98 . TRANSACTIONS OF THE [1890 



BiA Formation fits, and its fluviatik member fills out the 

 borders of old channels, basins and coves, chiefly near tide- 

 water. The interfluvial member extends up to a level of about 

 250 feet above tide in the city of Baltimore, while the other is 

 frequently met with at levels from below tide up to 75 feet. It 

 is mostly composed of pale ferruginous sands and loams, charged 

 with coarse boulders, interspaced with areas of brick clay, 

 throughout its tideward member ; while it is less regularly 

 stratified, charged with beds of angular sands ranging from 

 white to red, and is overlaid by earthy clay full of small, chiefly 

 rounded boulders, in the elevated member which rests between 

 the rivers and creeks. 



This formation belongs to the Quaternary period, and lies 

 farther inland than the section included in the accompanying 

 plate. 



The Albieupean Formation next succeeds the Potomac, 

 and rests upon its outward slope. 



It is M^ell characterized by thick strata of white sandstone, 

 white sand and white clay, which form the hills and cliffs 

 along the Severn river, from above its head to Sullivan's Cove 

 at the upper end of Round Bay. Immediately east of this 

 great body of clean sands and clay appears a prominent arrest 

 in the continuity of the region, and we at once pass to a 

 diiferent type of structure, showing a marked change in the 

 component elements of the beds. 



This is the point where the typical Cretaceous System of 

 strata comes into view, underlaid by a peculiar division com- 

 posed in great part of alternate layers of drab or yellowish 

 fossiliferous clay and fine white sand, which for convenience 

 may be called the Alternate Clay-Sands member. This forms a 

 body of beds and strata underlying the Lower Black Marl Bed, 

 and underlaid in common therewith by a stratum of ferruginous 

 coarse sand and sandstone. It is greatly eroded beyond the 

 pavilion, and again below the hotel, on the Round Bay picnic 

 grounds. Near its inner border it rises into hills 30 to 50 feet 

 high, and overlaps the clay of the Albirupean shore. Next the 

 base it displays a laminated bed of black earthy matter, which 

 is loaded with iron pyrites, lignite and fragments of twigs and 

 leaves of trees. It is also interrupted by large beds of coarse. 



