16 PEEFACE 



nominated by geologists as the Tertiary. As -oill be shown in later 

 IDages the Tertiary rocks of Maryland are of wide extent and contain 

 much of interest from both a scientific and practical standpoint. 



The Eocene deposits of Maryland have received for many years the 

 close attention of the senior author of this paper, and his observations 

 have been supplemented recently by the work of the junior author. A 

 report made by the senior author to the Director <jl the U. S. Geo- 

 logical Survey in 1896 is extensively drawn upon for the present vol- 

 ume, many of the general descriptions being taken directly therefrom, 

 with such changes and additions as the present enlarged knowledge of 

 the subject may require. 



Dr. R. M. Bagg, Jr., also spent portions of two field seasons in a 

 study of the local stratigraphy under the personal direction of the State 

 Geologist and prepared a series of preliminary maps covering a large 

 part of the area. 



The paleontological investigations have been jointly conducted by 

 several experts. In addition to the sections for which the authors of 

 the report are personally responsible, aid has been rendered in others 

 by several well-known students. 



The Eeptilia have been studied by Dr. E. C. Case of Milwaukee, Wis- 

 consin; the Fishes by Dr. Charles E. Eastman of Harvard University, 

 Cambridge, Massachusetts; the Crustacea and Bryozoa by Mr. E. 0. 

 Ulrich of Newport, Kentucky; the Corals by Mr. T. Wa5dand Yaughan 

 of the U. S. Geological Survey; the Protozoa by Dr. R. M. Bagg, Jr., 

 of Colorado Springs, Colorado; and the Plants by Dr. Arthur Hollick of 

 Columbia University, New York. Mr. Charles Schuchert of the U. S. 

 National Museum has revised the descriptions of the Brachiopoda. 



Extensive collections of material were made preparatory to this work, 

 and all the leading fossiliferous localities of the state were visited. The 

 greatest amount of material was obtained, however, from the bluffs along 

 the banks of the Potomac river, which afford the most complete section 

 of the Eocene in the Middle Atlantic Slope. In general, the fossils of 

 this region arc difficult of removal, as they readily crumble at the touch, 

 so that some process of hardening had to be employed to preserve them 

 permanently. To this fact more than to any other cause, has been due 



