MUSEUM OF COMPARATIVE ZOOLOGY. 233 



mens from the interior ; but most of them seem to be quite like the ones 

 described by Professor Baird. The mice living on the extensive sand- 

 dunes at Ipswich, under circumstances similar to those of the Muskeget 

 mice, often present, as I have recently ascertained, the half-white appear- 

 ance of the A. " Breiceri." 



The A. albo-rufescens, described by Dr. Emmons from two nearly white 

 or cream-colored specimens procured at Williamstown, is, as first suggested 

 by Audubon, undoubtedly but an albinic variety of A. riparlus. Having 

 obtained two specimens at Springfield that almost exactly accorded with 

 Emmons's description of A. albo-rufescens, I was led at first to consider it a 

 valid species. Subsequent experience convinced me that this is not its 

 character. Two similarly colored specimens of the woodchuck (Arclomys 

 monax), unquestionably albinic, have been since obtained at Springfield, 

 which differ from the ordinary condition of that animal in the same 

 way that these specimens of Arvicola do from the ordinary state of A. 

 riparius. Aububon and Bachman mention similar examples that came 

 under their notice ; in one case different stages of albinism were observed 

 in the different individuals of the same litter. A short time since I myself 

 received an interesting albinic example of this species from Weathersfield, 

 Vermont, from my friend Mr. J. P. Stoughton, of which the following 

 is a description : Beneath, except the extreme posterior part of the body, 

 pure white ; mainly white above, with a wide, rather irregular band of 

 dusky along the back; the anterior part of the head and the cheeks dusky; 

 posterior part of the head white, with several dusky spots ; ears, thighs, 

 and a large spot on the left shoulder, dusky, with small axillary spots of 

 the same color ; all the feet and the terminal third of the tail, white. 

 Irides a little lighter than the natural color, but not red. Ears conspicuous ; 

 much longer than the short, soft fur. A little smaller, and rather slenderer 

 than ordinary specimens. Apparently a mature female, taken August 18, 

 1868. Albinos of this species appear to be not infrequent, the capture of 

 a litter in which all the individuals greatly resembled the parti-colored one 

 above described having come to my knowledge since the above was written. 



The single specimen from Holmes's Hole, described as A. rujidorsum* 

 which is thus far the only recognized specimen of this supposed species ex- 

 tant, seems to be but an unusually highly colored example of .1 riparius. 

 At Springfield, where I have examined hundreds of specimens at different 

 seasons of the year, the variation in color is very considerable, ranging from 

 decidedly gray on the one extreme to as decidedly rufous chestnut-brown 

 on the other. They are usually much grayer in March and April than 

 they are late in the fall. 



* See N. Am. Mam., p. 526, as previously cited. 

 30 



