370 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 
triangular bone supported, directly or indirectly, the great 
pectoral spines. | 
There are found also frequently associated with the remains 
of Gyracanthus large thin layers or patches of matter, almost 
entirely composed of minute compressed bodies, of which 
there are two kinds. One, much smaller than the other, and 
by far the more numerous, is upwards of one-twentieth of an 
inch high and not quite so broad; it has usually two, some- 
times three, conical, recurved, diverging points rising from an 
expanded base. ‘The large kind is usually one-tenth of an 
inch high, and is somewhat wider at the base; it is sometimes 
a little larger, but more frequently much smaller. It is much 
compressed, and the base is considerably widened; the upper 
margin is divided into from four to seven much recurved 
conical denticles, which are sharp-pointed, and have four or five 
stout longitudinal ridges on the arched or dorsal surface. Several 
large patches of these bodies have occurred, one of which mea- 
sures twenty inches by fifteen inches. It is therefore pretty 
clear that they cannot be teeth, which are not usually found 
together in such vast multitudes; they are much more likely 
to be dermal tubercles, and these patches to be the remains of 
the skin of Gyracanthus. It should also be mentioned that 
Cladodus mirabilis has occurred three or four times at News- 
ham, and always associated with these dermal patches. May 
it not, therefore, prove to be the tooth of Gyracanthus? 
Note.—Mitrodus quadricornis of Prof. Owen (pl. 3) is un- 
doubtedly nothing more than the larger kind of these dermal 
tubercles. In size, proportion, and form it agrees exactly with 
them ; and in the minute structure there is no difference what- 
ever, as is demonstrated by the numerous sections of them 
which we have had the advantage of examining. ‘This 
“minnow,” then, of our shales is found to be identical with 
Gyracanthus tuberculatus, perhaps the largest fish of the coal- 
measures, 
In the figure of Mitrodus only a small portion of the den- 
ticles is shown ; the points, being strongly recurved, are neces- 
sarily cut: away in such a section as that represented. It is 
only the base of the toothlets that Prof. Owen has seen; and 
consequently his knowledge of the true form must be v 
impertect.. The angles represented at the margin of the den- 
ticles indicate the external ridges described above. 
Diplodus gibbosus, Agassiz. 
This is a common fossil at Newsham and Cramlington, and 
is usually found in connexion with a thick granular layer of 
