1892] MARYLAND ACADEMY OF SCIENCES. 195 



distance, the leaves of plants and trees described by Prof. 

 Fontaine, in Volume XV of Monographs of the United 

 States Geological Survey, 1889, are found, and serve to 

 emphasize the formation. The beautiful Vitiphyllum 

 muUifidum Font, is, perhaps, the most abundant and 

 perfect of the few dicotyledonous plants discovered in the 

 formation. While the greater part of the assemblage con- 

 sists of ferns, conifers and cycads of old types, the small 

 percentage of dicotyledons is a marked incident of the flora. 



Resting upon these narrow strata is a bed of dark lead- 

 colored plastic clay, which often rises unbroken through a 

 thickness of forty feet; above this it occasionally becomes 

 more sandy, in some places has slender drifts of sand pass- 

 ing through it, and its upper part is generally broken, 

 locally dislocated, and changed by atmospheric agencies 

 into the " Variegated Clays " of Prof. Fontaine. As the 

 formation extends eastward and bayward it becomes mixed 

 and sandy. This sandy portion forms a series of beds ad- 

 joining the Albirupean along the stretch of country lying 

 between the Washinc^ton branch of the Baltimore and Ohio 

 and the Baltimore and Potomac railroads. In this region 

 the sands of the Albirupean have been mixed with the 

 Potomac clays by overflows of water. These have been 

 repeated in Quaternary time, and the resulting mixtures 

 now form broken beds of reddish or gray color in the 

 troughs between the hills and over some of the ridges. 



An erosion interval of great activity followed the depo- 

 sition of the variegated clays. During this time the huge 

 deposits of dark clay which we know, from Federal Hill as 

 it stood before the civil war of 1861-65, and from other 

 deposits in Howard and the northern part of Anne Arun- 

 del county, formed a thickness of fully one hundred feet, 

 was cut through to within a few feet of the present high- 

 tide level. Up to the top of this part of the series, which 

 terminates with the " Variegated Clays," either broken or 



June 8. 



