In coloration (being but slightly paler), and in small size, this specimen resembles the description of _R. g. pacificus_ given by Hooper (1952:135) and ten specimens of _pacificus_ (nine from Guatemala and one from Chiapas) examined by us. Because of this resemblance and the marked contrast with specimens of _R. g. anthonyi_ discussed above we assign this specimen to _pacificus_. In comparison with two topotypes (AMNH 79062, 79090) of _R. g. anthonyi_ from Sacapulas, Guatemala, taken on February 9 and March 2 that are essentially the same age as KU 71396, the latter specimen is darker dorsally, the tail is darker both dorsally and ventrally, and the skull is smaller. In paleness of upper surface of hind feet, length of palate relative to length of incisive foramina, and size of bullae, KU 71396 resembles _anthonyi_. We interpret these resemblances to _anthonyi_ as evidence of intergradation between _pacificus_ and _anthonyi_. Felten (1958:9) referred two specimens from El Salvador (one from San Salvador and one from Amate de Campo, Departmento de La Paz) to _anthonyi_, without comparison with _pacificus_ and with no mention of examination of other specimens of _Reithrodontomys gracilis_. When the distribution and variation of _R. gracilis_ in this region are more adequately known these two specimens may well be reassigned to _pacificus_. Hooper (1952:134) observed that two specimens from Monte Cristo Mine in eastern El Salvador were the smallest and darkest of the _R. g. anthonyi_ examined by him and approached _R. g. pacificus_ in these particulars. Possibly these specimens from Monte Cristo Mine also should be assigned to _pacificus_ rather than _anthonyi_. External measurements of KU 71396 are: total length, 167; length of tail, 99; length of hind foot, 19; length of ear from notch, 13. The specimen contained four embryos that measured 10 mm. in crown-rump length. ~_Reithrodontomys microdon microdon_~ Merriam.--GUATEMALA.--Huehuetenango: 2 mi. S San Juan Ixcoy, 9340 ft., 10 (KU 65404-13--December 24 and 25, 1954); 3-1/2 mi. SW San Juan Ixcoy, 10,120 ft., 4 (KU 65210, 65414-15, 65417--December 27 and 28, 1954). San Marcos: 3-1/4 mi. N, 3/4 mi. E San Marcos, 9500 ft, 1 (KU 65420--March 22, 1955). Totonicapán: 5 mi. ESE Totonicapán, 4 (KU 68897-900--July 17, 1955). All the localities from which we have examined specimens fall within the geographic range of the subspecies as mapped by Hooper (1952:168). He examined six specimens of _R. m. microdon_ and listed external and cranial measurements for only two specimens.