RODENTIA-MURINAE-REITHRODON LONGICAUDA. 
451 
REITHRODON MEGALOTIS, Baird. 
Sp. Ch.—L argest of North American species. Head and body from 2.50 to 3.00 inches ; tail about two-tenths shorter. 
Hind foot near .70. Ears large, moderately clothed with hair. Above mouse-gray, lined with darker, and tinged with 
rusty ; on the rump and sides a fulvous wash. Beneath, soiled yellowish white. 
Two specimens of Eeithrodon were collected by Dr. Kennerly, between Janos, Sonora, and San 
Luis Spring, which I cannot readily refer to any of the described North American species. 
For a fuller account I would refer to the report of the United States and Mexican Boundary 
Survey. 
List of specimens. 
Catalogue number, j 
Corresponding No. 
of skull. 
Locality. 
Whence obtained. 
Nature of specimen. 
Measurements. 
Collected by— 
From tip of nose to— 
Tail to end of— 
Length of— 
Length of 
skull. 
Height of 
ear. 
Eye. 
Ear. 
Occip. 
Tail. 
Verteb. 
Hairs. 
Fore ft. 
Hindft. 
.1039 
2281 
Janos to San Luis 
Maj. W. H. Emory, 
Mounted. 
3.00 
2.25 
2.30 
.68 
.84 
.43 
Dr. C.B. Ken¬ 
Spring. 
U. S. A. 
nerly. 
1040 
.40 
.72 
88 
2.42 
2.25 
.30 
.50 
EEITHRODON LONGICAUDA, Baird. 
Sp. Ch.—S ize small. Tail considerably longer than the head and body, (which measure from 2.10 to 2.30 inches,) 
usually from three to eight tenths of an inch longer. Hind foot . 65 to .70 of an inch. Above dark brown ; beneath white, 
tinged with reddish yellow. A broad wash of bright fulvous on the sides and cheeks. 
This animal, in the character of head, ears, nose, and feet, is very similar to what has been 
described in Eeithrodon humilis. It is, however, of larger size, the ear and tail absolutely 
larger. The tail is rather longer than the body, instead of shorter. 
The colors are very similar ; the back is a dark brown, rather darker than in the house mouse, 
but otherwise very similar. The belly is soiled white tinged with reddish yellow ; on the sides 
is a broad wash of fulvous extending to the cheeks. The feet, chin, and under parts of the tail 
are white. In some specimens, apparently younger ones, the belly approaches more to the 
whiteness of Hesperomys, though never attaining it. The cheeks are, perhaps, brighter than in 
E. humilis. The hind feet are considerably longer than in E. humilis , in accordance with the 
increased length of the tail; these two members in mammals being usually in strict proportion 
to each other—the longer the tail the longer the hind feet, and vice versa. 
