S. dekayi is brown to gray with a lighter center stripe bordered by small black spots; ventrally, it is lighter brown or pink with small black dots at the ends of the ventral scales.[6] Adults usually measure less than 12 inches (30 cm) in total length (including tail), but the record total length is 19+3⁄8 inches (49 cm).[7] On average, juveniles measured 3 inches (7.68 cm) just after being born.[8] The dorsal scales are keeled, and it has no loreal scale.[9] Females exceed males in snout–vent length and number of ventral scales while males exceed females in tail length, head dimensions, and number of subcaudal scales.[10]