122 PALEONTOLOGY OF NEW YORK. 



the margin of the elevation there is a prominent conical node which fre- 

 quently projects over the fenestrules. On some fronds the dissepiments and 

 branches are also granulose. Fenestrules oval, frequently appearing trian- 

 gular from the projecting node of the dissepiments, length from .40 to .50 

 mm., width usually from one-half to three-fourths the length, but sometimes 

 equal to it. 



On the celluliferous face the dissepiments are rounded, much depressed. 

 Fenestrules much smaller than on the opposite face ; the width of the dis- 

 sepiment being greater than the length of the fenestrule. Cell apertures in 

 two ranges, opening directly outward, twenty in the space of 5 mm., sepa- 

 rated by half the diameter of an aperture ; margins elevated, strongly 

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

 apertures carinated ; height of carina .30 mm. ; very thin below, expanding 

 to a width of .30 mm. at the summit. 



This species may be easily distinguished by the lunate elevations, with 

 conical nodes, on the non-celluliferous face ; even when worn or macerated it 

 preserves evidence of these characteristics. 



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



Fenestella bi-imbricata. 



PLATE XLVin, FIGS. 6-11. 



FenestMa hi-iinbricatti. Hall. Trans. Albany Institue, vol. x, abstract, p. 31. 1881. 



" " " Report of St*te Geologrist for 1885, ail vance sheets. Expl. pi. 48, figs. 6-11. 



1886. 



Bbyozodm infundibuliform, fronds large. Branches moderately slender, width 

 above bifurcation .38 mm., increasing to .50 mm., sub-parallel, the enlargement 

 scarcely perceptible, angular, slightly carinated, decidedly zig-zag and very 

 irregular, anastomosing or connected by short dissepiments; thickness 1 

 mm., transverse section sub-cuneiform. Dissepiments stronger than the 

 branches, oblique, the summit frequently forming a semi-circular elevation 

 which extends upon the branches, the extremities connecting with those of 

 adjacent dissepiments, giving to the frond the appearance of a festooned- 



