air, Charles M. Bogert, Doris M. Cochran, William
B. Davis, James R. Dixon, the late Emmett R. Dunn, Josef Eiselt, Alice
G. C. Grandison, Norman Hartweg, Robert F. Inger, Arthur Loveridge, the
late Karl P. Schmidt, Hobart M. Smith, Robert C. Stebbins, Margaret
Storey, Edward H. Taylor, and Richard G. Zweifel.

Several people have aided me in the study of specimens and in the
analysis of data; I am grateful to Donald D. Brand, who first introduced
me to Michoacan; since that time I have benefited much from his
knowledge of the area. James A. Peters provided me with essential
information concerning his field work in southern Michoacan in 1950.
James R. Dixon and Floyd L. Downs have permitted me to use freely the
material and data that they accumulated in their recent field work in
Michoacan. Norman E. Hartweg allowed me to use the specimens and data
that he gathered in his survey of the herpetofauna in the region of
Volcan Paricutin. L. C. Stuart, Charles F. Walker, and Richard G.
Zweifel have helped in unraveling some of the systematic and
distributional problems.

I am especially grateful to my wife, Ann, who for six months helped me
track down elusive species and explore new areas. Furthermore, she has
stimulated me to carry this study to completion.

Many people in Michoacan favored the field parties with quarters,
transportation, and valuable information, which greatly facilitated the
field work. In this respect I am especially indebted to Ingeniero Ruben
Erbina of Ingenieros Civiles Asociados, who not only let us use his home
as our headquarters, but through a letter of introduction gave us the
"key" to southern Michoacan. Ingeniero Pedro Tonda aided us in Arteaga
and San Salvador. Ingeniero Anastacio Perez Alfaro of the Comision
Tepalcatepec in Uruapan provided the latest maps of southern Michoacan
and much essential information pertaining to travel conditions in the
area. Senor Nefty Mendoza gave us a home in Dos Aguas; this kindness
allowed us to work in this interesting region during the height of the
rainy season. Mr. and Mrs. Bob Thomas let us make use of their
facilities at Hacienda Zirimicuaro. The naval officers at the Estacion
Marina at Playa Azul made pleasant what might have been a dreadful stay
in that small coastal village. To the managers and pilots of Lineas
Aereas Picho in Uruapan I owe special thanks for going out of their way
on more than one occasion to transport a stranded snake-hunter.
Throu