84 
William E. Sanderson 
status for the two forms. Conant and Collins (1991) followed this 
suggestion and treated the two taxa as separate species. 
In this article I present the results of a morphological com- 
parison of Nerodia cyclopion and N. floridana and report previously 
unpublished collection localities for green water snakes in western 
Florida. 
MATERIAL AND METHODS 
I examined 381 preserved specimens of green water snakes. 
Complete data (head, body, and tail length; scale counts; and head 
scale measurements) were obtained from 217 specimens. Fewer data 
(usually head, body, and tail lengths, and scale counts) were re- 
corded for the remaining ones. 
Snout-vent length and tail length (for specimens with complete 
tails) were measured to the nearest millimeter with a 1-m rule. 
Head length was measured with dividers and a 10-cm rule to the 
nearest millimeter from the tip of the rostral scale to the posteriormost 
point of the mandible. 
Ventral scutes were counted by the method of Dowling (1951). 
Subcaudal counts did not include the terminal scale. Dorsal row 
counts were made one head length posterior to the head, at midbody, 
and one head length anterior to the vent. Meristic data on head 
sealation included the number of suboculars, preoculars, postoculars, 
temporals, supralabials, and infralabials. Student’s Mest of equiva- 
lency of sample means was used to determine if any of these char- 
acters were useful in separating the two taxa. Relative tail length 
was found to decrease ontogenetically, and thus was treated by re- 
gression analysis. 
Certain head scales were measured to quantify head shape (Fig. 
1). These dimensions were determined to the nearest 0.01 mm with 
a dissecting microscope fitted with an ocular micrometer. For dis- 
criminant analysis of this mensural data, I used release 2.1 of the 
Statistical Package for the Social Sciences (SPSS), available through 
the Louisiana State University Systems Computing Center. For the 
discriminant analysis of head scale data, the raw measurements 
were separated into two groups. One group, termed the holdout 
group, contained data derived from 49 specimens of both taxa 
(46 cyclopion, 3 floridana ) from Alabama and the Florida pan- 
handle. This group, then contained those specimens most likely to 
possess intermediate character states if gene flow is occurring be- 
tween the two taxa. The second group, termed the calibration group, 
contained data from all remaining specimens: 90 cyclopion and 78 
floridana. 
