148 PALAEONTOLOGY OF NEW YORK. 



Fenestella (Hemitrvpa) favosa. 



NOT FIGURBD. 



tinettella (Hemitrypa) favosa. Hall. Trans. Albany Institute, vol. x, absti-act, p. 35. 1881. 



Bryozocm infundibuliform, compact. Branches very slender, bifurcating at 

 varying distances ; width above a bifurcation .25 mm., increasing to .50 mm. ; 

 rapidly enlarging when the bifurcations are frequent ; often increasing in 

 size, then contracting and again enlarging before bifurcation ; angular and 

 slightly carinated when well preserved. Interstices of the same width, or 

 slightly narrower than the branches. Dissepiments extremely slender, width 

 from .15 to .18 mm., angular, slightly carinated, depressed, rounded when 

 worn or macerated, from eight to ten in the space of 5 mm. Fenestrules 

 oval, length from .35 to .40 mm., width usually about .25 mm. 



On the celluliferous face the frond has a more compact appearance. Dis- 

 sepiments angular, slightly carinated, much depressed. Fenestrules smaller 

 than on the opposite face. Cell apertures in two ranges, opening laterally, 

 twenty in the space of 5 mm., separated by a little less than the diameter of 

 an aperture ; margins equally elevated, slightly indenting the borders of the 

 fenestrules. Carina thin, height .25 mm., summit not expanded. Scalar and 

 pseudo-carina of the same strength as the summits of the carinas proper ; 

 eighteen scalae in the space of 5 mm. The carinaB and pseudo-carinae are 

 frequently zig-zag, the interstices then having the appearance of hexagonal 

 cell apertures ; when the carina is broken away the base has the appearance 

 of a row of prominent triangular nodes, along the middle of the branch. 



The non-celluliferous face of this species resembles that of F. ( Unitrypd) nana, 

 but the branches are more closely disposed, the fenestrules narrower, and when 

 the bifurcations are frequent the branches increase in size more rapidly ; the frond 

 also presents a more compact appearance ; on the celluliferous face the difference 

 is at once observed. From F. (H.) columellaia it differs by the less uniform size 

 of the branches and the more slender dissepiments, those of that species being 

 as wide or wider than the branches ; on the celluliferous face the summit of the 

 carinsB and the scalsB are more slender. The non-celluliferous face so closely re- 



