Unitbypa acclivis, Hall. 

 Fig. 15. An enlargement. The lower left-hand corner shows the cella- 

 liferous face of the branches ; the other portion showing 

 the irregular summits of the carinse and the connecting 

 scalse . 

 Upper Helderberg group. Falls of the Ohio . 



UnITRYPA LA.TA. 



Fig. 16. An enlargement, showing the summits of the carinse and con- 

 necting scalse, the celluliferous face of the branches, and 

 also the interior of the branches. 



Fig. 17. A fragment of a frond, showing the unitrypic face, natural 

 size. 



Fig. 18. A side view of a portion of a-branch and its carina. x6. 



Fig. 19. A transverse section of branches and their carinas. x6. 



629 



