Reithrodontomys gracilis anthonyi Goodwin.—El Salvador.—Santa Ana: 2 mi. SE San Cristóbal, 2950 ft., 2 (KU 65401-02—March 6, 1955). Guatemala.—Jutiapa: 2-1/2 mi. W, 2-1/4 mi. N San Cristóbal [El Salvador], 2900 ft., 5 (KU 65396-400—March 6, 1955).
The subspecies anthonyi has been known previously by seven specimens, none of which is fully adult, judging from Hooper's (1952:134) comment that the adult pelage of anthonyi is unknown. Six of our seven specimens are clearly adults as is shown by well-worn teeth and degree of development of temporal ridges. The seventh is a young animal in process of postjuvenal molt. Individuals from our series in general resemble specimens of Reithrodontomys mexicanus orinus from the vicinity of Guatemala City but differ from the latter as follows: dorsal pelage brighter (with less suffusion of black), "peppered" in appearance, shorter and sparser; ears distinctly paler, owing both to the paler color of the skin and the paleness of the hairs inside the pinna; dark tarsal stripe not extending onto hind foot; ears and hind feet uniformly smaller; averaging smaller in cranial dimensions (but there is considerable overlap), braincase less convex dorsally.
Measurements of the adult anthonyi now available show that the subspecies reaches a greater size than was apparent in the sample available to Hooper. Consequently the three largest adults would be identified as R. mexicanus according to Hooper's key (1952:31), rather than R. gracilis, and the three smallest adults could not be unequivocably identified as either one species or the other.
The ranges of R. gracilis and R. mexicanus are allopatric except in southern Guatemala where the ranges overlap. However, the two species have not been taken there at the same place.
In comparison with May-taken adults of R. g. harrisi from 3 mi. SW Managua, Nicaragua, the adult anthonyi average brighter (more orange) in color (but two of the anthonyi cannot be distinguished by color when placed with the harrisi), and are larger in total length, length of tail, and size of skull.
One female (KU 65400) contained two embryos that measured 18 mm. in crown-rump length.
Average and extreme external and cranial measurements of the six adults are: total length, 183.6 (170-198); length of tail, 106.0 (95-113); length of hind foot, 18.0 (18); length of ear from notch, 14.0 (14); total length of skull, 22.21 (21.4-22.8); zygomatic breadth, 11.20 (10.9-11.7); breadth of braincase, 10.90 (10.3-11.4); depth of skull, 8.36 (8.0-9.0); length of rostrum, 7.60 (7.3-7.8); breadth of rostrum, 4.24 (4.0-4.6); interorbital constriction, 3.78 (3.6-4.0); length of incisive foramen, 4.05 (3.8-4.3); length of upper molar tooth-row, 3.28 (3.1-3.4). Weight in grams of the adults averaged 14.3 (12-17).
Reithrodontomys gracilis gracilis Allen and Chapman.—Guatemala.—El Petén: Uaxactún, 1500 ft., 2 (KU 65384-85—April 3, 1955).
These specimens are the first of the subspecies to be recorded from Guatemala. Uaxactún is near, but not within, the range of R. g. gracilis as mapped by Hooper (1952:131). The male, KU 65384, and female, KU 65385, are adults with comparatively unworn molar teeth. Respective external measurements are: total length, 178, 175; length of tail, 106, 102; length of hind foot, 18.5, 19; length of ear from notch, 14, 14.
Reithrodontomys gracilis harrisi Goodwin.—Nicaragua.—Estelí: 9 mi. NNW Estelí, 1 (KU 71342—July 15, 1956). Managua: 3 mi. SW Managua, 15 (KU 71345-59—February, May, June, 1956); 4 mi. W Managua, 2 (KU 71360-61—June 26, 28, 1956).