CORALS AND BRYOZOA. 
183 
or less prominent ridges, which are sometimes straight, but usually sinuous 
and occasionally irregular; generally only one ridge between adjacent rows, 
but rarely two ; when the apertures are irregularly disposed the ridges appear 
interrupted and involved. Peristomes very slight, scarcely perceptible. 
Between adjacent cell apertures there are usually two comparatively promi¬ 
nent, hollow, conical nodes, which, in the course of growth, form minute 
curved tubuli between the cells. One specimen shows indications of the 
longitudinal structure characteristic of the genus Riiombopora. 
Some specimens of this species closely resemble forms of Accmthoclema 
Hamiltonense, but the longitudinal ridges are less prominent and more irreg¬ 
ular, and there are prominent nodes between the cell apertures in place 
of pits, internally it is without the filiform axis characteristic of the genus 
Acanthoclema. From A. alternatum of the Upper Helderberg group it may 
be distinguished by the. less prominent and more irregular, longitudinal ridges, 
and by the smaller size and greater number of nodes : from T. (0.) irregularis 
it is distinguished by its less prominent and more irregular longitudinal ridges 
and the conspicuous nodes. Its general appearance is similar to T. ( 0 .) cari- 
nata, but there are more ranges of apertures on a branch, the longitudinal 
ridges are not so rigid and prominent and are more irregular, and there are 
usually two nodes between adjacent apertures, there being only one in that 
species. 
Formation and locality. Hamilton group, Moscow, Livingston county, N. Y. 
Trematopora (Orthopora) elongata, n. sp. 
PLATE LV, FIG. U ; AND PLATE LVI, FIG. 15. 
Zoarium ramose; bifurcations infrequent, sometimes distant 30 mm.; branches 
frequently diverging at an angle of nearly or quite ninety degrees, diameter 
about 1.25 mm. Cells tubular, arising from the centre of the branch, 
about 1.50 mm. long, oblique, straight and in contact for the greater portion 
of their length, abruptly bending outward near the surface, apparently 
without septa. Cell apertures elongate-oval, length about .25 mm., width a 
