nhabiting the lowlands. Zweifel (1960) discussed in detail the
herpetofauna of the Tres Marias Islands and commented on the derivation
of the fauna. Duellman (1960d) provided a detailed account of the
geographic distribution of the amphibians known to occur in the lowlands
of the Isthmus of Tehuantepec and attempted to account for the present
patterns of distribution.

The present report is the first of two parts dealing with the
herpetofauna of Michoacan. The purpose of this part is to present a full
account of the species of amphibians and reptiles known to inhabit the
state of Michoacan; the accounts of the species are accompanied by a
brief description of the natural landscape and of the various
assemblages of species comprising the major faunistic groups within the
region. A gazetteer of collecting localities is appended. The second
part of the study, now in preparation, deals with the ecological and
historical geography of the herpetofauna. Since the present part will be
of interest primarily to systematic herpetologists, I have decided to
separate it from the more general material of interest to
biogeographers.

One of the major problems that faces the worker undertaking a faunal
study is the presence of species or genera of unsettled systematic
status. My work in Michoacan has been no exception; fifteen separate
studies were undertaken in an attempt to solve systematic problems in
certain groups. Some systematic problems still remain but are of little
consequence insofar as the entire faunal picture is concerned, or are so
involved as to be impractical to undertake at this time. In accounts of
species, such problems are mentioned in the hope that they will interest
some worker who will be inclined to investigate them.

ACKNOWLEDGMENTS

While engaged in the study of the herpetofauna of Michoacan I have built
up a debt of gratitude to many individuals, without whose aid my
ambition to complete my study never would have been realized. I am
especially grateful to those individuals who accompanied me in the
field; Lee D. Beatty, Richard E. Etheridge, Carter R. Gilbert, Fred G.
Thompson, Jerome Tulecke, and John Wellman offered stimulating
companionship and valuable assistance. On many occasions they suffered
hardships on behalf of my interests.

Studies of my own specimens have been augmented by material from other
institutions. For permitting me to examine specimens in their care I am
indebted to W. Frank Bl