CORALS AND BRYOZOA. 
151 
Cell apertures usually in two and three ranges, three ranges occurring on the 
greater portion of a branch, the central range strongly elevated, twenty in the 
space of 5 mm., nearly or quite in contact; margins strongly elevated, indent¬ 
ing the borders of the fenestrules. Ranges of apertures separated by more or 
less prominent ridges. 
This species very closely resembles F. (P.) fistulata of the Hamilton group, 
but may be distinguished as follows : the branches are not angular, nor so strong, 
the dissepiments are more distant, and the branches on the celluliferous face are 
not so closely arranged, in that species the branches being frequently in contact. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Polypora) celsipora, var. minor. 
PLATE ALT, FIGS. 14, 15. 
Fenestella celsipora, var. minor, Hall. Trans. Albany Institute, vol. x, abstract, p. 24. 1SS1. 
“ ( Polypora) celsipora, var. minor. Report of State Geologist for 1885, advance sheets. Expl. pi. 41, 
figs. 14, 15. 1886. 
This form is very similar in appearance to F. celsipora proper, but the branches 
and dissepiments are smaller and more closely arranged. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Polypora) celsipora, var. minima. 
PLATE XXXV, FIGS. 1-4 ; and PLATE XLI, FIGS 11-13. 
Fenestella celsipora, var. minima. Hall. Trans. Albany Institute, vol. x, abstract, p. 24. 1881. 
“ (Polypora) celsipora, Hall. Report of State Geologist for 1882. Expl. pi. 28, figs. 1-4. 18S8. 
“ “ “ var. minima, Hall. Report of State Geologist for 1885. Expl. pi. 41, figs. 
11-13. 1886. 
Bryozoum infundibuliform, compact. Branches slender, width above a bifurca¬ 
tion usually about .25 mm., increasing to .40 and .50 mm., but on some fronds 
the branches are stronger, rounded or angular. Interstices generally wider 
than the branches. Dissepiments slender, width .20 mm., rounded, on a 
plane with the branches, nine or ten in the space of 5 mm. Fenestrules 
usually sub-quadrangular, sometimes oval or circular, length about .35 mm., 
width usually from one-half to three-fourths the length, but frequently equal¬ 
ling or greater than the length. 
