The discovery of several fossil tortoises contribute significantly to our understanding of tortoise distribution in western North America. These include: Gopherus neglectus, n. sp. from the Oligocene part of the Sespe formation, California; Testudo milleri, n. sp. from the Barstow Miocene of California; and Gopherus depressus, n. sp. from the Tehachapi Miocene of California. New material of previously known fossil tortoises is described. A technique for the determination of past climates by the use of fossil reptiles and amphibians and the temperature requirements of modern reptiles and amphibians assumes that the animals have not greatly changed their ecological requirements in the course of their evolution. One chance to test this assumption in one group of reptiles is afforded by the proximity (stratigraphically and geographically) of fossil plant and fossil tortoise sites. Some of the zoogeographic implications of the paleoecological data are discussed.

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