TS OF THE SPECIES 475
_Hyla bistincta_ Cope 475
_Hyla charadricola_ new species 478
_Hyla robertsorum_ Taylor 481
_Hyla pachyderma_ Taylor 485
_Hyla crassa_ (Brocchi) 486
RELATIONSHIPS 489
LITERATURE CITED 491

INTRODUCTION

In the mountainous regions of Middle America there are several groups
of hylid frogs that inhabit mountain streams. Some of these groups,
such as _Plectrohyla_ and _Ptychohyla_, have been elevated to generic
rank, whereas others are retained in the large and complex genus
_Hyla_. In the mountains of Mexico five species of hylids that seem to
compose a phyletic unit are herein referred to as the _Hyla bistincta_
group. Since 1955 I have been accumulating specimens of, and data on,
this group with the result that all specimens known to me, including
the types of all named taxa, have been studied. Detailed observations
have been made on the ecology and life histories of three of the
species; the other two species are known to me only from preserved
specimens.

Acknowledgments

For permission to examine specimens in their care I am indebted to
Charles M. Bogert, American Museum of Natural History (AMNH); Doris
M. Cochran, United States National Museum (USNM); Jean Guibe, Museum
National d'Histoire Naturelle, Paris (MNHN); Robert F. Inger, Chicago
Natural History Museum (CNHM); Hobart M. Smith, University of Illinois
Museum of Natural History (UIMNH); Charles F. Walker, University of
Michigan Museum of Zoology (UMMZ). (Abbreviations of institutions
given above in parentheses are used throughout; the Museum of Natural
History, University of Kansas is abbreviated KU.)

For their willing assistance in the field I am grateful to Ann S.
Duellman, Dale L. Hoyt, and John Wellman. Permits for collecting in
Mexico were generously issued by the late Ing. Luis Macias Arellano,
Departamento de la Fauna Silvestre, Direccion General de Caza. The
drawings in figures 1 and 3 were executed by Gail Selfridge. This
research has been supported by the National Science Foundation (NSF
G-9827).

THE HYLA BISTINCTA GROUP

The five species comprising the _Hyla bistincta_ gro