Three Great Fossil Placoderms of Ohio. — Claypole. 91 
Hertzer deserves great credit for the care and skill with which 
hundreds of fragments were carefully gathered and each 
cemented into its proper place. A head and mandible of 
Dinichthys restored nearly to their former integrity now con- 
stitute the pride of the collection of the School of Mines of 
Columbia College."— p. 320. 
Following this remarkable outburst of ichthyic life comes 
the great mass of the shale, a greenish layer of several 
hundred feet in thickness and almost devoid of life saving 
here and there a few lonely brachiopods representing very 
few species. Its poverty is most remarkable in contrast with 
the preceding, and not less so when we regard the period that 
followed it after this long interruption. The story of the 
fishes is again taken up in the black Cleveland Shale at a 
higher level, and new genera and species of closely related 
but different forms are found in its concretions. 
What became of the great fishes during the long interval 
that elapsed between these dates is unknown. Similar depos- 
its were going on in the seas and so far as we know similar 
conditions generally prevailed around them, but the huge 
placoderms of the early stratum disappeared and not a bone 
or a fragment has yet come to light in Ohio that indicates 
their continued existence. A very few detached plates and 
pieces of plates have been described from other states, suffi- 
cient to remove all doubt of their survival were such doubt 
in the present day at all possible. But these are all. 
Several hundred feet of shale — the Erie Shale of Newberry 
— contributed to fill this ancient sea or rather gulf, whose 
bottom subsided as deposition progressed (perhaps its cause) 
and yet no sign of ichthyic life appears. It is not probable 
that the muddy shores of the Appalachian Gulf were forsaken 
by the descendents of the finny tribe that had frequented 
them in previous ages and whose progeny returned in later 
times. It is more likely that all the relics were destroyed 
after their death owing to unfavorable conditions. For it is 
always to be recollected in this connection that it forms no 
part of Nature's proceedings to preserve the relics of Iht 
dead. "Dust to dust and ashes to ashes" is her motto. She 
sets her agents of destruction at work as s i as the life has 
left the body and they quickly reduce it in most cases to an 
