Rocky Mountains. 499 



herbage, which always marks the area of the prairie-dog vil- 

 lages. Indeed we have observed several large villages, with 

 scarce a trace of \egetation about them. The food of the 

 marmot consisting of grasses and herbaceous plants, it is not 

 perhaps easy to assign a reason for the preference which, in 

 selecting the site of his habitation, he always shows for the 

 most barren places, unless it be that he may enjoy an unob- 

 structed view of the surrounding country, in order to be 

 seasonably warned of the approach of wolves, or other ene- 

 mies. 



Rattle snakes of a particular species* are sometimes seen 

 in these villages. They are found between the Mississippi 

 and the Rocky Mountains, and appear to prefer an unpro- 

 ductive soil, where their sluggish gait may not be retarded 

 by the opposing obstacles of grass and weeds. Whilst ex- 

 ploring Boyer Creek, of the Missouri, in the Spring of 

 1820, our party met with six or eight of them during one 

 day's march on the prairie, and on our subsequent journey 

 to the Rocky Mountains we several times encountered equal 

 or even greater numbers, in the same space of time. This 

 is the species of serpent which travellers have observed to 



* Crotalus tergeminus, S. Body dusky cinereous, a triple series of 

 deep brown spots; beoeaih with a double series of btack spots. 



Body pale cinereous brown, a triple series of fuscous spots, dorsal se- 

 ries consisting of about forty-two large, transversely oblong-oval spots, 

 each widely emarginate before, and obsoletely edged with whitish; lateral 

 series, spots transversely oval, opposite to those of the back; between the 

 dorsal and lateral series, is a. series of obsolete, fuliginous spots alternating 

 with those of the two other series; head above with nine plates on the ante- 

 rior part, on which area band and about three spots, two undulated vittae 

 terminating in and confluent with the first spot of the neck, a black vitta 

 passes through the eye, aud terminates on the neck each side; beneath 

 white a double irregular series of black spots, more confused towards the 

 tail; tail above with five or six fuscous fasciae, beneath white irrorate with 

 black points, six terminal plates bifid. 



Length 2ft. 2 1-8 in. 



tail 2 1-8 in. 

 Plates of body 151. 



of tail 19. 

 Bifid plates at tip 6. 

 Another specimen, much smaller, PI. 152, subcaudal, 20, scales at tip 3. 



