162 
PALAEONTOLOGY OF NEW YORK . 
the branches. Dissepiments slender, width .30 mm., rounded, depressed. 
Fenestrules sub-quadrangular, length generally a little more than 2 mm., 
width from .70 to .90 mm. Cell apertures minute, in from three to five 
ranges, fourteen in the space of 5 mm., separated by more than the diameter 
of an aperture ; margins slightly elevated, and separated by comparatively 
prominent, gently sinuous ridges. 
This species will be readily distinguished, as it is the only flabellate form at 
present known, from this geological formation. 
Formation and locality. Upper Helderberg group, Onondaga Yalley, Onondaga 
county, N. Y. 
Fenestella (Polypora) perangulata. 
PLATE XXXVII, FIGS. 13, 14. 
Fenestella perangulata, Hall. Trans. Albany Institute, vol. x, abstract, p. 23. 18S1. 
“ ( Polypora ) perangulata, Hall. Report of State Geologist for 1882. Expl. pi. 30, figs. 13, 14. 
1883. 
Bryozoum infundibuliform. Branches strong, width above a bifurcation .50 
mm., increasing to .80 or .90 mm., acutely angular, with a very slight carina, 
which is sometimes sinuous. Interstices wider than the branches. Dissepi¬ 
ments comparatively slender, width .40 mm., angular, carinated, depressed, 
about three in the space of 5 mm. Fenestrules oval, length 1 mm., width 
usually about .70 mm., but sometimes the fenestrules are nearly circular; at 
other times the width is not more than half the length. 
The celluliferous face has not been observed. 
This species may be distinguished from F. (P.) rigida by the coarser appear¬ 
ance of the frond, and from F. (P.) distans, by the more compact growth of the 
frond and the oval fenestrules. 
Formation and locality. Upper Helderberg group, Western New York. 
