470 



BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



The species eDumerated in the foregoing list may, for the purpose of 

 discussion, be divided in the following manner : — 



A. Species widely distributed over the continent in about the same 

 latitude : (a) Those not extending westward ; (b) Those not extending 

 eastward. 



B. Species characteristic of the arid plains and hilly ground each side 

 of the high mountains: {a) Those confined to the eastern plains; (6) 

 Those limited to the western regions. 



C. Hyperborean species : {a) Those not found in Alaska or the west- 

 ern part of the Hudson Bay Territory ; (&) Those found in the north- 

 western regions. 



D. Local species, thus far known only from the mountain chain. 

 The collection is not large enough to furnish any accurate numerical 



relations between these different groups; but in addition to a rough 

 approximation, subject to future correction, it exhibits a number of 

 interesting phenomena, both as regards the intrusion of hyperborean 

 species, and the creeping up along the mountain-slopes of the species 

 of the plains, as high as the supply of food is sufficient and the rigors of 

 the Alpine climate can be endured. The numerical results so far as I 

 can judge from the material on hand are as follows : — 



A. Species of wide distribution in both directions about 30 ; in addi- 

 tion, 9 or 10 are not found west, and 6 not east of the mountain mass. 

 Total about 46. 



B. Species of conterminous arid regions east and west about 46 ; in 

 addition, 10 are found only on the eastern side, and 20 on the western 

 side of the mountains. Total about 76. 



C. Hyperborean species 43 : in addition, 14 have a northwestern dis- 

 tribution only-; and 3 (RoUophilus Hardyi, Flatijnus ehalceus, and Car- 

 diopMrus convexulus) have an eastern range only. 



D. The species thus far known from the mountains only are 30. 

 Those in italics occur at lower elevations, though not strictly belonging 

 to the fauna of the plains. It will be observed that, with few excep- 

 tions, these species are closely related to others previously known from 

 different parts of the United States. 



LIST OF SPECIES PECULIAR TO THE MOUNTAIN REGION. 



Nebria trifaria (9,500). 



purpurata (9-10,000). 



longula (?). 



obliqua (?). 



obtusa (6-7,000). 

 Calathus duhius (8,000). 

 Pfcero8tichu8 longulus (9-10,000). 

 surgens (9-13,000). 

 Amara cylindrica (8-10,000). 

 Harpalus clandestinus (8-10,000). 



Bembidium Bowditcbii (6-7,000). 



recticolle (6-7,000). 



nebraskense (6-7,000). 



obtusangulum (8-10,000). 



Scudderi (4,300). 

 Gaurodytes nanus (8,000), 

 Geodromicus ovipennis (10-11,000). 

 Scymnus nigrlpennis (d,000). 

 Aphodius antbracinus (9,500). 

 Anthaxia delefca (9,500). 



