PLATE XXVIII. 



PAGE. 



Fig. 1. Phylloporina angulata Hall.. 600 



A small form for which the specific name Ph. Daytonensis was suggested by Hall 

 and Whitfield. Fig, 4, Plate V, Ohio Pal., should show four rows of cells on the 

 branches. S. H. O, 



Fig. 2. Hemitrvpa ulrichi Foerste 599 



Part of the infundibuliform frond. B. O. 



Fig. 3. Clathropora frondosa Hall 598 



Lower part of a frond separated along the epithecal membrane. S. H. O. 



Fig. 4. Clathropora clintonensis Hall and Whitfield 598 



Lower part of a frond, separated along the epithecal membrane; both in this 

 specimen and the last the line of articulation with the basal segment is shown 

 S. H. O. 



Fig. 5. Ptilodictya whitfieldi Foerste , 598 



A typical specimen of this species (now distinguished from Pt.expansa, Hall and 

 Whitfield,) parted along the epithecal membrane. T F. O. 

 Fig. 6. Ph^Enopora magna Hall and Whitfield 599 



A fragment showing the surface ; the monticules are usualty lower and broader. 

 S. H. O. 

 Fig. 7. Ph.Enopora fimbriata James 599 



A t3 pical frond parted along the epithecal membrane. S. H. O 

 Fig. 8. Pachydictya emaciata Foerste 599 



Showing surface. S. H. O. 

 Fig. 9. Pachydictya bifurcaTa ( Van Cleve ) Hall 599 



Part of a very large specimen. S. H. O. 



Fig. 10. . Pachydictya bifurcata var instabilis Foerste 599 



One of the extreme forms, with more than one row of monticules on the branches. 

 B. O. 



Fig. 11. Pachydictya turgida Foerste 599 



The distinctions between this form and the next are not yet well understood. S. H. O. 



Fig. 12. Pachydictya obesa Foerste 599 



Specimens of this species usually have the fronds broader and strongly undulate 

 S. H. O. 



Fig. 13. Rhinopora yerrucosa Hall 599 



a, the form of preservation called Rh. venosa, Spencer; C. O. b, the same weath- 

 ered leaving only the grooves, called then Ph. fi-ondosa, Hall and Whitfield ; CO. 

 c, areas with more distant cells more or less regularly disposed are notinfre- 

 quent, and are usuallv associated with the " frondose " phenomena, occurring 

 then at the intersections of " veins " S. H. O. 



Fig. 14. Aspidopora parmula Foerste 600 



A fragment; H. O. The perfect fronds are thin, discoid, curved so as to be moder- 

 ately covex above, about 25 inches in diameter, the cells form diagonal intersect- 

 ing and concentrically arranged rows. H. O. Marl. 



