18 



locality I obtained young specimens in the fall that in general char- 

 acters are referable to A. riparius, but which in the character of the 

 fur are quite different from the ordinary type of this species at the same 

 age at the East, the coat being longer and heavier; the longer hairs 

 presented a more bristly appearance, many of which were hoary, thus 

 giving a well-marked grizzly aspect to the pelage. In the long heavy 

 coat it seems to correspond with the prairie variety mentioned by 

 Prof. Baird, and to which he applied the name long ip Us, in reference 

 to this peculiarity; but they differ from it in color, which may, how- 

 ever, and most probably does, result from a difference in age. The 

 longer and coarser pelage noticeable in the Arvicola of the prairie is 

 similar to that previously referred to in this paper as characterizing 

 the prairie minks. 



The two following species of Arvicola also doubtless exist, at least 

 in portions of the State, as they are not uncommon in the adjoining 

 State of Illinois. 



44. Arvicola austera LeConte. (Prairie Meadow Mouse.) 



45. Arvicola pinetorum LeConte. (Pine Mouse.) 



46. Fiber zibethicus Cuvier. (Muskrat.) 

 Common along the streams. 



LEPORID^E. 



47. Lepus Sylvaticus Bachman. (Gray Rabbit.) 



Common about the groves and thickets. In respect to the distribu- 

 tion of this species in Iowa, Dr. White has written me as follows: " It 

 occurs all over the State, but is not common in the northwestern part. 

 Indeed it is most common in the most cultivated districts, especially 

 in southern and southeastern Iowa." He adds that this is the only 

 species of rabbit occurring in the State, to his knowledge. 



It is probable that the Prairie Hare (L. campestris Bach.), the 

 western representative of the L. americanus of the northern tier of 

 States east of the Mississippi (if there is, in fact, any reason to con- 

 sider them distinct), may occur in the northern part of the State. 



DIDELPHID^. 



48. Didelphys virginiana Shaw. (Opossum.) 



From its general known distribution, this species might well be 

 expected to be more or less frequent in the southern part of the State. 

 Dr. White, however, informs me that it is very rare there, but that 

 he saw two specimens some years since in the southeastern part. 



