732 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



darker purer gray than chose from the more desert region southward; Fort 

 Tejon specimens, as compared with others from Oregon, presenting a 

 bleached or faded appearance. The skulls show no appreciable difference 

 in size with locality; southern specimens are certainly not smaller than north- 

 ern ones. 



This species differs from the Eastern Gray Squirrel (S. carolinensis) in its 

 larger size, relatively much longer tail, and in the gray of the upper parts 

 wholly lacking the fulvous suffusion seen in that species, and in being purer 

 white below. S. fossor much more resembles the wholly gray phase of S. 

 aberti, the two species being of about the same size. S. aberti, however, has 

 a shorter and whiter tail, especially beneath, and has usually a dark reddish- 

 brown area on the back and a very distinct black lateral line. It is further 

 distinguished, especially in winter, by the presence of long conspicuous ear- 

 tufts, as well as by the much larger size of the ears themselves. 



S. fossor is apparently wholly restricted to the Pacific slope, no speci- 

 mens having been reported as occurring east of the Sierra Nevada and Coast 

 Ranges of mountains. Specimens are in the collection from as far north as 

 Fort Dalles, Oreg., and from intermediate localities thence southward to Fort 

 Tejon, much beyond which, in either direction, its occurrence has not been 

 reported. Its habitat is hence quite restricted. Its nearest ally is to be found 

 in S. colliaii " of Mexico, with which it agrees in. size and in the relative length 

 of the tail, differing from it, however, greatly in coloration. 



Melanistic phases of coloration are thus far unknown in this species; 

 but since they occur in all the other North American Sciuri, they are to be 

 looked for also in this. 



The Sciurus leporinus of Bachman, doubtfully referred by Professor 

 Baird to S. fossor, agrees much better with S. collixci than with S. fossor. It 

 may, however, have been based on an abnormal specimen of S. fossor. A 

 specimen in abnormal pelage, collected by Mr. H. "W. Henshaw in Southern 

 California in 1875, I at first identified as satisfactorily meeting the require- 

 ments of Audubon and Bach man's S. leporinus, but a reexamination of the 

 subject convinces me that their description of S. leporinus better agrees with 

 certain phases of S. collicci than with any known phase of S. fossor, and that 

 the locality of the specimen was Western Mexico instead of "Northern Cali- 

 fornia", as supposed. 



