Allen.] 278 [February 4, 



the British Provinces. Sciurus carolinensis is perhaps a still more 

 marked example, in which the color varies from the light pure gray 

 of the upper parts in New England specimens, with a restricted pale 

 yellowish brown dorsal area, to the rusty gray dorsal surface of the 

 Florida type, in which the whole upper surface is usually strongly 

 yellowish-rusty. This increase of color southward is, however, still 

 more strongly marked in the fox squirrels of the Mississippi Basin, 

 the so-called Sciurus " ludovicianus." In specimens from Ohio, 

 Northern Illinois, Southern Michigan, Wisconsin and Iowa, the lower 

 parts are pale fulvous, varying in some specimens to nearly white. In 

 Southern Illinois, and at St. Louis, Mo., the color has increased to a 

 strong bright fulvous, while in specimens from lower Louisiana the 

 color has become reddish fulvous or deep orange. At the same time, 

 the color of the dorsal surface becomes proportionally darker at the 

 southward, through the greater breadth of the black annulations at 

 the tips of the hairs, the dorsal surface in Louisiana specimens being 

 many shades darker than in those from the Upper Mississippi. This 

 variety also finely illustrates the variation in color seen in speci- 

 mens from comparatively dry and moist regions, its habitat ex- 

 tending up the Missouri and its western tributaries to a point consid- 

 erably above Sioux City. Beginning with Ohio specimens and pass- 

 ing westward, we find an increase of color in those from Northern 

 Illinois, Wisconsin and Iowa, west of which point the color rapidly 



As I have felt it proper to notice this already somewhat at length in the Amer- 

 ican Naturalist (Vol. viii, pp. 227-229, April, 1874), I need not go into details 

 here. Suffice it to say, then, that he seems to have failed to appreciate the differ- 

 ence between calling attention to a few instances of variation with locality in 

 respect to proportions and color, and their combination with hundreds of others 

 of a similar character, and noting their correlation with differences in the phys- 

 ical conditions of the localities at which these variations occur. In short, I think 

 he hardly fairly states the case when he assumes that Prof. Baird, in stating, in 

 1866, that the representatives of certain species of birds in Florida and Lower Cal- 

 ifornia had relatively larger bills than their more northern relatives, and that in 

 several instances the western representatives of certain species had longer tails than 

 their eastern relatives, anticipated my announcement in 1871 and 1872 of a law of 

 enlargement of peripheral parts to the southward, including in birds the lengthen- 

 ing of the tail and claws, as well as the lengthening and enlargement of the bill 

 (the lengthening of the tail really occurring at the southward, rather than at the 

 westward) ; or, in stating again that the birds of the plains were apt to present a 

 bleached or weather-worn appearance, and were darker again on the Pacific Coast, 

 that he also anticipates my announcement of the laws of the greater intensity, 

 depth and extent of the dark colors southward, and their increase also in depth 

 and extent at localities varying in longitude with the increase of atmospheric hu- 

 midity. 



