Pennsylvania Geology Final Report Volume 1 1981

FOSSILS OF ONEIDA AND MEDINA NO. IV. 715
Chapter LIY. !
Fossils of Oneida and Medina No. IV.
The whole formation is remarkably destitute of remains:
of animal and vegetable life. The abundance of moUuscan'
and crustacean forms in the preceding Trenton and Hudson
River ages seem to have given place to a barrenness of all ,
living existence. Nothing but the stony casts of macerated
seaweeds are to be found in the two or three thousand feet
of rock strata of Oneida and Medina age in Pennsylvania.
These are so abundant in some places as to cover extensive
surfaces of the sandstone beds. Their forms are represented
on plate CXI, page 716. They are most abundant
in the upx)er division.* This species of seaweed is called
Arthroyhycus liarlani. The surfaces of great slabs torn
from the Tussey Mountain outcrops on the Juniata and
floated by ice down the bed of the river, are completely
covered with a network of its stony casts in high relief.
In New York State James Hall describes from the mid-
dle division of TV two small lamellibranch shells Cypricardla
orthonota, and ModlomorpJia alata (Conrad's Unio
prlmlgenhis)., and two small gasteropod shells, BelleropJion
trilohatus (Conrad's Planorbls irilobatus) and EuompJialus
{Cyclostoma., Pleurotomarld) pertietustus, the earliest
known appearance of this kind of shell. Dana says that
one of the most common Medina brachiopod shells is the
*Prof. W. B. Rogers, Geo. Va., 1884, p. 175, says that "near the upper limits
of the group, as well as in the shaly bands beneath, organic impressions are:
often abundantly discovered. The thin slabs of buff and olive sandstone
lying near the top are particularly rich in these remains, among -which may,
be noted as abundant a small globose tcrebratula, and at least two well
characterized species offucoides [sea weeds]. Cylindrical markings, simi-
lar to those of No. I, are often exhibited in great numbers in the more com-;
pact and fine-grained white or pinkish white strata.