1896.] NATURAL SCIENCES OF PHILADELPHIA. 355 



the eastern drainage of the Mackenzie to its mouth in latitude 67°. 

 The distribution between Great Bear Lake and Nulato is uncertain, 

 but may be restricted to the Yukon drainage southwestward to 

 Kuskoquim Bay, BehringSea, in latitude 60°. North of this line, 

 the Polar Hare is likely to be found in greater or less abundance, 

 as far as explorations have reached. The Greenland Hare, ac- 

 cording to Fabricius,'^ abounds throughout that country. His 

 observations were probably restricted to the southern half of 

 Greenland, but they equally apply to the nortliern sections. It is 

 also found on the west side of Robeson Channel and Hall Basin in 

 Grinnell Land,^® and on the northeast coast of Greenland in lati- 

 tude 75°." The Baffin Land Hare, in its typical form, occupies the 

 northern half of the Barren Ground Fauna of America, north 

 of latitude 70°, exclusive of Alaska and the habitat of grcenlandicus. 

 Its subspecies, bangsi, may be provisionally restricted to the 

 country east of Hudson Bay, including south Baffin Land. The 

 Polar Hares of the southern interior, west of Hudson Bay, as al- 

 ready stated, probably constitute another race of ardicus, while the 

 Siberio-Alaskan species occupies the remaining portions of the 

 " Alaskan Arctic " range of the Polar Hare in the northwest. 



The causes of geographic variation in arcticus and its subspecies 

 are nowadays so well understood, as far as they relate to color char- 

 acters, as to need little comment. It is interesting to note, however, 

 how they are correlated with the variations of some other animal forms 

 inhabiting the same areas. In the extreme north, where it is never 

 dissociated from snow-covered areas, ardicus practically retains its 

 winter coat throughout the year. In those southern areas where 

 snow largely disappears for a short summer season, we find an as- 

 sumption of colors to correspond with the environment, blackest in 

 rocky, fog-clouded Newfoundland, and hoary in the arid, gray 

 wastes of the interior. On the verdant, humid shores of Alaska, a 

 very distinct Old World species, in sooty-brown summer dress, takes 

 the place of its eastern congener. 



When we come, however, to inquire into the origin of the Green- 

 land species, with the peculiar dental characters which seem to sep- 

 arate it, not only from its Polar allies, but from all other members 

 of the genus, the problem is more difficult. It is not unlikely that 



>5Faun. Gronl., 1780, p. 25. 



'Teilden, in Nares' Voy., 1878, II, Appx., p 204. 



^" Zweite Deutsche Nordpolarf., II, 1874, pp. 165-167. 



