174 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



is approximately that of /. clavata from the British Carboniferous Limestone, 

 the width being 1.4 cm., and the height 0.9 cm. The cutting-margin is com- 

 pressed to a sharp edge, and the thickness at the base of the crown is onlj' 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 sr.ulptus and T. 2}olymor2)hus St. J. and W. The general delicacy of the 

 specimen is suggestive of Feltodus unguiformis 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 descrii> 

 tions of /. strigilina and /. garleyana 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. John and Worthen. 



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 G. inaequalis, 

 was held by St. John and Worthen to be distinct from Fissodus in that the 

 cutting-margin was eccentrically lobed. The circumstance that tlie imjierfect 

 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. John and Worthen). 



(Plate 3, Fig. 11 ; Plate 3, Fig. 36.) 



1875. Cholodus inaequalis St. John and Worthen, Pal. Illinois, Vol. VI,, p. 41(5, PI. 

 XIII., 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 fnnn 

 the Upper Coal Measures of Iowa 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 symphj'sial 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 Jana.s.sa is well 



