CORALS AND BRYOZOA. 
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and the prominent nodes at the junction of the longitudinal ridges; from all 
other species, of this geological formation, by the strong, longitudinal ridges, 
which coalesce between the apertures, and the prominent conical nodes at the 
points of junction. 
Formation and locality. Hamilton group, York, Livingston county, N. Y. 
Acanthoclema Hamiltonense. 
PLATE LV, EIGS. 18-26. 
Ceriopora? Hamiltonensis, Nicholson. Geological Magazine, April, 1874. 
CaUopora “ Hall. Trans. Albany Institute, vol. x, p. 1S2. 1881. 
“ bipunctata, “ Report of State Geologist for 1S83, p. 15. 1881. 
Zoarium ramose, solid; bifurcations infrequent; branches diverging at an angle 
of from fifty to ninety degrees, diameter about .75 mm. Cells tubular, 
arising from a filiform axis at the center of the branch, a little oblique to 
the surface, and slightly curved. Cell apertures oval, length .20 mm., width 
from one-half to two-thirds the length, usually disposed in longitudinal, 
parallel rows, frequently alternating and forming oblique, transverse rows; 
sometimes, on portions of the frond, they are somewhat irregularly disposed. 
Peristomes thin, scarcely elevated. The longitudinal ranges of apertures 
are separated by prominent ridges, which are sometimes straight, but 
usually slightly sinuous, frequently approaching each other between the 
apertures, but rarely in contact. In the transverse space between the 
apertures there are usually two small, usually quadrangular pits, generally 
situated one above the other; when the cell apertures are irregularly 
arranged, they are occasionally entirely surrounded by these pits; a small 
node also often occurs at the base of each aperture, and sometimes at each 
end of the aperture, obscuring the pits. These pits in the course of growth 
form minute, curved tubuli between the cell apertures. 
This species most nearly resembles Trematopora ( Orthopora ) bispinulata, both 
species having the cell apertures disposed in longitudinal ranges separated bv 
ridges, but the ridges of this species are much more prominent and regular, 
and the surface is marked by inter-apertural pits; the frond has also a more 
