CORALS AND BRYOZOA. 123 



reticulate structure (fig. 8). At otlier times the reticulate structure has be- 

 come obsolete and the surface presents the aspect of an explanate frond, 

 penetrated by large oblique cells as in fig. 7. At other times the dissepi- 

 ments, or anastomosed portions, are elevated above the branches continuing 

 across them, coalescing with those of adjacent branches and forming very 

 irregular transverse, continuous elevations, which form the most prominent 

 feature ; this condition of the frond so obscures the branches that it is nearly 

 impossible to trace them, the frond presenting a stelliform reticulate appear- 

 ance. Fenestrules variable in size and form, oval, circular or sub-triangular. 

 The celluliferous face is very regular, the branches slightly sinuous, very 

 closely disposed, nearly parallel. Dissepiments strong, width from .90 to 

 1.15 mm., oblique, rounded, depressed, three in the space of 5 mm. Fenes- 

 trules regularly oval, small, length .40 to .45 mm., width .25 mm. Cell 

 apertures in two ranges, opening directly outward, twenty-two in the space 

 of 5 mm., very closely disposed, nearly or quite in contact : margins thin, 

 distinctly elevated. Surface between ranges of apertures carinated, height 

 of carina .50 mm., thin below, then expanding, the summit flat and having 

 a width of nearly .50 mm. ; generally one side of the carina is more expanded 

 than the other, the summits imbricating, as shown in figs. 10, 11. Some of 

 the fronds have no resemblance to the branches and dissepiments of a 

 Fenestella, but resemble some forms of Lichenalia 



This species most nearly resembles F. interrupta, but may be distinguished by 

 its oblique, much wider dissepiments, and the coarser appearance of the frond. 

 Formation and locality. Upper Helderberg group. Falls of the Ohio river. 



Fenestella interrupta. 



PLATE XLVIII, FIGS. 12-17. 



Finestella iiUeirupta, Hall. Trans. Albany Institute, voL x/abstract, p. 32. 1881. 



" " " Report of State Geologist for 1885, advance sheets. Expl. pi. 48, figs. 12-17. 



1886. 



Bryozoum infundibuliform, fronds large, compact. The non-celluliferous face 

 of the frond is so irregular, that it is usually almost impossible to trace the 



