852 iMONOC.KAPHS OF NORTH AMERICAN RODENTFA. 



texture of the pelage, the two are entirely distinct, and, as respects the form 

 of the skull, arc almost at the opposite extremes of the genus. In coloration, 

 S. richardsoni, as represented in some phases of var. townsendi, makes a close 

 approach to S. mollis, so that half-grown specimens of the former, in a bad 

 stale of preservation, might l>e distinguished with difficulty from S. mollis. 

 The two species are, however (as will be shown later), radically different. 

 N. richardsoni hence has no very intimately allied American affine. Its rela- 

 tionship to some of the Spermophiles of the Old World seems to be somewhat 

 closer than to any American species. The coloration of the mottled phase of 

 var. townsendi somewhat resembles that of S. guttatus, to which it was referred 

 by Richardson and subsequently by other authors, on the ground of Richard- 

 sou's description. Audubon and Bachman state that they compared a speci- 

 men of their S. townsendi with specimens of S. gvttatus in the Berlin 

 Museum, and found that though there was "a general resemblance" between 

 them, they were "scarcely more alike than the Red Squirrel of Europe 

 (Sciurus vulgaris) and the Red Squirrel of America (Sciurus hudsonius)" . 

 They add : — "They may be distinguished from each other at a glance hy 

 the large rounded spots on the back of the Russian animal, compared with 

 the white and irregular specks in the American species." Two examples of 

 S. guttatus now before me seem to fully bear out this latter statement. 



<S. richardsoni presents a wide range of geographical variation, but can 

 he only rather arbitrarily subdivided into geographical races or subspecies. 

 Northern specimens are not only considerably larger than southern ones, but 

 are much more fulvous, with a minimum amount of black, and smaller ears. 

 The southern form, as contrasted with the northern, is not only smaller, but 

 the fulvous suffusion of the northern type is replaced hy a reddish- or ochrey- 

 brown tint, and there is a great accession of black above, and especially in 

 the tail. This form is developed in its most strongly differentiated phase in 

 the region where also occurs the richardsoni type of Sciurus hudsonius, a 

 reddish-brown phase of Tamias asiaticus, and the smaller dark phase of 

 Spermophilus empetra. 



The Pembina specimens, as well as all of those collected thence west- 

 ward to l he Rocky Mountains, agree perfectly with Sabine's and Richardson's 

 descriptions of S. richardsoni, based on specimens from localities much fur- 

 ther north. The specimens from along the forty-ninth parallel are the palest 

 of any before me; others, however, from Fort Ellis, Montana, and from 



