The King Snakes 



extending slightly over the southwestern border, from Mexico. 

 With the exception of one other species and its several varieties 

 (inhabiting Mexico and Central America) this number represents 

 the entire genus. Several of the species exhibit bewildering 

 variations of the pattern in fact, some of the varieties have 

 attained such distinction in form and si%e as well as their differ- 

 ences in colouration from the typical reptile, that the writer 

 feels none too sure he is correct in describing them as sub- 

 species. Among them, however, we may trace a chain of charac- 

 ters, one appealing to another. Thus it appears best to regard 

 them provisionally as varieties. They form an admirable ex- 

 ample of the march of evolution, where the extension of habitat 

 has brought adout different climatic conditions, inducing a change 

 of habits; with this change, the pattern is gradually altered and 

 Time points to the formation of a distinct species. 



Following is a key to the King Snakes, embracing both the 

 typical forms and their varieties:* 



Key to the King Snakes 



I. Pattern: Alternating half-rings of black, and red (black-bordered) 



on gray ground. 



Gray, with half rings of red (black-bordered), in alternation with 

 narrow half-rings of black. 

 Beneath blotched with black. 



DAVIS MOUNTAIN KING SNAKE, O. altemUS. 



Distribution. One specimen known from western Texas. 



II. Pattern : Red, yellow and black, in rings. 



Red rings very wide; black rings about a quarter the width of 



tr e former and containing a very narrow and indistinct ring of 



yejlow. MEXICAN RINGED SNAKE, O. micropholis. 



Distribution. This phase of a Mexican species occurs in the 



extreme southern portion of Arizona, southwestern Texas 



and northern Mexico. 



Red rings of moderate width ; yellow rings about half the width 

 of the former and bordered by narrower rings of black. 



ARIZONA RINGED SNAKE, 't?. ZonatUS. 



Distribution. Arizona and southern California. 

 Similar to the former on forward portion of body ; on latter 

 portion the black rings widen, obscuring the red this character 

 usually most pronounced on abdomen. 



WESTERN MILK SNAKE ; RED KING SNAKE; RINGED KING SNAKE, 



[O. doliatus gentilis. 



Distribution. Nebraska and Louisiana to S.W.Texas ; north- 

 ern Mexico. 



* Although the keys to the greater number of genera have not been 

 arranged in tgis fashion, the writer has considered it best to thus treat 

 this genus, owing to the striking variations in pattern as well as in colours. 



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