Perhaps the most important character that is subject to geographic variation in the racer, and certainly one of the most neglected, is body size. With information now available it is not possible to compare the sizes of different populations except in a general way. The best sources of information concerning size in several subspecies other than _flaviventris_, are the publications of Auffenberg (1949 and 1955). Comparison of these data with my own is not entirely satisfactory because Auffenberg did not indicate clearly differences in size between the sexes, nor indicate the boundary line between young and adults. Also, his measurements are of overall length. For the purpose of comparison I have subtracted 22.5 per cent, an approximation of ratio of average tail length, from Auffenberg's figures. He stated (1955:98) that the series of specimens on which measurements were based were those "with a uniform coloration," that is to say they had lost the juvenal pattern and were probably sexually mature. Whether the same statement applied to the large series of _stejnegerianus_ in the same author's earlier paper (1949:55) is doubtful. _C. c. constrictor_: 34 New York specimens averaged 806 millimeters (Auffenberg, 1955:96). _C. c. flaviventris_: 100 Kansas specimens averaged 791 millimeters (males, 746; females, 836). _C. c. priapus_: 171 Florida specimens averaged 713 millimeters (Auffenberg, 1955:96). _C. c. stejnegerianus_: 291 Texas specimens averaged 664 millimeters (Auffenberg, 1949:54). _C. c. mormon_: 94 West Coast specimens (Museum of Vertebrate Zoology) averaged 563 millimeters (males 515, females 600). _C. c. anthicus_: 35 northern Louisiana specimens estimated to average 582 millimeters (Clark, 1949:249--the author did not present individual measurements, but indicated the numbers in several size groups in his sample). The 100 _flaviventris_ in the above list were recorded in June, July and August, a season when the young of the preceding year are still small, and these young were not included. In a fall sample 63 males averaged 729 millimeters and 65 females averaged 886 millimeters, but with the nearly grown young (44 males and 40 females) included, the averages were changed to 651 and 768 respectively. Maximum length perhaps express differences between the subspecies as well as, or even better than, the averages listed above. The following figures indicate some of the maximum overall length measurements in inches that have been published by various authors. These measurements pertain to females unless otherwise indicated. _C. c. constrictor_: 74-3/4, 74-1/4, 73, 65-1/2 (Auffenberg, 1955:96). _C. c. flaviventris_: 71 (Pope, 1944:172), 72 (Conant, 1958:147). _C. c. priapus_: 52-1/2 ([M]) (Auffenberg, 1955:98). _C. c. stejnegerianus_: 37 (Auffenberg, 1949:54), 40 (Conant, 1958:148).