122 
PALAEONTOLOGY 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 XLVIII, FIGS. 6-11. 
Fenestella bi-imbricata, Hall. Trans. Albany Institue, vol. x, abstract, p. 31. 1881. 
“ “ “ Report of State Geologist for 1885, advance sheets. Expl. pi. 48, figs. 6-11. 
1SS6. 
Bryozoum 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- 
