THE MOLLUSKS OF THE ROCKY MOUNTAINS. 43 



meuts of great mountain-heights in the more elevated regions of the 

 globe. The extensive survey of coasts, prominent among which is our 

 own great Coast Survey. The trigonometrical surveys carried on in 

 many countries in Europe.' The investigation of the cause of the 

 glacial epoch, and possibly of inter-glacial epochs, or a succession of 

 alternate warm and cold periods, each extending over long epochs of 

 time, and their effect in bringing about the present condition of the 

 earth's surface by changes in the level of the sea and the submergence 

 of the land. 



This very inadequate statement will show how great, wide-spread, 

 and constant has been the work of exploration and research within the 

 period referred to, and how truly it may be denominated a geographi- 

 cal age. 



-*- 



THE MOLLUSKS OF THE EOCKY MOUNTAINS. 



Br ERNEST INGERSOLL. 



IX the summer of 1874 it was my privilege to accompany one of the 

 parties of the United States Geological Survey of the Territories, 

 of which Dr. F. V. Hayden is chief. The field of operations was the 

 mountainous region of Southern Colorado, and it afforded a good op- 

 portunity to examine the natural history of the region traversed. 



The mammals of the Rocky Mountains have long been well known, 

 particularly the large game, which, except in the distant portions of 

 the Territory of Colorado, has been greatly depleted by the constant 

 pursuit of hunters and trappers. The case is somewhat the same with 

 the game-birds ; while the enthusiastic labors of Henshaw, Aiken, 

 Allen, Coues, and other ornithologists, have given us a very complete 

 knowledge of all the birds and their habitats. The fishes and reptiles 

 have received some attention too ; and, in the lower, invertebrate forms 

 of life, the investigations of Thomas upon the grasshoppers, Carpenter 

 on the butterflies and moths, and Edwards, Packard, and Hagen on 

 other insects, and the reports upon Crustacea and worms by Verrill, 

 Smith, Leidy and others, have given us a tolerable knowledge of the 

 extent to which those forms are to be found in that region. But the 

 mollusks of the mountains land-snails, pond-snails, river-snails, and 

 fresh-water mussels have been almost entirely neglected, except by 

 Dr. Cooper, in the north. From Colorado only seven had been reported, 

 which were collected by Lieutenant Carpenter. This, then, seemed to be 

 the field most needing cultivation, and my attention was chiefly turned 

 to it during three months of wandering over the mountain-ranges, 

 parks, and sterile plains, that diversify the country between Middle 

 Park and the corner of Arizona. Something was found at nearly 

 every camp, and, when the collection was at home and counted, it was 



