CORALS AND BRYOZOA. 
49 
comparatively infrequent. Interstices usually narrower than the branches. 
Dissepiments slender, six in the space of 5 mm., on the same plane as the 
branches and much expanded at their junction. Fenestrules oval or sub- 
quadrangular, width from one-third to one-half the length. 
On the celluliferous face the branches are angular. Dissepiments angular 
and much depressed. Cell apertures circular, in two ranges, opening some¬ 
what laterally, twenty in the space of 5 min., closely disposed, frequently 
in contact: margins strong, elevated and indenting the borders of the 
fenestrules. Between the ranges of cell apertures there is a thin carina, 
having a height of about .30 mm. 
Width of branch above a bifurcation from .35 to .40 mm., increasing to 
.75 mm.; diameter of dissepiments .20 mm. ; length of fenestrules .65 mm. 
This species, on the non-celluliferous face, is characterized by its flat cari- 
nated branches, in which feature it differs from any other of this formation. 
Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 
Fenestella Sylvia. 
PI,ATE XX, FIGS. 4-7. 
Fenestella Sylvia, Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist.., p. 96. 1S74. 
“ “ “ Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 167. 1879. 
“ “ “ Report of State Geologist for 1882. Expl. pi. 20, figs. 4-7. 1883. 
Bryozoum infundibuliform, broadly spreading, strongly undulating. Branches 
slender, gradually and regularly increasing in size to the bifurcations, which 
occur at intervals of from 5 to 15 mm., generally not less than 10 mm.; 
marked by from three to five moderately strong striae on each branch. 
Sometimes the central striation is so prominent as to give an angular or 
carinated appearance to the branch. Interstices wider than the branches. 
Dissepiments very slender, expanding at their junction and on the same 
plane with the branches, eight in the space of 5 mm. Fenestrules variable 
in form, regularly oval near the base, becoming broadly oval or sub-quad¬ 
rangular above. Width usually from one-half to two-thirds the length, but 
sometimes equal to, or greater than, the length. 
