288 
PALAEONTOLOGY OF NEW YORK. 
Prismopora sparsipora. 
PLATE XXXII, FIGS. 24-28. 
Thallostigma sparsipora, Hall. Trans. Albany Institute, vol. x, abstract, p. 13. 1881. 
Prismopora “ “ Report of State Geologist for IS85, advance sheets. PI. 32, figs. 25-28. 
1886. 
Zoarium consisting of triangular, bifurcating branches, sides concave, two of 
them equal in length, the third a little wider. Cell apertures minute, oval 
or obscurely trilobate, arranged in oblique, ascending rows, from the middle 
of each face, comparatively infrequent; the apertures at the middle of the 
branch are the smallest, having a length of about .18 mm., gradually growing 
larger to the margin, where they have a length of from .22 to .25 mm., and 
are frequently pustuliform. Peristomes strong, equally elevated, and with two 
slight denticulations on the posterior portion. Surface flat, finely granulose. 
All the specimens observed are flattened, and in this condition have very 
much the appearance of Liciienalia. It may be distinguished from P. subcon- 
cava and P. triquetra by its wider branches and more distant apertures; from 
P. paucirama by its smaller and more infrequent cell apertures; from P. lata by 
its narrower branches, smaller and more infrequent cell apertures. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
