The common racer has been recorded in each of the 48 states of the mainland of the United States, also in New Brunswick, Nova Scotia, southern British Columbia, and southward through Mexico where it is limited to a narrow strip of east coast lowlands but extends as far as Guatemala. _C. c. constrictor_ occupies the northeastern states and extends south into the Appalachian and Piedmont. _C. c. priapus_ with its associated races _paludicola_, _helvigularis_, and _anthicus_ has an Austroriparian distribution, occupying the Atlantic Coastal plain and the Gulf Region, and extending north in the Mississippi Valley to southern Illinois and Indiana. _C. c. paludicola_ is localized with two disjunct populations--in the Everglades and on Cape Canaveral, Florida. _C. c. helvigularis_ is even more restricted in range and is known only from the Appalachicola region of the Florida Panhandle and the adjacent corners of Alabama and Georgia. _C. c. anthicus_ occupies much of central and western Louisiana and adjacent Texas. _C. c. flaviventris_ occurs throughout the Great Plains, east in the "Prairie Peninsula" through Michigan and northern Ohio and west to the Rocky Mountains. _C. c. stejnegerianus_ occurs from Matagorda Bay in Texas southward through eastern Mexico, with a seemingly isolated population in the Sierra del Carmen region of northern Coahulia. _C. c. mormon_ occurs in the Pacific Coast states and Great Basin. Actually, the range limits and the continuity of distribution within the area outlined are still poorly known. The species has not been recorded from the northern parts of Maine, Vermont, New Hampshire, Michigan, Wisconsin, or Minnesota, nor from northeastern New York. It is generally absent from southwestern desert areas. Records are particularly scarce and scattered in the Rocky Mountain states, suggesting that the distribution in this area may be discontinuous. In a large area comprising all of New Mexico and Arizona, the western half of Colorado, and the southern halves of Utah and Nevada, records are so scarce as to indicate that the species is there represented by only a few well isolated relict colonies. The type locality of _mormon_ is "Valley of the Great Salt Lake," and there are numerous records from the northern part of Utah east of Great Salt Lake (Woodbury, 1931:75), but a record from Moab is the only one known to me from the southern half of the state. The only records from western Colorado are from three miles east of Fruita and two miles west of Grand Junction, Mesa County (Maslin, 1959:56). Apparently the only valid record from Arizona is that of Shannon (1950:59) from Eagar, Apache County, in the east-central part. Shannon also recorded the racer from Boulder Dam in extreme southern Nevada. Brattstrom (1955:152) has recorded the species from the lower Pleistocene of southeastern Arizona (Curtis Ranch), bearing out the idea that the racer has partly withdrawn from a range formerly occupied in the