Early in 1960 an unusual opportunity arose to carry on biological field work in the midst of virgin rainforest in southern El PetÉn, Guatemala. At that time the Ohio Oil Company of Guatemala had an air strip and camp at ChinajÁ, from which place the company was constructing a road northward through the forest. In mid-February, 1960, J. Knox Jones, Jr. and I flew into El PetÉn to collect and study mammals, reptiles, and amphibians. While enjoying the comforts of the fine field camp at ChinajÁ, we worked in the surrounding forest and availed ourselves of the opportunity to be on hand when the road crews were cutting the tall trees in the forest, thereby bringing to the ground many interesting specimens of the arboreal fauna. We stayed at ChinajÁ until late March, with the exception of a week spent at Toocog, another camp of the Ohio Oil Company located 15 kilometers southeast of La Libertad and on the edge of the savanna. Thus, at Toocog we were able to work both in the forest and on the savanna. In the summer of 1960, John Wellman accompanied me to El PetÉn for two weeks in June and July. Most of our time was spent at ChinajÁ, but a few days were spent at Toocog and other localities in south-central El PetÉn.

Many areas in Guatemala have been studied intensively by L. C. Stuart, who has published on the herpetofauna of the forested area of northeastern El PetÉn (1958), the savannas of central El PetÉn (1935), and the humid mountainous region to the south of El PetÉn in Alta Verapaz (1948 and 1950). The area studied by me and my companions is covered with rainforest and lies to the north of the highlands of Alta Verapaz and to the south of the savannas of central El PetÉn. A few specimens of amphibians and reptiles were obtained in this area in 1935 by C. L. Hubbs and Henry van der Schalie; this collection, reported on by Stuart (1937), contained only one species, Cochranella fleischmanni, not present in our collection of 77 species and 617 specimens.

Acknowledgments

I am grateful to L. C. Stuart of the University of Michigan, who made the initial arrangements for our work in El PetÉn, aided me in the identification of certain specimens, and helped in the preparation of this report. J. Knox Jones, Jr. and John Wellman were able field companions, who added greatly to the number of specimens in the collection. In Guatemala, Clark M. Shimeall and Harold Hoopman of the Ohio Oil Company of Guatemala made available to us the facilities of the company's camps at ChinajÁ and Toocog. Alberto Alcain and Luis Escaler welcomed us at ChinajÁ and gave us every possible assistance. Juan Monteras and Antonio AldaÑa made our stay at Toocog enjoyable and profitable. During our visits to southern El PetÉn, Julio BolÓn C. worked for us as a collector, and between March and June he collected and saved many valuable specimens; his knowledge of the forest and its inhabitants was a great asset to our work. Jorge A. Ibarra, Director of the Museo Nacional de Historia Natural in Guatemala assisted us in obtaining necessary permits and extended other kindnesses. To all of these people I am indebted for the essential parts that they played in the completion of this study.

Field work in the winter of 1960 was made possible by funds from the American Heart Association for the purposes of collecting mammalian hearts. My field work in the summer of 1960 was supported by a grant from the Graduate Research Fund of the University of Kansas.