482 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
width, almost reduced to a point and considerably curved inwards. It was 
probably attached to the lateral margin of the first pair of dental plates, its. 
accuminate anterior extremity conforming to the curvature of the jaw. 
There is still a triangular form (Pl. LVI, figs. 6,7) which has been found 
abundantly at Bristol, but is less frequent, or absent, from the limestones of 
Armagh. They may have occupied a position anterior to the large central teeth or 
on each side the most anterior one. A diagrammatic representation of the recon- 
structed jaw is here given from which the arrangement of the teeth indicated above 
may be interred. 
An occasional tooth exhibits a more or less gibbous surface of the crown, this 
appears to be an abnormal character, possibly due to some imperfection of the 
corresponding tooch of the opposite jaw. 
Group.—Copodontide, Davis. 
Tn the “ Poissons Fossiles,’ Vol. ILJ., page 174, an undescribed tooth is named 
Psammodus cornutus by Prof. Agassiz. The species is again referred to by 
Portlock in the ‘Geological report of Londonderry, Fermanagh, Armagh,” &c., p. 
466, and a figure is given of it (plate xiv.a, fig. 3). Portlock’s description consists 
of some observations made by Captain Jones as follows : “ Several specimens have 
been obtained where two teeth were in their natural position. The form is quite 
distinct from that of its congeners ; it is trapezoidal, having a long and a short 
side, the long being more or less concave, the short more or less convex, and, when 
joined together, the convex side of the one tooth fitted into the concave side of 
the adjacent one.” The specimen figured bears a great resemblance, to the figure 
of Characodus angulatus to be hereafter described. Psammodus cornutus is again 
