14 TEAXSACTIOXS OF THE - [1888 



that when Wharton's Creek is reached, these deposits have almost 

 disappeared from view, and lower cliffs appear along the shores. 

 Back of this section the country is low and comparatively level, 

 and the debris of a great variety of rocks goes to make up the 

 apparently Quaternary surface of the soil. 



In the deep ravines, near the head of the creeks, the black 

 and green marls make their appearance ; and farther south to 

 within a short distance from the Chester river, the greensand 

 marls are accessible wherever the streams have cut deep chan- 

 nels. The characteristic fossil shells, such as Gryphea vesicu- 

 laris and Exogyra costata, have been found in the black marls 

 near the mouth of the Sassafras, as well as farther up that 

 stream, likewise at various points along the upper Elk and 

 Bohemia rivers and in the ravines of their tributaries. Near 

 the southeastern border of Cecil county, as also in the eastern 

 part of Kent county, multitudes of Exogyra, BeUmnitella, Tere- 

 hratula and other shells have been taken out of the marls exca- 

 vated for use in fertilizing the soil. 



Crossing Chesapeake Bay to beyond the mouth of the 

 Patapsco river, the same black marls as those on the Sassafras 

 river make their appearance above tide level. At first they 

 are seen in the base of the low hills which rise near Bodkin 

 Creek, and then they become much thicker in the islands and 

 cliffs of the little bay inside the mouth of the Magothy river. They 

 may be observed for a distance of about three miles up this 

 river, back of which the laminated sands come in and extend 

 through to the upper fork of the stream. Crossing the Magothy 

 towards the southwest, these marls form high beds rising from 

 the base of the elevated hills and stretching up the river at 

 least two miles. From that point, continuing still in a south- 

 west direction across the ridge of Broad Neck, the black marls 

 come out in thickest exposures at the lower end of Round Bay, 

 on the Severn river. Here we observe the marl rising thirty 

 to sixty feet above the level of the river, immediately overlaid 

 by mixed green sands, more or less obscured above by ferrugi- 

 nous and gray sands. Over these the Upper Marl strata are 

 seen in thick beds, chiefly composed of coarse gray-green 

 sands which are more or less enclosed in elongated i30ckets of 



