PREFACE 



AS foreshadowed in the Preface to Part V. of this Memoir, the present contri- 

 ii bution completes the work begun in 1885. It contains the remainder of 

 the Pelecypoda and the Brachiopoda, together with a general summary of the 

 geological and paleontological results and a few additions and corrections to 

 earlier parts. 



As the student of these volumes will have observed (as is inevitable in such 

 an undertaking, extending over eighteen years of labor in the field and in the 

 laboratory), there are some modifications of the original method, some shifting 

 of the point of view with greater knowledge of the facts, and the introduction 

 of some improvements due to increased experience. It may be well to restate 

 the conditions under which it was prepared, at the suggestion and with the 

 cordial cooperation of Mr. Joseph Willcox, of the Wagner Institute. 



Originally the exploitation of the Tampa silex beds, the Chesapeake 

 Miocene, and the rich fauna of the Caloosahatchie marls was contemplated. In 

 the field work necessary to make our collections complete within these limits 

 other horizons were examined, and the cooperation of the United States Geo- 

 logical Survey through its officers, Mr. Gilbert D. Harris (now of Cornell 

 University) and Mr. Frank Burns ; of the Wagner Institute through Mr. Will- 

 cox and Mr. C. W. Johnson ; of the Hon. T. H. Aldrich and Professor E. A. 

 Smith, of Alabama, was constant and cordial. New material came in each 

 season, until in self-defence much of it had to be put aside in order to complete 

 the work at all. 



In the earlier part of the work it was recognized that the so-called Miocene 

 of Florida comprised two very dissimilar faunas, and to the earlier the term 

 Old Miocene was applied in this work. Further study and material showed 

 that this " Old Miocene" had nothing to do with the Miocene of the United 

 States in its most typical development, as in Virginia and Maryland, but repre- 

 sented a group of horizons strictly analogous to those which had received from 

 European geologists the name of Oligocene. 



These horizons contained a very rich warm-water fauna which was soon 

 lound to be more or less distinctly represented in the Tertiaries of Middle 

 America and the West Indian Islands. This fauna then had to be examined 

 and collections made at Bowden, Jamaica, and other important points in order 



