468 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
I have already referred to some of the differences between this species and H. leucopus. They 
may always be distinguished by the bright cinnamon color of nuttalli, and especially by the 
cinnamon ears; in the other species, though there is an approximation to the bright colors of 
the back, the ears are always dusky brown, with or without a hoary edging. The under parts, 
too, of nuttalli are never pure white, but yellowish cinnamon, with the line separating the 
colors of sides and belly indistinct. 
The skull of this species differs from that of H. leucopus in the broader muzzle, and a greater 
width of the space between the pterygoid processes. The notch at the posterior portion of the 
bony palate is thus considerably wider. t 
It is with very decided regret that I am impelled, by a strict regard for the law of priority, 
to change the expressive name of awreolus, hitherto applied exclusively to this species, for the 
less meaning one of nuttalli. There can, however, be little, if any, doubt that the species 
described by Harlan, in 1832, belongs to the present animal. It could belong only to one of 
two species, awreolus of Audubon and Bachman, or leucopus. The description refers to the 
fawn color of the upper parts, the whitish of the lower, (not sharply defined white as in Jewcopus,) 
and concludes by remarking the very striking similarity in color to the Gerbillus canadensis. 
This comparison would not apply at all to ZH. leucopus, although very suitable to the other. 
The figure, moreover, is quite a good representation of the color and size of the species, and 
indicating very appreciably the cinnamon ears, the indistinct line of demarcation of the colors 
of back and sides of body and tail, and the extension of the reddish of the sides to the wrist 
joint. 
The use of Arvicola as the generic term for this animal is quite in accordance with Harlan’s 
views of the genera of North American Rodents, Sigmodon and Neotoma, as well as the Oryzo- 
mys palustris, being all placed in the same genus. 
List of specimens. 
& | Measurements. 
Balle Tee 
= é . Locality. Whence and how ob- Nature of EK oe e = g aa 
a 4 So tained. specimen. S 5 3] =| S Ss 2 = = 3 
el eetl ltrs SS ap Set ete Seg Be eae 
g\2s S| Se Se lo 
o o |a a Zz Zz za & & & x n i] 
? 966 |....| Carlisle, Pa... sscooees S. F. Baird............ Skull........ Pe Gene esi PMs me fd) HLA 1.00 Jeccecs 
?548 | 1667 |....| Falls of Schuylkill, Pa.) J. H. Richard.......... BED crcsjeens nia sone uiaisial festre «5 Stl ames SOO oceania’ 1.05 |escccs 
981 | 2023 |....| Society Hill, S. C....., Rev. M. A. Curtis &sons|,..do......... {iohSea banede] cocker | ebeWanlwenosuiupeee dies: eehiaseuate LoUd Joddeas 
QSL |awsesslecccloccecs dO... cc ceee cccevclecece dO.. cevececcceeces dO. cove sccclcscerelecccndlccccssleccces|evcces|evecce|soccee|scsces|secses|eseess 
652 | 1805 |....| Charleston, 8. C.......0|sse005 dO. pcccsccceccvece weeOrsecccccelccccasleccnce|vecce [escecslccvver(coccce|scces [ocvus: |¥eeteu|eummnle 
653 | 1806 |....Jsecee- Ov. ccccvecccesces Dr. J. MOrrow...... cece |sesdO.ceeeceee |svecccleccses|cccesc|eccevclescecs|cccccclescces|coosedieus « |seecee 
32 947 |....| Kemper county, Miss ..| D. C. Lloyd........se0s eee AGseusajsess| bqoceh|| anes eaeeceleccese) vocues|nsscenltscpeslecesss 1,01 |occoss 
1580 | 2416 | @ | Knoxville, Tenn........ Prof. J, B. Mitchell ....]...dO.cceessss[eoecec|covecs 1.17 | 2.83 | 3.00 | 3.08 |......Jeeeeee 1.05 |eceeee 
QTI2A. |vccccslecee|eccce. Ode sccans welesisccclooccea GO. secccrccocceee 
511 | 1646 | © | St. Louis,Mo.........+ Dr. Engelmann 
700 | 1863 | © |eeeee. Udine xnuiescanens'y| on’ une GOsccovececses pace 
Cairo, Ill coccvevcescecs R. Kennicott . 
Columbus, Georgia....| Dr, Gesner...... esses 
