PREFACE 



IX 



particular horizons which accident or special conditions of preservation of the 

 contained fossils had made conspicuous, and that numerous other beds also im- 

 portant stratigraphically and faunally remained to be exploited, was not then 

 and is hardly yet appreciated. 



The excellent work of Professor Harris on the Midwayan and Chickasawan 

 divisions of the lower Eocene in his " Bulletins of American Paleontology," 

 and the results set forth in the present work, aided by the advances in faunal 

 knowledge of the vertebrate Tertiary faunas made by Scott, Osborne, and 

 other energetic workers, have rendered the last ten or fifteen years more fruit- 

 ful in American Tertiary geology than any period since that of Lyell. 



When we remember that the successive Tertiary strata on our southeastern 

 coastal plain are composed of nearly identical materials, one stratum being 

 often built of the debris of those immediately preceding it ; that their chemical 

 and mineralogical constituents are necessarily practically the same; that the 

 soft nature of the rocks, even when consolidated, lends itself to erosion and to 

 obscuration by the subtropical luxuriant vegetation, it would seem hardly 

 necessary to reassert the truth so often lost sight of, that geological work 

 which does not take careful account of the paleontological data in this region 

 is practically futile. Nearly all the errors into which geologists have been led 

 in this part of the country, practically all the inaccurate theorizing and inci- 

 dental controversy, have arisen from ignorance of or too superficial examina- 

 tion of the fossil contents of these rocks. The work already done is still insuf- 

 ficient for any final consensus of opinion. Those beds which have afforded a 

 well-preserved fauna are doubtless fairly well understood, that there are others 

 like them not yet known is eminently probable, and that there are numerous 

 others in which the removal of the fossils by solution has delayed recognition 

 of their existence and relative importance is certain. The latter, affording only 

 casts, or, in some fortunate cases, silicious pseudomorphs of the contained 

 fossils, can only be intelligently studied when the intervening better-preserved 

 faunas are thoroughly known. 



Thus a rich field is open for the paleontologist, and the explorations and 

 publications of the Wagner Institute have had exceptional importance in calling 

 attention to the opportunities it presents. It is earnestly to be hoped that the 

 students needed to reap the harvest will soon be forthcoming. 



A certain number of the belated accessions to the collection which belong 

 to groups which had been passed in the text before they were received were 

 described by me in the " Proceedings of the United States National Museum," 

 No. 1035, volume xviii., pp. 21-46, 1895. These species were not then figured, 



