CORALS AND BRYOZOA. 
53 
This species is distinguished by the lateral spreading of the frond at a short 
distance above the base, the compactly arranged branches and the very slender 
dissepiments and small fenestrules. 
Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 
Fenestella quaurula. 
PLATE XXI, FIGS. 19-22. 
Fenestella quadrula, Hall. Thirty-second Rept. N. Y. State Mas. Nat. Hist., p. 172. 1S79. 
“ “ “ Report of State Geologist for 1SS2. Expl. pi. 21, figs. 19-22. 18813. 
Bryozoum infundibuliforin, gradually expanding. Branches moderately strong, 
rounded, very gradually increasing in size and becoming flattened before bifur¬ 
cating; marked by from one to three striations on each branch. Sometimes, 
for a short distance above a bifurcation, there is a single striation along the 
middle of the branch, which then appears angular and carinated. Trans¬ 
verse section of the branch usually nearly circular. The bifurcations are at 
intervals of from 3 to 5 mm. Width of the interstices nearly equal to the 
branches. Dissepiments very slender, nine in the space of 5 mm., on the 
same plane with the branches, and not expanding at their junction. Fenes¬ 
trules quadrangular, occasionally square. 
On the celluliferous face the branches are angular, the dissepiments are 
rounded and much depressed The fenestrules appear slightly narrower 
than on the opposite face. Cell apertures in two ranges opening directly 
outward, twenty in the space of 5 mm., separated by less than the diameter 
of an aperture: margins elevated, indenting the borders of the fenestrules. 
Branches with prominent, thin carinse, which is abruptly expanded along 
the summit and marked in the middle by a thin, sharp crest. The 
margins of the expanded summits bear a row of small nodes which fre¬ 
quently have the appearance of minute apertures, live in the space of 
1 mm. 
Width of branch at first .33 mm., increasing to .50 or .60 mm.; diameter 
of dissepiments .16 mm.; fenestrules .40 mm. long and .30 mm. wide; height 
of carina .40 mm. 
