2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



from western Alaska, in the great amount of black in the coat. Two 

 young males have the whole crown, nape, lower back, and feet, 

 black ; and the tail black above and below, narrowly edged with 

 ochraceous. 



Skull and teeth. — The skulls of females are slightly larger than 

 male skulls of M. caligata, and are about the size of male skulls of 

 M. olympus. Compared with skulls of adult females of caligata, the 

 female skulls of M. sibila are very much larger, relatively narrower, 

 and with elongated rostra. The orbital ring is relatively much 

 smaller ; the tip of postorbital process, as viewed from above, almost 

 in center between maxillary and squamosal arms of zygomatic arch 

 [in caligata much further back, or forward only about one-third the 

 distance from squamosal arm] ; coronoid process of mandible re- 

 duced, the superior notch one and one-half times as long as high at 

 point of coronoid process [in caligata same length as height to point 

 of coronoid] ; teeth slightly smaller. 



Measurements of type (adult female). — Head and body, 510 milli- 

 meters; tail vertebras, 210; hind foot, 95. Skull of type and female 

 topotype, the latter in parentheses: Condylobasal length, 101.5 

 (104.2) ; palatal length, 56.5 (62.1) ; postpalatal length, 40.9 (38.5) ; 

 zygomatic breadth, 67 (66.3) ; length of nasals, 44 (40.5) ; alveolar 

 length of upper tooth row, 22.5 (23.5) ; alveolar length of mandibu- 

 lar tooth row, ,21 (22.3). 



Remarks.— A large series of hoary marmot skulls from the Alaska 

 Peninsula around the coast to Mount Rainier, Washington, including 

 topotypes of M. vigilis, shows remarkably little variation in size ; and 

 the relative size of male and female skulls is constant. The males 

 are considerably larger. As the female skulls of M. sibila about 

 equal the male skulls of M. olympus, the new species must be the 

 largest American marmot. Specimens of the hoary maraiot from 

 Stuart Lake, Barkerville, Glacier, and other points in British Colum- 

 bia, west of the main Rockies, and from northern Idaho, are much 

 like true caligata from western Alaska, and show no approach toward 

 M. sibila in cranial characters. The name Arctomys okanaganus, 

 proposed by King in 1836 ' for a hoary marmot from the southern 

 interior of British Columbia thus remains in synonymy, unless the 

 caligata-Vik& marmots of these interior ranges prove subspecifically 

 separable from true caligata from Bristol Bay. A female specimen 



' Narrative of a Journey to the Arctic Ocean, Vol. 2, p. 236, 1836. 



