106 
PALEONTOLOGY OF NEW YORK. 
diameter of an aperture. Surface carinated; car in 93 slightly elevated, 
strong, nodose; nodes small, regularly disposed. 
This species may be distinguished from F. depressa, by the smaller size of the 
branches; from F. tenuis by its larger branches, and from F. serrata and allied 
forms by its more delicate appearance. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
Fenestella pertenuis. 
PLATE XLV, FIGS. 22, 23. 
Fenestella pertemois, Hall. Trans. Albany Institute, vol. x, abstract, p. 29. 1881. 
“ “ “ Report of State Geologist for 1SS5, advance sheets. Expl. pi. 45, tigs. 22, 23. 
1886. 
Bryozoum infundibuliform. Branches very slender, rigid, rounded, smooth, 
width just above a bifurcation .15 mm., increasing to .25 mm. Interstices 
as wide or wider than the branches. Dissepiments comparatively strong, 
width .15 to .18 mm., rounded, on a plane with the branches, twelve in the 
space of 5 mm. Fenestrules oval or sub-quadrangular, length from .25 to 
.30 mm., width from .20 to .30 mm. 
On the celluliferous face the dissejiiments are rounded, depressed. Fenes¬ 
trules narrower than on opposite face. Cell apertures in two ranges, opening 
outward; thirty in the space of 5 mm.; separated by less than the diameter 
of an aperture : margins indenting the borders of the fenestrules. Branches 
carinated; carinse broad, slightly elevated, nodose; nodes comparatively 
large, regularly disposed, equal in number to the cell apertures. 
This species may be distinguished from F. tenella by the nearly equal size of 
the branches and dissepiments; the dissepiments being on a plane with the 
branches. From nearly all other species it may be distinguished by the small 
size and close arrangement of the branches and dissepiments. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
