174 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
is approximately that of J. clavata from the British Carboniferous Limestone, 
the width being 1.4 cm., and the height 0.9cm. The cutting-margin is com- 
pressed to a sharp edge, and the thickness at the base of the crown is only 2 mm. 
From the general symmetry of the crown, and shallow sinus in the middle of 
the cutting-edge, it is to be inferred that the tooth occupied a position in the 
symphysial series. The area overlapped by the tooth immediately preceding 
on the anterior face of the crown is very plainly demarcated. The darker 
colored band along the cutting-margin appears to be due to fortuitous 
mineralization. 
The present species does not appear to be at all closely related to other 
American or European forms, and only remotely resembles certain teeth 
described from the St. Louis and Chester formations under the names of Tanao- 
dus sculptus and T. polymorphus St. J.and W. The general delicacy of the 
specimen is suggestive of Peltodus unguifornis N. and W., from the Coal 
Measures of Illinois, but the form and surface markings are different. Tanaodus 
and Peltodus are probably both synonyms of Janassa. Cope’s original descrip- 
tions of J. strigilina and J. gurleyana have recently been republished with 
figures by E. C. Case, in the Journal of Geology, Vol. VIII., 1900. 
Formation and Locality. — Atchison shales (Missourian) ; Cedar Creek, 
Nebraska. 
FISSODUS St. Joun and WortuHen. 
The chief distinguishing character between this genus and Janassa is that 
the trenchant margin is cleft or divided into two or three broad acuminate 
points. The so-called Cholodus, comprising the single species C. inaequalis, 
was held by St. John and Worthen to be distinct from Fissodus in that the 
cutting-margin was eccentrically lobed. The circumstance that the imperfect 
specimens studied by these authors were unsymmetrically worn is attributable 
to their having occupied a position among the lateral series of the mouth in 
Fissodus. 
Fissodus inaequalis (St. Joun and WorrtuHen). 
(Plate 2, Fig. 11; Plate 3, Fig. 26.) 
1875. Cholodus inaequalis St. John and Worthen, Pal. Illinois, Vol. VI., p. 416, Pl. 
XIIL., Figs. 4, 5. 
There can be no question that the well-preserved crown shown in the accom- 
panying illustrations is specifically identical with the fragmentary teeth from 
the Upper Coal Measures of Jowa and Illinois, described by St. John and 
Worthen as Cholodus inaequalis. The symmetrically formed outlines of the 
present specimen indicate its having pertained to the symphysial series, and by 
the same token those figured by St. John and Worthen occupied a lateral posi- 
tion. The root has been broken away from the specimen in hand, but the 
imbricated belt corresponding to the triturating surface in Janassa is well 
