4.1 per cent of
length of body. For cranial measurements see Table 2.

_Remarks._--For comparisons with _Reithrodontomys megalotis dychei_,
geographically adjacent to the northeast, see account of that
subspecies.

When Howell (1935:143) named _Reithrodontomys megalotis caryi_ from the
San Luis Valley of Colorado he compared it directly only with _R. m.
megalotis_ from southern New Mexico and northern Chihuahua. Few adults
were available to Howell from the San Luis Valley, accounting for the
fact, we think, that the published measurements of _caryi_ average less
than those given for _R. m. aztecus_ by Howell (_op. cit._:144) and
herein. We have examined 16 of the 23 specimens from Medano Ranch and
the single specimen from Del Norte that Howell listed. Unfortunately,
none is fully adult. The specimens from Medano Ranch, collected in late
October and early November, are mostly in fresh winter pelage or molting
from subadult pelage, and closely resemble topotypes of _aztecus_ in
comparable pelages. Comparison of skulls of the specimens from Medano
Ranch with skulls of topotypes and other individuals of _aztecus_ of
approximately equal age indicates that the Coloradan specimens may
average slightly smaller and have somewhat shorter rostra. Externally,
topotypes of _caryi_ have the relatively long tail of _aztecus_ and
approach it in length of ear (measured on dry specimens). To us, they
appear to be intergrades between _aztecus_ and _dychei_, but to bear
closer resemblance to the former, and we tentatively regard _caryi_ as a
synonym of _aztecus_. Benson (1935:140) noted that two adult topotypes
of _caryi_ were "similar to adult topotypes of _aztecus_." Specimens
from southern Colorado east of the San Luis Valley, assigned to
_aztecus_, are intergrades between it and _dychei_, as are two specimens
from El Paso County, to the north, which resemble _aztecus_ in color but
resemble _dychei_ in other characters and are tentatively assigned to
the latter.

Specimens from southwestern Kansas and adjacent Oklahoma, herein
referred to _aztecus_, also are intergrades with _dychei_. Individuals
from Meade County, for example, are intermediate on the average between
typical specimens of the two subspecies in color of upper parts (if
anything, nearer _dychei_), resemble _dychei_ in length of ear, but
resemble _aztecus_ in length of tail and rostral proportions
(consequently also in length of skull). Although a case could be mad