EEVISION OF THE KING SNAKES. 17 



a\ Last two maxillary teeth usually not longer and stouter than those preceding; 

 spines of penis stout, extending one-third to one-half the distance to base of 

 organ. 

 6^ Penis bilobed or bifurcate; pattern in black, and white or yellow, in rings, 

 bands, or stripes, but fundamentally of a light spot on a dark scale. 



getulus group. 

 62. Penis scarcely bilobed; pattern of dorsal blotches of brown with black bor- 

 ders calUgaster group. 



a^. Last two maxillary teeth usually larger and stouter than those preceding; spines 

 of penis slender, extending half way or more than half way to base of organ; 

 pattern fundamentally of rings of black, red, and yellow triangulum group^ 



The greatest separation in the genus (still excluding alterna and 

 mexicana) is undoubtedly between the sections a^ and a^ above. 

 The getulus group includes 10 very closely allied forms spread over 

 the southern two-thirds of the United States, Lower California, and 

 northern Mexico. This group is distinctly marked off by style of 

 color pattern from all other forms in the genus, but is closely allied 

 with the calUgaster group in characters of skull, dentition, copulatory 

 organ, proportions, and scutellation. 



The calUgaster group includes but three forms, one of which is 

 known from only a single specimen. The other two are found only 

 east of the Rocky Mountains, one in the Mississippi Valley and the 

 other east and south of the Alleghenies. Both are more specialized 

 than any of the forms of getulus, and this together v/ith the fact 

 that the group to which they belong is far less diversified than the 

 latter indicates that it is the result of an older radiation than the 

 getulus group. 



In the triangulum group the anterior maxillary and particularly 

 the anterior dentary teeth are longer than the corresponding teeth in 

 the other two groups. The relative size of the last two maxillaries is 

 a fairly, although not fully, distinctive feature. The penial characters 

 are likev/ise for the most part distinctive; the calyces are commonl}^ 

 more numerous and have more and longer fringes, and the spines are 

 more slender, more numerous, and do not stop as abruptly. 



The name mexicana has been applied to two specimens from San 

 Luis Potosi. The description will show that these can not be assigned 

 on structiu"e or pattern to any of the above three groups, but, as the 

 genus is now defined, they must be assigned to Lampropeltis. Prac- 

 tically the same situation holds with respect to the specimen said to 

 have come from the Davis Mountains, Texas, and named by Brown, 

 alterna. Penial characters can not be determined, since all three of 

 these specimens are females. 



A fuller discussion of the three major groups is reserved for the 

 summaries following the descriptions of their component forms. 



The following key is expected to work for the great majority of 

 specimens, but difficulty may be expected from occasional individuals. 



