432 U. Ss. 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. 
BIB) wil Pion? 587. 
Penn. /jRocky Mts.| W. T. 
Nose:to,occiput.-5:2-- eet eee Se aaa e SOR io a 2k 1.00 
BY eee gai SAA os |p sca .40 
ry ehh tits ft ec pee St RSL 75 
TOOL Of tale. + ane mee eee ae ome 2.92 4.04 3. 08 
end of outstretched hind legs..--------- AOS. PLS EELS 4. 04 
Tail, from root to end of vertebre --.----------- 4.75 4, 83 5. 04 
hainse. $2 s:eaeett las as 4. 92 4.96 5.16 
Marg, Height posteriorly... - 552 = -~ == ens en 42 . 38 - 42 
PLC ULOULY toca ee A Og | ee - 40 
internally above:skally- 2 ope cee p Aatis ac mcm eee ee - 50 
WIth 8 oon ee ee ae eee sie Al sckaateae 38 
Arm,“lenetin of fore arm’ 2522 ooo teen a See AL |e | Sp fees a - 83 
fore foot to end of claws.---------------- 42 - 50 - 56 
Jonrest claw. 24=-Sh ose CMe oan eae - 06 2 | See es — 
Tipp irbie i. See de pee ee ae eee OBien Wea 1.00 
hind foot from heel to end of claw ---.----- 1 Ay, 1.33 + 1.13 
longesticlawine ne (ee ee eee een - 08 ep | PSS = = 
Longest toe from end of metatarsi --..---------- 740) OG. o5oeee a eee = 
Specimen in alcohol. * Dry skin; somewhat defective. 
