Syrrhophus leprus Cope
Oaxaca: 33 km. N of Matías Romero; Santa Efigenia. Veracruz: San Lorenzo.
Although the type locality is stated to be Santa Efigenia on the Pacific slopes of the Sierra Madre de Chiapas in eastern Oaxaca, the type specimen probably came from the northern slopes of the mountains. All other known specimens are from the Gulf slopes and lowlands, and from several localities in Los Tuxtlas. Details concerning specimens from the isthmus and other parts of the range were given by Duellman (1958c:8).
Smith (1947:408) reported a specimen of Syrrhophus verruculatus Peters from San Lorenzo, Veracruz; he stated that this specimen (USNM 123530) could not be S. leprus, because it had a gray belly, nor S. cystignathoides, because of the dark and light dorsal coloration. Firschein (1954:57) in his review of the species of Syrrhophus in eastern México referred the specimen to S. cystignathoides. The specimen is in poor condition. Nevertheless, specific determination is possible. Numerous specimens of S. leprus from Los Tuxtlas have gray bellies; some have heavier pigmentation than the specimen from San Lorenzo. In preservative the dorsum is dark brown with lighter mottling. There is little doubt that the specimen from San Lorenzo is a Syrrhophus leprus, an abundant and widespread species in the humid Gulf lowlands of southern México, and not verruculatus, if this is a valid species (see Firschein, op. cit.:58), and not cystignathoides, a species known from San Luis Potosí southward to central Veracruz.
Syrrhophus pipilans pipilans Taylor
Oaxaca: Cerro Arenal; Cerro San Pedro; 6 km. N of Chivela; 14 km. W of Tehuantepec (2).
In the isthmian region this frog is known only from the Pacific slopes and the Plains of Tehuantepec. Males call from the ground and from trees to heights of about four meters. The call is a single, high, long "peep."
Engystomops pustulosus Cope
Oaxaca: Chivela; La Ventosa (3); Santo Domingo; Tapanatepec (14); Tehuantepec (61); Unión Hidalgo (62). Veracruz: Acayucan; Cuatotolapam (7); 10 km. SE of Hueyapan (11).
Large congregations were breeding at Tehuantepec on July 5, at Tapanatepec on July 13, and at Hueyapan on July 24, 1956. The frogs were breeding in open ponds in scrub forest and savanna; none was found in the rainforest. Males call while floating on the water ([Pl. 7, fig. 1]); the call is a soft "do-ing, do-ing" with a rising tone on the last note. Numerous individual egg masses were along the bank of a pond near Tehuantepec; one large composite egg mass there had a surface area of about one square meter ([Pl. 7, fig. 2]). The large series from Unión Hidalgo was obtained by digging specimens out of a dry sandy river bank in the dry season. Some of the individuals were buried to a depth of 25 centimeters.