_Remarks._--The Raft River Mountains of extreme northwestern Utah, where _C. c. pallidus_ occurs, are the only mountains of the state within the drainage of the Snake River. The Snake River proper lies 50 miles to the northward in Idaho and contains another kind of beaver, _C. c. taylori_ (Davis, 1939: 273). Although occurring within the same drainage as _C. c. taylori_, _C. c. pallidus_ is as distinct from it as from any other named kind. The relationships of _C. c. pallidus_, as indicated by the short rostrum and short, wide nasals, are rather more with _C. c. rostralis_ of the Wasatch Mountains, than with _C. c. taylori_. The pale color of the animals belonging to _C. c. pallidus_ was noted at the time of capture, and is the same in the young specimen (625 mm. total length) as in the type, an adult. _Specimens examined._--Total, 2, distributed as follows: _Boxelder County_: Raft River, 5 mi. S Yost, Raft River Mountains, 6,000 ft., 1; Lynn Canyon, Raft River Mountains, 7,500 ft., 1. ~Castor canadensis rostralis~ new subspecies _Type._--Male, young adult, skin and skull, number 5199, Museum of Zoology, University of Utah; Red Butte Canyon, Fort Douglas, 5,000 ft., Salt Lake County, Utah; October 13, 1947; collected by Harold S. Crane and Clifton M. Greenhalgh, original number 446 of Crane. _Range._--Known from the western streams of the Wasatch Mountains; probably occurs in all streams draining westward into the basin of Pleistocene Lake Bonneville. _Diagnosis._--Size large; tail and hind foot long (see measurements). Color (type): Upper parts Snuff Brown, purest on head; underfur Brownish Black (2); base of tail Cinnamon Buff; hind feet Carob Brown; ears Blackish Brown (2); underparts Auburn, grading posteriorly to Cinnamon Buff; underfur Light Drab. Skull: Large, massive; nasals short and broad (breadth averaging 54 per cent of length) and moderately convex transversely; rostrum deep and broad; ventral surface of rostrum moderately concave dorsally; dorsal surface of lacrimal bone small; frontal region generally flat; zygomatic arches robust and widely spreading (zygomatic breadth averaging 82 per cent of basilar length). _Measurements._--Measurements of the type and average and extreme cranial measurements of 6 unsexed adults from Charleston, are, respectively, as follows: Total length, 1,330; length of tail, 470; length of hind foot, 170; length of ear, 34; occipitonasal length, 128.2, 134.3 (142.1-129.5); basilar length, 112.4, 117.2 (128.2-113.2); mastoid breadth, 62.5, 64.3 (68.9-60.2); interorbital breadth, 27.9, 26.0 (26.9-26.0); zygomatic breadth, 91.3, 93.8 (105.8-90.8); length of nasals, 44.9, 43.9 (51.3-41.5); breadth of nasals, 24.5, 23.7 (25.7-22.0); alveolar length of upper molariform teeth, 28.3, 30.9 (32.5-28.7).