8. Shaft more than 4.5 mm. in length; tip 16 per
cent of length of shaft; shaft strongly incised
on dorsal side of base
_Eutamias merriami_, p. 621
8'. Shaft less than 4.4 mm. in length; tip more than
25 per cent of length of shaft; shaft not incised
on dorsal side of base.
9. Height of keel 1/7 of length of tip; angle
formed by tip and shaft distinct
_Eutamias alpinus_, p. 616
9'. Height of keel at least 1/5 of length of tip;
angle formed by tip and shaft poorly defined.
10. Height of keel 1/3 of length of tip;
angle formed by tip and shaft 140 deg.
_Eutamias dorsalis_, p. 620
10'. Height of keel 1/5 of length of tip;
angle formed by tip and shaft 130 deg. or
less.
11. Tip more than 29 per cent of length
of shaft. _Eutamias amoenus_, p. 619
11'. Tip less than 28 per cent of length
of shaft. _Eutamias minimus_, p. 617
7'. Base widened and dorsoventrally thickened.
_Eutamias townsendii_, p. 618
5'. Shaft thick; shaft more than .25 mm. in diameter at widest
point.
12. Length of shaft less than 3.00 mm.; length of tip less
than 1.10 mm. _Eutamias quadrivittatus hopiensis_, p. 622
12'. Length of shaft more than 3.10 mm.; length of tip more
than 1.15 mm.
13. Tip less than 28 per cent of length of shaft.
_Eutamias quadrimaculatus_, p. 624
13'. Tip more than 29 per cent of length of shaft.
14. Angle formed by tip and shaft more than 140 deg.;
ridges on either side of tip indistinct.
_Eutamias cinereicollis_, p. 624
14'. Angle formed by tip and shaft less than 135 deg.;
ridges on either side of tip distinct.
15. Shaft less than 3.65 mm. in length, and .55
mm. or less in diameter at widest point.
_Eutamias quadrivittatus quadrivittatus_, p. 621
15'. Shaft usually more than 3.65 mm. in length,
but when shorter, diameter is .60 mm. or more
at widest point.
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