FISHES OF THE CARBONIFEROUS SYSTEM. 165 
Formation and locality: Cleveland shale; valley of Vermilion River, 
Erie County, Ohio. Collected by Mr. Jay Terrell. 
MyLosToMA VARIABILIS, Newb. 
Plate XV, Figs. 1-5; Plate XVI, Figs. 1-4. 
Mylostoma variabilis, N.; Trans. N. Y. Acad. Sci., vol. 2, 1883, p. 146. 
Inferior dental plates probably of several forms, the larger ones long- 
ovoid in outline, three inches long by one and an eighth inches wide in the 
broadest part, supported on and anchylosed to a vertically flattened, spatu- 
late bone eight or ten inches long by two inches wide; the crown is com- 
posed of dense bony tissue half an inch in thickness anteriorly, but thinner 
near the narrow posterior end; crown surface dense and enamel-like, granu- 
lar or roughened with a vermicular marking, rising near the middle and on 
the outer side into a strong oblique tubercle or boss. Another pair of 
teeth, probably joining these anteriorly, are long-triangular, with the pos- 
terior ends obliquely notched, apparently to receive the obtuse points of the 
larger teeth. These triangular teeth are arched above and the sides are pro- 
longed downward in root-like wings which were once buried in the integu- 
ment. Possibly other teeth were joined to these to make up the pavement 
of the under jaw. Considerable diversity is shown in the character of the 
crown-surface in corresponding teeth. Three of these, nearly of the same 
size, show marked differences, viz: One bears a rudimentary irregular boss 
near the outer angle; another, from the opposite side, rises into a strong, 
furrowed, depressed, obtuse tubercle half an inch in height; while the third, 
corresponding in position with the last, is a little shorter and broader, and 
the tubercle is laterally deflected and compressed. Still another and very 
imperfect tooth of smaller size has the crown elliptical in outline, carrying 
a blunt, furrowed tubercle, relatively larger than that on either of the others. 
All these teeth just described are convex above, and probably formed part 
of the dentition of the lower jaw. 
The dental plates of the upper jaw form several pairs, of which the 
central and largest are rudely triangular in outline, with a flattened or con- 
cave triturating surface, bearing, as do some of the inferior teeth, evidences 
