MURID.E— SIGMODONTES— OCITETODON I1UMILIS. 125 



The Kansas specimens there enumerated are identical in every respect 

 with typical Carolina and Georgia ones, but with this exception : we find that 

 directly we turn from South Atlantic to other skins we are met by a devia- 

 tion from the type that threatens difficulty in determination of other western 

 forms that have been described as distinct. Thus, the two Saint Louis skins, 

 569-570, have the tail at least equaling the head and body. They are, how- 

 ever, in too imperfect condition to admit of positive determination, and we 

 assign them to humilis with a query, just as Baird did. The Nebraska skin, 

 No. 3095, shows the same thing; but the tail has been skinned and stretched 

 on a straw, so that probably in life it was really shorter than the head and 

 body. It further differs in its paler colors; but this is like what is seen in 

 the Hesperomys, Neotoma, and Arvicola, from the same region, and need not 

 worry us at all. The Iowa skin, No. 9339, is one of the largest we have ever 

 seen, and unusually bright fulvous on the sides — not pale like the Nebraskan, 

 nor dark like the Carolinian. It falls, however, within ordinary limits of 

 variation, and does not excite a suspicion of distintness. 



The Mus leconlii of Audubon and Bachman is certainly the same as 

 their M. humilis ; but the determination of their M. carolinensis offers some" 

 difficulty, as the description above quoted ascribes characters that we do not 

 recognize in our specimens from Carolina. We have never seen an Ochetodon 

 from the South Atlantic States with a tail even equaling the head and body, 

 much less as 2.33 to 2.75, nor a specimen from any locality in which the under 

 parts were not decidedly lighter than the upper. But as it is improbable that 

 a second good species, differing as these authors say, occurs in South Carolina 

 alongside O. humilis, we are forced to believe either that there is some mis- 

 take in the measurements given* and colors ascribed, or else that O. humilis 

 varies to the degree indicated in the description of Mus carolinensis. This 

 latter supposition is very likely ; we have already cited instances of color-varia- 

 tion quite as great as those ascribed to carolinensis, and have seen, in Saint 

 Louis and other specimens, tails at least equaling, if they do not exceed, the 

 head and body. After all, the variation in this latter respect is quite within 

 the limits we elsewhere establish for species of Hesperomys, Sigmodon, and 

 other genera. The case is noteworthy in connection with the long-tailed 

 species O. longicauda, that we next describe. 



There can be but little doubt, and there is none at all in our mind, that 



* More glaring inaccuracies than this occur iu the work in question. 



