370 Description of a new Fossil Fish. 
rough, irregular surfaces, in the median line, and occupying the 
posterior portion of the fossil, are two smooth, divergent planes, 
slightly convex anteriorly, and turning forwards and outwards, 
forming, together, an arch two and a half inches long, one and 
nine tenths of an inch wide at their outer and most divergent 
edges, and seven tenths of an inch deep. These surfaces do not 
meet precisely at the top of the arch, but are separated by a small 
and. slightly elevated angular groove, divergent anteriorly and 
posteriorly, in which latter direction it seems to terminate in two 
slightly convex articulating surfaces, sloping off, posteriorly, into 
asmooth concave depression, forming the segment of an arch, 
which is separated by a bow-shaped and rather sharp ridge from 
the before mentioned ovoid condyloid surfaces. 
This arch formed, perhaps; the pharyngeal walls, while the 
angular groove in its vertex, which was a closed canal before the 
fracture of the fossil, served for the lodgment of medullary matter. 
Geological position.—With a view to ascertain the exact stra- 
tigraphical place of this specimen, we visited the quarry 4 few 
weeks since, and were fortunate enough to discover the rock con- 
taining the mould.of the fossil in question, so that its exact geo- 
logical position has been most satisfactorily ascertained. ‘This 
interesting relic was split out of a subcrystalline layer of light 
grey limestone, containing numerous Atrypa prisca and Spirifer 
euruteines (perhaps a small variety of Delthyris congesta) ; &S80- 
ciated with Strophomena euglypha, Pterinea cardiiformis, Fa- 
vosites spongites, Pileopsis tubifer? Calymene bufo, Tentaci- 
lites scalaris, Cardiwm aleformis, Calymene crassimarginata, 
Astrea flecuosa? and other fossils characteristic of the shell beds 
which form part of the chain of rocks in the bed of the Ohio riv- 
er at the falls, immediately under the water limestone found in 
digging the Louisville canal. On Lewis’s creek, however, the : 
water lime is absent, or represented only by a thin layer of chert, 
and the black slate is found in the bank of the creek, not four 
feet above the layer containing our fossil fish. This black slate 
is most likely the equivalent of the Genesee slate, and not of the 
Marcellus shale of the New York survey, since the underlying pele 
layers, though they contain several Onondaga and corniferous 
fossils, yield, also, many organic remains of the Hamilton group. — 
If this fossil fish should prove to be a new genus, as would | 
seem to be indicated, not only by the great size of the scutcheon 
