CORALS AND BRYOZOA. 
91 
Mr. Ulrich has founded the family Cystodictyonhle on the characters presented 
by C. ocellata, but they are similar to those of all other species of Stictopora 
of which we have been able to observe the internal characters. 
Formation and locality. Upper Helderberg group, Falls of the Ohio river. 
Stictopora crescens. 
PLATE XXVII, FIGS. 5-11. 
Stictopora crescehs, Hall. Report of State Geologist for 1885, advance sheets. Expl. pi. 27, figs 5-11. 1886. 
Zoarium consisting of a flattened, rigid, dichotomously branched frond; transverse 
section broadly lenticular, nearly oval; branches from 3 to 3.50 mm. wide, 
very gradually increasing in width; margins essentially parallel; greatest thick¬ 
ness 1.20 mm.; non-celluliferous margin with fine, oblique striations. Cells 
tubular, length about 1.20 mm., regularly curving to the surface. Cell aper¬ 
tures broadly oval, length from .25 to .33 mm., width three-fourths the length, 
sometimes nearly equal to it, marginal apertures larger than the others; all 
disposed in longitudinal parallel rows; about nine rows on each face of the 
branch; rows separated by prominent ridges. Peristomes thin, distinctly 
and equally elevated, apparently not denticulated. Intercellular space 
irregularly vesicular. 
This species most closely resembles S. rigida, but is thicker, the non-cellulif¬ 
erous space at the margin of the branch is wider and striated, the ridges 
separating the ranges of apertures are rounded, those of $. rigida being acutely 
angular; the peristomes are equally elevated and withoutdenticulations. From 
S. fruticosa it differs in its much fewer bifurcations and more rigid appearance; 
from & incissurata, by its essentially parallel ranges of cell apertures. 
Formation and locality. Upper Helderberg group, Ontario, Canada. 
Stictopora rigida. 
PLATE XXVIII, FIGS. 15, 10. 
Stictopora rigida, Hall. Trans. Albany Institute, vol. x, abstract, p. 14. 1881. 
“ “ Report of State Geologist for 1882. Expl. pi. 25, figs. 15, 16. 18S3. 
Zoarium consisting of a flattened, rigid, dichotomously branching stipe; trans¬ 
verse section lenticular ; width of branches from 2 to 3 mm., margins essen- 
