_Reithrodontomys saturatus_ Allen and Chapman, Bull. Amer. Mus. Nat. Hist., 9:201, June 16, 1897, type from Las Vigas, Veracruz. _Reithrodontomys megalotis saturatus_, Howell, N. Amer. Fauna, 36:36, June 5, 1914. _Range._--Northeastern part of state. _Specimens examined_, 12: nos. 100202-100212, 100273, from 1 mi. N Zamora, 5,450 ft. _Remarks._--Howell (1914:37) referred nine specimens from Nahuatzin to this race and two from the same place to the subspecies _R. m. zacatecae_. Our specimens from Zamora agree with topotypes of _R. m. saturatus_ and with specimens of that subspecies from the Valley of México in dark color and large size. If our specimens of _Reithrodontomys megalotis_ are correctly identified, subspecifically, _R. m. zacatecae_ ranges southward around the western end of the geographic range of _R. m. saturatus_. Where _R. megalotis_ and _R. fulvescens_ occur together, we find the skull of the latter to be distinguishable by: a median spine on the posterior border of the hard palate (truncate in _R. megalotis_); an S-shaped instead of a C-shaped pattern on the worn occlusal face of the last lower molar; and two re-entrant angles, on the lateral side on the worn occlusal surface of the third upper molar, reaching halfway across the tooth whereas in _R. megalotis_ the anterior re-entrant angle is wanting or extends less than a third of the way across the crown surface of the tooth. =Reithrodontomys megalotis zacatecae= Merriam Western Harvest Mouse; Spanish, Ratón Orejudo _Reithrodontomys megalotis zacatecae_ Merriam, Proc. Washington Acad. Sci., 3:557, November 29, 1901, type from Valparaiso Mountains, Zacatecas. _Range._--From northwestern part of state south through its central part. _Specimens examined_, 53: nos. 100217-100269; distributed by localities, with reference to Pátzcuaro, as follows: 3 mi. N, 6,700 ft., 3; 3 mi. N, 6,800 ft., 1; 3-1/2 mi. S, 7,900 ft., 3; 4 mi. S, 7,800 ft., 31; 5 mi. S, 7,800 ft., 9; 9 mi. SE, 8,000 ft., 6. _Remarks._--Howell (1914:40) has referred four specimens from Patambán to this subspecies, and our large series from the vicinity of Pátzcuaro is also referred to _R. m. zacatecae_ because of small size and reddish (less blackish) color. We lack typical specimens of _R. m. zacatecae_ from the type locality for comparison and our knowledge of _zacatecae_ is derived from Howell's (1914:39) description of it.