432 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
animal would be in strict accordance with the law of growth of mammals. As to the darker 
colors of his smaller animal, they resemble almost exactly one of our largest specimens, (536,) 
in which the fulvous of the sides is much obscured by black hairs. 
I find nothing in Dr. Harlan’s description of Meriones microcephalus, which seems to indicate 
a species different from the common one. 
Differences in the size of the ear has been considered to indicate two species. It must be 
remembered, however, that a smaller specimen would naturally have a smaller ear ; and I have 
not been able, in the extensive series before me, to realize any proportional differences-in 
different specimens. 
The following detailed measurement of a specimen in alcohol, from Pennsylvania, will show 
the difference in size between it and a large skin collected in the Rocky Mountains by Captain 
Beckwith : 
Measurements. 
538 1 . 
Penn. 
53 2 . 
Rocky Mts. 
587. 
W. T. 
Nose to occiput._ 
. 96 
1. 21 
1. 00 
.44 
. 42 
.40 
ear_-_-_ 
. 83 
. 96 
.75 
root of tail_ 
2. 92 
4. 04 
3. 08 
end of outstretched hind legs_ 
4. 08 
4. 04 
Tail, from root to end of vertebrae_ 
4. 75 
4. 83 
5. 04 
hairs___ 
4. 92 
4. 96 
5.16 
Ears, height posteriorly.___ 
.42 
. 38 
.42 
anteriorly. _ 
.42 
.40 
internally above skull_-_ 
.42 
.50 
width_ 
. 33 
.38 
Arm, length of fore arm___ 
. 60 
. 83 
fore foot to end of claws_ 
.42 
. 50 
.56 
longest claw__ 
.06 
. 12 
Leg, tibia 
. 96 
1. 00 
hind foot from heel to end of claw_ 
1.17 
1.33 + 
.14 
1.13 . 
longest claw . - _ 
. 08 
Longest toe from end of metatarsi__ 
.40 
Specimen in alcohol. 2 Dry skin ; somewhat defective. 
