CORALS AND BRYOZOA. 63 



Fenestella (Polypora) compacta. 



PLATE XVIII, FIGS. 1-3; PLATE 22, FIGS. 4, ,1. 



Fmextdla compacta. Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 163. 1879. 



Report of State Geologist for 1882. Expl. pi. 18, figs. 1-3. 1883. 

 In part Fenestella (Hemilrypa) Nereia, Hall. Report of State Geologist for 1882. 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 mm., 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., increa.sing 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. 



fhiettella Arta, Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 163. 1879. 



In i>art Fenestella Arta, Hall. Report of State Geologist for 1882. Expl. pi. 18, 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 



