64 TRANSACTIONS OF THE 



[1889 



bonaceous matter, is charged with coarse sand, and becomes a 

 tough, tenacious clay at base. 



Several other varieties of marl, clay, and marly sand form 

 thick strata in other parts of the Eocene territory of Anne 

 Arundel county, but we cannot give place to them at this time. 

 They are not characterized by fossils diiferent from those of 

 the other marl beds, and are of interest chiefly as complementary 

 members of the great Eocene column. 



It is of much interest to observe that on the outer boundary 

 of this formation in Maryland there rests a thick stratum of 

 pure white clay, in which no distinguishable fossils have yet 

 been detected, that forms the transition to the Miocene formation 

 next above it. 



The Miocene, however, rather overlaps the outer boundary of 

 this white clay at the upper end of Herring bay, and does not 

 pass far over it in that section which appears above the water of 

 Chesapeake bay, Parker's creek, and West river. 



From the observations thus far recorded it is seen that the 

 fossiliferous strata of our Eocene formation vary greatly in com- 

 position and contents, but that we fail to find decided parallelism 

 between them and the strata which occur at Claiborne, Alabama. 

 Identical species of fossil shells occur, it is true, at both locali- 

 ties, but the Maryland beds appear to belong chiefly to a lower 

 horizon. Possibly the deep-laid strata, which here hold the 

 gigantic specimens of Ostrea comipressirostra, the large Latiarca 

 gigantea, and the other species of this genus, will hereafter be 

 discovered beneath the beds at Claiborne, if not in other parts 

 of the South that have yielded so many interesting forms of 

 fossil shells. We here append a list of all the genera and 

 species of fossil mollusca which have thus far been recognized 

 ID. the Eocene beds of the State of Maryland. 



