Fenestella freqtjens n. sp. 

 Plate ix, Figs. 12-15. 



Bryozoum consisting of infundibuliform fronds. Branches moderately 

 strong, width just above a bifurcation .25 to .35 mm., increasing to .50 or 

 .60 mm., and sometimes more, rounded or angular, occasionally granulose. 



Interstices sometimes narrower, at other times wider than the branches. 



Dissepiments moderately strong, width .25 to .30 mm., rounded or sub- 

 angular, on a plane, with the branches frequently extending upon them, 

 sometimes nearly to the middle, causing the branches to appear much 

 narrower than they really are ; very closely disposed, about twelve in the 

 space of 5 mm. 



Fenestrules usually oval or broadly lenticular, sometimes very irregular, 

 length transversely about .40 or .45 mm., width from one-half to two-thirds 

 the length. 



On the celluliferous face the branches are angular. Dissepiments angu- 

 lar and much depressed, fenestrules of about the same appearance as on 

 the opposite face. 



Cell apertures in two ranges, opening laterally, separated by about the 

 diameter of an aperture ; twenty in the space of 5 mm. ; margins thin ; 

 slightly elevated. Surface between the ranges of apertures carinated ; 

 carina moderately strong, elevated about .40 or .45 mm., more or less 

 expanded at the summit, smooth. 



This species is regularly distinguished from any other at present known, 

 by the closely disposed dissepiments, the branches and dissepiments of 

 the non-celluliferous face having precisely the appearance of the carinas 

 and scalfe of a Unitrypa. On the celluliferous face it is distinguished by 

 the closely disposed dissepiments and the elevated carinse. 



Formation and Locality. — Lower Helderberg group, near Clarksville, 

 Albany county, N. Y. 



