John A. White, The Baculum in the Chipmunks of Western North America
“ Eutamias sonomae GrinnellFigure 4Upper parts rich reddish, more or less dulled by gray; backs of pinnae of ears nearly bare; tail long and bushy; size large; skull large, long, and narrow; rostrum deep.Baculum: Shaft thin; keel low, 1/10 of length of tip; tip 27 to 31 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/4 of shaft slightly compressed laterally; base deeper and wider than shaft; shaft of medium length, 3.03 to 3.30 mm.; ridges on either side of tip strongly developed, partly obscuring keel from side. ”
