482 U. 8S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
was said to be abundant in the prairie. That of Audubon and Bachman was found near Fort 
Union. 
List of specimens. 
Measurements. 
Whence and how | Nature of 
obtained. specimen. | From tip of nose to— 
Locality. | Length of-- 
Catalogue number. 
Corresponding num- 
ber of skull. 
Tail to end 
of verteb. 
Fore ft.) Hind ft. 
ile When collected. 
] ] 
Eye.| Ear. Occip.| Tail. 
| | 
_ 
oc 
i) 
= 
880 Bijoux hills, Neb., near Mo. river...) 1855 | Dr. F. V. Hayden,.| Skin ...... |... 
2549 |......| Vermilion prairie, near MO. river...|}..00.-|secccscccsacescncees Alcohol ...| .60 
| 
| 
| 
J 38s, 
1.07) 1.25 | 4.00 
| | 
HESPEROMYS (ORYZOMYS) PALUSTRIS. 
Rice-field Mouse. 
Mus palustris, Harwan, Sill. Am. Jour. Sc. XX XI, Jan. 1837, 386, (Fast Land, near Salem, N. J.) 
Isis, 1840, 178. 
Hesperomys palustris, WaGNeR, Suppl. Schreb. III, 1843, 543. 
Leconte, Pr. A. N. Sc. Phila. VI, 1853, 410. 
Arvicola oryzivora, Aup. & Bacu. N. Am. Quad. III, 1853, 214; plate exliv, fig. 3 
Sp. Cu.—Color above mixed black and pale brownish ash, sometimes with a tinge of yellowish brown on the sides; 
beneath ashy white without any distinct separating line. Tail dusky, scarcely lighter beneath. Feet whitish. For generic 
characters see page 458. 
This species is quite different in appearance from the ordinary species of Hesperomys, as found 
in the United States, and indeed would be taken rather for an Arvicola or Sigmodon than anything 
else. In size it exceeds any North American species, unless that from Santa Clara, California, 
be an exception. The ears are unusually short for the genus, in the dried skin, scarcely projecting 
beyond the skin, although distinctly visible from the side; they are rather higher than broad 
in life, but nearly orbicular in the skin, the edge completely rounded without any angle. 
The antitragus is rather lower and less distinct than in H. leucopus. The ear has much the 
appearance of Arvicola in respect to its hairs, which are long and coarse instead of being short 
and velvet-like, as in H. leucopus. A peculiarity of this group is seen in the existence of a 
patch on the concavity of the ear of longer hairs than elsewhere, a short distance from the 
naked area around the meatus. 
The eyes in this species are small, appreciably less than in H. leucopus. There is a peculiar 
appendage to the lower internal corner of the nostril, in the shape of a cartilaginous pad, 
indented by two furrows which meet below, enclosing an elongated depressed eminence. The 
axes of these eminences of opposite sides would, if produced, meet on the lower border of the 
nose ; in fact, the pads themselves are very nearly in contact. Something similar is seen in H. 
leucopus, but it is much less conspicuous. The upper lip is cleft or acutely emarginate to the 
base of the incisor ; the furrow, continued thence to the nose, is shallower than in H. leucopus, 
and does not permit as great a separation of the parts, causing the lip to appear less deeply 
cleft. 
The feet present many striking peculiarities, among which is the complete nakedness of the 
sole from the extremity of the heel. There are six tubercles, the posterior one very long and 
narrow, as in Mus, measuring 0.15 of an inch in one specimen, or more than one-seventh 
