CORALS AND BRYOZOA. 133 



5 mm., on a plane with the branches or elevated above them, very frequently 

 extending across the branch, uniting with adjacent dissepiments and forming 

 prominent, irregular, transverse elevations, which are the most conspicuous 

 feature of the frond and give to it a very irregular appearance. Fenestrules 

 oval, length .50 mm. or more, width from .25 to .30 mm. 



On the celluliferous face the scaloe have a width of .25 to .30 mm., twelve 

 in the space of 5 mm. ; summit of carina angular, slightly carinated, elevated 

 above the scalae. 



This species most nearly resembles F. (U) stipata; on the non-celluliferous 

 face the branches are more slender and much more irregular ; the dissepiments 

 more prominent: on the celluliferous face the scalae have broader summits, 

 which are not oblique ; on the side of the carina the scalae are directed obliquely 

 toward the base of the frond only, not bent as in F. (U.) stipata and F. (U.) 

 tegulata. 



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



Fenestella (Unitrypa) nana, n. sp. 



NOT FIODRBD. 



Beyozoum infundibuliform. Fronds small, rapidly expanding. Branches very 

 slender, width above a bifurcation about .16 mm., increasing to .30 mm., 

 straight, rounded or sub-angular; when perfectly preserved slightly carinated, 

 when a little worn or marcerated, smooth ; bifurcations frequent. Inter- 

 stices wider than the branches. Dissepiments extremely slender, width .12 

 mm., rounded, much expanded at their junction with the branches, slightly 

 depressed, ten in the space of 5 mm. Fenestrules oval, length .38 mm., 

 width .28 mm. 



On the celluliferous face the dissepiments are rounded, slightly carinated, 

 very much depressed. Fenestrules narrower than on the opposite face. Cells 

 in two ranges, opening outward, twenty in the space of 5 mm., separated by less 

 than the diameter of an aperture : margins thin, indenting the borders of the 

 fenestrules. Summit of carina .10 mm. in width ; scalae very thin, oblique, 

 twenty-two in the space of 5 mm. 



