VARIATIONS OF GARTER-SNAKES. 



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As will bo seen later, its western limit can not be drawn exactly 

 owin<j; to the fact that it in- 

 tergrades with another form 

 on the Pacific coast, but if 

 specimens with a scale for- 

 mula of not less than 19-21- 

 19-17 are considered elegans, 

 it is found to the foot of the 

 Sierra Xevada-Cascade range 

 on the west side, throughout 

 the length of the chain, bend- 

 ing westward in the moun- 

 tainous region of northern 

 California to the coast. The 

 range, as far as it is definitely 

 known at present, is shown on 

 the accompanying map (fig. 

 59). 



Variation. — We have ex- 

 amined 218 specimens of ele- 

 gans from various localities 

 scattered over the entire 

 range of the form and fmd 

 that there is very little geo- 

 graphic variation in the scu- 

 tellation. In fact the only 

 two characters that exhibit 

 geographic differences are the 

 dorsal scale formula and pre- 

 oculars. In fig. 60 we have 

 plotted the dorsal scale for- 

 mula for suites of specimens 

 representing the range of the 

 form. It will be noted from 

 this diagram that while the 

 fornuda 21-19-17 occurs most 

 frequently, the fornnda 19- 

 21-19-17 apparently occurs 

 throughout the range, so that 

 the average formula for the 

 form maybe considered some- 

 what intermediate between 

 21-19-17 and 19-21-19-17. 

 It will be noticed, however, 

 that in western specimens 

 (from British Columbia and in the Sierra Nevada-Cascade range) 



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