152 
PALAEONTOLOGY OF NEW YORK. 
On the celluliferous face the branches are gently rounded. Dissepiments 
extremely slender, rounded, depressed. Fenestrules much narrower than on 
the opposite face, frequently appearing as mere slits. Cell apertures in from 
two to four ranges, twenty-four in the space of 5 mm., distant less than the 
diameter of an aperture, sometimes nearly or quite in contact ; margins 
strongly elevated; ranges sometimes separated by a narrow striation. 
This variety will be easily recognized by the narrow interstices of the cellu¬ 
liferous lace, the closely disposed apertures and their very prominent margins. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
Fenestella (Polypora) adnata. 
PLATE XLI, FIGS. 1-8, 10. 
Fenestella adnata, Hall. Trans. Albany Institute, vol. x, abstract, p. 25. 1881. 
“ (Polypora) adnata, Hall. Report of State Geologist for 1S85, advance sheets. Expl. pi. 41, figs. 
1-8, 10. 1886. 
Bryozoum infundibuliform. Branches moderately slender, width above a bifur¬ 
cation about .35 mm., increasing to .45 or .50 mm., very gradually enlarging, 
anastomosing or connected by very short dissepiments, sinuous or zig-zag, 
angular, carinated; carime slight, those of adjacent branches frequently uniting 
on the anastomosed portion. Bifurcations distant. Interstices slightly nar¬ 
rower than the branches. Dissepiments strong, width .65 or .70 mm;, angu¬ 
lar, on a plane with the branches, six in the space of 7 mm. Fenestrules 
oval, length .50 mm., width usually two-thirds the length, sometimes nearly 
equal to it. This face of the frond frequently presents a reticulated ap¬ 
pearance. 
The celluliferous face presents a more regular appearance, the branches are 
rounded, slightly sinuous, essentially parallel. Dissepiments rounded, de¬ 
pressed. Fenestrules smaller than on the opposite face. Cell apertures 
usually in three ranges, twenty-two in the space of 5 mm., nearly or quite in 
contact; margins strong. There are, occasionally, apertures much larger 
than the ordinary ones. 
