iapas (UMMZ 88351-58,
96810-13), and three from 3 mi. NW San Cristobal, Chiapas (KU
66680-82).

_R. m. howelli_ may occur at moderate elevations along the coast of
southern Guatemala, or possibly this specimen represents a population
of dark-colored mice that is isolated from similarly colored
populations to the north and west. According to the field notes of
Albert A. Alcorn, the collector, this specimen was taken in a "tree
set." Perhaps pale-colored and dark-colored populations of _R.
mexicanus_ are sympatric but ecologically segregated in this region.

~_Reithrodontomys mexicanus lucifrons_~ Howell.--NICARAGUA.--Jinotega:
1 mi. NW Jinotega, 1 (KU 71344--April 12, 1956); 5 mi. S, 2 mi. E
Jinotega, 1 (KU 71343--April 12, 1956).

Comments on these specimens have appeared earlier (Englert, 1959:153).

~_Reithrodontomys mexicanus orinus_~ Hooper.--GUATEMALA.--Guatemala: 5
mi. S Guatemala City, 4950 ft., 2 (KU 65388-89--March 11, 1955); 6 mi.
S Guatemala City, 4680 ft., 3 (KU 65390-92--March 10, 1955); 7 mi. S,
6 mi. E Guatemala City, 5800 ft., 2 (KU 65393-94--March 14, 1955).

Our seven specimens are from near the northwestern edge of the
geographic range of _orinus_ (where it meets that of _howelli_) as
mapped by Hooper (1952:141). Nevertheless, they are distinctly brighter
dorsally, paler ventrally, and average larger than the specimens listed
in the account of _R. m. howelli_ above. Also, they match well in size
and coloration the specimens from nearby Lago de Amatitlan (USNM
275406-09) and Finca San Rafael (CNHM 41770) that were referred by
Hooper to _R. m. orinus_. He (_op. cit._:149) noted that these
last-mentioned specimens were slightly darker than topotypes of
_orinus_ and differed from them in several minor cranial features,
which he interpreted as evidence of intergradation with _howelli_.

~_Reithrodontomys brevirostris_~ Goodwin.--COSTA RICA.--Alajuela: 5 mi.
SW San Ramon, 1 (KU 71362--July 11, 1956). NICARAGUA.--Carazo: 3 mi.
NNW Diriamba, 2 (KU 71390-91--June 16, 21, 1956).

External measurements of these three specimens are respectively: total
length, 179, 167, 173; length of tail, 107, 96, 101; length of hind
foot, 19, 18, 18; length of ear from notch, 15, 13, 13. The teeth show
about the same moderate wear in each of the three specimens. Our
_brevirostris_ differ noticeably from specimens of _Reithrodontomys
mexicanus cherriei_ and _R. m. lucifrons_ that we have seen in duller,
darker, and less