THE NATIONAL INSTITUTION. 
17 ? 
of the Patuxent, below Benedict, As we trace the strata south, the species found 
on St. Mary’s river, make their appearance, and yet the group of the latter locality 
compared with that nearest to Benedict, will be found to hold scarcely one kind of 
fossil in common. I have seen from Italy and Great Britain, organic remains so 
similar in general character, though mostly of species different from those of the 
medial tertiary of the Union, that I could not doubt the geological relations to be 
the same, and hence the inference, that a comparison of tertiary formations in dis¬ 
tant countries, will exhibit by peculiarity of forms, and not unfrequently identity of 
species, the evidence of having originated at the same period of time. According 
to the classification of formations upon the relative amount of recent and extinct 
forms, that which we have designated as the medial tertiary formation, comes 
within the limits of the miocene. Yet, it is singular that a greater amount of dif¬ 
ference should exist between the eocene and miocene, or two consecutive divi¬ 
sions of the tertiary, than obtains between secondary and tertiary, or between 
the devonian and carboniferous systems. No single form connects the lower 
with the medial tertiary formation, even when they are in juxtaposition ; yet three 
species of organic remains link the upper secondary with the lower tertiary 
group of this country. It is, therefore, not unlikely that some deposits may yet 
be found, which occupy a position between the lower and medial tertiary, con¬ 
nected with both by the interchange of a certain number of forms, as is the case in 
Europe. There may be such a formation, circumscribed within narrow limits, or it 
may have been swept away in one of those unfathomed revolutions, which have so 
mysteriously and so frequently passed over the surface of the globe. 
The following table will exhibit the most prominent characters of the supracre- 
taceous formations of the Atlantic coast, premising, however, that of the two new¬ 
est of these, the relative position is yet undetermined. 
Table of Atlantic Svpracretaceous Deposits. 
Elevation above 
the sea. • 
Localities. 
r 
Upper 
Tertiary. 
Medial 
Tertiarv. 
Lower J 
Tertiary.! 
200 
feet. 
Pleistocene, 
Organic remains chiefly of existing spe¬ 
cies, supposed as a group to show evidence 
of a lower temperature in the period of 
their deposition than prevails now in the 
same parallel; yet most of the species live 
on the coast of Massachusetts. 
1 
Lake Champlain; St. 
Lawrence river. 
15 
feet. 
Or 
Organic remains, the same as occur re¬ 
cent in the neighboring waters. 
Raritan bay; many of 
the beds of Ostvea vir- 
giniana in Maryland and 
Virginia. 
12 
feet. 
Post- 
Pliocene. 
O rganic remains chiefly of recent species, 
but some of which now exist only in more 
southern latitudes, as the Gulf of Mexico. 
The most remarkable of these is Gnathodon 
cuneatus. 
Meuse river, belowNew- 
bern, N. C.; beds of Gna¬ 
thodon on Potomac, St. 
Mary’s county, Md. 
100 
feet. 
Miocene. 
Organic remains with about seventeen 
per cent, of known recent species. No form 
of the lower tertiary found no this division. 
Eastern counties of Ma¬ 
ryland, Virginia and N. 
Carolina. 
200 
feet. 
Eocene. 
Organie remains similar as a group to 
those of the calcaire grossiere and London 
clay ; many species identical with the eo¬ 
cene fossils of the Paris basin. No recent 
species. 
Claiborne, Al.; Natchez, 
Mis.; Washita river, La.; 
Fort Washington, Pisea- 
taway, and Upper Marl¬ 
borough, Maryland. 
