Despite much recent scientific study, bats are still among our least known creatures. Their insectivorous diet surely makes them of great importance to man. Beyond this, their immense numbers indicate that ecologically they must have tremendous influence on any area in which they live. REFERENCES Bailey, Vernon 1931. _Mammals of New Mexico._ North American Fauna, No. 53, Washington, D. C., U. S. Department of Agriculture, Bureau of Biological Survey. Barnes, Claude T. 1927. _Utah Mammals._ Salt Lake City, The University of Utah. Burt, William Henry and Grossenheider, Richard Philip 1952. _A Field Guide to the Mammals._ Boston. Houghton Mifflin Co., The Riverside Press, Cambridge. Hall, Raymond E. 1946. _Mammals of Nevada._ Berkeley. University of California Press. Ingles, Lloyd Glenn 1954. _Mammals of California and its Coastal Waters._ Stanford University Press. Stanford, California. Jaeger, Edmund C. 1950. _Our Desert Neighbors._ Stanford University Press. Stanford, California. Mearns, Edgar Alexander 1907. _Mammals of the Mexican Boundary of the United States._ Part 1. Washington D. C.: Government Printing Office. Miller, Gerrit S. and Kellogg, Remington 1955. _List of North American Recent Mammals._ Washington: United States National Museum, Bulletin 205. Nelson, E. W. 1918. _Wild Animals of North America._ National Geographic Society. Warren, Edward Royal 1910. _The Mammals of Colorado._ New York: G. P. Putnam’s Sons. Cockrum, E. Lendell 1960. _The Recent Mammals of Arizona._ Tucson: University of Arizona Press. INDEX A Abert’s squirrel. _See_ Tassel-eared squirrel. Alpine Life Zone, xiv Antelope. _See_ Pronghorn. _Antilocapra americana_, 4 Arizona gray squirrel, 36 Artiodactyla, 1 B Bats, 121 Bear, black, 112 grizzly, 117 Beaver, 67 Bighorn, 2 Bison, 8 _Bison bison_, 8 Black bear, 112 Black-tailed deer, 11 Bobcat, 85 Buffalo. _See_ Bison. Bushy-tailed woodrat, 60 C Canadian Life Zone, xiii _Canis latrans_, 92 _lupus_, 89 Carnivores, 79 _Castor canadensis_, 67 Catamount. _See_ Mountain lion. _Cervus canadensis_, 16 Chickaree. _See_ Spruce squirrel. Chipmunks, western, 44 cliff, 45 Colorado, 44 gray-necked, 44 least, 45 Uinta, 44 Chiroptera, 79, 121 _Citellus lateralis_, 48 Classification of animals, xv Cliff chipmunk, 45 Colorado chipmunk, 44 Cottontail, mountain, 26 Cougar. _See_ Mountain lion. Coyote, 92 _Cynomys gunnisoni_, 51 _leucurus_, 51 _parvidens_, 51