Nerodia cyclopion and N. floridana 
87 
Fig. 2. Typical head profiles of large adult Nerodia cyclopion (A) and 
N. floridana (B). Bar = 20 mm. 
There are no discernible patterns of geographic variation in 
the number of dorsal scale rows in either taxa. Significant sexual 
dimorphism occurs, with females typically having two rows more 
than conspecific males. The two taxa are separable on the basis of 
sample means (P < 0.01). Abbreviated dorsal scale row data are 
summarized in Table 1, and complete scale row data are in Sanderson 
(1983). 
Head Scale Measurements 
The head shape of cyclopion is distinctly different from that 
of floridana , particularly in the region of the snout. This difference 
is not pronounced in juveniles and small adults, but is conspicuous 
in larger individuals (Fig. 2). Particularly noteworthy is the abruptly 
sloped snout of floridana. Also, the head of floridana is narrower 
in dorsal view, being more laterally compressed than that of cyclopion. 
Discriminant analysis of the head scale data from the calibra- 
tion group indicated that the two taxa are distinct groups, with an 
