16. Diameter of shaft at widest point less than .58 mm.; tip less than 35 per cent of length of shaft. _Eutamias ruficaudus ruficaudus_, p. 622 16'. Diameter of shaft at widest point more than .65 mm.; tip more than 40 per cent of length of shaft. _Eutamias ruficaudus simulans_, p. 623 ACCOUNTS BY SPECIES #Eutamias alpinus# (Merriam) Figure 1 Pelage silky; tail bright orange beneath; markings relatively obscure; size small; skull broad, flattened, and large in proportion to body. Baculum: Shaft thin; keel low, 1/7 of length of tip; tip 39 per cent of length of shaft; angle formed by tip and shaft 135°; distal 1/3 of shaft slightly compressed laterally; base slightly wider than shaft; shaft short, 2.17 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, and shaft thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum shorter; from _E. townsendii_, in base not dorsoventrally thickened, base not so widened; from _E. sonomae_, in ridges on either side of tip not enlarged, base not dorsoventrally thickened; from _E. amoenus_, _E. minimus_, and _E. dorsalis_, in keel lower, angle formed by tip and shaft more distinct; from _E. merriami_, in baculum markedly shorter, base not incised dorsally. _Specimen examined_: One from Big Cottonwood Meadows, S of Mount Whitney, 10,000 ft., Inyo Co., California (CN). #Eutamias minimus# (Bachman) Figure 2 Coloration varying from light to dark depending on subspecies; size small to medium; rostrum short and stout. Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 18 to 28 per cent of length of shaft; angle formed by tip and shaft 125°; distal 1/2 of shaft slightly compressed laterally; shaft short to long, 2.44 to 4.35 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in shaft thinner, base not markedly widened; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, tip shorter; from _E. amoenus_, in tip less than 28 per cent of length of shaft; from _E. dorsalis_, in angle formed by tip and shaft smaller; from _E. townsendii_, in tip less than 28 per cent of length of shaft, angle formed by tip and shaft 125° instead of 130°; from _E. sonomae_, in ridges on either side of tip less well-developed, keel higher; from _E. merriami_, in shaft shorter (less than 4.40 mm.), base not incised, tip proportionally longer. For comparison with _E. alpinus_ see the account of that species.