CORALS AND BRYOZOA. 
63 
Fenestella (Polypora) compacta. 
PLATE XVIII, FIGS. 1-3 ; PLATE 22, FIGS. 4, 5. 
Fenestella compact,a. Hall. Thirty-second Rept. N. A’. State Mus. Nat. Hist., p. 163. 1879. 
•• “ “ Report of State Geologist for 1882. Ex 2 il. pi. 18, figs. 1-3. 1883. 
In part Fenestella ( Hemitrypa ) Nervia, Hall. Report of State Geologist for 18S2. Expl. pi. 22, figs. 1-6. 
1883. 
Bryozoum infundibuliform, compact. Branches on the non-celluliferous side 
moderately strong, rounded, marked by obscure, granulose striations. Bifur¬ 
cations occurring at intervals of from 3 to 7 mm.; width of the interstices 
usually less than the narrower portion of the branches. Dissepiments strong, 
rounded, on a plane with the branches, seven or eight in the space of 5 mm. 
Fenestrules oval, width from one-half to three-fourths the length. 
On the celluliferous face the branches are rounded, and the dissepiments 
angular, while the fenestrules appear much narrower than on the opposite 
face, the branches being, sometimes, nearly in contact. Cell apertures 
minute, circular, in two and three ranges, opening directly outward, from 
fifteen to seventeen in the space of 5 min., separated by less than the 
diameter of an aperture: margins distinctly elevated, those of the lateral 
ranges indenting the borders of the fenestrules. 
Width of branches .33 mm., increasing to .66 mm.; width of dissepiments 
from .25 to .33 mm.; length of fenestrules from .25 to .33 mm. 
Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 
Fenestella (Polypora) Arta. 
PLATE XVIII, FIGS. 4-7. 
Fenestella Arta, Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 163. 1879. 
In part Fenestella Arta, Hall. Report of State Geologist for 1882. Expl. pi. IS, figs. 4-9. 1883. 
Bryozoum infundibuliform. Branches on the non-celluliferous side very strong 
near the base, becoming more slender above; angular, usually straight; 
sometimes sinuous or zigzag and presenting an irregular appearance; bifur¬ 
cating at intervals of 10 mm. or more. Width of the interstices less than 
that of the branches. Dissepiments strong, angular, expanded at their 
