PLATE 15. 



fistulipora triloba. 

 Figs. 1, 2. 

 Fistulipora triloba, Hall. Pal. N. Y., Vol. VI, page 29 (not figured). 

 Fig. 1. An enlargement of the surface, in its natural condition, showing 

 the form and arrangement of the cell apertures and the openings 

 of the septate intercellular tubuli. 

 Fig. 2. A vertical section of the frond enlarged, showing the striated 

 interior cellwalls, and the intercellular tubuli, which are in part 

 irregularly vesiculose below and regularly septate above. 

 Lower Helderberg group. 



llohenalia subtrigona. 



Figs. 3, 4, 



Lichenalia subtrigona, Hall. Pal. N. Y., Vol. VI, page 196 (not figured). 



Fig. 3. A portion of the surface in its natural condition, enlarged to show 

 more distinctly the form and arrangement of the cell apertures, 

 and the absence of intercellular pits. 



Fig. 4. A vertical section of the preceding enlarged, showing the open 

 tubular cells and the intermediate septate tubuli, with vesicular 

 texture at the base, which, on one side, extends nearly to the 

 surface of the mass. 



Lichenalia distensa. 



Fig. 5. 



Lichenalia distans, in error; Pal. N. Y., Vol. VI, page 197; also Index page 

 297, reference to L. distans, page 197, to be Lichenalia distensa. Not 

 Lichenalia distans, Pal. N. Y., Vol. VI, page 32. 



Fig. 5. A portion of the surface enlarged, to show the form and arrange- 

 ment of the cell apertures and the smooth intercellular surface, 



Lichenalia cornuta. 

 Fig. 6. 

 Lichenalia cornuta, Hall. Pal. N. Y., Vol. VI, page 203 (not figured). 

 Fig. 6. A portion of the surface enlarged, to show the regular form and 

 arrangement of the cell apertures, the thickening and crescenti- 

 form projection upon the margin of the aperture. The inter- 

 cellular surface is minutely pustulose. 



