(a4 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
In the third (No. 9433), the nape-patch is strongly colored, but is more 
extended and not sharply defined ; the rump-patch, as in the others, is partly 
hidden by the gray tips of the hairs. These all have the hairs of the tail 
orange-yellow at base, with a broad subterminal zone of black, and broadly 
tipped with white. The yellow of the base is traversed by a narrow line 
of black. 
Three other specimens, from the Sierre Madre Mountains, Durango, have 
each the chestnut nape and rump patches sharply defined, the latter very 
large. The general color above is pure dark gray, and that of the ventral 
surface pure white. The pelage of the dorsal surface is generally ringed sub- 
terminally with rufous, but there are many rufous hairs intermixed with the gray. 
Th two of these specimens, the tail presents no yellow, the hairs being banded 
with black and white. In one (No. 7176), the hairs of the tail have a faint 
wash of yellow at the base. This specimen very closely resembles the right- 
hand figure of Geoffroy’s Plate X in the Zodlogy of the Voyage of the Venus. 
No. 9434, from Tehuantepec, corresponds with the other figure of the same 
plate, while No. 9433 might apparently have served as the original of the 
figure given in Plate XI of the same work. 
This species was first describedein 1855 by Is. Geoffroy, from specimens 
obtained at Monterey by the naturalist of the Vénus, but erroneously referred 
to the S. aureogaster of F. Cuvier. Geoffroy, in his article on this species, 
refers to its great variability in color, some of the specimens examined by 
him being clear white beneath, others grayish-white, while others had the 
same parts varied with rufous and white. Dr. Gray’s Macroxus griseoflavus 
and Ins Af. deucops are unquestionably, I think, referable to this species. 
The JL. leucops agrees well with Geoffroy’s figures and description of 
his S. aureogaster; the M. griscoflavus better with my Durango specimens, 
except that the nape-patch is not mentioned. In both, the hairs of the back 
are lead-colored at the base, broadly ringed with brown, with a narrow sub- 
terminal ring of black and a white tip, while JL /eucops has the ‘crown, 
nape, and rump yellow-washed”; the lower surface in griseoflavus is ‘“yellow- 
red”, in deucops “bright red”. Geoffroy says, of the upper parts, ‘mais le 
gris n’est pas pur, les poils, noirs & leur base, blancs & leur pointe, ayant une 
zone intermédiaire rousse qui se montre un peu au dehors, et jette sur 
Pensemble du pelage une Iégére nuance rousse. Sur la croupe et la nuque 
le roux devient méme dominant.” 
