106 RODENTS OP IOWA 



ceptions the great plains muskrat -closely resembles the common 

 muskrat; but its distribution is more to the westward. Hollister 

 (1. c.), gives the geographical distribution of the present form as 

 follows : ' ' Great central plains region of western United States and 

 Canada; from Manitoba south to northern Texas; east to central 

 Iowa and west to the Eocky Mountains.'/ A single individual is 

 recorded from Knoxville, Iowa. The writer has not obtained speci- 

 mens of this muskrat, but collectors and trappers should be on the 

 lookout for it in western Iowa where the area of intergradation oc- 

 curs. It is found in the sloughs and streams of the interior plains 

 region, and its habits are practically the same as those of the com- 

 mon, muskrat. 



GOSS' LEMMING MOUSE. 

 Synaptomys cooperi gossii (Merriam). 



Synaptomys helaletes gossii Merriam, Proc. Biol. Soc. Wash., X, 

 60, 1896. 



Description. Summer: General color above rusty brown or red- 

 dish brown, with which are intermingled black-tipped hairs; a 

 blackish mark at base of whiskers ; tail short, brownish above, pale 

 below; color below slaty gray, the hairs tipped with white but the 

 gray showing through. Winter: Grayer and with less reddish 

 brown. The young are slaty or grayish brown above, the color vary- 

 ing with the age. 



.Measurements. Total length, 5.00 inches; tail vertebrae, 0.70 

 inch ; hind foot, 0.75 inch. 



Some little variation in size and color obtains in this form, which, 

 in our fauna probably most nearly resembles Dyche's harvest mouse. 

 However, it may be distinguished from that species by the much 

 shorter tail, the absence of a distinct line along the middle of the 

 back, and the fact that the upper incisors (front teeth) have the 

 longitudinal groove on the anterior face much narrower and near 

 the outer edge. The crowns of the molars (cheek teeth) have trans- 

 verse loops. These two mice are our only representatives of the 

 family which have grooved upper incisors, though the extent of the 

 groove in the two forms differs markedly and in other respe2ts they 

 are rather widely separated. 



Habits, Distribution, Etc. This is one of our smallest mice 

 and appears to inhabit grassy fields and hillsides and open places 



