192 
PALAEONTOLOGY OF NEW YORK. 
delicate appearance. When well preserved this species does not resemble A. 
scutnlatum , but when worn or macerated it sometimes presents a similar 
appearance, the inter-apertural pits being obsolete, and the ridges nearly or 
quite in contact between the cell apertures; but it is always without the 
node at the junction of the ridges, which is a characteristic feature of that 
species, from A. alternatwn, of the Upper Helderberg group, it may be distin¬ 
guished by its inter-apertural pits, and from T. (0.) regularis, of the Lower and 
Upper Helderberg groups, by its larger cell apertures and the presence of inter- 
apertural pits. 
Formation and localities. Hamilton group, West Hamburg, Erie county, 
and near New Berlin, N. Y. 
Acantiioclema sulcatum, n. sp. 
PLATE LV, FIG. 7; PLATE LVI, FIG. 7. 
Zoarium ramose, solid ; bifurcations comparatively infrequent; branches widely 
diverging, diameter about .50 mm. Cells tubular, arising from a filiform 
axis at the center of the branch, in contact for the greater portion of their 
length. Cell apertures oval, length .20 mm., width about one-half their 
length, disposed in longitudinal parallel rows, distant more than the 
length of an aperture; six rows on a branch, separated by very prominent, 
angular, granulose ridges; the surface between the ridges is concave, giving 
to the cell apertures the appearance of being situated in channels. Peri¬ 
stomes very thin, scarcely elevated. 
This species most nearly resembles Acantiioclema triseriale of the Upper Helder¬ 
berg group, but may be distinguished as follows: the branches are somewhat 
more slender, the longitudinal ridges are more prominent, the cell apertures are 
much smaller. From Trematopora ( Orthopora) regularis it may be distinguished 
by the more prominent, angular, longitudinal ridges, the comparatively larger 
cell apertures, and the concave surface between the longitudinal ridges; nearly 
the same features distinguish it from T. (0.) lortalinea: from Acantiioclema 
alternatwn of the Upper Helderberg it is distinguished by its angular ridges and 
absence of nodes between the cell apertures. 
Formation and locality. Hamilton group, near Canandaigua Lake, N. Y. 
