20 INTRODUCTION. 
ness than we can at present, the parallel of these de- 
posits, and men of science being now engaged in Mary- 
land, by order of the legislature, to make geological re- 
searches, we may hope, ere long, to have this, with other 
deposits of the state, better known than they are at pre- 
sent. © The deposit at Vance’s Ferry, South Carolina, has 
been observed by Dr Blanding to contain one of the 
characteristic fossils of the Eocene Period, the Venericardia 
planicosta, and in the cabinet of that naturalist I have 
observed several other genera, which distinctly identify it 
with that epoch. 
It is a matter of considerable doubt, if any Tertiary de- 
posit, contemporaneous with the Miocene Period of Mr 
Lyell, has yet been observed in our Formations. The de- 
posits of Bourdeaux, Dax, Turin, Ronca, Vienna, and some 
other places on the Continent, are of this period, but it is 
not, I believe, known to exist in England. Future inves- 
tigations may, in the vast extent of our southern deposits, 
discover its existence. 
The Older Pliocene Period of Mr Lyell, finds its equiva- 
lent, I think, in the well known deposit of St Mary’s, 
Maryland. Mr Conrad, who has carefully examined the 
deposit at this place, has given us a catalogue of fifty-six 
speciesobserved there by himself. Of these, about one third 
are known to exist on our coast; but some of them in more 
southern latitudes. The deposits of York Town, Smith- 
field, and Suffolk in Virginia, and those of Easton and St 
Mary’s in Maryland, as well as that of Cumberland county, 
in New Jersey, are referred by that geologist to the Upper 
Tertiary, and, without doubt, belong to the Older Pliocene 
Period of the Tertiary. 
Of the Newer Pliocene Period we have an equivalent 
in the deposit at the mouth of the Potomac; the dis- 
tance of which, in a direct line, is about forty-five miles 
from the ocean, the intervening country being low and 
