562 The Formation of Cape Cod. [September, 
however, I had found a fragment of the same shelly rock in the 
fossiliferous layer of gravel first described, one mile south from 
the head of Pamet river; and subsequently I found two other 
bits of it at the most northern locality of shelly gravel and sand. 
last mentioned. These pieces were enclosed in stratified beds, in 
each case some thirty feet above the sea, evidently occupying 
their original position in the thick deposits of modified drift which 
form this part of Cape Cod. The fossiliferous pebbles are thus 
shown to have been brought to their present place by the same 
agencies which accumulated these beds of gravel and sand. As 
no similar formation is known on the land to the north from 
which they could be derived, it seems quite certain that they rep- 
resent beds that were in place at the bottom of Massachusetts f 
bay, whence they were ploughed up by the ice-sheet and carried 
forward and upward in it, till at its final melting they were depos- 
ited here. 
The scarcity of these fragments is such, that a search of six or 
seven hours was required, where the whole bank, one hundred 
and fifty feet high, was plentifully strown with pebbles, to find a 
dozen of them. These, to the amount in all of perhaps twenty 
pounds’ weight, were presented to the Boston Society of Natural 
History, and their fossils have been examined by Mr. W. O. 
Crosby, who regards them as satisfactory proof that the rock is 
Eocene Tertiary. The species which he has identified are Camp- 
tonectes calvatus Conrad, found in the Middle Eocene of South 
arolina; Venericardia planicostata Lamarck, found in the 
Lower Bocede of Virginia; probably V. parva Lea, found in — 
the Eocene of Alabama; and another similar to the common 
V. alticostata Conrad, occurring with the last; probably Ostrea 
divaricata Lea, of Middle Eocene in Alabama, though per- 
haps young of O. selleformis Conrad, a characteristic species 
of the Lower Eocene from that State to Virginia ; another, prin- 
cipally in fragments, is similar to the recent O. virginiana Lister; 
another species of this genus is represented by fragments of shell 
fully one and a half inches thick, not enclosed in the matrix of 
calacreous sandstone like the rest, but found with these shelly 
pebbles on the cliff a half mile south of the lighthouse, and also 
in the shelly gravel south of Pamet river ; an Anomia similar to 
A. tellinoides Morton, of the Cretaceous in New Jersey, Alabama 7 
-o 1 Proceedings of Boston Society of Natural History, Vol. xx. 
