 
4.00 | 1.25 | 0.30 ] 0.70 | 
4.40 | 1.50 | 0.35 | 0.:0 | 
4.25} 1.25 } 0.31 | 0.70 | 
4.12 | 1.30 | 0.36 | 0.78 
4.40 | 1.30 | 0.34 | 0.75 
4.30 | 1.25 | 0.37 | 0.£0 
| 
PVG) Et eee SCE ET Pacem ese pms | oac4 sosee 35s ecea| [boreceSosos ee esc bass 4.35 | 1.42 | 0.35 | 0.77 
| 
| 
| 
} 
| 
It appears from this table that the average length is 4.35, and, in the 
best of our judgment, no allowance for shrinkage in the dimension is to be 
made. The extremes are from 4.00 to 4.75, a variation of three-fourths of 
an inch, or about 17 per cent.of the mean. The average of the tail, without 
its hairs, being 1.42, we may similarly set its true average length at an inch 
and a half; its variation amounts to 0.37, about the same percentage. The 
fore foot, averaging 0.85 in its present state, ranges from 0.30 to 0.38, that 
is, a variation of over 20 per cent.; but from the smallness of the measure- 
ment, the difficulty of placing the calipers upon exactly the same spot in the 
several specimens, and an actual difference in the position of the ball of the 
thumb when this is dried, the true percentage of variation would probably 
fall below 0.20, and thus be nearly the same as in the cases of the head and 
body and tail. The average dimension of the fore foot in life may be set at 
three-twelfths of an inch, or three lines. The hind foot, from the tuberosity 
of the heel to the end of the longest claw, can be measured with great exact- 
ness; it averages 0.77, and so may be fixed at 0.80, or four-fifths of an inch, 
in life; it varies 0.12, or very nearly 17 per cent. as before. With these 
calculations for absolute dimensions and variation, we may further consider 
