FIELD BOOK OF MAMMALS 



and at several other places the genus has been found in grass- 

 land, both moist and dry. 



"Observations on food habits have been confined practically 

 to the recording of the presence of cut green grasses in the 

 runways, but judging from the habits of related rodents, these 

 animals may occasionally feed upon a variety of bulbs and 

 even insects, as well as succulent herbage. Examination in 

 the Biological Survey of 1 1 stomachs from Kansas and i from 

 Minnesota also showed contents of finely ground grass and 

 sedge leaves and a few insignificant traces of other green 

 vegetation. Further observations on the food habits of 

 Synaptomys are greatly needed. 



"Well-defined runways are maintained, and burrows are 

 constructed in the ground or through beds of sphagnum. 

 Nests are occasionally placed in tussocks of grass or amid other 

 surface cover, according to published reports. 



"Collectors, mostly those of the Bureau of Biological 

 Survey, have trapped females containing from four to six 

 embryos, from March ii to October 7. This indicates that 

 litters are only of moderate size. Probably several litters are 

 borne each year, the period of greatest reproductive activity 

 being largely confined to the warmer months. 



"Lemming mice are so rarely obtained that collectors are 

 likely to seek them whenever possible. Further material from 

 certain critical localities is badly needed, however, and it is 

 hoped that field parties will make special efforts to procure 

 such desiderata. Until more specimens are obtained further 

 progress in the proper understanding of the relationships of 

 several races can hardly be expected." (Howell) 



Genus Lemmus 



Dentition: Incisors, \; Canines, [J ; Premolars, %\ Molars, f = 16. 



Lemming. — Lemmus trimucronatus 



and related forms 



Names. — Lemming; Brown Lemming; Back Lemming. 



General Description. — A small, thickset rodent with much 

 the appearance of a large, short-tailed Meadow Mouse. 

 Soles of feet hairy, without well-developed tubercles; forefeet 

 large and strong, with well-developed claws, thumb much 



398 



