FISHES OF THE DEVONIAN AGE, 3D 
outline, and seem to have been thin cones of bone or enamel, supported by 
cartilaginous centers. As the latter are decomposed, the sides, which were 
once widely separated, were brought together or crushed in like broken 
shells. 
The external surface of these plates is tuberculated in a variety of 
ways. In some instances the tubercles are large, scattered, smooth and 
rounded, and resemble pustules. In other cases they are irregular and 
crowded; while occasionally they are in rows, the interstices between them 
being beautifully chased and ornamented. Along the margins of the spi- 
nous extremities of the plates the tubercles are elongated until they become 
conical denticles. 
On Pl. XXXI, Figs. 5, 5* represent a large pair of plates in their rel- 
ative positions; Fig. 5", two such pairs. A number of groups of this kind 
have been found, though the individual plates are oftener met with entirely 
separated from their connections. The extremity of Fig. 5 is not quite com- 
plete. Other specimens show that it was produced to a moderately acute 
flattened point. This narrow end was beautifully denticulated, was tuber- 
culated on both sides, and evidently projected from the body or head as a 
defensive spine. 
Formation and locality: Corniferous limestone; Delaware, and San- 
dusky. Ohio. 
Genus ACANTHASPIS, Newb. 
This name is used to designate certain cranial bones of what seems to 
have been a Cephalaspid, found in the Corniferous limestone of Ohio. Con- 
siderable variety is noticeable in the shape of these plates, and it is apparent 
that they formed parts of a tessellated cranium. They are generally some- 
what oblong in form, the greater part of the plate being quadrangular, while 
one of the margins is oblique and prolonged into an acute point, and to this 
margin is spliced a carinated, toothed spine, sometimes four or five inches in 
length. These spines bear considerable resemblance to the dorsal defenses 
of some extinct Sharks. They might, indeed, under some circumstances be 
accepted as the spines of Ctenacanthus, since they are marked with pectinated 
ribs much in the same way, but their attachment to bony plates and the 
