30 ' CROTALOPHORUS TERGEMINUS. 



cinereous, tinged slightly with olive. The head is marked with a dusky bar 

 between the orbits, whence depart two dark bands, one of which runs along the 

 neck for an inch or more, and then joins the band of the opposite side, leaving 

 an oblong lighter coloured blotch on the vertebral line; the other dusky band 

 descends from the orbit to behind the angle of the mouth; beneath this latter 

 dusky band is a white one of equal length, and of nearly the same breadth. 

 The upper jaw is dusky. The body is marked with a triple series of dusky 

 blotches, those on the vertebral line largest, and about forty-two in number; they 

 are oval, emarginate in front, and most extensive transversely, and are all 

 bordered with a thin margin of black; opposite to these oval spots and on each 

 side is another series of dusky spots, sub-round and bordered also with black, 

 and this again, but indistinctly, with a lighter colour. The tail is banded with 

 dusky. The belly is whitish, tinged with flesh colour, mottled with black spots; 

 and each plate has two or more dusky blotches, disposed in two irregular series. 



Dimensions. Length of head, 1 inch 2 lines; length of body, 22 inches 10 

 lines; length of tail 2 inches 2 lines: total length, 2 feet 2 inches 2 lines. In the 

 specimen here described there were 150 abdominal plates, 19 entire plates, and 

 bitid under the tail, which sustained five rattles. 



Habits. Mr. Say observes — "they seem to prefer an unproductive soil, where 

 their sluggish gait may not meet with the opposing obstacles of grass and mud;" 

 for their hiding places they seek the holes of the prairie dog, (Arctomys Ludo- 

 viciana.) 



Geographical Distribution. The Crotalophorus tergeminus inhabits the region 

 of country bordering on the Rocky Mountains, near the sources of the Missouri. 



General Remarks. This Rattlesnake was first observed and accurately 

 described by Mr. Say, in Long's Expedition to the Rocky Mountains. The 

 colour of the accompanying plate was done from a preserved specimen. 



