Variation in Crotalus horridus 



61 



Table 1. Characters examined in this study of variation in Crotalus horridus. The first 13 

 were used by Pisani et al. (1973). 



No. 



Character 



Description 



12 



13 



14 



ADS 



DSM 

 PDS 



VS 



CS 



6 



DCS 



7 



LSL 



8 



RSL 



9 



LIL 







RIL 



1 



BCB 



TCB 



SVL 



5 



TL 



6 



HL 



7 



MS 



8 



GC 



19 



POS 



Anterior dorsal scale rows, counted at one head-length posterior 

 to the occipit (see Fig. 3). 



Dorsal scale rows at midbody. 



Posterior dorsal scale rows at one head-length anterior to the 

 anal plate. 



Number of ventral scales, not including the anal plate (Dowling 

 1951). This method was not used by Pisani et al. (1973T 



Number of caudal scales, starting with the first complete scale 

 posterior to the anal plate. 



Number of divided caudal scales. 



Left supralabials. 



Right supralabials. 



Left infralabials. 



Right infralabials. 



Number of complete body crossbands, counted between the 

 head and anal plate (Fig. 3). This is not the method used by 

 Pisani et al. (1973), who were not sufficiently clear on how 

 crossbands were distinguished from blotches. 



Number of complete tail crossbands. Although many specimens 

 possessed tail markings that suggested banding, relatively few 

 had tail crossbands that were clearly entire. Most specimens had 

 a dark-colored tail with no markings, the dark color extending 

 well anterior to the vent. 



Ratio of tail length to snout-vent length. Tail length was mea- 

 sured from the posterior margin of the anal plate to the base of 

 the first rattle segment. 



Adult snout-vent length. Individuals longer than 750 mm were 

 considered adults, but this may have failed to exclude a few 

 sub-adults. 



Adult tail length. 



Adult head length, measured from tip of rostrum to line joining 

 posterior tips of mandible (Peters 1964). 



Middorsal stripe, coded as zero for either faint or completely 

 absent and as one for clearly present. 



Ground color, an attempt to measure pattern contrast. Because 

 many museum specimens had lost some of their original color, 

 this was coded as either zero to denote light colors, such as pale 

 brown, tan, pinkish, yellowish, and pale gray, or as one to 

 denote dark colors, such as plain brown, dark gray, and dark 

 olive-greenish. Some melanistic specimens were examined, but 

 none were used in the analyses because they lacked other essen- 

 tial characters. 



Postocular stripe, coded as zero for absent or faint and as one 

 for clearly present on one or both sides of the head. 



