224 CALIFORNIA ACADEMY OF SCIENCES. 



Habits. In certain parts of its range, this species is 

 very numerous. "Its local name is derived from its 

 peculiar mode of progression: when disturbed it moves 

 away sideways, keeping its broadside toward the observer, 

 instead of proceeding in the usual serpentine manner. 

 * One was shot containing a kangaroo 

 rat (Dipodomys) and two pocket mice (Perognathus) . 

 During the latter part of April and the 

 early part of May these rattlesnakes were often found 

 in pairs and were doubtless mating. At such times they 

 remained out in plain sight over night instead of re- 

 treating to holes or shelter under desert brush, and on 

 two occasions they were found by us on cold mornings 

 so early that they were too chilled to move until consid- 

 erably disturbed."* 



76 Crotalus mitchellii Cope. BLEACHED RATTLESNAKE. 



Caudisona milchellii, COPE, Proc. Ac. Nat. Sci. Phila., 1861, p. 293 



(type locality Cape St. Lucas, Lower California). 

 Caudisona pyrrha, COPE, Proc. Ac. Nat. Sci. Phila., 1866, pp. 308, 



310 (type locality Canon Prieto near Ft. Whipple, Arizona); 



COUES, Surv. W. 100th Merid., V, 1875, p. 608, pi. XXII. 

 Crotalus mitchellii, COPE, Bull. U. S. Nat. Mus., No. 1, 1875, pp. 33, 



92; VAN DENBURGH, Proc. Cal. Acad. Sci., (2), IV, 1894, p. 450; 



Id. ibid., V, 1895, p. 159; STEJNEGER, Eep. U. S. Nat. Mus., 



1893 (1895), p. 454. 



Crotalus pyrrhus, STEJN., W. Am. Scient., VII, April, 1891, p. 165. 

 Crotalus Mitchellii pyrrhus, STEJN., Kep. U. S. Nat. Mus., 1893 



(1895), p. 456. 



Description. Moderately large. Head rather small, 

 with flattened top, varying in outline according to posi- 

 tion of fangs, etc. Rostral either higher than wide or 

 wider than high, separated from anterior nasal by one 

 or two rows of granular scales. Usually two nasals. 

 Supraocular large, somewhat projecting laterally, sepa- 

 rated from its fellow by from four to eight scales. 



*Merriam, N. A. Fauna No. 7. 1893, p. 217. 



