Remarks.—Hooper (1952a:93-94) reported specimens from the coastal strip of southern Chiapas as the most intensely pigmented, whereas, specimens from central and western Chiapas were distinctly paler. Crania of specimens from the coastal region of southern Chiapas were smaller than crania from the central highlands and mountains of Chiapas. My studies essentially corroborate the findings of Hooper. The gradation of color between the pale brown pallidus to the north in Oaxaca, and the brownish-black nigrescens to the south in Chiapas is extremely gradual. Specimens from the central and western parts of Chiapas (see [Figure 10] for localities) are difficult to assign to either pallidus or nigrescens. Equal justification exists for assignment to either subspecies. I have assigned the specimens to nigrescens because they are geographically closer to the type locality of nigrescens. Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, to nigrescens), are nearly identical in size and color to paratypes of pallidus. I assign the Reforma specimens to pallidus.
The darkest of all the specimens examined and assigned to nigrescens are from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The variations in color in this subspecies closely correspond to degree of relative humidity; the palest samples are from areas of low relative humidity and the darkest are from areas of high relative humidity. In view of the present state of differentiation of specimens from the southern coastal areas of Chiapas and mountainous areas of El Salvador, it would seem that populations there might be incipient subspecies.
Specimens examined.—Total 319. Chiapas: 17 mi. W Bochil, 1[14]; 15 mi. W Bochil, 1[14]; 14 mi. W Bochil, 1[14]; Bochil, 6[15]; Ocuilapa, 3500 ft., 5[16]; 5 mi. NNW Tuxtla Gutiérrez, 9; 11 km. W Tuxtla Gutiérrez, 800 m., 2[15]; 10 km. W Tuxtla Gutiérrez, 800 m., 2[15]; Tuxtla Gutiérrez, 2600 ft., 8[16], 11; Ocozocoautla, 10[15], 2[16]; 25 mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m., 1[14], 18[15], 3[17]; Jiquilpilas, 2000 ft., 1[16]; San Bartolome, 3[16]; type locality, 5700 ft., 26[16] (including the type); 15 mi. SW Las Cruces, 1; Villa Flores, 600 m., 12[15]; 23 mi. S Comitán, 1[14]; 15 mi. S, 2 mi. E La Trinitaria, 4; 30 mi. S Comitán, 2[14]; 35 mi. S Comitán, 1[14]; 3 mi. E Arriga, 1[14]; 6 mi. NW Tonalá, 19; Tonalá, 8[16]; Los Amates, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m., 25[15], 4[17].
Guatemala: Chanquejelve, 1[14]; Nentón, 3000 ft., 1[16]; Jacaltenango, 5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3; 5 mi. S Guatemala City, 4050 ft., 10; 6 mi. S Guatemala City, 4680 ft., 1; Lake Amatitlán, 4500 ft., 13[16]; El Progresso (Distrito Santa Rosa), 3[15]; 2 mi. N, 1 mi. W Cuilapa, 2980 ft., 1[14]; 1 mi. WSW El Molino (Distrito Santa Rosa), 2; 21/2 mi. W, 21/4 mi. N San Cristobal, 2900 ft., 1; El Zapote, 1[15].
El Salvador: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.
Marginal Records.—Chiapas: Bochil; 25 mi. E Comitán, Las Margaritas, 1250 ft. Guatemala: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.; 4 mi. S Guatemala City, 4700 ft.; El Progresso. El Salvador: 1 mi. NW San Salvador; 1 mi. S Los Planes. Guatemala: El Zapote. Chiapas: Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.
[14] American Museum of Natural History.
[15] Univ. Michigan, Museum of Zoology.
[16] U. S. Nat. Museum (Biol. Surv. Coll.).