Pisces. | UPPER PALAZOZOIC VERTEBRATA. 619 
rather more pointed lower end of root; crown flattened, bent at an angle of 120° with the long root, which is 
nearly straight in profile; surface of the crown finely punctured, as in Psammodus ; root hard and polished, with 
two or three obscure longitudinal furrows, almost entirely surrounded by a raised marginal extension of the 
thick, prominent, simple, coronal ridge; the posterior side is concave. Length six and half lines, width six lines, 
length of crown two lines. 
Besides its oblong form this species is very remarkably distinguished by the continuation of the coronal 
ridge into a raised margin to the outer face of the root, which latter was in consequence mistaken for the grinding 
surface by Agassiz, and thus gave rise to his specific name. Capt. Jones, on partially clearing the true grinding 
surface (see Portlock, Geol. Rep. p. 462), supposed it to be a Psammodus, but I have now cleared and figured 
the whole crown and concave posterior side, proving it to be of the Petaloid section of Chomatodus. 
Position and Locality—Rare in the carboniferous limestone of Armagh. 
Explanation of Figures—P1. 3. 1. fig. 1, front view, natural size, of average tooth; fig. 1 a, do. profile. 
Genus. CLADODUS (Ag.) 
Gen. Char—Teeth with a broad, horizontal, semicircular, thick, bony, coarsely fibrous base, rounded 
behind, truncated in front; crown divided into long, sharp, subulate conical points, arranged along the straight 
truncated edge of the base; medial cone much larger than the secondary ones, which latter increase in size 
from the mid-cone to the ends; all the cones sulcated longitudinally, and either circular in section, or with 
simple cutting edges slightly compressed. Fin-rays unknown. 
Viewed in front those teeth resemble Hybodus, but the small lateral cones increase in size from the great 
mid-cone to the ends, instead of decreasing; and when seen behind the great dilated base of the present genus 
separates it completely. This dilated base is not alluded to in Agassiz’ generic character. 
CLADopUS Laivis (AZ°Coy). PI. 3. K. fig. 5. 
Ref—M Coy, Ann. Nat. Hist. 2nd Series, Vol. II. p. 133. 
Desc.—Principal cone very thick, slightly oblique, its height equal to half the width of the root ; secondary 
cones two on each side, very strong, the outer largest and divaricating, nearly half the length of the principal 
cone; all the cones obtusely rounded at the summit, very slightly tapering, and the height of each slightly 
exceeding the width of its own base; base of the crown and osseous root concave; surface of all the cones 
smooth, highly polished. Width of crown nine lines, height of principal cone from the basal margin five lines. 
This closely resembles the C. marginatus (Ag.) in size and form, but the cones taper less, and the species 
is fully distinguished by its smooth surface, destitute of the coarse longitudinal plaits or strize of that or the 
allied species. 
Position and Locality.—Carboniferous limestone of Armagh. 
Explanation of Figures.—P1. 3. K. fig. 5, average-sized tooth, natural size; middle cusp worn; lateral 
cusps broken at apex. 
CLADODUS MIRABILIS (Ag.) 
Ref. and Syn.=C. mirabilis Ag. Pal. Foss. t. 22 4, f. 9 to 13+ CO. marginatus id. ib. fig. 18 to 20. 
Desc.—Semicircular, base very thick and coarsely osseous; crown having the middle cusp very thick at 
base, and only slightly compressed, the lateral edges being less acute than in the C. striatus; abruptly tapering 
towards the apex, and slightly inclined backwards ; ridges of the surface coarse, thread-like, widely separated, so 
that three or four occupy a space of one line ; secondary cones very thick, tumid, very abruptly tapering to their 
apices, very rarely more than two on each side, their surface striated like that of the principal cone. Average 
