6 CROTALUS. 



angle of the moutli ; a second from tlie anterior extremity, nearly 

 parallel with the first, the two enclosing an indistinct patch, and sepa- 

 rated on the labials by 4J scales. There is also a single narrow 

 light line across the superciliary perpendicular to its length, obsolete 

 in old specimens. 



It may readily be distinguished from C. o.damanteus by its light 

 color and the truncations of the rhomboids, as well as the general 

 obsoleteness of the lateral markings. The rhomboids are longer in 

 proportion and more rounded. The two lateral rows of scales are 

 smooth, the next two more strongly carinated than in C. adaman- 

 teus. The 5th upper labial is largest, and transverse ; the rest nearly 

 uniform. The stripes on the side of the head are less distinct. 



From G. conflucntus, it may be distinguished by the greater com- 

 parative size of the interval between the dorsal blotches, especially 

 posteriorly. In G. covjiuentus, there are two light lines across the 

 superciliary plate, dividing it into three sections, the central rather 

 narrower. Here, too, the posterior facial stripe, instead of passing to 

 the angle of the mouth, goes back of it on the 2d row above the 

 labials, in C. atrox, passing directly to the angle of the mouth. 

 Other important distinctions are seen in the narrower scales of 

 G. conjiuentus, &c. 



From G. hici/er, the more narrow head, fewer and larger inter- 

 superciliary scales, lighter color, arrangement of color along the head, 



will at once distinguish it. 



Col. J. D. Graham. 

 » 



j> 

 }) 



4. CrotaiMS Baacller, B. & G. Muzzle broad. Scales between the 

 superciliaries numerous, small, and uniform. Plates on top of bead, 4 pre- 

 frontal, 4 postfrontal, or else irregular. Three rows scales between the sub- 

 orbitals and labials. Labials 16 above ; 1st and 5th largest ; — 15 below. Dor- 

 sal rows 25, exterior smooth, 2d and 3d with obsolete carination. Tail, and 

 posterior portion of body with 16 or 17 half rings. A succession of brown 

 dorsal hexagons or octagons, separated throughout by a narrow lighter 

 line. Light stripe from superciliary crosses the angle of tlie mouth on the 

 od and 4th row above labial. 



Stx. Crdalus ludfer, B. & G. Froc- Acad. Nat. Sc. Phila. YI., 1852, 177 . 



