16. CROTALIDAE 



The general color is yellowish brown, or brownish yel- 

 low, with a series of large darker brown blotches along the 

 back. These blotches are well defined, are usually enclosed 

 in continuous light borders laterally as well as dorsally, and 

 show little of the punctulate or pepper-and-salt style of 

 coloration so characteristic of C. atrox. The sides are clouded 

 or blotched with brown more or less indefinitely outlined 

 with light yellow or white. The head is somewhat mottled 

 above. A yellow or white stripe runs across the side of the 

 face from the preocular plates to the mouth. The scales 

 behind and above this light stripe are darker than the ground 

 color and are set off posteriorly by a light streak which runs 

 down and back from the corner of the eye and strikes the 

 supralabials in front of the corner of the mouth. The tail 

 is grayish with about four to six black cross-bands. The 

 lower surfaces are yellowish white. 



Length to anus 900 925 93 5 1062 1070 



Length of tail to base of rattle— 47 53 80 78 90 



Distribution. — Crotalus lucasensis may be restricted to 

 the Cape Region of Lower California, where it has been 

 taken at Cape San Lucas, La Paz, Pidulingua [Pichilinque?] 

 Bay, San Jose del Cabo, Sierra El Taste, and Agua Caliente. 



Five rattlesnakes from San Jose Island seem to belong 

 to this species. 



213. Crotalus confluentus Say 



Prairie Rattlesnake 



Plates 101 and 110 



? Crotalus viridis Rafinesque, Am. Month. Mag., Vol. IV, i8i8, p. 

 41. 



Crotalus confluentus Say, In Long's Exped. Rocky Mts., Vol. II, 1823, 

 p. 48 (type locality, "Valley of the Arkansa," near Bell's 

 Springs, Colorado); Baird & Girard, Cat. N. Amer. Rept., Pt. i. 

 Serpents, 1853, p. 8; Baird & Girard, in Marcy's Expl. Red River, 



