SERPENTS OF NOKTHEASTEEN UNITED STATES 365- 



CEOTALIT)AE 



B. Beep pit between eye and nostril; upper jaw with erectile poison fangs; form 

 stout; head more or less triangular; neck constricted; subcaudaJs entire 



a Tail without rattle A n c i s tr o d o n (p. 385)' 



b Tail with small rattle; top of head covered with 



plates , . S i s t r u r u s (p. 386>- 



c Tail with larger rattle; top of head covered with small 



scales C r o t a 1 u s (p. 387)' 



Color key to species 



The author has prepared a purely artiiicial key, based almost 

 entirely on color and pattern, which is here appended. As it does- 

 not require handling of the specimen, it furnishes a convenient, 

 means of identifying live specimens whose specific character is in 

 doubt. The numbers at the right refer to the similarly numbered. 

 specific descriptions which begin on p. 366 of this bulletin. 



Owing to the great, variation in color and pattern sometimes 

 -shown by individual specimens, identifications made by means of any 

 key based purely on these characters must not be accepted as deci- 

 sive, but should be^verified by reading over the characters given in. 

 the specific descriptions, under the head of that species to which th& 

 key seems to point ; and by careful comparison of the specimen, 

 with the figure given for each species. 



a Color of back uniform; no marked spots, blotches or stripes 



Color green; scales smooth 4 



Scales rough 5; 



Color black; no lighter markings 6- 



Some scales white-edged 8- 



Conspicuous yellowish neck ring 2' 



Color reddish brown; below pink; head not distinct from body 1 



Color chestnut brown; below pink; head distinct from body 17 



Below grayish 16 



b Striped longitudinally; with, or without additional spots 



Striped black and brown; no spots. ■. 14 



Brown and yellow; no spots; abdomen unicolor; very slender. . 18 

 Olivaceous and yellow or brown; dark spots on back and sides 



in several rows 20- 



Greenish brown and hrown; below reddish yellow, with dark 



spots IS 



e Spotted, blotched or transversely banded above 



1) No rattle; head tapering into neck and body, not triangular 



