296 PROCEEDINGS OF THE ACADEMY OF [Maxch, 



The only other name with which it has been confused is E. couchi 

 Kenn., which has been shown to be in all probability an aberrant 

 E.e. vagrans. 



The geographical relations of the species here discussed are as fol- 

 lows : E. e. elegans meets with E. e. vagrans and E. s. parieialis through- 

 out its range. At its southern extension it is overlapped by E. ham- 

 niondi and at its northern it touches E. s. Icptocephala. E. e. vagrans 

 meets E. hamnwndi in California, and is in contact with E. s. parie- 

 talis almost everywhere except in Arizona, although the latter does 

 not appear to ascend as high in the mountains. In the northwest it 

 merges into E. e. hiscutata and reaches E. s. leptocephala. On the 

 plains it meets E. radix, and in the southwest comes more or less in 

 touch with E. marciana, E. eques and perhaps E. 7negalops. 



E. s. parietalis meets all of these except the last. In the east it 

 overlaps scattering examples of E. s. sirtalis and probably E. proxima. 

 In the far northwest it merges into E. s. leptocephala and E. s. pick- 

 eringi. 



E. hammondi meets with E. marciana in the eastern part of its 

 range in Arizona. 



The connection between moisture and variability, especially in the 

 direction of color intensity, may be profitably observed in these snakes. 



More than a million square miles of the territory occupied by the 

 widely ranging E. e. vagrans and E. s. parietalis lies east of the high 

 mountain chains of the Pacific coast and has an annual rainfall of 

 from 10 to 25 inches. Over this vast expanse the characters of these 

 two species are very constant, and variation has contributed to the 

 list of synonyms only E. dorsalis B. and G., in which melanism is 

 in its earliest stage, and the one specimen of E. henshawi Yarr. (=E. e. 

 plutonia Cope) from Walla Walla. 



The region of great moisture, with a rainfall of from 50 to over 100 

 inches, occupies not more than a hundred thousand square miles, 

 extending from latitude 40° in northern California to British Columbia. 

 The type localities of the following five forms, characterized by pro- 

 nounced melanism and often an excess of red, all fall within this re- 

 stricted area: E. ordinoides, E. concinna, E. pickeringi, E. s. tetrcdetnia 

 and E. s. trilineata. In addition to these, E. e. hiscutata and E. s. 

 leptocephala, found there, also show marked tendencies to develop 

 dark colors as well as instability in scutellation. 



Five forms — E. infernalis Blain., E. i. inferncdis Cope, E. i. vidua, 

 E. atrata and E. e. elegans — were described from the neighborhood 

 of San Francisco, where the actual rainfall does not exceed 25 inches, 



