126 PALEONTOLOGY OF NEW YORK. 



quently witli numerous, irregularly disposed, small conical nodes. The 

 branches are sometimes regular, at other times very irregular. Interstices 

 wider than the branches. Dissepiments strong, width usually about .50 mm., 

 on a plane with the branches or elevated above, sometimes continuing across 

 the branch, coalescing with those of adjacent branches and forming continuous, 

 very irregular transverse ridges, which are more prominent than the branches, 

 often giving to the frond a reticulated appearance, five dissepiments in the 

 space of 5 mm. Fenestrules oval, length .50 mm., width from .30 to 40 mm. 

 On the celluliferous face the frond is more regular. Dissepiments rounded, 

 very much depressed. Fenestrules smaller than on the opposite face. Cell 

 apertures in two ranges, opening directly outward, twenty in the space of 5 

 mm., closely disposed, nearly or quite in contact : margins thin, distinctly 

 elevated, indenting the borders of the fenestrules. Surface between ranges 

 of apertures carinated ; carina about .50 mm. in height, at first thin, expanding 

 for about one-half the height, then contracting, the summit being thin ; on 

 each margin of the expanded portion there is a row of small triangular nodes, 

 about equal in number to the cell apertures. There are calso, at irregular 

 distances, but always over a dissepiment, semicircular projections, extending 

 half way to the adjacent carina ; these when occurring opposite to each other 

 frequently coalesce 



The non-celluliferous face of this species resembles that of F. interrupta, but 

 the branches are smaller ; the celluliferous face may be readily distinguished 

 from any other species of this formation by the semicircular projections on the 

 dissepiments ; from F. labiata of the Hamilton group, it may be distinguished 

 by its .smaller and more closely disposed branches and dissepiments, the 

 presence of nodes on the carinae, and the more irreguhar appearance of the 

 non-celluliferous face. 



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



