THE LOWER EMBAR OF WYOMING 647 



much less overlap. The shape of the overlapping tooth is rarely 

 the same as that of the tooth which it overlaps, and it is significant 

 that none of the overlapping teeth are lobed. Fig. 10 lay next 

 to a much narrower tooth, while all of the rest were overlapped by 

 teeth of almost their own size. 



This series indicates that some genera and several species of 

 this type of teeth will probably prove to be invalid when more 

 specimens are known. Eastman 1 says that the chief characteristic 

 distinguishing this genus (Fissodus) from Janassa is that the tren- 

 chant margin is cleft or divided into two or three broad acuminate 

 points; but that characteristic seems not to be of specific value in 

 this case. 



The type of Janassa unguicula would be like the tooth shown 

 in Fig. 14, if the slight lobation of the latter were not present, and 

 it is like that shown in Fig. 15, but the latter is a worn tooth, 

 while the type is not worn. The type is not as thick and strong as 

 the Embar teeth. 



A specimen from Nebraska that Eastman refers to, Fissodus 

 inaequalis St. J. and W., has the cutting end almost exactly dupli- 

 cated in four specimens from the Embar, one of which is shown in 

 Fig. 7 of PI. II. This specimen is not preserved to the region where 

 the posteriorly curved folds occur on the Nebraska form, and they 

 were probably not present in the Embar tooth, as they do not appear 

 on other teeth that have that part preserved. 



The Carlinville, Illinois, specimen (Fig. 18 of PI. II) is much 

 thinner than those from the Embar but otherwise agrees with them. 



Janassa angularis n. sp. (PI. II, Figs. 5 and 6) 



The type specimen of this species is incomplete but presents 

 some marked peculiarities. From the cutting edge, which is 

 17mm. wide, the tooth narrows gradually toward the other end, 

 but only 14 mm. of the length is preserved and the condition at the 

 missing end is not known. The cutting end is sharply curved and 

 much worn. It seems to have been lobed originally, but wear has 

 reduced the projecting points to the level of the bottom of the 

 lobe. On the convex surface, 7 mm. from the edge, a shallow groove 



1 Bull. Mus. Comp. Zool., XXXIX, 174. 



