268 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



northern boundary line, its distribution appears to be determined verj 

 nearly by the Missouri watershed, as limited by the Coteau. This car- 

 ries its range somewhat into the British Possessions, so that it is prob- 

 ably the most northern species of the genus. It does not appear to 

 exist along that portion of the line represented by the watershed of the 

 Bed River of the North, where none were observed by the commission. 

 1 shall have frequent occasion to allude to the great difference in the 

 fauna and flora of these two portions of the line sharply divided by 

 the Ooteau of the Missouri. The presence among plants of the Opuntia 

 missouriensis and the prevalence of Artemisia, the occurrence of Centro- 

 oercus uropliasianus among birds, of Cynomys ludovicianus among mam- 

 mals, and of Phrynosoma douglasi and Grotalus confluentus among rep- 

 tiles, are some of the prominent features of the Missouri watershed as 

 contrasted with that of the Eed Elver. C. confluentus is also found 

 extending to New Mexico, Utah, Colorado, Arizona, California, Nevada, 

 and even to the islands of Santa Barbara Channel, California; but the 

 typical Grotalus of the Sonoran region is G. adamanteus atrojc, a sub- 

 species of our Southern serpent, of the Pacific. C. hicifer, a well- 

 marked and distinct form, is found in Arizona aud the Pacific region. 



The pairing season of these serpents is in midsummer, when they 

 have several times been observed in coitu. Little, however, has been 

 ascertained respecting their reproduction. About half the year, in most 

 latitudes, they hibernate in holes in the ground. They have, however, 

 been observed abroad after severe frosts in the Yellowstone region. At 

 Fort Eandall, on the Missouri, they were stated to reappear iu May 

 with the loosening of the ground from frost. As in the case of other 

 species, there is a regular annual, or perhaps, as in some other 0[)hi- 

 dians and as in Saurians, a more frequent casting of the skin. During 

 the moult, they are reported to be specially venomous, but probably 

 upon no other foundation than that at this time their sluggishness 

 results in the accumulation of a large supply of the poisonous fluid. In 

 one of the specimens secured were found the remains of a Prairie Squir- 

 rel {SpermopMlus richardsoni), the most abundant mammal of the Milk 

 Eiver region ; and it is probable that these animals, together with the 

 allied species, form a large part of their subsistence. 



While the venomous properties of these reptiles, not easily overrated, 

 should suffice to ensure due caution in capturing or killing them, it is as 

 well to remember that the utmost range of a rattlesnake's blow is less 

 than its own length. They may readily be captured alive by pinning 

 down the neck with a forked stick, and may be handled with impunity, 

 when not too large aud powerful, if seized immediately behind the head. 

 In case of a strong snake, however, the power of constriction is suffi- 

 cient to paralyze the muscles of both arms, as iu the case of a person 

 we knew who had seized two of these reptiles by the back of the neck. 

 He had to be relieved by a bystander. A method employed in the South 

 to capture the G. adamanteus is perhaps worthy of mention. A silk 



