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.) jistulata 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 XLI, FIGS. 14, 15. 



Fenestella ceUApora, var. minor. Hall. Trans. Albany Institute, vol. x, abstract, p. 24. 1881. 



" ( Polypora) celsipora, var. minor. Report of State Geologfist 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 dis.sepiments 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. 



Fenutdla celHpora, 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. 1883. 

 " " " 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 ram., 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. 



