MAEYLAND GEOLOGICAL SURVEY 193 



in the former. It would then appear that as the region was gradually 

 lowered again beneath the present ocean the upper portions of the 

 stream-channel in time passed below wave-base and whatever has col- 

 lected in them since that period will be preserved beneath the ad- 

 vancing sea as a more or less fossiliferous clay lens apparently un- 

 conformable beneath beach debris. 



The barrier beaches which exist at intervals along the Atlantic 

 coast of New Jersey, Delaware, Maryland, Virginia, and southward 

 show us how portions of the ocean-bed, which were formerly bathed 

 by salt water and sustained a marine fauna, are now converted to 

 lagoons behind barrier beaches, and have passed over in varying 

 degrees to brackish-water conditions bearing estuarine faunas. 



Similar deposits to those just described have been seen by the 

 author along the Rappahannock river, especially at Mosquito Point, 

 and there is no reason to doubt that they occur in many other places 

 along Chesapeake Bay and its estuaries, within the State of Virginia. 

 From analogy, it would be expected that similar deposits should be 

 discovered along Delaware Bay where conditions must have been 

 identical to those which prevailed in Chesapeake Bay. That such 

 deposits do occur along the shores of the Delaware there can be no 

 doubt. The most noted of these is at Fish House on the ISTew Jersey 

 side of the Delaware river a few miles above Philadelphia. 



The drab clays at Fish House, ISTew Jersey, which have occasioned 

 a large amount of discussion and have given rise to a somewhat volumi- 

 nous literature, have been variously assigned to deposits ranging all 

 the way from Cretaceous to post-Wicomico. Mr. Lewis Woolman 

 has very admirably summed up the literature regarding this forma- 

 tion as well as all the evidence which is at hand. 1 It is clear from 

 the facts which he brings forward that the Pish House clays are ex- 

 tremely late in geologic history. Mr. Woolman inclines to assign 

 them to the Pensauken of Professor P. D. Salisbury, in this respect 

 following Professor Salisbury's last utterance on this point. It ap- 

 pears that the reason for assigning the Fish House clay beds to 



1 Annual Keport State Geologist of New Jersey, 1896. 

 13 



