86 
PALAEONTOLOGY OF NEW YORK. 
cell walls, extending partially across the tube. Apertures paliform, diameter 
.20 mm.; very closely disposed, frequently in diagonally intersecting rows, 
the surface presenting a reticulated appearance. Surface between apertures 
elevated, forming ridges ; frequently a prominent node at the intersection of 
the ridges, sometimes a depression or pit. Surface with prominent monti¬ 
cules, which are transversely in contact, and longitudinally distant about 2 
mm., giving to the frond an annulated appearance. Intercellular structure 
vesiculose. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
SELENOPOEA, s. g., Hall. 1886. 
Lichenalia (Selenopora) circincta. 
PLATE XXV, PIGS. 13-15. 
Lichenalia circincta, Hall. Trans. Albany Institute, vol. x, abstract, p. 11. 1881. 
Selenopora “ “ Report of State Geologist for 1885, advance sheets. Expl. pi. 25, figs. 
13-15. 1886. 
Zoarium consisting of very thin lamellate expansions, encrusting other objects. 
Cells oblique, frequently alternating and imbricating. Apertures circular or 
broadly oval, diameter .10 mm.: anterior margin of peristome slightly ele¬ 
vated ; posterior portion strongly elevated, denticulated, projecting over and 
partially concealing the opening. The posterior portions of the peristomes 
are connected by oblique walls which traverse the surface between the aper¬ 
tures, uniting and forming polygonal vestibular areas. Maculae distant from 
each other 4 mm., consisting of circular spaces, destitute of apertures, having 
a diameter slightly less than 1 mm.; the cells immediately adjacent, radiating 
from them, being larger and more oblique than on other portions of the frond. 
This species may be distinguished from S. complexa by its much smaller cell 
apertures and vestibular areas. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
