PREFACE 



The following study of the Pelecypoda of the Miocene of Maryland 

 was undertaken at the suggestion of Dr. W. B. Clark, and was prosecuted 

 in connection with the author's work on the stratigraphy and areal dis- 

 tribution of the Miocene of Maryland under the auspices of the Maryland 

 Geological Survey. The summer of 1898 and a part of that of 1899 

 were spent in the field studying the various formations of the Miocene 

 and later overlying deposits and mapping their areal distribution. Dur- 

 ing this areal field work the material for this paper was collected and 

 the stratigraphic relationships of each bed collected from ascertained 

 as exactly as was possible. Many points at which fossils were collected 

 afforded excellent stratigraphic sections so that as a result of this com- 

 bined stratigraphic and paleontologic work no doubt can be left as to 

 either the lithological or fauna! sequence. 



Since the stratigraphic column of the Atlantic Coast Miocene nat- 

 urally exposed i-n Maryland is much longer than that of any other State, 

 and is usually so abundantly fossiliferous, it affords a most excellent 

 opportunity for the study of paleontological problems. The present 

 monograph is presented as a contribution toward such a study by fur- 

 nishing the materials on which study must be based. 



The classification adopted is that of Dr. W. H. Dall as presented in 

 various publications but most fully elaborated by him in A^olume III 

 of the Transactions of the Wagner Free Institute of Science of Phila- 

 delphia. 



The thanks of the author are primarily due to Dr. W. B. Clark, 

 without whose aid as Director of the Maryland Geological Survey the 

 work could never have been undertaken. Acknowledgments are also 

 due to the authorities of Cornell University and of both the Academy 

 of Natural Science and the Wagner Free Institute of Science of Phila- 

 delphia for the opportunity to study the collections in their charge and 



