REVISION OF THE KING SNAKES. 



69 



Variation and affinities. — The number of specimens at present 

 available is too small to establish dependable averages. They are 

 well distributed, however, and a consideration of their structural 

 variations will be significant in relation to the intermediate or con- 

 necting position that this form occupies between hoylii and splendida. 



By reference to the accompanying table comparison may be made 

 of the extremes and averages of the numbers of ventral plates in 

 these forms for typical and for boundary regions. Southern New 

 Mexico and western Texas may be considered the region where 

 splendida is typical; the vicinity of Tucson, where this form inter- 

 grades with yumensis; Yuma, where yumensis is typical; and San 

 Diego County, California, where hoylii is typical. 



From the graphic presentation of these figures (fig. 14) it will be 

 apparent that yumensis, in the eastern portion of its range, commonly 

 has numbers of ventral plates characteristic of splendida, and, in the 

 western portion, numbers characteristic of hoylii. The nine speci- 

 mens from the Yuma region exhibit the ordinary variation and 

 usual average of hoylii; those from the Tucson region exhibit a range 

 of variation and an average that is strongly suggestive of splendida, 

 and that in fact bridges the gap between the latter and hoylii. 



It is at Tucson as well that great variability occurs in the pattern, 

 and that all the transitional conditions are found between the pat- 

 terns of yumensis and splendida. 



Table for comparison of splendida, yumensis, and hoylii. 



Name. 



splendida 



yumensis 



boylii 



Region. 



Whole range 



Southern I"Tew Mexico and 



western Texas. 

 Tucson and vicinity 



{Tucson ". , 

 G rahara County 

 Yuma 



rwhole range 



\San Diego County 



Num- 

 ber of 

 speci- 

 mens. 



7 

 3 

 3 

 9 

 110 

 18 



Ventrals, 



Ex- 

 tremes. 



207-225 

 207-225 



210-220 

 212-229 

 215-225 

 219-240 

 206-254 

 206-254 



Aver- 



210 

 216 



216 



220 

 221 

 230 

 232 

 232 



Cross bands 

 or rings. 



Ex- 

 tremes. 



41-85 



69-85 



41-71 

 33-37 

 30-35 

 29-42 

 28-49 

 29-41 



Aver- 



A comparison of the numbers of rings or dorsal bands of these 

 related forms will be even more striking than the numbers of ven- 

 trals. From the table and diagram (fig. 15) it will be seen that the 

 normal lower limit of variation in cross bands of splendida (in southern 

 New Mexico) is above the upper limit of variation in rings of hoylii. 

 But in the vicinity of Tucson the lower limit of splendida overlaps the 

 upper limit of hoylii, and that, in specimens from this region in which 

 the pattern is so altered as to be no longer recognized as splendida, 

 but as yumensis, the number of bands — now changed to rings — has 



