^v 48 Expedition to the 



We also captured a rattlesnake,* which like the tergemi' 

 nuSy we have found to inhabit a barren soil, and to frequent 

 the villages of the Arctomys of the prairie, but its range ap- 

 peared to us confined chiefly to the vicinity of the Rocky 

 Mountains. Its rattle is proportionally much larger than that 

 of the species just mentioned, and the head is destitute of 

 large plates. It seems by the number of plates and scales, to 

 be allied to the atracaudatus of Bosc and Daud, but their 

 description induces the conclusion that their species is en- 

 tirely white beneath. It is also allied to the Crotalus durissus^ 

 L. (C. rhombifer Beauv.) but is smaller, and the dorsal spots 

 are more rounded. A specimen is placed in the Philadelphia 

 Museum- A new species of Coluber also occurred. f 



The only specimens of organic reliquise from this vicinity, 

 which we have been so fortunate as to preserve, are very in- 

 distinct in their character, and are only impressions on the 

 gray sandstone. One of them appears to have been a phytoid 

 Millepore^ and the other a subequilateral bivalve, which may 

 possibly have been a Mactra. It is suborbicular, and its 

 surface is marked by concentric grooves or undulations. At 



* Genus Crotalus. Lin. 



1. C. confluentus. Say. Brownish varied with greenish-yellow, a triple 

 series of brown spots, the anterior vertebral ones confluent, and the pos- 

 terior ones separated into bands. 



Body brownish cinereous, varied with greenish-yellow; a triple series 

 of fuscous spots; dorsal series consisting of about forty- four lar^i^e, trans- 

 versely oblong-oval spots, each widely emarginatc before and behind, 

 and, excepting the posterior ones, edg^ed with greenish-white, the ten 

 or twelve anterior ones crowded, confluent, those of the thicker part of 

 the body separate, those near the cloaca and upon the tail united with 

 the other spots of the lateral series, and funning bands; lateral series, spots 

 rounded and 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 scaly, scales of the superior orbits and of 

 the anterior margin larger striated; beneath yellowish-white, immaculate. 



Plates of the body i97, of the tail 27. 



Genus Coluber. Lin. 



•f- 2. C. testaceus. Pale sanguineous, or testaceous above, beneath san- 

 guineous, immaculate. 



Plates 1 98, scales HO? 



This is a large species, which inhabits near the Focky Mountains. It 

 moves with great rapidity, and in general form and size resembli-s C con- 

 strictor. The scales are large. A specimen is in the Philadelphia Museum. 



