Pisces. | UPPER PALAOZOIC VERTEBRATA. 643 
The strong, close, regular dentation of the edges easily separates this species from the P. Goughi; the deep 
triangular hollow in the anterior face, and the smoother surface, are also distinctive. 
Position and Locality.—Rare in the black upper carboniferous limestone of Derbyshire. 
Explanation of Figures.—P|. 3. G. fig. 2, tooth natural size, outer surface; 2a, base of ditto, on the 
inner side, seen from above; fig. 3, profile of another specimen, 
PristicLapopus GoucHt (M*Coy). PI. 8. K. fig. 11. 
Desc.—Crown compressed, triangular, moderately convex, marked with close, sharp, irregular, longitudinal 
striz, averaging five in one line, becoming obsolete at the apex, and close to the base of the crown: cutting 
edges sharp, marked with broad, slightly-marked, tooth-like undulations, nearly their width apart, and gradu- 
ally blending at their base into the edge, being obsolete in the upper third of the cone; lateral cones two, 
robust, subcylindrical, striated like the principal one. Height of principal cone, one inch two lines; width at 
base eight lines; height of side cone five lines; width at base three and half lines; width of whole tooth one 
inch three lines; lateral breadth of base six lines; lateral breadth or thickness of principal cone four lines. 
Position and Locality.—Very rare in the sandy lower carboniferous schists of Kettlewell, Kendal. 
Explanation of Figures.—P\. 3. K. fig. 11, front view, natural size, (apices of the cusps slightly im- 
perfect). 
Genus. PSAMMODUS (4g.) 
Gen. Char.—Teeth oblong, wide, thick, flat above, without cones or keels; surface porous or minutely 
rugose; base of the same form as the crown, very thick, coarse, osseous. 
The punctures of the surface are of the same size and distance apart as the vertical medullary tubes, 
and I have repeatedly traced their identity ; (Prof. Owen having thought differently in his Odontography). I 
have however clearly seen on occasional spots of the surface that they were originally covered with a thin 
impervious layer of ganoine, as I have stated when describing the allied genus Cochliodus. 
PSAMMODUS CANALICULATUS (Coy). PI. 3. G. fig. 12. 
Ref—M “Coy, Ann. Nat. Hist. 2nd Series, Vol. II. p. 122. 
Dese.—Tooth oblong 
g, generally about twice as long as wide, the two long sides straight and parallel; one 
of the short sides or ends very convex, the other equally concave (for articulation); the crown of the tooth 
concave along the middle, the two long margins being prominent and rounded; there is generally a consider- 
able hump-like elevation near the convex end; surface roughly wrinkled transversely, the ends generally more 
or less rudely plicated longitudinally. 
This remarkable tooth is much allied to the P. rugosus (Ag.), but is strongly distinguished by its ends 
being formed for articulation, one convex, the other concave, instead of being straight, as in that species ; 
also by the strong longitudinal plication of the surface near the ends, and the peculiar curved swelling near 
the convex extremity. When the ends are wanting, it is distinguished by its mesial concavity (the other 
being convex), and by the minute rugze of the surface running across instead of in the direction of the length. 
When much worn the surface becomes polished and porous, as in the P. porosus (Ag.), and as we constantly 
see on the prominent parts of the P. rugosus (Ag.) Length generally about two inches. : 
Position and Locality.—Rare in the carboniferous limestone of Armagh, 
Explanation of Figures.—P1. 3. G. fig. 12, tooth, natural size. 
PsAMMODUS CORNUTUS (4g.) 
Ref.—Portk. Geol. Rep. t. 14a, fig. 3. 
Desc.—Trapezoidal ; lateral sides long, straight, equal, posterior side usually shorter than the lateral 
ones, and concave, the latero-posterior angles being often a little produced in the line of the sides; anterior 
