DENTITION OF SOME DEVONIAN FISHES 39 
however, having been found by Professor Udden in the so-called 
‘“Kuomphalus bed” at Fairport, Muscatine county, which lies 
about eight feet below the summit of the Cedar Valley limestone, 
or Hamilton of Worthen and others. 
The plate is elliptical in outline, and moderately convex in 
an antero-posterior direction. Eight tuberculated ridges extend 
from the outer margin to about the center of the plate, the two 
anterior ones being the largest and elevated into a slight fold. 
Coronal surface considerably worn, and external margin partially 
broken. Tubercles conical and well separated, except those of 
the two anterior ridges, which are coalesced and worn on their 
summits. Total length of plate 3°". Named in honor of Pro- 
fessor Samuel Calvin, State Geologist of Iowa. 
3. D. costatus, sp. nov. (Fig. 4).—This plate agrees in size 
and general outline with D. calvini, but it has fewer and more 
widely separated coronal ridges which disappear before reaching 
the center of the plate. The distinguishing feature of this 
species consists in the elevated sharp ridge extending along the 
entire length of the inner margin, and separated from the 
remaining tuberculated ridges by a broad longitudinal furrow. 
This ridge appears to be of compound origin, or made up of 
three coalesced costae, of which the third counting from the 
inner margin is the largest. The two innermost costae are so 
faint as to be almost imperceptible on the steep face of the 
main ridge. The summit of the latter is sharp, and shows no 
evidence of being made up of tubercles. The tubercles of the 
five marginal ridges are also worn nearly smooth and more or 
less coalesced. But for the convexity (in a longitudinal direc- 
tion) of the coronal surface this might be taken for an upper 
dental plate. Several examples of this form have been obtained 
from the State Quarry fish-bed near North Liberty, in Johnson 
county, lowa. 
4. D. mordax, sp. nov. (Figs. 6, 8).— Dental plate attaining 
a length of over 3°", coronal surface gently convex, with six 
rows of very large, well separated conical or rounded tubercles 
which extend from the outer margin for a variable distance 
