80 EXTINCT AND VANISHING MAMMALS 



the years since its description by Heller in 1909, no recent 

 information is at hand. 



COLORADO RIVER BEAVER 

 CASTOR CANADENSIS REPENTINUS Goldman 



Castor canadensis repentinus Goldman, Journ. Mammalogy, vol. 13, p. 266, Aug., 1932 

 ("Bright Angel Creek, Grand Canyon of the Colorado River, Arizona"). 



This is said to be a "light-colored subspecies closely allied 

 to Castor canadensis frondator, of southeastern Arizona and 

 northeastern Sonora, but upper parts paler, yellowish cinna- 

 mon, instead of near pecan brown (Ridgway, 1912) as in the 

 type; cranial characters, especially the long nasals, distinctive. 

 Similar to C. c. baileyi, of Nevada, but slightly paler, upper 

 parts more yellowish, less rufescent; skull decidedly broader. 

 Differing from C. c. mexicanus, of New Mexico, in slightly 

 yellower coloration (duller brownish in mexicanus) and in 

 cranial details, especially the longer, less expanded nasals." 



Goldman lists specimens from Bright Angel Creek and Yuma, 

 Ariz.; those from the latter locality with shorter nasals "prob- 

 ably grade toward frondator" but in the massive jugal and 

 other respects seem "nearer to repentinus" He adds: "At the 

 type locality the beavers inhabit Bright Angel Creek which in 

 short reaches descends the terraced north side, below the outer 

 rim, of the Grand Canyon. None are known from the Colorado 

 River in that vicinity, and a measure of isolation would seem 

 to be due to the rapids and heavy current through rock-bound 

 gorges extending for many miles, and affording very few places 

 suitable for beavers to establish homes." According to Dr. 

 Joseph Grinnell (1933) it was "originally and recurrently 

 numerous along those parts of this river's course where willow 

 and cotton wood grow abundantly . . . Since 1911, bea- 

 vers have invaded Imperial Valley north of Mexican line 

 following Alamo River and larger distributary canals." 



CASTOR CANADENSIS SAGITTATUS Benson 



Castor canadensis sagitiatus Benson, Journ. Mammalogy, vol. 14, p. 320, Nov., 1933 

 ("Indianpoint Creek, 3200 feet, 16 miles northeast of Barkerville, British Colum- 

 bia")- 



FIG.: Benson, 1938, fig. c, p. 321 (skulD. 



This local race of beaver is described as dark colored, with 

 the ventral underfur dark grayish; "skull with narrow, pointed 



