66 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



Figs. 5 and 6. Tangential sections, X 20 and X 35. The angular thin- walled zocecia 

 and me.sopores often closely resemble each other, but the more rounded 

 form and slightly thicker walls of the former will serve as a means of dis- 

 tinguishing them. 



7. Natural size views of three of the type specimens figured by James. 



Waynesville formation of the Richmond group, Westboro, Ohio. 



Ilelopora harrisi (James). 



8. Two segments, X 12, from type locality (after Ulrich) . 



Waynesville formation of the Richmond group, Waynesville, Ohio. 



Batostoma rariabile Ulrich (restricted). 



9. Vertical section, X 20, passing through the mature and a portion of tlie 



immature region. 



10. Tangential section, X 20, exhibiting the angular, thick-walled contiguous 



zoa?cia, the comparatively small acanthopores and the absence of mesopores. 

 Top of Richmond group, Osgood, Indiana. 



FJixnopora Jimbriata (James) . 



11. Outline drawing of the type specimen, the basal extremity restored; natural 



size. 



12. Tangential section of type, X 20. 



Clinton formation, Clinton County, Ohio. 



