142 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
8. HETEROMYS MELANOLEUCUS Gray. 
WHITE AND BLACK POUCHED RAT. 
Local name: Mochilero, i. e., one vjJto c(irries a " morJiila," or knapaack. 
1868. Jleterornya meUmokuras Gray, Proc. Zool. Soc. London, p. 204. 
1900. Ileteromys ■melanoleucus Bangs, Proc. New Eng. Zool. C'lub, I, p. 98. 
Three (one adult and two young) were taken at San Julian and 
another immature specimen at Macuto. Mr. Oldfield Thomas says of 
these that they are essentially topotypes. They were taken among 
vines and underbrush, not far from open spots covered with coarse 
grass. Their pouches are lined scantily with short, whitish hairs, and 
will contain almost a teaspoonf ul. It is worthy of note that a portion 
of the contents of the pouches of the Macuto specimen and of one of 
the San Julian specimens consisted of fragments of a shed skin of a 
snake. 
Measurements of the adult female taken at San Julian August 7: 
Length, 282; tail, 156; hind foot, 33. 
g. SIGMODON SANCTiEMART^ Bangs. 
SANTA MARTA COTTON RAT. 
1898. Sigmodon sanctscmarlfc Baj^gs, Proc. Biol. Soc. Wash., XII, pp. 189-190. 
1900. Sigmodon sanclxmarUe Bangs, Proc. New Eng. Zool. Club, I, p. 98. 
Only one specimen, an adult male, trapped at San Julian on July 29. 
It was taken in a rat-killer baited with corn and set under some loose 
stones on the edge of a small cleared patch. Persistent trapping in 
the same locality for some days thereafter produced no result. 
Measurements: Length, 288; tail, 127; hind foot, 35. 
lo. ORYZOMYS MEDIUS, new species. 
LA GUAIRA RICE MOUSE. 
Type.— Young adult male, skin and skull. No. 105405, U. S. N. M. 
From San Julian, 8 miles east of LaGuaira, Venezuela, August 8, 1900. 
Characters. — Most nearly related to Ori/somys mollipilosus Allen and 
O. magdalince Allen, both from the Santa Marta district of Colombia. 
In external size and in coloration of the skin it most nearly resembles 
O. niagdalino}., but in size and shape of skull it agrees more closely 
with O. mollipilosus. 
Pelage. — Soft and velvety, hairs on the back about 9 or 10 milli- 
meters long; about half that length or a little less on the under parts. 
Color. — Type: The upper parts an indefinite mixture of raw sienna 
and a deep blackish brown, the latter predominating on the median 
