74 PATAGONIAN EXPEDITIONS : ZOOLOGY. 



Akodon canescens Thomas, P. Z. S., 1898, 211, Chubut, E. Patagonia. 



Aditlt (March and April). — General color above gray, faintly suffused 

 with fulvous and varied slightly with black-tipped hairs ; below whitish 

 gray, the basal portion of the fur plumbeous, the tips whitish ; sides and 

 front of nose pale rusty fulvous ; ears rusty brown ; upper surface of fore 

 and hind feet yellowish white or pale rusty fulvous ; tail rather indistinctly 

 bicolor, darker above and lighter below, with usually a faint rusty tinge 

 throughout. The ventral surface and sides are often faintly w^ashed with 

 pale fulvous. 



Half grown young are almost indistinguishable in coloration from the 

 adults. 



Adult (July). — Pelage longer and fuller, and general coloration above 

 yellowish gray-brown, the general tone darker and browner than in April 

 specimens; under parts whiter and with rarely any tinge of buff; sides of 

 nose more rusty, and upper surface of feet more buffy. The difference be- 

 tween the gray summer pelage and the darker and more fulvous brown win- 

 ter pelage is quite strongly shown in March, April and July specimens from 

 practically the same locality. 



The two series from the Rio Coy, consisting of five specimens taken 

 in November and others taken the last of August, well show the two 

 pelages, and indicate that the gray pelage is worn from about November 

 till May, and the brown pelage from about June to September as is further 

 shown by specimens from the vicinity of Cape FairAveather. 



Measurements. — Many of the specimens are more or less immature. 

 Throw^ing out these, save possibly a few young adults, the series, collected 

 and measured by Mr. Colburn, gives the following: 16 males, total length, 

 132 mm. (125-140, with one reaching 150); tail vertcbrcE, 50.9 (50-55); 

 hind foot, 19.7 (19-20): 16 females, total length, 135.3 (125-145); tail 

 vertebrae, 50 (45-55) ; hind foot, 20 (19-20). Fully adult specimens ap- 

 pear to rarely fall below 130 mm. in total length, and very few exceed 

 140 mm. 



Seven males and four females collected and measured by Mr. Peterson, 

 from the upper Rio Chico de Santa Cruz, give similar results, as fol- 

 lows : 7 males, total length, 136 (125-151); tail vertebrae, 50 (46-54), 

 hind foot, 20 (18-21): 4 females, total length, 137 (126-148); tail verte- 

 brae, 50.7 (45-55); hind foot, 20 (20-20). 



Thirteen specimens from Cape Fairweather, all males, collected and 



