72 
PALAEONTOLOGY OF NEW YORK. 
The interior of this species has not been studied, but the exterior characters 
are so different from other Trematoporoid forms that there seems a necessity 
of separating it as a distinct genus. 
Formation and locality. Upper Helderberg group, Onondaga Valley, N. Y. 
DIAMESOPORA, Hall. 1852. 
Diamesopora camerata. 
PLATE XXVI, FIGS. 9, 10. 
Trematopora camerata. Hall. Report of State Geologist for 1882. Ex pi. pi. 24, figs 9, 10. 1883. 
Zoarium ramose, hollow; branches 1.50 mm. in diameter; thickness of polyzoary 
.50 mm. Cell apertures usually circular or slightly oval, sometimes arched, 
diameter .33 mm.; generally irregularly disposed, but sometimes forming 
indistinct transverse rows. Anterior portion of peristome slightly elevated, 
posterior margin strongly elevated, oblique. 
This species may be distinguished by its hollow cylindrical stems and very 
oblique, somewhat scattered cell apertures. 
Formation and locality. Upper Helderberg group, near Caledonia, N. Y. 
AC ANTH'OCLEMA, Hall. 1886. 
Acanthoclema alternatum. 
PLATE XXV, FIGS. 8-10. 
Trematopora alternata, Hall. Trans. Albany Institute, vol. x, abstract, p. 6. 1881. 
Acanthoclema “ “ Report of State Geologist for 1S85, advance sheets. Expl. pi. 25, figs. 8-10. 
1886. 
Zoarium ramose, solid; branches slightly more than 1 mm. in diameter. Cells 
tubular, arising from a slender central axis, in contact for a little more than 
one-half their length. Cell apertures oval, length about .20 mm., width two- 
thirds the length; disposed in longitudinal parallel rows, ten rows on a 
branch, separated by strong longitudinal ridges, which are frequently granu- 
lose: peristomes thin, scarcely elevated. Between each two adjacent aper¬ 
tures, in the longitudinal direction, there is a prominent spiniform conical node. 
