1901.] NATURAL SCIENCES OF PHILADELPHIA. 57 



become fixed, and others in wliich more or less of the lateral 

 stripes have become likewise permanent, and even more distinct, 

 although in these last the narrow cross-bands have disappeared in 

 the young, which are striped. It must also be borne in mind that 

 there is a marked inequality in the color intensity of all the 

 American species, as there is a tendency for the color to remain 

 pale on the hinder half of the body, involving the disappearance 

 of the pattern. This is the case even in the uniformly colored 

 species, as Z. e. constrictor, in which the change to the light colors 

 of v/estern specimens first shows on the tail, and Z. f. pkeiis, in 

 which the bases of the scales posteriorly are pale. 



The relative proportions in width of the hinder part of the 

 frontal and supraocular plates are also growth characters and 

 therefore irregular, and in my belief will bear only a small part of 

 the weight which lias been placed upon them. 



Duly considering the various combinations in adults, of these 

 early characters, I conclude that the Z. flagellam group extends 

 from Florida to California, with two forms in addition to the 

 typical one which demand recognition ; these are Z. f. piceus and 

 Z. f. frenatus. The striped forms, extending from Texas to Cali- 

 fornia, have become differentiated to the point of wider separation, 

 and seem to me to fall into two species: Z. txeniatus (with a sub- 

 species Z. t. ornatiis) and Z. lateralis. Z. schotti B. and G. and 

 Z. semilineatus Cope, I can regard only as fortuitous examples of 

 tceniatas and lateralis respectively. 



This is almost a complete reversal of the views held by Prof. 

 Cope, but the facts appear to me to indicate that the subspecies 

 here admitted are tending in the direction of fixed characters, 

 while those rejected are no more than instances of incomplete 

 development. 



Key to the Species. 



A. — Adults not striped; 17 rows of scales: 



7 upper labials; black, bluish, olive or green, 



1. Z. constrictor. 



8 upper labials; pale brown, or dark in front, 



2. Z. flacjelhon. 

 B. — AVith stripes on the sides: 



17 rows; brown w'ith a narrow yellow stripe on third and 



fourth rows, 3. Z. lateralis. 



15 rows; brown with 3-5 narrow dark stripes on sides, 



4. Z. tieniatus. 



