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BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



and preoculars, there is more or less tendency toward an increase from 

 Mexico north and then west in Arizona to California and Lower 

 California, while from southern to northern New Mexico there is more 

 or less decrease apparent. The labials and oculars, however, all remain 

 remarkably constant throughout the range, as does the proportionate 

 tail length (fig. 61). The latter, however, decreases noticeably in 

 the Californian region, as does the average number of caudals to some 

 extent also. The number of spots appears to increase in general from 

 south to north, and the increase is sUghtly greater to the east than to 



Region , 



No. 1 2 3 4 5 



Figure 60.— Geographic variation in number of caudals in PituophU sayi affinis. 



the west, in contradistinction to the tendency found in most of the 

 scale characters (fig. 62). The average number, however, is fairly 

 constant, varying only between 56 and 64 in the specimens represented. 

 The sexual variation may be summarized as follows: Dorsal scale 

 formula varying from 25-28-20 to 31-35-25 in males, from 27-29-21 

 to 31-35-25 in females; ventrals from 215 to 248 (average 230.3) in 

 males, from 221 to 260 (average 236.1) in females; caudals 54 to 71 

 (average 63.8) in males, 51 to 65 (average 56.9) in females ; supralabials 

 average 8.1 in males, 8.2 in females; infralabials average 12.5 in 

 males, 12.6 in females; preoculars average 1.4 in males, 1.5 in females; 

 postoculars average 3.4 in males, 3.6 in females; body spots average 



