Rocky Mountains. 51 



longing to the Genus AmeivaJ was noticed in this day's 

 ride. It very much resembles the Lacerta Ameiva, as figur- 

 ed and described by Lacepede, but the tail is proportionably 

 much longer. Its movements were so extremely rapid, that 

 it was with much difficulty we were able to capture a few 

 of them. 



We had proceeded about eight or ten miles from our 

 camp, when we observed a very considerable change in the 

 character, both of the river and its valley; the former becom- 

 ing wider, less rapid, and filled with numerous islands; the 

 latter, bounded by sloping sand hills, instead of perpendicu- 

 lar precipices. Here the barren cedar ridges, are succeeded 

 by still more desolate plains, with scarce a green, or a living 

 thing upon them, except here and there a tuft of grass, an 

 orbicular lizard, basking on the scorching sand, a solitary 

 Pimelia, a Blaps, or a Galeodes; among the few stinted and 

 withered grasses, we distinguished a small cgespitose species 

 of Agrostis, and several others, which are thought to be un- 

 described. Near the river and in spots of uncommon ferti- 

 lity, the unicorn plant, (Martynia proboscidea^ Ph,) was 

 growing in considerable perfection. This plant, which is 

 sometimes cultivated in the gardens, where it is known by 

 the name of Cuckold's horns, is a native of the Platte and 

 Ark ansa, and is occasionally seen in every part of the open 

 country from St. Louis, westward to the mountains. 



2 with an intermediate small one at their tips; 1, 2, 1 the largest, 2 and 

 3, superior orbits of the eyes with four plates, of which the two interme- 

 diate ones are much the largest; belly bluish-v. hite; throat and necU ting- 

 ed with yellow, and covered with somewhat larger scales than those of the 

 back; anterior feet yellowish within, and covered with minute scales, on 

 the exterior and posterior sides greenish-white, with confluent black 

 spots and large scales; posterior feet behind greenish-white, with conllu- 

 ent black spots and minute scales, tiio anterior side yellowish, covered 

 with large scales; pores of the thigh very distinct and prominent; tail 

 elongated, rounded, above light brown, with a few lines of black spots 

 near the base; beneath yellowish-white, immaculate, the scales carinated, 

 and placed in transverse series. 



Total length 1 foot—Tail 8?, inches. 



