APPENDIX. 
25 
South Carolina. It was one contemporaneous sea bottom, holding living 
individuals of certain species throughout its entire length, and which is 
characterized by some of its species closely resembling existing ones, but 
many more having no affinity with American shells. In it culminated the 
geneiaBcsvcoN and Mercenaeia, species of which characterize it in almost 
every locality. The Post-Pliocene above it is easily recognized by having 
none but existing species of shells. The Territory formations in North <?*V ' ■ 
America are admirably distinguished by definite boundaries and a vast 
difference in their groups of organic remains. The formation which im- 
mediately preceded the Miocene is what I have named Oligocene, to dis- 
tinguish it from the Eocene below and the Miocene above it. Some 
writers object to the name Oligocene, I fear from want of knowledge of 
the fossils it contains, for if a unique fauna entitles a group of strata to a 
separate and independent name, none is more worthy of it than the^ icks- 
burg Group, which contains not one species of any animal, shell or coral 
in common with either the Eocene or Miocene. The corresponding beds 
in Europe are named Oligocene by Beyrich and Older Miocene by Lyell ; 
but the affinities of the Vicksburg shells are with the Eocene forms and 
are widely different from the Miocene, and therefore I protest against the 
term Miocene being applied to the Vicksburg group. It has a higher 
claim to be named Upper Eocene, but it is far better to follow what we 
observe in Nature and classify it by a name which has no reference to 
other formations, with which it holds no species in common. 
In the Eocene Check list, published by the Smithsonian Institution, I 
made the error of including (htrea sclloeformis in the Older Eocene. It 
should be in the Claiborne or Newer Eocene group, and the bottom of the 
bed which holds it is the line of division between Older and Newer 
Eocene. This latter group has a strictly marine fauna, and when it was 
elevated so that lagoons were formed, the Ostrea sellceformis made its 
first appearance, and continued its existence into the Claiborne sands but 
sparingly, and soon disappeared. It continued to live while a deposition 
ot TO feet of clay was deposited with scarcely any associated shells of 
other species, and then a gradual sinking of the deposit occurred, restoring- 
sea water with its vast abundance of marine shells, and forming a new 
epoch in the Eocene series. O. oellceformis is very rare in North Carolina, 
but it is not uncommon in Virginia and South Carolina. 
The Claiborne Group I regard as Newer Eocence ; the Jackson Group 
as Older Oligocence, and the Vicksburg Group as Newer Oligocene. The 
surveys and explorations in North America have been continued so long, 
that we may fairly assume the above divisions or formations to represent 
the succession of the groups, without supposing intermediate formations 
to have been deposited and swept away -without leaving a trace behind. 
4 
