_Oaxaca_: Santa Efigenia; Tehuantepec (10); 24 km. W of Tehuantepec; Tolosita (2). _Veracruz_: Ayentes (6); La Oaxaquena; Novillero (2); San Lorenzo. Calling males were found in open scrub forest near Tehuantepec and in savannas near Novillero. The specimens from Tolosita were found under cover in a clearing in the forest (Fugler and Webb, 1957:106). Specimens from the Pacific lowlands are typical of _Gastrophryne usta gadowi_ Boulenger in possessing a thin line on the posterior surface of the thighs and a thin line from the snout to the vent. Of nine specimens from the Gulf lowlands (Ayentes, Novillero, and San Lorenzo), seven have a middorsal line; this is narrow in four and wide in three. Five have the stripes on the thighs. Two specimens from the middle of the isthmus (Tolosita) have no stripes on the thighs; one has a thin middorsal line, and the other has a broad line. The adult males have a black throat; females have a mottled one. The brown reticulations on the bellies of specimens from the Gulf lowlands is bolder than on specimens from the Pacific lowlands. The presence of certain characters supposedly diagnostic of the subspecies _gadowi_ (line on dorsum and thighs) in the population of _usta_ in southern Veracruz suggests that a redefinition of the ranges of these subspecies will be in order when sufficient material is available to delimit them accurately. For the present I prefer to consider all specimens from the isthmus solely as _Gastrophryne usta_ without referring them to subspecies. =Rana palmipes= Spix _Oaxaca_: Matias Romero (11); 11 km. S of Santiago Chivela; Santo Domingo; Sarabia. _Veracruz_: Coatzacoalcos; Cuatotolapam; 25 km. SE of Jesus Carranza (4); Tlacotalpan (2); Tula. Adults were found along streams and in marshes in savannas and rainforest. These frogs are wary and difficult to capture, even at night. _Rana palmipes_ is another species that has a discontinuous distribution in the isthmus. The species does not occur on the Pacific lowlands of the isthmus, but does occur on the more humid Pacific slopes of Chiapas and Guatemala. Tadpoles were found in a small sluggish tributary to the Rio Sarabia. =Rana pipiens= Schreber _Oaxaca_: Agua Caliente; Cerro Quiengola; Escurano (14); Rio Sarabia (2); Tapanatepec (5); Tehuantepec (24). _Veracruz_: Acayucan; Cuatotolapam (15); Jesus Carranza (2); 20 km. S of Jesus Carranza (11); 25 km. SE of Jesus Carranza; 20 km. ENE of Jesus Carranza (10); San Lorenzo (10). As in most other places in Mexico and northern Central America, this species occurs wherever there is permanent water. Males were heard calling from woodland ponds and from savanna ponds. SUMMARY