FISHES OF THE DEVONIAN AGE. 71 
remarkable for their close proximity and regularity, but the jaws from Del- 
aware are much smaller and the teeth are apparently less acute. They are 
evidently closely allied, if not generically identical. 
In both the Huron and the Cleveland shales we occasionally find, scat- 
tered or in coprolites, rhomboidal polished scales similar to those of some 
species of Palconiscus, and I have supposed it probable that they belonged 
to precursors of the Paleoniscidee so abundant in the overlying rocks. 
These little jaws may naturally be supposed to have appertained to 
the same fishes with the scales, but it is evident that the fishes which carried 
the jaws could not have been Paleoniscids, since the form is that which 
prevails among all the larger fishes of the group of Dinichthidze, namely, 
the posterior half spatulate, smooth, evidently once buried in integument 
and sheathed by cartilage; the exposed portion thicker, denser, ornamented, 
and carrying along the upper margin a single row of nearly equal teeth, 
developed from the condensed jaw-tissue. 
In the Palzeoniscidee, on the contrary, the dentary bone is relatively 
much longer, is spliced on to the angular and articular portions of the man- 
dible, and carries several rows of acute, conical teeth of unequal sizes. 
But more material will be required before anything positive can be said in 
reference to the fishes which bore the jaws I have called Callognathus. 
Formation and locality: Cleveland shale; Lorain County, Ohio. Col- 
lected by Mr. J. Terrell. 
OnycHopus ORTONI, n. sp. 
Plate XIX, Fig. 1, 1. 
Intermandibular bone one and a half inches long by one-half an inch in 
width and one-quarter of an inch in thickness; long-ovoid in section, broad- 
est above, regularly arched in outline; its superior surface set with six 
equally spaced, recurved, acute, enameled teeth, implanted in the bone along 
the median line; these teeth are about equal in size, being one inch in 
length from point of insertion; the surface enameled and highly polished ; 
section slightly compressed laterally ; anterior margin rounded; sides flat- 
tened, and marked with three longitudinal planes, giving a somewhat angu 
lar section; the acute apex is turned forward. 
