_Length of tail in relation to total length._--The tail in _Eutamias_ is more than 40 per cent of the total length, whereas in _Tamias_ the tail is less than 38 per cent of the total length. In this respect _Tamias_ resembles most ground squirrels of the genus _Spermophilus_. _Color pattern._--The chipmunks vary but little in color pattern, for, even in _Eutamias dorsalis_, which is one of the most aberrant of the chipmunks in color pattern, the pattern is characteristic of _Eutamias_. The width of the longitudinal stripes is uniform in _Eutamias_ whereas in _Tamias_ the dorsal, longitudinal light stripes are more than twice as wide as the other stripes. In _Eutamias_, only the two lateralmost dark stripes are short, whereas in _Tamias_ all four of the lateral dark stripes are short; none extends to the rump or to the shoulder. The dark median stripe is present in both _Eutamias_ and _Tamias_ as well as in other genera such as _Callosciurus_ and _Menetes_ (Ellerman 1940:390). CHARACTERS IN WHICH THE SUBGENUS EUTAMIAS AND THE GENUS TAMIAS AGREE, BUT DIFFER FROM THE SUBGENUS NEOTAMIAS _Shape of the infraorbital foramen._--In the subgenus _Eutamias_ and in the genus _Tamias_ the infraorbital foramen is rounded, whereas in most species of the subgenus _Neotamias_ the foramen is slitlike. In _Eutamias townsendii_, however, the infraorbital foramen is rounded as much as in the subgenus _Eutamias_ and in the genus _Tamias_. _Width of the postorbital process at base._--The postorbital process is broader at the base in the subgenus _Eutamias_ and in the genus _Tamias_ than in most species of the subgenus _Neotamias_. In _E. townsendii_, however, this process is relatively as broad as in the subgenus _Eutamias_ and in the genus _Tamias_. _Position of the supraorbital notch in relation to the posterior notch of the zygomatic plate._--In the subgenus _Eutamias_ and in the genus _Tamias_ the supraorbital notch is distinctly anterior to the posterior notch of the zygomatic plate, whereas in the subgenus _Neotamias_, the supraorbital notch is only slightly anterior to the posterior notch of the zygomatic plate. This difference may be correlated with differences in size, since specimens of the subgenus _Eutamias_ and the genus _Tamias_ are larger than specimens of the subgenus _Neotamias_. _Degree of convergence of the upper tooth-rows._--The rows of upper cheek-teeth converge posteriorly in the subgenus _Eutamias_ and in the genus _Tamias_, except that in some specimens of _E. sibiricus asiaticus_ the rows of upper cheek-teeth are nearly parallel to each other. In most species of the subgenus _Neotamias_ the rows of upper cheek-teeth are nearly parallel to each other, although in the specimens that I have seen of _E. townsendii_, the upper rows of cheek-teeth converge posteriorly.