146 PALEONTOLOGY OF NEW YORK. 



irregularly disposed, at other times in one or more longitudinal lines ; there 

 are also fine, slightly elevated striations; when worn or macerated the 

 branches are flattened and smooth ; bifurcations frequent. Interstices nar- 

 rower than the branches. Dissepiments very slender, width about .18 mm., 

 rounded or sub-angular, very slightly depressed ; nine in the space of 5 mm. 

 Fenestrules oval, length .40 mm., width from .15 to 20 mm. 



On the celluliferous face the dissepiments are very much depressed, rounded. 

 Fenestrules very narrow. Cell apertures in two ranges, opening outward, 

 , twenty in the space of 5 mm., separated by the diameter of an aperture : 

 margins elevated, indenting the borders of the fenestrules. Carina having a 

 height of about .30 ram., thin, expanded and flat at the summit, width about 

 .12 mm., frequently sinuous or zig-zag. Scalaa and pseudo-carina flat and of the 

 same width as the carinaB ; twenty scalae in the space of 5 mm. Interstices 

 circular, diameter about .25 mm. Around each fenestrule is a slight elevation, 

 which gives to the summit of the carina? and scalae the appearance of being 

 concave. From each one of the scalae there is a slight elevation on the 

 sides of the carina extending inward to the branch ; in peculiar conditions of 

 weathering the intermediate thinner portions of the carina are destroyed, 

 leaving the summit with the appearance of being supported by rows of 

 miimte columns. 



This species may be distinguished by the characteristic pedicel, and by the 

 elevation around the interstices of the hemitrypic face ; also when ornamented, 

 by the peculiar appearance of the nodes of the non-celluliferous face. 



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



Fenestella (Hemitrypa) columellata. 



HOT riGORBD. 



BRyozoDM infundibuliform, frond compact. Branches slender, width above a 

 bifurcation .25 mm., increasing to .40 mm., very gradually enlarging, straight 

 or sinuous, angular or sub-angular, slightly carinated, usually with a small 

 node opposite each dissepiment ; bifurcations comparatively distant. Inter- 

 stices narrower than the branches. Dissepiments, compared with the 



