The Rattlesnakes 



and fed readily. They seldom rattled, and then but for five or 

 ten seconds' time. They would take young birds, mice and 

 frogs, and, like the copperhead snake, different kinds of food 

 according to the seasons, a trait probably developed by necessity 

 while in a wild state. One of the Michigan specimens gave 

 birth to seven young; the female was about two feet in length 

 and her youngsters so small that one of them could have readily 

 coiled upon a silver half-dollar and left a good margin about it. 



EDWARD'S MASSASAUGA 



Sistrurus catenatus, variety edwardsii, (B. & G.) 



This variety is distinguished by the much paler yellowish 

 ground-colour and the smaller spots on the back. The spots 

 on the sides are indistinct. In miniature, the pattern of this 

 snake is much like that of the prairie rattlesnake, (Crotalus 

 confluentus). 



While the typical form has twenty-five rows of scales, this 

 variety has but twenty-three. 



From all of the other rattlesnakes of the Southwest, it may 

 be instantly told by the large plates of the head. 



Dimensions. Like the typical form. 



Distribution. The range of this variety begins from the 

 extreme southern distribution of the typical form and extends 

 from the Indian Territory, throughout western Texas, and west- 

 ward to about the central portion of southern Arizona. It also 

 occurs in northern Mexico, adjacent to the boundary. 



Habits. It seems that this reptile is less partial to damp 

 situations than the preceding form. 



The Rattlesnakes Crotalus: The present genus embraces 

 the Rattlesnakes proper. The species may be recognised from 

 the preceding genus of small Rattlesnakes by the scalation of 

 the head; this small and granular. A few of the species have 

 small shields on the forward portion of the snout in front of 

 the eyes. 



Fifteen distinct species and several varieties of Crotalus 

 are known. Eleven of the species and two varieties are 

 found in the United States. Concerning the latter, a key is 

 given: 



438 



