172 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
argues from the worn condition of the triturating surface that the fare consisted 
of hard-shelled prey, such as Brachiopods and Pelecypods, and cites an example 
preserved in the Bergakademie in Berlin where a number of Productae are 
contained within the abdominal cavity. It is reasonable to suppose that the 
relative tenuity or thickness of the cutting-edge amongst different species of 
Janassa furnishes an approximate indication of their having subsisted on soft 
or hard shelled prey, as the case may be. 
Janassa maxima, sp. nov. 
(Plate 2, Fig. 21; Plate 3, Fig. 24.) 
Type. — Imperfect crown; University of Nebraska. 
Teeth extremely large and robust, with very high and strongly reflexed 
crown and thick cutting-margin. Posterior two-thirds of oral surface convex 
and covered with numerous prominent oblique plicae 
displaying indications of wear during life. Anterior 
face strongly convex, smooth, the posterior two-thirds 
elevated into two abrupt longitudinal ridges which 
are separated by a broad median longitudinal channel. 
Anterior face showing marks of contact with next 
oldest underlying tooth, the only indications of wear 
during life being directly along the cutting-margin. 
Of this species only the unique tooth shown of the 
natural size in the accompanying illustrations is known 
at present. This is at least twice the size of the Per- 
mian J. lituminosa (Schloth.), the largest previously 
known species, which it approaches more closely than 
any others. In fact, the relations of this new species 
are altogether with those of Permian, rather than 
with those of Carboniferous age. 
The whole of the root and posterior portion ot the 
Fs crown are missing, and a portion of the cutting-edge 
i . of the crown has also been broken away. Even in 
eral its mutilated condition, however, the crown exhibits a 
A lee total length of nearly 5 cm. Its lateral borders are 
f a straight, proving that the tooth was not deformed by 
4 interlocking with those of adjoining series. As to 
Fie. 5. the position in the mouth occupied by this tooth, the 
Janassa maxima, sp. marks of wear indicaté very clearly that it belonged 
nov. Profile, x 4. in one of the principal series to the left of the sym- 
physial inthe upper jaw. The tooth opposed to it in 
the lower jaw played inside its cutting-edge, and slightly to the left instead of 
squarely against it. The asymmetrically worn condition of the cutting-edge in 
is 
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