A study of the amphibians and reptiles in the rainforests of southern El PetÉn, Guatemala, reveals the presence of 78 species; an additional 13 species probably occur there. In this tropical area having a high amount of rainfall most of the species of amphibians and reptiles have extensive ranges in the wet forests on the Atlantic lowlands of southern MÉxico and northern Central America; some species that more frequently are found in sub-humid forests also occur.

Ecologically the fauna is divided into five major habitats—aquatic, aquatic margin, fossorial, terrestrial, and arboreal. Forty-two per cent of the 78 species are wholly or partly arboreal. The fauna is most closely related to that in Alta Verapaz, Guatemala, but includes many species that occur in the Tikal-UaxactÚn area in northeastern Guatemala.

Eleutherodactylus rostralis (Werner) and E. rhodopis (Cope) are redefined and their relationships are suggested. The color phases of Dryadophis melanolomus laevis and D. m. alternatus are discussed; Dryadophis sanguiventris Taylor is synonymized with Dryadophis melanolomus alternatus (Bocourt).

The breeding habits, eggs, and tadpoles of the hylid frogs Hyla ebraccata and Phyllomedusa callidryas taylori are described, as are the eggs and juveniles of Laemanctus deborrei.