SLIRATIGRAPHY OF THE POTOMAC GROUP 493 
The strike of the beds is ina generally north-northeast to 
south-southwest direction, corresponding to the Patapsco for- 
mation already described. The dip of the strata is probably 
Fic. 5. Section of Raritan formation near Rocky Point above Round Bay, 
Severn River, Anne Arundel County, showing hard sandstone ledges at the right and 
white cross-bedded sands in the center. 
slightly less than that of the underlying formation, and a slight 
transgression is noticeable to the northward. 
The thickness of the Raritan formation in central Maryland 
is probably not far from 500 feet. It declines in thickness 
gradually to the southward where it finally disappears near the 
limits of the District of Columbia. 
Characteristic local sections —Very characteristic sections of 
the Raritan formation are shown in the bluffs of the Severn 
River in the vicinity and about Round Bay. On Rocky Point 
just above Round Bay an excellent exposure of the Faritan 
sands with the interbedded clays is exhibited, with a capping 
