1908.] MAMMALS. 185 



here July 20 contained four embryos. On comparing the specimens 



of this series with examples of the various recognized species of this 

 boreal genus I found the Mackenzie series to represent an unrecog- 

 nized form, and not suspecting at that time the possible applicabil- 

 ity of Richardson's name, characterized the species tinder the name 

 Synaptomys (Mictomys) bullatvs, taking as the type a specimen 

 from near Fort Rae. 



In 1908, on again visiting the Mackenzie Valley, we further 

 extended the known range of the genus in this region. Early in 

 July Alfred E. Preble and Merritt Cary took a small series at Fort 

 Providence, and in August, during my trip northward from Great 

 Slave Lake, I took specimens on Sarahk Lake, just north of the 

 height of land, and on Lake St. Croix, midway between Great Slave 

 and Great Bear lakes. Later T found the species fairly common in 

 the marsh bordering Great Bear Lake near the site of Fort Frank- 

 lin, and took a series, as mentioned above. Two or three of these 

 specimens were trapped in runways of Microtus, and the remainder 

 near the border of the marsh about a small bushy ridge which seemed 

 tenanted solely by these lemmings, since my traps set there captured 

 nothing else. Considering the wide area over which many northern 

 species range without appreciable variation (and this is especially 

 true of the Microtinae), it is not surprising that these topotypes of 

 Arvicola borealis should prove identical in characters with the spec 

 imens taken in the Great Slave Lake region, tints proving bullatus 

 a synonym of borealis. 



In color this form differs from 8. dalli of Alaska in being much 

 darker at all seasons, and it has a shorter hind foot. Cranially the 

 two forms do not differ appreciably. Four adults from Fort Frank- 

 lin average in measurements: Total length 129. tail vertebra' 26.2, 

 hind foot 17.6. Seven adults of both sexes, selected from the series 

 taken in the Great Slave Lake region in 1901, average: 128, 24.8, 17.7. 



Synaptomys borealis dalli Merriam. Dall Lemming Vole. 



During his trip from Jasper House northward to Smoky River 

 in 1890 J. Alden Loring took two lemming voles on Stony River, 

 25 miles north of Jasper House, on August 25. About the middle 

 of October of the same year he found the animals rather common in 

 a high valley about 25 miles west of Henry House, where they in- 

 habited the sphagnum swamps, frequenting runways used by Micro- 

 tus. Here about a dozen specimens, including both adults and young, 

 were taken. These specimens are much lighter and redder than 

 typical borealis and agree so well with a series of S. dalli from 

 various points in Alaska that T refer them to that form. In cranial 

 characters S. borealis and daHU agree very closely. In the specimens 

 taken by Loring the hind foot averages a little Longer than in typical 



