36 THE PHYSICAL FEATURES OF ST. JIAET's COUNTY 



period, the later portion. He subdivided the Newer period again into 

 the Patuxent Group and the St. Mary's Group. The next year, the same 

 author revised his classification and divided the Miocene into three 

 groups as follows: the Carolinian or the Upper Atlantic Miocene, in- 

 eluding the Sumpter epoch of Dana; the Virginian or Middle Atlantic 

 iliocene, including part of the Yorktown of Dana and the ISTew^er group 

 of ilaryland ; and the Marylandian or the Older Atlantic ]\Iiocene, in- 

 cluding the rest of Dana's Yorktown and the older period of Maryland. 

 He suggested that the Virginian was of the same age as the second 

 Mediterranean of Austrian geologists and the faluns of Touraine, and 

 that the Marylandian was, at least in part, equivalent to the first Medi- 

 terranean of Austrian geologists and faluns of Leognan and Saucats. 

 Three years later the same author published a map showing the distribu- 

 tion of these formations along the Atlantic coast. In 1888 Otto Meyer 

 took exception to Heilprin's correlation and conclusions, and introduced 

 the term Atlantic Group to embrace the Tertiary of the Atlantic States, 

 and Gulf Group for that of the Gulf States. 



Three years later Darton employed the term " Chesapeake Group " to 

 cover a portion of the Miocene, and in the following year Dall and 

 Harris published their report on the Miocene deposits in the Correlation 

 Papers of the U. S. Geological Survey, and used the term " Chesapeake 

 Group " to include the Miocene strata extending from Delaware to 

 Florida. These deposits were made during the Yorktown epoch of 

 Dana and the group included a largo part of Heilprin's Marylandian, 

 Virginian, and Carolinian. Two years later Harris, basing his work on 

 a study of the organic remains found in the Miocene, subdivided the 

 Miocene faunas of Maryland into the Plum Point fauna, the Jones 

 Wharf fauna, and the St. Mary's fauna. 



The following year Darton, by bringing together a large number of 

 well records throughout the Coastal Plain from New Jersey southward, 

 rendered a most important service to the study of the Miocene problem 

 in Maryland by suggesting the structure and extent of the beds through- 

 out the region. The following year Dana admitted Harris's faunal 

 zones, but still retained the term •■' Yorktown," to part of which he as- 



