642 BRITISH PALZZOZOIC FOSSILS. [ Pisces. 
Explanation of Figures—PI1. 8. K. fig. 6, average sized tooth, front view, natural size; fig. 7, ditto, 
section and perspective end view, natural size, shewing the much lower level of the ridge defining the base of 
the crown on the posterior than on the anterior base; fig. 8, ditto, portion of entire width of crown, from 
cutting edge to base, magnified three diameters. 
Po.yrHizopus Ppusitius (Af‘Coy). Pl. 3. K. fig. 2. 
Ref—M‘Coy, Ann. Nat. Hist. 2nd Series, Vol. II. p. 127. 
Desc_—Crown compressed, raised into a rounded obtuse lobe, less than half the width of the base in 
height; base of the crown forming a very prominent obtusely-rounded ridge; root divided into about ten 
small rounded fangs; surface of the crown coarsely punctured, a few of the punctures near the apex longitu- 
dinally confluent, so as to give it a slightly pectinated appearance ; width of crown two and a half lines. 
Easily distinguished by its small size, coarsely punctured surface, and the raised lobe of the margin of the 
crown. ‘There is a more distinct specimen than that in the University collection in the cabinet of Capt. Jones 
R.N., M.P. 
Position and Locality.—Rare in the carboniferous limestone of Armagh. 
Explanation of Figures—PI. 3. K. fig. 2, natural size, front view; fig. 2a, ditto, magnified two dia- 
meters; fig. 24, ditto, section and end view magnified two diameters. 
Genus. PRISTICLADODUS (M/°Coy). 
Gen. Char.—Base of tooth expanded at right angles to the crown, large, sub-semicircular, thick, coarsely 
osseous ; from the truncated straight edge of the base in front the crown rises as one large thick, sharply- 
pointed, compressed cone, with two denticulated cutting edges; lateral cones very few (? one on each side or 
none) ; surface of crown highly polished, and marked with fine longitudinal ridges, or smooth. 
These teeth agree with Cladodus in general character of crown, and the remarkable, large, horizontal, 
sub-semicircular base, but differ in the greater robustness of the principal cone, and most remarkably in the 
denticulation of the edges. The first specimen which I saw of this genus I supposed might have been the 
Carcharopsis prototypus of Agassiz’ lists, but subsequently finding a second species, which was still more 
nearly like Carcharodon, to which he likens his species, I hesitated to identify an undescribed fossil which I 
had never seen, more especially as neither of my specimens shewed any trace of the ridges at the base of the 
crown, alluded to by Agassiz; and the horizontally-dilated base was so remarkable a character, totally sepa- 
rating them from Carcharodon, and nearly allying them to Cladodus, that I could not suppose that the true 
Carcharopsis prototypus was identical with my fossils, or the one resemblance would not have been stated, 
and the other affinity overlooked. 
PRISTICLADODUS DENTATUS (M°Coy). Pl. 3. G. fig. 2. 
Desc.—Medial cone large, triangular, rather flattened on the outer side, and with a deep triangular, 
hollow, the base of which is parallel with, and a little above, the base of the tooth, which is narrow, arched 
upwards in the middle, and not prominent; the sides of the hollow are parallel with the sides of the tooth ; 
back of the crown rounded, strongly convex ; cutting edges set with a row of strong, equal, sharply defined, 
sub-cylindrical, obtusely pointed teeth, set at right angles to the edge (about three in the space of one line), 
about half their diameter apart, and rather longer than wide; base on inner side horizontally extended, thick, 
fibrous, almost semicircularly rounded ; surface of large cone smooth on the outside, faintly striated longitudi- 
nally on the inner side. Lateral cones unknown. Length of base about one inch; horizontal extension at right 
angles thereto five lines; depth of root one and half lines; height of cone about nine lines (tip imperfect) ; 
width about six lines. 
