no UNIVERSITY OF COLORADO STUDIES 



C. confluentus is the common rattlesnake of the state. It is one 

 of the medium-sized rattlesnakes, average specimens being between 

 three and four feet in length. It ranges from southern Canada south 

 almost to Mexico, east into Kansas and Nebraska, and west into 

 Idaho, Utah and Arizona. 



Colorado specimens. — University Museum: Colorado (580 mm., 5 rattles), 

 No. 78; Lajunta, July, 1905 (620 mm., 8 rattles), G. S. Dodds, No. 257; Wray, 

 October 27, 191 2 (shed skin, 650 mm.), M. M. Ellis; Colorado State Historical and 

 Natural History Museum: Denver, August 10, 1903 (370 mm., 4 rattles), H. 

 Davies; Denver, October i, 1904 (2 specimens, 210 and 230 mm.), A. T. Allen; 

 Watervale, August 7, 1906 (780 mm., 9 rattles), H. G. Smith; State Teachers^ 

 College Museum: top of Pole Hill near Loveland, Greeley and Las Animas 

 County, A. E. Beardsley; reported by Henderson from Crow Creek near Cornish, 

 1904; from Osgood, 191 1; from foothills northeast of Lyons, the mountains 

 north of Lyons and Owl Canyon, west of Ft. Collins; from Boulder, near Sani- 

 tarium, October 13, 191 2; common just south of the northern state line from 

 the Union Pacific Railway to Pawnee Butte, and one northeast of Ault; by Sam 

 Service from Estes Park, September 18, 1908; by Cockerell, from Boulder, 191 1. 



Genus SISTRURUS Garman 



Sistrurus Garman, N. Am. Reptiles, p. no, 1883. 



Tail with a rattle; head with nine plates instead of the small 

 scales found in Crotalus; other characters much the same as Crotalus. 

 The snakes of this genus because of their small size are known as 

 Pigmy Rattlesnakes. It is to be remembered, however, that although 

 they are small they are dangerous. One species is recorded from 

 Colorado. 



Sistrurus catenatus (Rafinesque) 

 The Massasauga 

 Crotalinus catenatus Rafinesque, Am. Monthly Mag., Vol. IV, p. 41, 1818. 



Two subspecies of this little rattlesnake are known. They may 

 be little more than geographical varieties. 



a. Scales in 23 rows; colors light; range, southwestern United States. 



5. c. edwardsii (Baird and Girard) . 



aa. Scales in 25 rows; colors dark; range, eastern and northern United States 



east of the Rocky Mountains . . . . S. c. catenatus (Rafinesque). 



