98 PROCEEDINGS OF THE ACADEMY OF [Jau.^ 



Key to the Species in United States. 



Post-nasal in contact with preocular; the hght line to angle of 



mouth begin at nostril, 1. *S. catenatus. 



Post-nasal separated from preocular, by loreal; light line to angle 

 of mouth begins at the eye, 2. >S'. miliar ius. 



Sistrurus catenatus Kafinesqne. 



Crotaliiius calenatus Eaf., Amer. Monthly 3Iag., 1818, p. 41. 



Short and stout; tail about one-ninth of length; rattle small; 

 head plates normal; there is no large loreal, and the upper pre- 

 ocular is in contact with the post-nasal; occasionally the anterior 

 end of the preocular is cutoff, forming a small upper loreal; scales 

 in 23-27 rows, one or two of the outer smooth; ventrals 135-157; 

 subcaudals 17-34. 



The color is gray, brown or even black, with seven series of 

 blotches on the back; the dorsal series dark brown with a narrow 

 light border, anteriorly often crescent-shaped, posteriorly becoming 

 subcircular; the second series roundish and indistinct, more or less 

 alternating with the dorsals; third, vertically elongated, colored 

 like the dorsals and opposite to them; fourth small and on the 

 outer rows and ends of the ventrals; belly yellowish, more or less 

 marked with black. Top of head with a light band across the 

 anterior end of frontal; two dark bands running back from the 

 supraoculars to the first dorsal spot, and a dark spot between them 

 on the parietals and frontal ; a dark oblique streak behind the eye 

 bordered above and below by a light line, the lower one beginning 

 at the nostril and running to the angle of the mouth; two lisrht 

 lines from the loreal pit to the labial border. 



It has been customary to divide this species into a northern and a 

 southern race, but the characters ascribed to them are less constant 

 than has been supposed, and they were, in fact, united by Mr. 

 Boulenger; nevertheless, the greater proportion of the individuals 

 found within each geographical area do present sufficient differ- 

 ences to warrant their separation : 



Scales usually in 25 rows; dorsal spots usually less than 40, 



1. S. c. catenatus. 

 Scales usually in 23 rows; dorsal spots usually more than 40, 



2 S. c. eonsoi's. 



