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754 



MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



Ill tlic tliinl (No. 9433), tlie nape-pntcli 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 subterniinal zone of black, and broadly 

 tipped with white. The yellow of the base is traversed by a irrow 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 coloi»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. 

 In 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. Tiiis specimen very closely resembles the right- 

 hand figure of Geoffroy's Plate X in the Zoology of the Voyage of the Venus. 

 No. 0434, from Tohiuuitopcc, corre.spond.s 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 i\t". same work. 



This species was first descrii)ed in 1855 by Is. Geoffrey, from specimens 

 obtained at Monterey by the naturalist of the Venus, but erroneously referred 

 to the iS. aitrfiogasfer of F. Cuvier. GeoflTroy, in his article on this species, 

 refers to its great variability in color, some of the specimens examined by 

 him being clear white beneath, otiiers grayish-white, while others had tiie 

 same parts varied with rufous and white. Dr. Gray's Marroxus griseo/lavtts 

 and iiis M. Icucops are unquestionably, I think, referable to this species. 



The M. Icucops agrees well with Geoffrey's figures and description of 

 his iS. nureogasfer; the M. griscojlavus 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 M. leucops has the "crown, 

 nape, and rump yellow-washed"; the lower surface in griseoflavus is "yellow- 

 red"', in kucops "bright red". GeofTroy says, of the upper parts, "mais le 

 gris n'est pas pur, les polls, noirs h leur base, blancs h leur poiiite, ayant uno 

 zone intermi'diaire roussc qui se niontrc un peu au dehors, et jetle sur 

 I'enscmble du pelage une b'gfcre nuance rousse. Sur la croupe et hi nuque 

 Ic roux devient meine dominant." 



