. Bulletin. Natural history; Natural history. 262 Illinois Natlral History Survey Bulletin \'o1. 28. Art. 1 Table 85.—Sexual variation in Illinois Natrix sipedon confluens. Figures in parentheses are numbers of specimens. Charactkristic Males (9) Females (11) Range Mean Range Mean Caudals 69-78 60-66 Tail length as i>ercentage of total length Variation.—Males in this subspecies have longer tails and greater numbers of caudals than females, table 85. The juveniles are more distinctly banded than the adults, and the groundcolor is usu- ally clear yellow
. Bulletin. Natural history; Natural history. 262 Illinois Natlral History Survey Bulletin \'o1. 28. Art. 1 Table 85.—Sexual variation in Illinois Natrix sipedon confluens. Figures in parentheses are numbers of specimens. Charactkristic Males (9) Females (11) Range Mean Range Mean Caudals 69-78 60-66 Tail length as i>ercentage of total length Variation.—Males in this subspecies have longer tails and greater numbers of caudals than females, table 85. The juveniles are more distinctly banded than the adults, and the groundcolor is usu- ally clear yellow or tan, lacking the dusky suffusion of large specimens. Individual variation in scutellation of 21 specimens from a single Illinois locality is slight. Ventrals range from 133 to 143, av- eraging ; supralabials 8 + 8 in 80 per cent of specimens, 8 + 9 in 15 per cent, 9 + 9 in 5 per cent; infralabials 9 + 10 in 10 per cent, 10 + 10 in 65 per cent, 10+11 in 20 per cent, 11 + 11 in 5 per cent; preoculars 1 + 1 in 95 per cent, 1 + 2 in 5 per cent; postoculars 2 + 2 in 15 per cent, 2 + 3 in 35 per cent, 3 + 3 in 50 per cent. In this series the pattern is more variable than the scutellation. The number of dorsal blotches ranges from 14 to 26, averaging The number of dark lateral bands per side ranges from 20 to 35, averaging The ventral pattern varies from a predom- inantly black venter to a yellow venter with scattered black or brown squares. This series is somewhat atypical because of the high blotch count, and it is, in fact, intermediate in this character between con- fluens and Gulf Coast fasciata. Specimens with high blotch counts tend to have better- defined lateral bands; and, although these may be interpreted as expressions of slight pleuralis influence, the Illinois specimens are actually almost identical with coastal fasci- ata. They are best regarded as confluens, however, since fasciata is restricted to the Gulf region between the Mississippi River
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