156 PALEONTOLOGY OF NEW YORK. 



, Fenestella (Polypora) robusta. 



PLATE XSXIV, KIG8 4-7 ; PLATE XXXVII, FIG. 1 ; PLATE XXXIX, FIGS. 1-3 ; AND I'LATE XLVI, FIG. 6. 



Flmettella ivbust-a. Hall. Ti-iins. Albany Institute, vol. x, abstract, p. 22. IS81. 



" (Polffpora) robusta. Report of SUte Geologist for 1882. Expl. pi. 27, figs. 4-7 ; pi. 30, fig. 1 ; 



pi. 32, fipp. 1-3. 1883. 



Bryozoum infundibuliform. Brunches very strong, angular, sometimes with a 

 slight carina; width just above a bifurcation .66 mm., increasing to 1.50 mm ; 

 bifurcations usually occur at intervals of from 20 to 50 mm. Interstices 

 slightly wider than the branches. Dissepiments .66 mm. wide, four or five 

 in the space of 5 mm., on the same plane with the branches and expanding 

 at their junction. Fenestrules broadly oval. 



On the celluliferous face the branches are rounded. Dissepiments rounded 

 or sub-angular, much depressed. Fenestrules elongate-oval, narrower than 

 on the opposite face. Cell apertures in from four to seven ranges, eighteen 

 in the space of 5 mm., separated longitudinally by slightly less than the 

 diameter of an aperture ; transversely they are nearly or quite in contact ; 

 margins strong, equally elevated. 



This is a characteristic species and will be easily distinguished from the 

 associated forms, by the large size and rigid appearance of the branches. 

 Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 



Fenestella (Polypora) largissima. 



PLATE XXXIV, FIGS. 8, 9. 



FenesteUa largissiina. Hall. Trans. Albany Institute, vol. x, abstract, p 22. 1881. 



(Polypora) lorgixsima. Hall. Report of State Geologist for 1882. Expl. pi. 27, figs. 8, 9. 1883. 



Bryozoum infundibuliform, of coarse and irregular growth. Branches strong, 

 angular, width above a bifurcation .90 mm., increasing to 1.50 or 2 mm.; 

 bifurcations at intervals of from 6 to 10 mm. Dissepiments strong, width 

 about 1 mm. Fenestrules sub-quadrangular or oval, variable in appearance, 

 length from 2 to 4 mm., width from 1 to 1.50 mm. Cell apertures in four to 

 six ranges. 



This species may be distinguished by the large size of the branches and 

 dissepiments and its irregular growth. 



