NATURAL SCIENCES OP PHILADELPHIA. 49 



also made a collection of the better formed implements and 

 weapons. I examined this locality critically, to get some clue to 

 its antiquity. 



North, half a mile farther, another old site was reached, marked 

 by four large boulders, placed on end in some sort of rude order. 

 Crossing a small valley I reached another spot indicated by 

 similar rude monuments, and characterized by heaps of ancient 

 implements and chiplings of the most primitive kind ; these are 

 strewn in every direction on a grassy ridge sloping down into a 

 small valley. The boulders here and elsewhere may have been 

 placed as rallying points for the family circle of the " Pre-abo- 

 riginal" man. 



Located on points of land and extended promontories, these 

 ancient sites favor strongly the idea of location near some ancient 

 estuary or fresh-water lake ; whose vestiges the present topography 

 of this region favors. 



Note on the Shells accompanying the Flints. These represent four 

 species, three only determinable. My friend, T. A. Conrad, to whom I 

 submitted them, states that one of them is a Corbicula, the other a Eangia, 

 both estuary shells, "certainly not of later age than older Pliocene, or 

 possibly Miocene, but there is no trace of Rangia in the Eocene." E.D. 

 Cope. 



1872.] 



