SCIURID^E— SCIURUS NIGER AND VARIETIES. 721 



ventral surface, passing into fulvous anteriorly, and is also much lighter above 

 than specimens from Northern Illinois. No. 7773, from Sioux City, Iowa, is 

 also pale whitish-fulvous below and light above. Specimens from Northern 

 Illinois are also very pale fulvous beneath, lighter gray above. Fort Des 

 Moines specimens are considerably brighter below than are those from North- 

 eastern Illinois and adjoining portions of Michigan, more approaching the 

 southern type of coloration. In a large series of specimens from Saint Louis, 

 Mo., the ventral surface is strongly rufous, and the dorsal surface is of a darker 

 gray. In others, from Prairie Mer Rouge, La., the under parts are deep 

 orange, with a perceptible further darkening of the color above. We have 

 hence a gradual transition in the color of the under parts from pale yellowish- 

 white, through pale fulvous, deep fulvous, and ferrugineous, to bright reddish- 

 orange, in passing from the Plains and the more northern localities to the 

 swampy region of the Lower Red River in Louisiana. While the upper 

 parts show a less striking change in depth of color, there is a correspondent 

 darkening of the dorsal surface through the larger amount of black and the 

 brighter tint of rufous. 



Habitat. — The whole region drained by the Mississippi River and its 

 tributaries, and that bordering the Missouri as far northward as Southern 

 Dakota, extending westward along the wooded streams into the Plains. In 

 other words, from the Alleghanies on the east (where it meets the range of 

 vars. cinereus and niger) to the eastern portion of the Plains on the west, and 

 from the Great Lakes, Minnesota, and Dakota on the north, to the Gulf coast 

 and the highlands of Mexico on the south. Its habitat is hence far more 

 extended than that of either cinereus or niger, and includes a far greater range 

 of climatic conditions. 



GENERAL REMARKS ON SCIURUS NIGER AND ITS VARIETIES. 



Differential characters. — As already stated, var. cinereus differs from 

 var. niger mainly in being rather smaller, and in having, as a rule, the nose 

 and ears not white, or not strongly contrasting in color with the rest of the 

 dorsal surface. Audubon and Bachman, and also Professor Baird, refer to the 

 longer and more pointed ears of var. niger, but, judging from the specimens 

 before me, this is not a very appreciable character. That such should be the 

 case would be only in accordance with the law of the enlargement of periph- 

 eral parts southward, so often exemplified in other Mammals. The more 

 46 M 



