alley. In an attempt to fill in gaps in
the known distributions of many species and to sample the fauna in some
previously uncollected areas, I returned to Michoacan in June, 1958.
Accompanied by Jerome B. Tulecke and John Wellman, I collected on the
Mexican Plateau in the northwestern part of the state, on the southern
slopes of the Cordillera Volcanica, and in the Tepalcatepec Valley. Most
of our time was spent in the Sierra de Coalcoman, where we collected at
Aguililla, Artega, and Dos Aguas. In 1960 two days were spent in
Michoacan; a small collection was made in the eastern part of the
Cordillera Volcanica. With the exception of the specimens collected in
1960, which are at the Museum of Natural History at the University of
Kansas, the specimens that I have collected in Michoacan are in the
Museum of Zoology at the University of Michigan.

NATURAL LANDSCAPE

A proper understanding of the geographical distribution of animals in a
given region is possible only after a thorough acquaintance with the
geography of the region. Likewise, in order to gain a knowledge of the
ecological distribution and relationships of the components of the
fauna, it is necessary to study the animals in their natural
environments. In order to give the reader a picture of the physical
features and the major animal habitats within the state of Michoacan,
the following brief description is offered. Each of these facets
mentioned below will be elaborated in detail in my final report on the
herpetofauna of Michoacan.

Physiography

The state of Michoacan comprises an area of 60,093 square kilometers
(Vivo, 1953). Within this area the rugged terrain has a total relief of
nearly 4000 meters. There have been several attempts to classify the
physiographic provinces of Mexico; the classification used here is a
slight modification of the scheme proposed by Tamayo (1949). I have
tried to keep the system as simple as possible, but still useful in
discussing the distribution of animals living in the region. For general
purposes the state of Michoacan can be divided into lowlands and
highlands as follows:

LOWLANDS
Pacific Coastal Plain
Balsas-Tepalcatepec Basin

HIGHLANDS
Mexican Plateau
Cordillera Volcanica
Sierra de Coalcoman

Although the lowlands in the state are continuous, they are only
narrowly connected and thus form two distinct physiographic and biotic
areas. The Pacific Coastal Plain