MARYLAND GEOLOGICAL SURVEY 165 



forms, with here and there some iron, case-hardened material in the 

 form of nodules and bands. Towards the town of Sassafras the 

 Aqnia formation becomes less distinct and finally disappears beneath 

 a deposit of Columbia gravel. 



The formation, as a whole, dips toward the southeast at the rate 

 of about 20 feet to the mile, and strikes across the country from 

 northeast to southwest. A few imperfect casts of marine mollusks 

 have been found in the formation. Such fossils as the formation 

 has yielded point to its Eocene age. 



The determination of the full extent of the Aquia formation in 

 Cecil county has been attended with no little uncertainty. The diffi- 

 culty consists in separating the Aquia from the Rancoeas formation. 

 The latter undoubtedly is present across the border in Delaware 

 where the Bryozoan limestone is well developed. In Kent county, 

 however, fossil forms which have heretofore been considered as be- 

 longing to the Rancoeas fauna are found above othei forms, which 

 undoubtedly belong to the Aquia period. As the deposits at Ered- 

 ericktown contain an Eocene fauna, and as no deposit carrying an 

 undoubted Rancoeas fauna has been discovered in Cecil county, it 

 has seemed best to refer all the greensand beds lying above the Red 

 Bank sands and beneath the deposits of the Columbia group to the 

 Aquia formation. 



The Neocene. 

 the lafayette formation. 



The name of this formation was suggested by Lafayette county, in 

 Mississippi, where the beds were found to be well developed. The 

 age of the Lafayette is problematical. No fossils have, up to the 

 present time, been found within its body of sufficient diagnostic char- 

 acter to show conclusively where the formation belongs in the geo- 

 logical scale. It has been supposed, however, for some time that it 

 belongs in the Pliocene. The Lafayette formation, as a whole, is 

 developed along the Atlantic coast, either as continuous masses, or as 

 isolated remnants from Pennsylvania to South Carolina. In the 

 northern portion of the Atlantic Coastal Plain the Lafayette is rep- 



