CORALS AND BRYOZOA. 127 



Fenestella permarginata. 



PLATE XLIX, FIGS. l-IO. 



Fenestella pennarginata. Hall. Trans. Albany Institute, vol. x, abstract p. 30. 1881. 



" " " Report of State Geologist for 1885, advance sheets. Expl. pi. 49, figs. 



1-10. 1886. 



Bryozoum infundibuliform. Branches moderately slender, width above a bifur- 

 cation .30 mm., increasing to .50 mm., rounded or flattened. Interstices 

 slightly wider than the branches. Dissepiments strong, width .60 to .65 mm., 

 gently rounded or flattened, on a plane with the branches, about four in the 

 space of 5 mm. Fenestrules oval, length .60 mm., width .25 or .30 mm.; in 

 well preserved specimens there is usually an elevation .20 mm. wide and of 

 about the same height, extending around each fenestrule, giving to the 

 branches and dissepiments the appearance of being concave. 



The celluliferous face of the frond is more regular. Dissepiments rounded, 

 much depressed. Fenestrules smaller than on the opposite face. Cell aper- 

 tures in two ranges, opening directly outward, twenty in the space of 5 mm., 

 separated by less than one-half the diameter of an aperture : margins strongly 

 elevated, indenting the border of the fenestrule. Surface between ranges of 

 apertures carinated ; carina about .60 mm. high, slightly expanding for 

 about one-half its height, then contracting, the summit sharp ; on each mar- 

 gin of the expanded portion there is a row of triangular concave nodes, 

 equal in number to the cell apertures. 



This species may readily be distinguished from any other of this formation, 

 by the prominent elevation surrounding the fenestrules ; from F. exornata of the 

 Hamilton group, it may be distinguished by the much smaller and more closely 

 disposed branches and dissepiments, and the rows of nodes on the margins of 

 the expanded portion of the carina. 



Formation and locality. Upper Helderberg group. Falls of the Ohio river. 



