FISHES OF THE DEVONIAN AGE. 59 
Mr. Hertzer also found in these concretions the bones of smaller indi- 
viduals of Dinichthys, probably a distinct species, inasmuch as the form of 
the dorsal shield is different and the neck is relatively much longer than in 
D. Hertzervi. 
F In the shale outside the concretions Mr. Hertzer discovered the greater 
part of a dorsomedian plate which apparently belonged to a Pterichthoid 
fish. This was about eighteen inches long by thirteen inches wide, some- 
what six-sided and short coffin-shaped; the exterior surface is set with large, 
smooth tubercles which may be compared to split peas. I have named this 
fish Aspidichthys, and have supposed that this was the central plate of a dor- 
sal carapace, as it corresponds in form to that plate in Pferichthys, but is a 
hundred times larger in area. A few fragments of plates bearing this pecul- 
iar tuberculation have been found in the Huron shale at the Falls of the 
Ohio, but this seems to be the rarest of all the great Placoderms of which 
the remains are found in our Devonian and Lower Carboniferous rocks.* 
No one has thoroughly explored the exposures of the Huron shale in 
Ohio and Kentucky, and yet fragments of the plates of fishes have been 
obtained from so many localities, that we may be sure a rich harvest will 
some time be gathered there. In the valley of Paint Creek, near Chillicothe, 
and in the cliffs bordering the Scioto and the Ohio near Portsmouth, splendid 
exposures of this shale may be seen, and there is little doubt that fishes may 
be found at all these localities. 
In central Kentucky Mr. William Linney has found in the Huron shale, 
which forms a kind of border to the blue-grass region, many fragments 
of large fishes; among other things two dorsomedian plates much like those 
of Dinichthys, and quite as large. Outline sketches of some of these have 
been kindly sent to me by Mr. Moritz Fisher, of the Kentucky Geological 
Survey, but I have been unable to identify them with any of the fish 
1 Prof. A. von Koenen, of Géttingen, has obtained from the Devonian rocks of Germany what 
seems to be the central dorsal plate of another species of Aspidichthys, which he has called A. ingens, and 
described in vol. 30, Abhandl. der Kénigl. Gesell. der Wissen. zu Gottingen, p. 34, pl. 3, fig. 1. I 
have had an opportunity of examining this specimen, and confirm fully von Koenen’s view of it. It 
scarcely differs from the plate discovered by Mr. Hertzer, except that the tubercles are much less uni- 
form in size and the anterior margin is produced in a kind of point at the center. This plate is very 
strongly arched, while that obtained at Delaware is nearly flat; but this is donbtless in a large degree 
due to vertical pressure. 
