Joseph Grinnell and Joseph Dixon

“ Size larger: body alone more than 103⁄4 inches (273 mm.) long; general tone of coloration darker Catalina Island Ground Squirrel (p. 49) .
4'. Size smaller: body alone less than 103⁄4 inches (273 mm.) ; general tone of coloration lighter. 5. Coloration pale in general tone, near light cinnamon-drab; shoulder patches clear silvery white and more extensive Fisher Ground Squirrel (p. 44) .
5'. Coloration somewhat darker, near wood brown; shoulder patches duller white and less extensive California Ground Squirrel (p. 9) .
1'. Size medium or small: body alone less than 9 inches (228 mm.) ”

“ No blackish patch on back. 3. Tail longer: without hairs, about 8 inches (203 mm.) ; no sharply defined triangular whitish patch on each shoulder Rock Squirrel (p. 58) .
3'. Tail shorter: without hairs, 71⁄2 inches (190 mm.) or less; a more or less sharply defined triangular whitish patch on each shoulder. 4. ”