LECONTE ON ROCKY MOUNTAIN COLEOPTERA. 449 



geological and meteorological changes are all-powerful in increasing or 

 diminishing the districts of distribution, and in determining the direc- 

 tions from which additions to the fauna may have been made. I have 

 purposely avoided mentioning in the discussion among these categories 

 the modification in situ of pre-existing forms, because this is an influence 

 which is easily invoked and but rarely manifested. Its effects, there- 

 fore, if capable of being demonstrated, can be appreciated better only 

 after the elimination of the coarser and more tangible machinery of 

 topography and climate in producing migrations. 



DESCRIPTIONS OF NEW SPECIES. 



I avail myself of the present opportunity to describe several species 

 from Colorado, which have the appearance of being mountain species, 

 though their localities are not definitely known to me. For the purpose 

 of making this memoir more useful to those who will pursue the inves- 

 tigation, I have availed myself of the kindness of Mr. O. Reinecke, of 

 Buffalo, who has submitted to me a very good set of species collected 

 last summer at Atlanta, Idaho, by Mr. L. Allgewahr. Several new 

 forms were contained in this series, and a complete list of all the species 

 collected is added as an appendix. The elevation of Atlanta is estimated 

 at about 7,800 feet. 



The Nehrice mentioned in the list of Alpine species are fully described 

 in the short essay ou the North American species of that genus, added 

 as a second appendix. 



CAEABID^. 



1. Pterostichus (Cryobius) surgens, n. sp. 



Shining black, with bronze-brown lustre ; antennse dark brown ; palpi 

 and legs red-brown. Prothorax wider than long, rounded on the sides 

 for two-thirds the length, narrowed behind, and sinuate towards the 

 base ; basal angles rectangular ; anterior transverse impression well 

 defined, dorsal line distinct, basal impressions double, the inner one 

 long ami deep, the outer one short and fine ; base not margined. Elytra 

 not wider than prothorax, elongate-oval, humeri not rounded ; strife 

 fine, interspaces flat, 3d with two dorsal punctures situated on the 2d 

 stria behind the middle. Length 8.5°''" (0.34 inch). Alma (10,000 feet), 

 Argentine Pass (13,000 feet), Colorado. Closely allied to F.fatuus from 

 Alaska, but the prothorax is not so broad, and the sides are much less 

 rounded and less sinuate towards the base. 



2. Platynus jejunus, n. sp. 



Elongate and very slender, j)iceous, not shining. Head narrow, eyes 

 small, not prominent. Antennse half as long as the body, 3d joint a 

 little longer than the 4th. Prothorax elongate-oval, narrower behind, 

 sides very slightly sinuate near the base, reflexed margin narrow, 



