ALLEN ON THE GENUS NASUA. 163 



neck whitish, varying from fulvous-white to silvery, this color usually 

 extending over the fore-limbs as far as the elbow, and posteriorly along 

 the sides of the body; 011 the sides of the neck it often forms a well- 

 defined patch extending upward to the ear. The thighs are also more 

 or less whitish. Distal portions of the limbs dark brown, passing into 

 blackish on the feet. Chin, to beyond the syinphysis of the jaw, pure 

 white ; throat, breast, and anterior half of the ventral surface, whitish or 

 grayish-white, more or less obscured by the brown of the basal portions 

 of the hairs. The pure white of the chin is usually separated from the 

 grayish-white of the throat by a dusky band, formed by the extension 

 and confluence of the dark brown of the cheeks ; this, however, is an ex- 

 tremely variable feature, being sometimes wholly absent, often indistinct^ 

 but sometimes very broad and prominent. The color of the ventral sur- 

 face is variable, being sometimes wholly silvery, or grayish- white, or en- 

 tirely dusky, with no whitish anywhere cm the lower surface except on 

 the chin and a patch of dingy or yellowish-white on the throat and breast. 

 Usually the anterior half of the ventral surface is more or less whitish r 

 through which the fuscous bases of the hairs show, the whitish surface- 

 color being formed by the white tips of the hairs. A similar whitish or 

 yellowish-white tint is seen over the inguinal region. On the chin, the 

 hairs are short and white to the base ; on the rest of the lower surface 

 they are dusky at base and whitish at the tips, resulting usually in the 

 production of a dingy gray. 



The pelage is full, long, and soft, and the tail full and bushy. The 

 hairs composing the whitish patches on the sides of the neck are usually 

 longer than those of the adjoining parts. 



Judging by the specimens in hand, there are no sexual differences in 

 color, one of the darkest specimens of the series being a female. 



In very young specimens, the pelage is softer and more woolly, with 

 the look of immaturity usually characteristic of young animals. They 

 show, however, the same facial markings as the adults. The annulations 

 of the tail appear to be generally more strongly marked in the young,, 

 being, in some cases, quite conspicuous, but are sometimes entirely absent. 



A series of fourteen skins from various parts of Mexico and Central 

 America presents a wide range of individual variation in color, but not 

 greater than most mammals present, and not nearly so great as is seen 

 in Nasna fusca. There seems, also, to be a recognizable amount of geo- 

 graphical variation, the Mexican specimens being much lighter-colored 

 than those from Guatemala and Costa Rica, The lightest-colored spe- 

 cimen of all comes from the Texan side of the Eio Grande, near Fort 

 Brown. In this example (Nat, Mus., No. 12757, Dr. J. C. Merrill), the 

 general aspect of the dorsal surface is yellowish-gray, with a large, 

 whitish area on the sides of the neck, and much white along the sides of 

 the body; below, strongly whitish throughout. The white eye-markings 

 do not quite form a continuous ring, but the spot above the eye has a 

 whitish band connecting it with the white nasal area. The pelage is 



