SCIUEIDyE— CYNOMYS COLUMBIANUS. 903 



back ami below like the ventral surface. Ears and general proportions as in 

 C. ludovicianus, except that the tail is shorter. 



Different specimens, even from the same locality, vary considerably in 

 respect to color, the dorsal surface being in some pale reddish, as strong as 

 in very pale specimens of C. ludovicianus, and in others with only a slight 

 tinge of rufous. The proportion of black hairs also varies greatly, being 

 sometimes so abundant as to give a decidedly dusky shade to the whole 

 dorsal surface, with the head quite blackish and the tail strongly mixed with 

 black, with a narrow, partly concealed, subterminal bar of dusky within the 

 terminal white area. The extremes of variation in color thus give rise to 

 widely diverse phases, but a large series presents every possible stage of inter- 

 gradation between these extremes. The lower surface varies from pale 

 yellowish-white to bright yellowish-brown or tawny. 



Although occasionally specimens of C. columbianus are met with that 

 present almost exactly the shade of coloration sometimes seen in C. ludovici- 

 anus, as a rule the two species are readily distinguishable by coloration alone. 



In C. columbianus, the general color above is yellowish-brown rather than 

 reddish-brown, with a greater admixture of blackish. C columbianus also 

 averages considerably smaller (nearly two inches shorter in head and body 

 length), and has relatively a very much shorter and differently colored tail, 

 it being only about one-half as long as in C. ludovicianus. 



As already stated, this species, like the preceding, was first discovered 

 by Lewis and Clarke, and was first named by Ord, in 1815, from the descrip- 

 tion of it given in the "Biddle-AUen" i:arrative of their journey. Rafinesque, 

 two years later, founded his genus Anisonyx on a misinterpretation of Lewis 

 and Clarke's description, and renamed the species Anisonyx brachiura. Ord's 

 prior name was either overlooked or ignored by subsequent authors (Harlan, 

 Richardson, and several foreign compilers), who, however, while adopting 

 Rafiuesque's specific appellation, referred the species to Arctomys. Their 

 accounts are either simply a quotation of, or a compilation from, Lewis and 

 Clarke's description. Audubon and Bachman, in 1853, renamed the species 

 Arctomys leivisi, basing their description on a specimen in the Museum of the 

 Zoological Society of London labelled " Arctomys brachyura? Harlan", and 

 said to have come from the Plains of the Columbia. Audubon and Bachman 

 found, as they thought, sufficient discrepancies between the specimen 

 described by them and Lewis and Clarke's description to warrant them in 



