134 PALEONTOLOGY OF NEW YORK. 



This species may be distinguished from F. (U.) acaulis, by the more slender 

 and closely disposed dissepiments, which are slightly depressed below the plane 

 of the branches; from F. (U.) stipata, by the more slender and more rapidly 

 enlarging branches, the narrower and more frequent dissepiments, there 

 being eleven in the same space occupied by seven in that species, and by the 

 much more numerous scalae; from F. (U.) tegulata by the much more closely 

 disposed scalae. 



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



Fenestella (Unitrypa) stipata. 



PLATE LI, FIGS. 7-U. 



fhiesUlla (Haaitrypa) stipata, Hall. Trans. Albany Institute, vol. x, abstract, p. 34. 1881. 



" {Unitrypa) " " Report of State Geologist for 188.'), advance sheets. Expl. pi. 51, 



figs. 7-14. 1886. 



Brvozoum infundibuliform, compact. Branches slender, width above a bifurca- 

 tion .25 mm., increasing to .50 mm., sometimes straight, but generally sinuous 

 or zig-zag, connected by very short dissepiments, angular, carinated ; carina 

 slight," sometimes granulose or nodose ; on some fronds the carinas of adjacent 

 branches unite on the dissepiments, having a small, conical node at the junc- 

 tion. Interstices usually a little narrower than the branches. Dissepiments 

 strong, width generally from .35 to .40 mm., angular, carinated ; carinse similar 

 to tho.se of the branches and connecting with them, six in the space of 5 mm., 

 on the same plane or elevated above the branches, very frequently extending 

 across them, coalescing with adjacent dissepiments, forming irregular, con- 

 tinuous elevations, which are more conspicuous than the branches, and give 

 to the frond an irregular appearance. Fenestrules oval, length generally 

 from .45 to .50 mm., width .33 mm. ; on one frond length .25 mm., width 

 .20 to .25 mm. 



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

 Fenestrules narrower than on the opposite face, length more than twice the 

 width. Cell apertures in two ranges, opening nearly directly outward, eight- 

 een in the space of 5 mm., closely disposed, nearly or quite in contact: mar- 

 gins elevated, indenting the borders of the fenestrules. Surface between 



