a. 
EASTMAN: CARBONIFEROUS FISHES FROM THE CENTRAL WEST. 175 
preserved, and exhibits four prominent, posteriorly curved folds which have 
become worn either by attrition during life, or by postmortem abrasion, or 
both. 
Indications of at least one pair of rudimentary lobes appear along the lateral 
border half-way between the terminal apices and the plicated area. The 
cutting-margin is moderately thin, and below it for some distance on either 
face the dentine tubules have become exposed through atmospheric erosion. 
The marks of overlap by the tooth immediately preceding this are rather indis- 
tinctly shown. A shallow longitudinal depression occupies the middle portion 
of the anterior face opposite the imbricated area, a condition similar to that 
observed in Janassa maaima. 
Formation and Locality. — Missourian; Peru and Louisville, Nebraska; 
Topeka, Kansas; also in Iowa, Illinois, and Missouri. 
Fissodus dentatus, sp. nov. 
(Plate 2, Fig. 12.) 
Type. — Detached crown; Museum of Comparative Zoology. 
Definition. — Teeth of comparatively small size, oval in general outline, 
with faintly serrated lateral border and cutting-margin divided by a median 
cleft into two strong, acuminate cusps. Anterior face smooth, uniformly and 
strongly convex in a vertical direction, more gently arched from side to side. 
About one-half of the anterior face overlapped by the next older tooth in 
front. 
A small, beautifully preserved crown from the Missourian of Topeka, 
Kansas, collected by the late S. A. Miller, and now belonging to the Museum of 
Comparative Zoology, is taken as the type of this species, which differs from 
other Fissodus teeth in having serrated lateral margins. This character is of 
interest inasmuch as it determines Fissodus to be intermediate in position 
between Janassa and Ctenoptychius. The general configuration of the crown 
resembles that of F’. tricuspidatus, but on the other hand it agrees with F’. bifidus 
in possessing a deeply cleft, equilobed cutting-margin. There are three toler- 
ably distinct serrations along the upper third of the lateral margin on either 
side, below which are several faint crimpings of the delicate edge. The pos- 
terior face is concealed by matrix, and the root has been broken away. The 
total height of the crown is a fraction over, and the extreme width a fraction 
under 7 mm. 
Formation and Locality. — Missourian; Topeka, Kansas. 
PETALODUS Owen. 
The teeth of this genus have petal-shaped crowns which are much elongated 
from side to side, and shortened in the opposite direction. The cutting- 
margin is smooth or at most delicately crenulated, but not serrated, and the 
