17 



//. tonoriensis as indistinguishable as a species from H. lencopus. I 

 am the more inclined to the latter opinion from the almost exact resem- 

 blance which authentic specimens of the former that I have examined 

 bear to othej-s unquestionably of H. leucopun. Its recognized wide dis- 

 tribution in latitude does not at all accord with its supposed limited 

 range eastward, in a region of so uniform a character as the one now 

 in question. In regard to H. sonoriemis, Professor Baird observes : 

 4 This species has the general characters of the white-footed mouse 

 of the eastern States ; and it is only after the comparison of extensive 

 series that I have been able to detect differences which, though slight, 

 are so constant and of such a character as to appear something more 

 than a mere local variation. I shall, however, be obliged to indicate 

 the differences rather by comparison than as absolute characters." 

 As I have previously observed, 1 I believe that a considerable number 

 of merely nominal species of Hesperomys have been recognized as 

 valid, and in a group presenting such a wide range of variation in 

 color and in the proportions of the different parts of the body as 

 different representatives of even the restricted H. leucopus do, I fail 

 to see the propriety of basing species on such intangible differences 

 as distinguish //. sonoriensis. 



42. Hesperomys michiganensis Wagner. (Prairie White- 

 footed Mouse.) 



Apparently common; several specimens taken. I made my first 

 acquaintance with this species in life, in Ogle county, Illinois, where 

 I found a pair in June in their nest under a flat stone at the edge of a 

 cornfield. A newly born litter of young were attached to the teats 

 of the female. The contrast of color between the dorsal and ventral 

 areas of the body was well marked, and the line of separation along 

 he sides clearly defined. 2 



The Wood Rat (Neotoma ftoridana) has been found in northwest- 

 ern Kansas, about a hundred miles from the southwestern corner of 

 Iowa, and judging from what is known of its distribution, it may be 

 expected to occur in portions of the latter State. 



43. Arvicola riparius Ord. (Meadow Mouse.) 

 Apparently common. I obtained several specimens, some of which 



are scarcely appreciably different from Massachusetts ones; others more 

 resemble some obtained by me in Northern Illinois. In the latter 



1 Bull. Mus. Comp. Zo81., No. vni, p. 227. 



1 Compare with this the remarks of Mr. Kennicott and Prof. Baird in reference 

 to " Afus Bairdii." Pat. Office Rep., Agr., 1866, p. 92 ; Mam. N. Amer., p. 477. 



