30 , NOKTH AMKKU'AN FAUNA. [no. 19. 



then one of hhick, tlu'ii yeilowisli white, and Hiially a black ti}). In 

 S. cmipetni, tlic arranoeiiHMit is ])iiU'tically tlie same, but the upper 

 part of the li^'ht gray zone; blends into ful\'ous. As this is the widest 

 zone, it gives a fulvous suti'usion to the entire u])perparts of the ani- 

 mal. Injjlesius the black sul)inaroin of the tail never shows through 

 on the under side. Wodi xprhuj j^tdaijc: Upperparts 3'ellowish gray; 

 top of head, forehead, and nose cinnamon rufous; thighs with faint 

 suggestions of rufous; shoulders and neck hoary; sides and under- 

 parts grayish white washed with yellowish and flecked with ochrace- 

 ous; feet pale buffy ochraceous; tail paler than in postbreeding pelage. 



Skull. — Similar to that of S. emjpetra from Unalaska, but smaller 

 and lighter; nasals shorter and wider in proportion to their length; 

 postpalatal notch extending fai'ther f(jrward, being almost on a 

 plane with the last molar; molar teeth decidedly larger than those of 

 kadiace7ims. 



Measureiiients. — Tjqje (from dry skin): Total length 845; tail verte- 

 brae 93; hind foot 50. Skull of type: Basal length 45; zygomatic 

 breadth 35', postorbital constriction 13; length of nasals IS; least 

 width of nasals G; alveolar length of molar series 13. 



Refmarlxs. — The material representing SjjermojjJdlus eiiijpetnt is still 

 very scanty and imperfect. Specimens from the Arctic coast are few 

 in number and poor in quality, while from Hudson Bay one flat skin, 

 unaccompanied by a skull, is all I am able to find. I have considered 

 this (No. 13932, U.S.N.M.) to bo typical of emjjetra and have used 

 it in making skin comparisons. Since it agrees fairly well wdth speci- 

 mens of the ground squirrel which has been introduced on Unalaska, I 

 have used the skulls of these for skull comparisons. Specimens from 

 Bristol Bay and the Alaska peninsula are apparentl}' intermediate 

 between efmxjetra and j)l&slus. jS. kadiacensis is apparently confined to 

 Kadiak Island, as specimens from the mainland immediately opposite 

 the island are cranially and dentally distinct. The southern members 

 of the group, colu7nbianu» and erythroglutceus, also need not be con- 

 sidered, as they are very difierent from erripefra and 2jlesl'm. 



K plexitis was first met with on the south side of White Pass near 

 Glacier, where a small colony was found on a steep rocky slope above 

 the canyon. They were active here in early June while patches of 

 snow still lay on the ground. On the summit of White Pass another 

 small colony was found, and at Lake Bennett they were very abundant. 

 Here their burrows are to be found wherever the conformation of the 

 rocks affords lodgment of sufficient soil. From Bennett on to Fort 

 Selkirk they are exceedingly abundant. We saw them daily about all 

 the lakes, and as we floated down Fifty-Mile and Thirty -Mile rivers, 

 we often saw them bobbing in and out of their burrows or scurrying 

 along their little trails which score the banks. 



From sunrise till late in the afternoon, their sharp clicking cries 



