CORALS AND BRYOZOA. 
165 
other associated species of this geological formation, it differs in having angular, 
sinuous branches, and in the size of the branches and fenestrules. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Polypora) hexagonalis, var. foraminulosa. 
PLATE XXXIX, FIGS. 16-20. 
Fenestella hexagonalis, var. foraminulosa, Hail. Trans. Albany Institute, vol. x, abstract, p. 27. 1SS1. 
“ [Polypora) hexagonalis, var. foraminulosa, Hall. Report of State Geologist for 1SS2. Expl. 
pi. 32, figs. 16-20. 1883. 
This variety is very similar to the ordinary forms of F. (P.) hexagonalis , but 
on the celluliferous face it has numerous, very prominent, hollow, conical nodes. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Polypora) nexa. 
PLATE XXXIX, FIGS. 4-9. 
Fenestella nexa, Hall. Trans. Albany Institute, vol. x, abstract, p. 25. 1881. 
“ ( Polypora) nexa, Hall. Report of State Geologist for 1882. Expl. pi. 32, figs. 4-9. 1883. 
Bryozoum infundibuliform. Branches moderately strong, very gradually in¬ 
creasing in size, width above a bifurcation .33 mm., increasing to .65 mm., 
angular, slightly carinated, very seldom sinuous. Interstices usually a little 
wider than the branches. Dissepiments comparatively slender, width .33 
mm., angular, slightly carinated, on a plane with the branches, about three 
in the space of 5 mm. Fenestrules oval, length about 1.20 mm., width 
.50 mm. 
On the celluliferous face the branches are rounded. Dissepiments angular, 
slightly carinated, much depressed. Fenestrules narrower than on the 
opposite face, the interstices being slightly narrower than the branches. 
Cell apertures in from two to four ranges, sixteen in the space of 5 mm., 
separated by about the diameter of an aperture; where only two ranges of 
apertures occur, they are separated by a slightly elevated carina. 
This species may be distinguished from F. (P.) separata by the somewhat more 
lax appearance of the frond, the more slender and less frequent branches and 
dissepiments. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
