ART. XXII -PALEONTOLOGICAL PAPERS NO. 3,-CATALOGUE 

 OF THE INVERTEBRATE FOSSILS HITHERTO PUBLISHED 

 FROM THE FRESH- AND BRACKISH-WATEH DEPOSITS OF 

 THE WESTERN PORTION OF NORTH AMERICA. 



By 0. A. White, M. D. 



The principal object of the following catalogue is to present a synop- 

 sis of the invertebrate fresh- and brackish- water species, including the 

 terrestrial Mollusks, hitherto discovered in the Mesozoic and Cenozoic 

 strata of Western North America, so that the faunas of the different 

 groups and those now living may be briefly compared. Only a small 

 part of the great region indicated has yet been carefully examined, and 

 therefore great additions to our knowledge of these fossil faunae are yet 

 to be made. At present, our knowledge of them is mostly confined 

 within two quite large and distinct regions, namely, the Upper Missouri 

 Eiver region and the Green River region. 



Limiting the scope of the catalogue by excluding the marine faunre, 

 it has been found difficult to draw a distinct line between the brackish- 

 water and marine forms, because of the well-known fact that there is 

 no precisely fixed limit of habitat in this respect among such living 

 species as are represented generically by some of these fossil forms. In 

 such cases of doubt, I have included only those species that seem to 

 indicate clearly a brackish condition of the waters in which they lived ; 

 but, in all cases, all undoubted fresh-water invertebrates and land Mol- 

 lusks are included. Thus, while the catalogue is intended to embrace 

 all the invertebrate species yet discovered in the strata of the Wahsatch, 

 Judith Eiver, Fort Union, Green Kiver, Bridger, Wind Eiver, and 

 White Eiver groups, besides some strata not yet correlated with either 

 of these groups, only a part of those found in the Laramie, Fox Hills, 

 Dakota, and Jurassic strata are included. This is because the fossils 

 of the last-named groups, except the Laramie, are usually found to be 

 of marine origin. Much the greater part of the fossils yet collected 

 from the Laramie group are of either brackish- or fresh-water origin. 

 These facts indicate that a much smaller area was occupied by brack- 

 ish and fresh waters in those earlier epochs than afterward prevailed 

 upon what is now the North American continent ; and that the area 

 they occupied increased until the saline waters were finally displaced 

 entirely by fresh waters. 



