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 he 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 hack, the ears are always dusky brown, with or without a hoary edging. The under parts, 
too, of nuttalli are never pure white, hut 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. 
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 aureolus, hitherto applied exclusively to this species, for the 
less meaning one of nuttalli. There can, however, he 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, aureolus 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 leucopus ,) 
and concludes by remarking the very striking similarity in color to the Gerbillus canadensis. 
This comparison would not apply at all to H. 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. 
Catalogue number. 
Corresp’g No. of skull. 
Sex and age. 
Locality. 
Whence and how ob¬ 
tained. 
Nature of 
specimen. 
Measurements. 
Nose to eye. 
Nose to ear. 
I 
s 
S5 
Nose to tail. 
Tail to end iff vert. 
Tail to end of hairs. 
Fore foot, length. 
Hind foot, length. 
Skull, length. 
| Ear, height. 
? 966 
Carlisle, Pa. 
S. F. Baird. 
Skull. 
1.00 
?548 
1667 
Falls of Schuylkill, Pa. 
J. H. Richard.... T T .. t . 
Skin. 
3.13 
3.00 
1.05 
981 
2023 
Society Hill, S. C., 
Rev. M. A. Curtis &sons 
.do. 
1.11 
1251 
652 
1805 
Charleston, S. C. 
653 
1806 
,,, T¥ T do...,. 
Dr. J. Morrow.. 
32 
947 
Kemper county, Miss .. 
D. C. Lloyd. 
1.01 
1580 
2416 
$ 
Knoxville, Tenn........ 
Prof. J. B. Mitchell 
.do_ T . 
1.17 
2.83 
3.00 
3.08 
1.05 
2772 
Alcohol .,, 
.52 
88 
1.20 
3.00 
2.90 
.40 
.75 
.63 
511 
1646 
9 
St. Louis, Mo. 
Dr. Engelmann .. 
Skin. 
.98 
700 
1863 
_.Oy 
n^iro Hi llllllllll)t 
Columbus, Georgia.... 
nr r»cn»r 
