SCIURIDiR— SCIU11U8 NHJKIl AND VAHIHTIKH. 



721 



ventral surface, passing into fulvotm nntcriurl}-, and in olso niiieli lighter nliove 

 tlmn 8|>eciineii8 from Northern Illinois. No. 7773, from Sioux City, lown, is 

 also pnle whitisli-fulvous holow an<l light uhovc. Specimens from Northern 

 Illinois urc also very pale fulvous IxMieatli, lighter gray ai»ovc. Fort I)es 

 Moines specimens are consitlerubly brighter helow 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 Siiint Louis, 

 Mo., the ventral surface is strongly rufous, and tlie dorsal surface is of a dark(>r 

 gray. In others, from Prairie Mer Rouge, La,, tlie under ports are «l(!ep 

 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 pole fulvous, deep fulvous, and ferrugincous, 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 tlie AUeghanies on the east (where it meets the range of 

 vars. cinereuM and niger) to the eastern jjortion 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 iiabitat is hence far more 

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

 of climatic conditions. 



i 



GENERAL BEHABK8 ON SCIURUS NIGER AND ITS VARIETIES. 



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

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

 and ears no' 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 }>arts southward, so oflen exemplified in other Mammals. The more 

 4C M 



