140 
PALAEONTOLOGY OF NEW YORK. 
sixteen in the space of 5 mm., separated by less than the diameter of an 
aperture : margins distinctly elevated and indenting the borders of the fenes- 
trules. Carina) thin, height .60 mm. Scake very thin, oblique; outer mar¬ 
gin strongly curved, forming a semicircle, the curvature being toward the 
base of the frond, and oblique in the same direction ; six in the space of 5 mm. 
Summit of the carina very thin, sometimes straight and distinct, at other 
times interrupted by the scalm and indistinct; sometimes this surface of the 
frond is so irregular that it closely resembles some forms of Alveolites. 
The obscured or interrupted branches, wide dissepiments and prominent 
nodes of this species will be sufficient to distinguish it from any other of this 
geological formation. 
Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 
Fenestella (Unitrypa) elegantissima. 
PLATE LIII, FIGS. P2-17. 
Fenestella ( Hemitrypa ) elegantissima, Hall. Trans. Albany Institute, vol. x, abstract, p. 36. 1881. 
“ ( Unitrypa ) “ “ Report of State Geologist for 1885, advance sheets. Expl. 
pi. 53, figs. 12-17. 1886. 
Bryozoum infundibuliform, fronds large. Branches moderately slender, width 
above a bifurcation .35 min., increasing to .65 mm., gently rounded or bat¬ 
tened, sub-angular, carinated; carina slightly elevated and with small but 
very distinct nodes, four in the space of 1 mm. Interstices wider than the 
branches. Dissepiments strong, width from .75 mm. to 1 mm., gently rounded 
or flattened, slightly depressed, four in the space of 9 mm. Fenestrules 
oval, length 1.25 mm., width .60 mm. 
On the celluliferous face the branches are rounded, usually sinuous. Dis¬ 
sepiments rounded, very much depressed. Fenestrules of nearly the same 
appearance as on the opposite face. Cell apertures in two ranges, opening 
directly outward, oblique to the axis of the branch, sixteen in the space of 
5 mm., separated by less than the diameter of an aperture. Carime thin, 1 
mm. in height. Scaloe thin, outer margin forming a semicircular or semi¬ 
oval curvature which is convex toward the base of the frond, oblique in the 
