Upper Devonian Placoderms of (Xhio. — Claypole. -\~>\ 
i DinicJithys terrelli 
'A 16' -, Gorgonichthys 
< I Titanichthys rectus 
03 q, \ Dinichthys intermedins 
g '/ Titanichthys 
1 -.-, ( Dinichthys intermedins 
't- ' / Coccosteus 
Only two stations have yet been worked, so that our know- 
ledge of these remarkable forms is very restricted, and we 
may reasonably anticipate great additions to the number of 
species and to the details of their anatomy when more workers 
are in the field and a wider region is searched. 
But with every addition to this marvellous fauna its sudden 
emergence only comes into more striking prominence by con- 
trast with the barrenness of the rocks immediately underlying 
the Cleveland shale. Whatever views may be taken of the 
general relations between these two the fact remains that in 
northern Ohio only a few feet of sediment separate the green- 
ish Erie, in which no fish remains occur, from the black 
Cleveland shale with its rich ichthyic fossil fauna. It is a 
step from death to life. So far as is yet known the latter con- 
sists of the following species: 
Dinichthys 9 species Brontichthys 1 species 
Titanichthys 4 " Glyptaspis 1 " 
Gorgonichthys 1 " Diplognathus 1 " 
Coccosteus 1 " Mylostoma 2 " 
Trachosteus 1 species 
The contrast of these 21 species from the Black shale with 
the total absence of fish fossils from the greenish shale imme- 
diately below it is striking, and of itself is sufficient to mark 
some great change in the conditions of deposition. What 
these were we cannot just now explain. 
Alongside of this remarkable lish fauna must be placed an 
almost total lack of every other organic trace. In the smooth 
shales and in the concretions alike the discovery of any other 
fossil is an exceedingly rare event. In all his years of work 
Dr. Clark has shown me only a half dozen specimens besides 
fishes. These consist of a la mel 1 i bra ncll shell. Eodon In Hi. 
striatus, and a few small fragments <Jf Lepidodendron spy. Dr. 
< Jlark's son has also found two specimens of a cephalopod very 
