[Illustration: FIG. 1. Rainforest near Tolosita, Oaxaca. March, 1956.] [Illustration: FIG. 2. Rainforest along the Rio Sarabia, Oaxaca. March, 1956.] PLATE 3 [Illustration: FIG. 1. Transition forest near La Princesa, Oaxaca. March, 1956.] [Illustration: FIG. 2. Palm Savanna on the Plains of Chivela, Oaxaca. March, 1956.] PLATE 4 [Illustration: FIG. 1. Scrub forest on the Plains of Tehuantepec in dry season. March, 1956.] [Illustration: FIG. 2. Scrub forest on the Plains of Tehuantepec in rainy season. View toward the north. In the distance is the Continental Divide in the hills of the Isthmus. July, 1958.] PLATE 5 [Illustration: FIG. 1. Low, dense scrub forest near La Ventosa, Oaxaca. July, 1958.] [Illustration: FIG. 2. Temporary pond in scrub forest north of Salina Cruz, Oaxaca. July 7, 1958. _Rhinophrynus dorsalis_, _Bufo marmoreus_, and _Diaglena reticulata_ were breeding here the previous night.] PLATE 6 [Illustration: FIG. 1. Calling male of _Rhinophrynus dorsalis_, photographed in a pond north of Santa Cruz, Oaxaca, on July 6, 1958. x 2/3.] [Illustration: FIG. 2. Color pattern variation in two adults of _Bufo canaliferus_ from Juchitan, Oaxaca. x 2/3.] PLATE 7 [Illustration: FIG. 1. Calling male of _Engystomops pustulosus_, photographed in a pond west of Tehuantepec, Oaxaca, on July 5, 1956. x 2.] [Illustration: FIG. 2. Foamy egg mass of _Engystomops pustulosus_ at the edge of a pond west of Tehuantepec, Oaxaca. July 5, 1956. x 3/8.] PLATE 8 [Illustration: FIG. 1. Calling male of _Diaglena reticulata_, photographed at a pond north of Salina Cruz, Oaxaca, on July 6, 1958. x 1/2.] [Illustration: FIG. 2. Clasping pair of _Diaglena reticulata_ at the edge of a pond north of Salina Cruz, Oaxaca, on July 6, 1958. x 1.] Breeding congregations were found after heavy rains at Tehuantepec on July 5, 1956, at Cosamaloapan, Novillero, and Amatitlan on July 26, 1956, and at Salina Cruz on July 6, 1958. The call is a long "worrp" made while the male is floating on the surface of the pond. The small heads, small limbs, and greatly inflated bodies cause the calling males to resemble miniature caricature balloons (Pl. 6, fig. 1). Amplexus is inguinal. These toads are notably wary, even when calling. Often the beam of a flashlight or the slightest disturbance of the water will cause the males to stop calling. The body is deflated with one last nauseous note, and the frog sinks beneath the surface of the water and swims away with short slow kicks of the hind feet. =Bufo canaliferus= Cope _Oaxaca_: Chivela; Salina Cruz; Santa Efigenia; Tapanatepec (6); Tehuantepec (10); Zanatepec (4).