5 of shaft slightly compressed
laterally; base slightly widened; shaft long, 4.09 to 4.56 mm.

Differs from _E. r. simulans_, in keel proportionally lower, tip
proportionally shorter, distal 1/5 of shaft less laterally compressed,
shaft usually longer; from _E. cinereicollis_, in angle formed by tip
and shaft smaller, shaft shorter, ridges on either side of tip distinct;
from _E. quadrimaculatus_, in tip proportionally longer, shaft usually
shorter; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E.
palmeri_, and _E. bulleri_, in base not markedly widened, shaft longer,
angle formed by tip and shaft larger.

For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E.
quadrivittatus_, see the accounts of those species.

Baculum of _E. r. simulans_: Shaft thick; keel proportionally low, 2/5
of length of tip; tip 40 to 48 per cent of length of shaft; angle formed
by tip and shaft 130 deg.; distal 2/5 of shaft laterally compressed; base
slightly wider than shaft; shaft medium to long, 3.30 to 4.26 mm.

Differs from _E. cinereicollis_ in, keel proportionally higher, shaft
shorter, tip proportionally longer, angle formed by tip and shaft
smaller, distal 2/5 of shaft more laterally compressed; from _E.
quadrimaculatus_ in, keel proportionally higher, angle formed by tip and
shaft larger, tip proportionally longer, distal 2/5 of shaft more
laterally compressed, shaft shorter; from _E. speciosus_, _E.
panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base
not markedly widened, shaft usually longer.

For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E.
sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E.
quadrivittatus_, see the accounts of those species.

The differences between the bacula of the subspecies _Eutamias
ruficaudus ruficaudus_ and _E. r. simulans_ are comparable to those
usually found between species of chipmunks. Consequently, I suspect that
_E. r. simulans_ and _E. r. ruficaudus_ are specifically distinct and
suggest that a search would be worth while for specimens in the
geographic area between the geographic ranges as now known for the two
kinds to ascertain whether intergradation (the criterion of subspecies)
occurs. I suppose there is no intergradation but in the absence of
precise information, I choose not to modify the current taxonomic
arrangement of _E. r. ruficaudus_ and _E. r. si