PLATE IX. 



PAGE. 



Orthoceras annulatum 147 



Fig. 1 . Yiew of a fragment o^an internal cast, showing the strength of the annnlations and the dis- 

 tance of the septa. 



Orthoceras crebescens 148 



Fig. 2. View of a fragment of the species, from Cedarville, Ohio, showing the size of the-shell, rate 

 of taper, and arrangement of septa, as well as their curvarture and the position of the 

 siphnDcle. 



Orthoceras strix 149 



Fig. 3. Lateral view of the specimen described, showing the features of the internal cast. 



