34 THE PHYSICAL FEATURES OF ST. MAKY's COUNTY 



Upper Marine, and included some which have since been shown to be 

 later than Miocene. During the same year Vanuxem divided the Allu- 

 vial and Tertiary of the Atlantic Coast into Secondary, Tertiary, and 

 Ancient and Modern Alluvial. In this classification the Miocene of 

 southern Mar3'land was included in a part of the Tertiary. He stated 

 further that vast numbers of " Littoral " shells occurred in the Tertiary 

 analogous to those of the Tertiary of the Paris and English basins. 



Conrad brought out his first publications bearing on the Miocene 

 geology of Maryland in 1830. He agreed with Vanuxem in placing 

 southern Maryland in the Tertiary and pointed out a number of locali- 

 ties where fossil shells were found. Two years later Conrad published 

 another paper in which he divided up the Coastal Plain deposits into six 

 formations. This was the first time that the Coastal Plain had been 

 classified so as to show its extreme complexity, and from this time on 

 it has been dealt with, not as a deposit containing a few formations but 

 as a series of deposits complex in composition and age. Conrad at this 

 time ascribed the Miocene of Maryland to the Upper Marine and made 

 it equivalent to the Upper Tertiary of Europe. 



The following year John Finch published another book on his travels 

 in Maryland which had been made almost a decade before. In this nar- 

 rative. Finch gives a most interesting account of the great delight which 

 he experienced in collecting from the enormous deposits of fossil shells in 

 St. Mary's County. 



The following year Morton published another paper in which he pro- 

 posed a classification of the Coastal Plain deposits. In this no distinct 

 reference was made to Maryland, but it is probable that he still regarded 

 the Miocene of this State as Upper Marine. 



During the same year also Isaac Lea described some fossils from the 

 St. Mary's Eiver and regarded then as older Pliocene. He, too, doubted 

 the existence of the Miocene in Maryland. 



The next paper of importance was published by Conrad, in 1835, in 

 which he assigned the Miocene deposits to the older Medial Pliocene. 

 In the following year Ducatel referred the deposits of St. Mary's County 

 to older Pliocene and distinctly stated that they were not Miocene. He 



