1889] MARYLAND ACADEMY OF SCIENCES. 47 



than the Albirupean, and to be composed chiefly of other ele- 

 ments, put together after a different mode of construction. In 

 the Cretaceous of Maryland no strata of homogeneous clean 

 clays appear, nor do we find extensive beds of unsullied sand, 

 such as form chief members of the underlying formation. 

 Originally, this system of Lower marls must have formed a 

 continuous sheet of friable and plastic materials scarcely less 

 than ninety feet in thickness. At the present time it is not 

 observed to be more than about seventy-five feet thick in any 

 single exposure, but in nearly all the places where it has suffered 

 least denudation it lacks the whole or a part of some one or 

 more of its members. 



On the inner border it is more highly inclined than along its 

 average base level, as may be seen on the high hill, called 

 Maulden's Mountain, at the mouth of North-East river, where 

 the Lower Marl beds rise about one hundred and fifty feet 

 above tide to pass over the ridge of Albirupean clay. No other 

 such conspicuous example of this kind occurs within the terri- 

 tory of Maryland, but the same series of beds rise to a some- 

 what less altitude to pass over the Albirupean hills north of 

 Round Bay, near the Severn river. Pursuing these strata 

 along the river last mentioned, as also on the exposed banks of 

 the Magothy and Patuxent rivers, we find them lying nearly 

 horizontal, and observable over a width of hardly more than 

 three miles, while on the Eastern Shore they are conspicuous in 

 the cliffs of all the rivers, from the North-East river to the end 

 of the southern side of the Sassafras. 



In the flats or terraces along the bayed-out shores of the 

 Potomac river, in Prince George's and Charles counties, no 

 outcrops of the Cretaceous marl beds have yet been reported. 

 In that portion of the region between Washington and Broad 

 Creek the country is composed of high hills of clay, sand, gravel, 

 and small boulders of apparently Quaternary age, so that we 

 are compelled to go north and east of the ridge on which Forest- 

 ville stands to find ravines or margins of streams where the beds 

 are laid open. The most southward exposure of any member 

 of the Cretaceous of Maryland, thus far noticed, appears in the 

 ravines of Charles county, above the bend in Mattawoman 



