476 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
postero-lateral angles obtuse. Base, not well defined ; does not appear to be large 
or thick. 
Characodus cuneatus is sufficiently distinct from C. angulatus ; and, whilst pos- 
sessing all the generic characters of the latter, its squarer outline, less produced 
lateral borders of the crown, and the folding of the ganoine over the base on the 
interior and lateral margins, and its crenated borders, vonstitute undoubted specific 
differences. 
Formation and locality : Carboniferous Limestone, Armagh. 
Lx coll. Karl of Enniskillen. 
Genus.—Pinacodus, Ag. MSS. 
Pinacodus—L. Agassiz, 1859. MSS. Enniskillen Collection. 
Palatal teeth, small, more or less cuniformly oblong in outline. Crown, flat or 
slightly curved. Coronal surface punctate or minutely rugose. Anterior margin, 
concave. Lateral margins straight or a little convex, diverging posteriorly ; posterior 
margin convex (in P. gelasimus concave). Base not well exposed, moderately thick,. 
and co-extensive with the crown. 
A second tooth, smaller than the one described, was connected to its anterior 
extremity, less than one-half the length of the larger tooth; its anterior and 
posterior margins are convex, the latter closely fitting to the concave margin of the 
first tooth ; surface convex, with raised lateral border, and conforming generally 
to the shape of the crown of the adjoining one, front portion worn by attrition. 
The genus Pinacodus is more closely allied to that of Characodus than any other, 
and it is perhaps possible that the two genera may at some future time be shown 
to have only specific differences ; the specimens at command do not afford sufficient 
evidence of this close relationship to justify their amalgamation at the present 
moment. The crown of Pinacodus is flatter than that of Characodus, and its 
lateral borders less prominent ; the posterior margin is convex in the one, concave 
in the other, and in Characodus the anterior margin is not hollowed for the 
accommodation of a second palate, which is perhaps the characteristic of greatest 
generic importance in Pinacodus. 
'The form of Pinacodus resembles that of Rhymodus in some respects, The 
latter possesses a deep sulcus, separating a portion of the anterior face of the tooth, 
which is probably a second tooth, as with Pinacodus. If this be the case, however, 
the smaller anterior palate differs very much from that of Pinacodus. It does not 
appear to have extended the whole breadth of the larger tooth, but becoming 
laterally acuminate, to have ended before the margin was reached. The basal 
portions of the tooth of the two genera are quite distinct ; that of Pinacodus is 
comparatively thin, and similar in shape and contour to that of the crown, whilst 
in Rhymodus the base equals in thickness the length of the coronal surface, 
and extends considerably beyond its lateral margin on each side. 
