1909] The 1907 Alexander Alaska Expedition. 251 
cheeks somewhat lhehter than the crown. Posteriorly the dark 
dorsum merges into a dark vandyke-brown on the rump and base 
of the tail. Under fur of upperparts very dark seal-brown, or 
blackish, becoming seal-brown on the head and lower sides. The 
long coat of the underparts is seal-brown, becoming slightly red- 
dish at the base of the tail and about the gular region and chin. 
Under fur of underparts seal-brown, darkening gradually on the 
sides to the darker coat of the upperparts. Ears black. 
SKuutu.—Nasals long and narrow, projecting considerably be- 
yond premaxillary sutures, much more so than in Vancouver Isl- 
and specimens. Lambdoidal crest rounded; sagittal crest di- 
verging a little posteriorly to frontal sutures. 
Specimens of pacificus in the Biological Survey collection 
are of the usual chestnut coloration, being very different from 
these dark Admiralty Island skins. The blackness of this form 
is due to a very considerable extent to the much darker under fur 
upon which the coloration of the thin coat of long hair has little 
effect. Specimens from Prince of Wales Island in the Biolog- 
ical Survey collection show much less difference in coloration 
and may be considered as intermediate with pacificus, although 
the lightest ones are considerably darker than any of the latter 
examined. The lightest skin from Admiralty Island is a rich 
dark bay and can be matched in depth by the darkest skin in 
the Prince of Wales series. A better color character, however, 
than the depth of the general body coloration seems to be the 
coloration of the rump and base of the tail. This area is much 
richer vandyke brown in all the Admiralty specimens, and serves 
to distinguish them at onee from the lighter rumped specimens 
from Prince of Wales Island. There is doubtless a gradual 
change in the intensity of the coloration in beavers alone the 
Pacific Coast from the chestnut coloration of the Washineton 
form to the very dark form of southeastern Alaska. Two skins 
of leucodontus Gray, from Vancouver Island have been examined 
in the Provincial Museum at Victoria. These are light chestnut 
brown and similar to the coloration of the skins of pacificus 
examined. : 
The skull differences exhibited by American beavers are ap- 
parently slight. The large series of skulls in the Biological 
