SCIURIDA—SCIURUS CAROLINENSIS VAR. LEUCOTIS. 703 
Professor Baird says they are rare in Hastern Pennsylvania, Maryland, and 
Virginia. At localities where the pure black phase occurs can usually be 
found every intermediate stage between the intensely glossy black individuals 
and those which scarcely differ from the ordinary type. In Western New 
York and Northeastern Illinois, where I have had the opportunity of observ- 
ing the two phases in life, I found that those representing the dusky, annulated 
phase of coloration were young animals, while all the intensely black ones 
were evidently aged. I felt at the time strongly inclined to the opinion that 
only the fully mature become intensely black,—in other words, that the 
intensity of the black increased with age, and that the black Squirrels when 
young were all more or less annulated with rusty. 
A series before me presents a gradual transition from the usual gray 
type to the pure black phase. No. 1150 (Fort Des Moines, Iowa, Dec., 1855) 
differs but little above from the usual gray form, except in having a rather 
stronger suffusion of rufous and less white; the sides are more strongly 
reddish-fulvous, and the white area of the ventral surface is narrow and of a 
- rather dingy white, with the breast strongly ochraceous. No. 1136 (?, same 
locality and season) has still less gray above, the brownish suffusion is still 
stronger, and the white of the ventral surface is restricted to a few irregular 
patches, more or less confluent. There are dusky areas around the teats ; 
the throat and upper part of the breast are mixed yellowish-brown and black; 
the inside of the limbs and lower part of the breast are washed with yellow- 
ish-rufous or gamboge, strongest on the inside of the thighs. No. 163 
(Coll. M. C. Z., from Wayne County, Ill, Sept., 1867) differs from the last 
mainly in having the middle of the belly grayish-white, mixed along the 
median line with pale rufous hairs annulated with dusky; the breast and 
sides of the abdomen are washed with dingy yellowish-brown. No. 970 
(West Northfield, Ill., Sept, 1855) has the lower parts with a small whitish 
area divided medially by bright yellowish-brown, the rest of the lower sur- 
face being gamboge-yellow. The sides of the back from the middle of the 
body posteriorly are strongly whitish-gray, in strong contrast with the rest 
of the dorsal surface, while the chin, lips, and edges of the fore feet are deep 
reddish-chestnut mixed with blackish. Next come a considerable series of 
specimens, obtained in 1847 by Professor Agassiz from the Boston markets, 
and probably killed either in New England or New York, that show various 
stages of intergradation between the three specimens last described and those 
