On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 469 
an inch in width, is convex.’ On each side this convexity, parallel with the lateral 
margin of the crown, extends a flat groove, ‘1 of an inch in width ; beyond this 
the surface is again raised, and forms prominent lateral ridges, as high or a little 
higher than the central convex surface. The ridges form the boundary of the 
coronal surface. Beyond the crown proper there is on each side a bold extension of 
the bony structure of the base along the whole lateral surface. Commencing with 
a slight projection near the anterior lateral angle, they become gradually wider 
and more prominent towards the posterior angle of the crown, where they are 
developed into processes extending diagonally beyond the postero-lateral angle of 
the enamelled surface to a distance of +25 of an inch, and standing at a higher ele- 
vation from the base than the central convexity of the crown. Anterior margin 
corresponds ina greater or less degree to the form of the crown, convex in the 
centre, with depressions on each side, and a slightly prominent antero-lateral angle. 
Lateral margin of enamelled crown convex ; osseous extension beyond this nearly 
straight, with persistent expansion in breadth to the posterior angle; posterior 
margin rounded, forming with the sides a more or less acute angle; surface of 
crown uniformly punctate ; the minute orifices rather pentagonal than circular. 
Base, breadth 1°25 inch diameter from back to front in central part; 4 of an inch 
at each side, it expands to °6 of an inch, In its longest diameter the surface is 
broadly convex, in the opposite direction concave ; greatest thickness, ‘3 of an inch 
in the centre of the tooth; diminishes in each direction.; thinnest at the lateral 
extremities, which are 175 of an inch in thickness. . 
The form of the base does not correspond with that of the crown, as will be seen 
by a reference to the figures. The posterior circular portion of the crown pro- 
jects considerably beyond the surface of the base ; and in the same manner, but to 
a smaller extent, does the anterior margin. 
The several teeth vary considerably in size and form, and their surface configu- 
ration depends greatly on the amount of attrition to which they have been 
subjected. The specimen selected for description is of average size, and its crown 
in a good state of preservation. Examples occur in which the crown surface—i.e., 
the surface covered with enamel—is almost square in form, the average being 
about one and a half times broader than long. A few specimens, seemingly derived 
from very aged fish, are deeply worn, and present the appearance of three wide, 
deep, longitudinal grooves—one in the centre and one on each side—with smaller 
intermediate ridges, the front of the tooth very thin, and the anterior margin quite 
worn away. 
Formation and locality : Mountain Limestone, Armagh. 
Ex coll, Karl of Enniskillen. 
