180 PALEOZGIC FISHES OF NORTH AMERICA. 
This discovery removes all doubt in regard to the character of the 
organs, and shows that Mazodus was an Elasmobranch fish, with strong 
pavement teeth, fitted for crushing mollusks and crustaceans, or for triturat- 
ing vegetable tissues; a Shark, perhaps allied to Psammodus, but differing 
from that genus in the pattern formed by the pavement teeth, and still more 
in their anatomical structure. 
Mazopus KEPLERI, n. sp. 
Plate X XI, Figs. 1-3. 
Teeth of various sizes and shapes, largest two and a half inches long 
by two inches wide and half an inch or more in thickness, outline pentago- 
nal or subtriangular, anterior angle subacute, lateral angles prominent, pos- 
terior angles obtuse and rounded, with a deep sulcus between them, or united 
to form an arched posterior extremity ; upper surface arched in both direc- 
tions; when unworn, granulated or pitted; under surface slightly concave, 
coarsely pitted, and more or less lobate or tubercled; -sides beveled or 
arched, and marked by irregular furrows, separated by pustulous or tumid 
ridges; whole surface polished; substance dense and enamel-like. The 
smaller teeth were arranged around the larger, and are trapezoidal, subtri- 
angular or elliptical in outline, and from half an inch to an inch in diameter. 
The angular outlines of these teeth will at once distinguish them from 
those with which they must be generically united, viz, Helodus rudis, Agas- 
siz,' and McCoy,’ and J. W. Davis,* as also with that described and figured 
in the Geology of Illinois.* 
The smaller of the two specimens first found (Fig. 1) is absolutely 
complete in all its parts; the surface being highly polished and having suf- 
fered no wear. The upper surface of the larger specimen is less perfect in 
its preservation, and shows a double depression, which seems to be the result 
of attrition. 
The under surface of these teeth is concave and peculiarly pitted and 
furrowed; that of the larger one somewhat lobed, and showing considerable 
1Ann. Nat. Hist., 2d series, vol. 2, p. 123. 
2 Brit. Pal. Fossils, 1854, p. 631, pl. 3, fig. 4. 
3 Fossil Fishes Carbonif. Limestone, p. 157, pl. 59, figs. 11, 11% 
4Vol. 4, p. 369, pl. 2, figs. 5, 5°. 
