In many parts of North America non-marine formations and faunas are unknown or of little importance. However, there are many local formations of the sort along the Atlantic coastal region, in the States bordering the Gulf of Mexico, and in the Pacific Coast States, as well as a few in the Ohio and Mississippi Valley region. In the vast interior region, in the Rocky Mountain States and the adjacent territory and extending far northward into British America, the non-marine formations are so extensive, of such thickness, and so associated with thick coal beds and other deposits of economic importance, that they are of great consequence to the geologist. They present more complex and difficult problems than marine deposits generally do, which results in much disagreement as to the age and correlation of some of the formations.
The literature of the subject is vast and scattered, considerable of it practically unavailable to all but specialists, because of the lack of a comprehensive, systematic review and index. It is the purpose of the present volume to supply this need, and at the same time to clear up many problems in synonymy, geologic and geographic distribution of species, and so on.
The most valuable single publication concerning these faunas is White’s “Review of the non-marine fossil mollusca of North America,” 1 listing and figuring the species known at that time. He gave few definite localities, no references except to the original descriptions, often omitted the formations, and in many cases . . .