Upper Devonian Placoderrns of Ohio. — Claypole. 349 
as the following may be established. The concretions are un¬ 
like those below in the Fort Pierre formation in form, sub¬ 
stance and arrangement. Their most surprising feature is the 
elongation of the concretions and this in a uniform direction. 
These features can scarcely be traced to a difference in per¬ 
meability of the imbedding formation in different directions. 
Moreover the initiative influence causing them must have 
Teen of wide extent. Nothing has seemed more rational than 
to suppose these systems of concretion mark ancient beaches^ 
and that the determining influence for their consolidation lay 
in the segregating effects of wave action. We can easily con¬ 
ceive that the sand, upon the ancient shores, was thrown into 
small ridges parallel with the edge of the water. There would 
be a differential accumulation of fine material between the 
ridges, not only from the action of the waves but from 
the motion of rains and the effect of winds. Here also or¬ 
ganic matter would be likely to accumulate and this might be 
sufficient to determine the centers for concretionary action: 
and so the log-like concretions which we have described may 
be traced to the influences attending the ancient shores of the 
Laramie lakes. It is not improbable that further study may 
enable us to map out the shore lines of the bodies of fresh 
water attending the different stages of the Laramie forma¬ 
tion. It seems probable that fossils may be found preserved 
in these deposits, although none were collected during the 
past season. 
This discovery opens up an interesting and novel field of 
investigation of other formations. Circumstances, however, 
may not have been so favorable for the formation of such con¬ 
cretions upon marine shores because of tidal fluctuations. 
THE ANCESTRY OF THE UPPER DEVONIAN 
PLACODERMS OF OHIO.* 
By E. W. Claypole, Akron, Ohio. 
The remarkable fish fauna which suddenly appears in the 
Upper Devonian shales of Ohio furnishes an illustration of a 
principle that has now become familiar to the paleontologist. 
*Th e substance of this paper was delivered before the Ohio Stat° 
Acad emy of Science at its annual meeting at Cincinnati in December, 
1895. 
