7.>4 MoxoGHArns or nortit American rodentia. 



In the third (No. 0433), 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 Mad re 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 suL- 

 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. This specimen very closely resembles the right- 

 hand figure of GeofFroy's Plate X in the Zoology 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 described in 1835 by Is. GeofTroy, from specimens 

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

 to the S. aurmgaster 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 griseqflavus 

 and his M. leucops are unquestionably, I think, referable to this species. 



The M. leucops agrees well with GeofFroy's figures and description of 

 his <S. aureogaster; the M. griseqflavus 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 griseqflavus is "yellow- 

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

 gris n'est pas pur, les poils, noirs a leur base, blancs a leur pointe, ay ant une 

 zone intcruK'diaire rousse qui se montre un peu au dehors, et jette sur 

 l'ensemble du pelage une legere nuance rousse. Sur la croupe et la nuque 

 le roux devient meme dominant." 



