348 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY -GENERAL REPORT. 



monax, No. 854,) the head and body measure 14 inches, and the hind foot S.I 4. The tail, with 

 the hairs, measures 7 inches. 



The most important point, however, is in the character of the thumb. Cynomys, as already 

 explained, differs from Arctomys in having the thumb moderately developed, and armed with a 

 distinct claw, nearly as long as the fifth, the soles hairy ; while in Arctomys, the thumb is more 

 rudimentary and armed only with a broad flat nail, very different in character from the promi 

 nent claw of the other. The soles also are perfectly smooth. Now, Audubon & Bachman 

 expressly mention that the " thumbs, instead of being remarkably short and equipped with 

 blunt nails, have long nails nearly the length of those on the other toes." Nothing is said of 

 the character of the soles. 



The next question that remains to be discussed is the relationship of the species to the bur- 

 rmoing squirrel of the Columbia, of Lewis and Clark. See article under Cynomys gunnisonii, 

 page 336. 



It is quite possible, judging from the descriptions, that the Arctomys lewisii may be the same 

 animal as Lewis and Clark described from afresh specimen 12^ inches long, which might easily 

 be stretched to 16. The dimensions of the tail are almost precisely the same. The flat dis 

 tichous tail of a living animal might easily become rounded' in a skin, especially if the caudal 

 vertebra) were removed. The discrepancies in the descriptions of the feet are more apparent 

 than real, especially if, in speaking of the " two inner thumbs of the fore feet," they meant only 

 one thumb to each foot, as is most probable. Nor do our authors make any special reference to 

 the claws ; they merely say that the thumbs are remarkably short, and equipped with blunt 

 nails, the remaining toes being long. Now, in Arctomys, the thumbs and their nails or claws 

 would probably not be mentioned at all by unscientific authors, as they are so minute and 

 inconspicuous as scarcely to attract attention. In color of body and tail the descriptions agree 

 almost precisely. 



The fact that Lewis and Clark refer to their animal as a squirrel does not militate against it 

 being a Cynomys, as they call the common prairie dog, the barking squirrel of the Missouri. 



For the above reasons I am inclined to consider the Arctomys lewisii rather as a Cynomys, 

 and quite possibly the game with the burrowing squirrel of Lewis and Clark, called Arctomys 

 cdumbianus, by Ord, and Anisonyx brachyura, by Kafinesque. 



