_Characters of the species._--Size small (extremes in external measurements of adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to almost black; underparts grayish to cream-buff. _Geographic variation._--Eight subspecies are here recognized (see Figure 11). Features that vary geographically are mostly the same as those that do so in _B. musculus_ (see page 609). External and cranial size is less in _B. t. allex_, the southernmost subspecies, and progressively more in _B. t. paulus_, _B. t. taylori_, _B. t. ater_, _B. t. subater_, _B. t. fuliginatus_, _B. t. canutus_, and _B. t. analogous_. Size is largest in subspecies that occur at higher altitudes. Those subspecies are _B. t. analogous_ and _B. t. fuliginatus_. The correlation with Bergman's Rule is less exact in _B. taylori_ than in _B. musculus_. It is noteworthy that the smallest subspecies, _B. t. allex_, occurs in the area where the two species are sympatric. There is close correlation in _B. taylori_, as also in _B. musculus_, of darker pelages with zones of high relative humidity. The subspecies having dark pelages are: _analogous_, _fuliginatus_, and _subater_. The two first-mentioned subspecies occur at high altitudes, and the other, _subater_, occurs in the humid coastal region of Texas. The paler subspecies, _taylori_, _canutus_, and _allex_, occur at lower altitudes. Two subspecies that occur at relatively high altitudes, _ater_ and _paulus_, are reddish-brown. The color of pelage in these subspecies resembles the color of soil upon which they live. Blair and Blossom (1948:5) demonstrated close correlation of color of soil with color of pelage in _B. t. ater_ by use of an Ives tint photometer. [Illustration: FIG. 11. Distribution of _Baiomys taylori_. Known localities of occurrence are represented by circles and black dots; the former denote localities that are peripheral (marginal) for the subspecies concerned. 1. _B. t. allex_ 2. _B. t. analogous_ 3. _B. t. ater_ 4. _B. t. canutus_ 5. _B. t. fuliginatus_ 6. _B. t. paulus_ 7. _B. t. subater_ 8. _B. t. taylori_] _Natural History_