REVISION OF THE KING SNAKES. 



69 



Variation and affinities. — The number of s})ecimens 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 boylii 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 tyi)ical; the vicinity of Tucson, where this form inter- 

 grades with yumensis; Yuma, where yumensis is tyj^ical; and San 

 Diego County, Cahfornia, where boylii 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 numbere of ventral plates characteristic of splendida, and, in the 

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

 mens from the Yuma region exliibit the ordinary variation and 

 usual average of boylii; 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 boylii. 



It is at Tucson as well that great variabihty 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 boylii. 



ipleiidida . . 



pnmensui. 

 boylii 



Region. 



I Whole range 

 Southern Xcw Mexico and 

 v,-o^t("rn Texa?. 

 Tiicson and vicinity 



(Tucson 



i I '.raham County 



[Yuma 



f Wiiole range 



\S&n I>iego County 



Mum- 

 bor of 

 speci- 

 tnens 



7 

 3 

 3 

 9 

 110 

 18 



Ventrals. 



Ex- 

 tremes. 



207-225 

 207-22.5 



210-220 

 212-229 



2ir>-22.'; 



219-240 

 206-2.'>4 

 206-254 



Aver- 

 age. 



216 

 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- 

 age. 



69 



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 boylii. 

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

 upper limit of boylii, 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 



