714 The American Naturalist. [August, 
every direction ; notably so in Bond's Retreat, Prince George county. 
The Cretaceous system is found in every deep washout or gully upon 
Mattawoman Swamp for ten miles above tide water ; the same is true 
of all the swamps between the Potomac and Patuxent rivers, and doubt- 
less beyond that river. Swainson's Swamp, the dividing line between 
Charles county and Prince George's county, gives Cretaceous clays over- 
laid by Miocene deposits; so does all that horizon. The Eocene and 
and Miocene can be found lapping the Cretaceous in all lower Maryland. 
Given these facts, it is in order to ask ; how is it that the Cretaceous 
has not been better worked up in this region ; and why have the deep 
cuts failed to give us the remains of some old saurian, — such as Hadro- 
saurus or Laelaps. Such a discovery would round out the Cretaceous 
most grandly, and might bring us out upon the Jurassic with an 
interest hitherto unknown. 
There have been already obtained in this deposit of Maryland from 
seventy to seventy-five species of fossil shells and casts of shells ; but 
no fossil plants except the one noted in this paper. 
We find but little to say upon the Cretaceous of the Virginia shore of 
the Potomac. We found upon examination years ago that the Acquia 
creek sandstone begins below Occoquan Bay, Fairfax county, Va., and 
runs out at Mt. Vernon, and that upon that formation nowhere upon 
the Potomac river could we find any other sign of the Cretaceous, 
except a deposit of very perfect leaves and stems at the White House 
—no black marl, no Cretaceous shells. That fact made the great cliff 
at Fort AVa-shington more incomprehensible. 
If our diagnosis is correct for the lower formation at Fort 
Washington — that it is Jurassic — then by a parity of reasoning that 
formation continues down at least to Smith's Point, Charles county, 
being occasionally lost below high water, and then rising from two to 
In the upper end of Charles county, upon the Potomac river, oi)posite 
Mt. Vernon, there are three thousand acres of land, a plateau from one 
to twenty feet above high tide, surrounded with an amphitheater of 
hills in which Eocene and Cretaceous are well developed. In the plain 
below there is no sign of fossils, neither Miocene, Eocene, nor Cre- 
taceous. 
To what formation then shall we assign this locality? If not Jurassic 
— then, what is it ? All the wells of this particular locality penetrate a 
variegated clay but no micaceous sand. — Oliver N. Bryan, Marshall 
Hall, Md. 
