CORALS AND BRYOZOA. 51 



when the dissepiments are opposite, becoming more or less sinuous or zigzag 

 when the dissepiments alternate. Bifurcations frequent. Interstices nar- 

 rower than the branches. Dissepiments strong, angular, seven or eight in 

 the space of 5 mm., on the same plane, or slightly elevated above the branches, 

 sometimes continuing across the branches, uniting with other dissepiments 

 forming a continuous irregular elevation, which is more prominent than the 

 branches. Fenestrules broadly oval, sometimes nearly circular. 



On the celluliferous face the branches are broadly angular and the dissepi- 

 ments rounded and much depressed. The fenestrules appear narrower than 

 on the opposite face. Cell apertui-es in two ranges, opening directly out- 

 ward, twenty in the space of 5 mm., distant a little more than the diameter 

 of an aperture : margins elevated, not indenting the borders of the fenes- 

 trules. Branches with comparatively strong carinae having a height of .10 

 mm., slightly expanded along the summits. 



Width of branch above a bifurcation .25 mm., increasing to .50 mm. ; 

 diameter of dissepiments .33 mm. ; fenestrules .38 mm. long. 



This species on the non-celluliferous face resembles F. Coronis, but is dis- 

 tinguished by its more compact growth, slender branches and oval fenestrules. 

 Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



Fenestella Coronis. 



PLATE XXI, FIGS. 10-13. 



FhuMteUa Cnrtmis, Hall. Thirty-second Rept. N. Y. State Mua. Nat. Hist., p. 171. 1879. 



Report of State Geologist for 1882. Expl. pi. 21, figs. 10-13. 1883. 



Bryozoum infundibuliform, radially undulating. Branches strong, angular or 

 rounded on the non-celluliferous side, and flattened for a short distance below 

 the bifurcation. Dissepiments strong, angular, slightly expanded at their 

 junction, and on the same plane with the branches.. Fenestrules oval or 

 quadrangular, varying in size and form, and generally wider than the 

 branches. 



On the celluliferous face, the branches and dissepiments are angular, and 

 the latter much depressed. The fenestrules appear narrower than on the 



