166 
PALEONTOLOGY OF NEW YORK. 
Fenestella (Polypora) separata. 
PLATE XXXIX, FIGS. 10, 11. 
Fenestella ( Polypora) separata. Hall. Report of State Geologist for 1882. Expl. pi. 32, figs. 10, 11. 1S83. 
Bryozoum infundibuliform. The non-celluliferous face has not been observed. 
On the celluliferous face the branches are moderately strong, width above 
a bifurcation .35 mm., increasing to 1 mm. Interstices narrower than the 
branches. Dissepiments comparatively strong, width .40 mm., rounded, 
slightly depressed, with a faint carina, three in the space of 5 mm. Fenes- 
trules elongate-oval, length 1 mm., width a little less than .40 mm. Cell 
apertures in from two to four ranges, eighteen in the space of 5 mm., 
separated by less than the diameter of an aperture; margins distinctly ele¬ 
vated. Ranges of apertures separated by narrow prominent ridges. 
This species may be distinguished from F. (P.) mutabilis by the more rigid 
appearance of the frond, straighter branches and prominent ridges separating 
the ranges of apertures. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Polypora) mutabilis. 
PLATE XXXIX, FIGS. 12-15. 
Fenestella mutabilis, Hall. Trans. Albany Institute, vol. x, abstract, p. 25. 1881. 
“ ( Polypora) mutabilis, Hall. Report of State Geologist for 1882. Expl. pi. 32, figs. 12-15. 1883. 
Bryozoum infundibuliform, of lax and irregular growth. Branches moderately 
strong, width above a bifurcation from .33 to .40 mm., increasing to .60 and 
.70 mm., straight, sinuous or zig-zag, according to the position of the dissepi¬ 
ments ; on some portions of the frond angular and carinated, becoming 
flattened below a bifurcation; on other portions rounded, with three or four 
prominent striations. Interstices of the same width as the branches. Dis¬ 
sepiments comparatively strong, width .35 mm., angular or carinated, on the 
same plane as the branches, four in the space of 5 mm. Fenestrules oval, 
length slightly less than 1 mm., width .45 mm. 
On the celluliferous face the branches are rounded. Dissepiments rounded, 
depressed. Fenestrules narrower than on the opposite face. Cell apertures 
