138 PALJEONTOLOGY OF NEW YORK. 



diameter of an aperture ; margins slightly elevated, not indenting the borders 

 of the fenestrules. Carina .60 mm. high; for a little less than half the 

 height very thin, expanding and contracting, the summit angular and slightly 

 carinate. Scalae very thin, oblique from the base, outer margin arched, 

 width, as seen from above, .35 mm., seven or eight in the space of 5 mm. 

 Interstices oval, of nearly the same width as the scalsB. 



This species may be distinguished from F. (U.) slipata, F. {U.) fastigata and 

 F. (U.) tegulata by the size of the branches and fenestrules, and from other 

 species of Unitrypa of this formation by the direction of the obliquity of the 

 scalae. 



Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 



Fenestella (Unitrypa) acclivis, n. sp. 



PLATE LU, FIGS. 16-23. 



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

 cation .30 mm., increasing to .55 or .60 mm., rounded or flattened, sometimes 

 with a prominent line of nodes along the middle of the branch, and scattered 

 nodes on each side; at other times with two equally prominent lines of nodes; 

 occasionally, on the wider portions of the branch, there are three rows of nodes, 

 which are small, but very distinct, four or five in the space of 1 mm. Inter- 

 stices wider than the branches. Dissepiments comparatively strong, width 

 .45 mm., rounded, irregularly nodose, very slightly depressed, four in the 

 spjice of 5 mm. Fenestrules regularly oval, length .80 mm., width .50 mm. 

 On the celluliferous face the branches are usually slightly sinuous. Dis- 

 sepiments short, rounded, very much depressed. Fenestrules narrower than 

 on the opposite face. Cell apertures in two ranges, opening almost directly 

 outward, sixteen in the space of 5 mm., separated by less than the diameter 

 of an aperture. Carina .60 mm. in height, thin. Scalae thin, strongly curved, 

 the outer margin forming a halt circle, with the convexity toward the base, 

 oblique in the same direction, five or six in the space of 5 mm. Summit of 

 carina interrupted, obscured by the scalae ; this surface of the frond has 



