16 
PALEONTOLOGY OF NEW YORK. 
mm. Through the thickening of the cell walls near the surface the apertures 
are constricted and oval in outline. The inter-apertural spaces are strongly 
elevated, frequently forming irregular ridges, the surface then resembling, 
in miniature, the roughened bark of a tree. 
This species is easily recognized by its polygonal cell tubes, oval apertures, 
its peculiarly roughened surface and the widely diverging branches. 
Formation and locality. In the shaly limestone of the Lower Helderberg 
group, near Clarksville, N. Y. 
N ote. —This form does not fully represent the characters of Trematella, but I prefer to leave it for the 
present under that designation. 
Orthopora, n. s. g. 
Zoarium ramose, cell apertures arranged in parallel, longitudinal rows. Inter¬ 
cellular space solid, or occupied near the surface, by minute tubuii, destitute 
of septa. 
Externally very similar to Rhombopora, but differing internally. These forms 
differ from Trematella in the regular arrangement of the cell apertures. 
Trematopora (Orthopora) regularis. 
PLATE XI, FIGS. 1-8; PLATE XIII, FIG. 1-3; and PLATE XXIII, FIG. 1. 
Trematopora regularis. Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 106. 1874. 
“ “ “ Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 151. 1S79. 
In part Trematopora regularis, Hall. Report of State Geologist for 1882. Expl. pi. 11, figs. 1-8; pi. 13, 
figs. 1-3. 1883. 
Zoarium ramose, solid; bifurcations infrequent; branches widely diverging, 
slender, the diameter seldom exceeding 1 mm. Branches having a diameter 
of only .50 mm. are not uncommon. Cells tubular, arising from the center 
of the branch and gradually diverging till within a short distance of the 
surface, when they turn quite abruptly outward. Near the center of the 
branch the cells are in contact and frequently sub-polygonal from mutual 
pressure, separating as they approach the surface. Apertures elongate-oval, 
length from .15 to .18 mm., width from one-fourth to one-half the length ; 
arranged in longitudinal parallel rows, fifteen in the space of five mm.; from 
