to specimens in the Museum of Natural History,
University of Kansas. For the loan of tape-recordings of mating calls I
thank Drs. W. Frank Blair, University of Texas, and Richard G. Zweifel,
American Museum of Natural History.

I am indebted to the Ford Foundation-Universidad de Oriente (Venezuela)
Science Project for a scholarship which enabled me to study for two
years at The University of Kansas, foster institution of the project. I
have benefited by being able to work in the Museum of Natural History
at The University of Kansas and I am grateful to Dr. E. Raymond Hall,
Director, for providing space and equipment.

I gratefully acknowledge the assistance and advice of Dr. William E.
Duellman, who suggested and directed this work, made available
specimens under his care and gave much of his time in reading the
manuscript and suggesting improvements. I am grateful to Dr. Frank B.
Cross who critically read the manuscript and made many editorial
suggestions. I am indebted to Linda Trueb for assistance with the
osteological aspects of this study; she helped to clarify many
confusing points. I am grateful to Charles W. Myers for making
available his field notes on these frogs in Panama, to Arthur C.
Echternacht for reading part of the manuscript, and to John D. Lynch
for many suggestions and helpful criticisms. The illustrations were
executed by David M. Dennis.

Materials and Methods

For the purposes of the present study I examined 1383 preserved
specimens, 50 skeletons, and 9 lots of tadpoles. External
characteristics used in the analysis of variation are those currently
employed in the study of anuran systematics. Twelve measurements
and six proportions were taken in the manner described by Duellman
(1956). Only the most important references are given in the synonymies,
except those of the two subspecies of _Hyla staufferi,_ which are
more nearly complete. The taxonomic history of each frog is discussed
under _Remarks_ in each account. The cranial osteology was studied
by using skeletons and cleared and stained specimens of all species.
Developmental stages of tadpoles were determined from Gosner's (1960)
table. Personal field work in Central America in the summer of 1966
provided an opportunity to make observations on the ecology, calling
sites, and color in life; these data were supplemented by field notes
from, and discussions with, Dr. William E. Duellman and Charles W.
Myers.

The mating calls of the frog