CORALS AND BRYOZOA. 91 



Mr. Ulrich has founded the family Cystodictyonid^ oa 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-U. 

 Stictopora ere»ce7ts,'HAi,u Reportof State Geologist for 1885, advance sheets. Expl. pi. 27, figs 5-11. 1886. 



ZoARiU-M consisting ofa 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-cell uliferous 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 S. rigida being acutely 

 angular ; the peristomes are equally elevated and without denticulations. From 

 S. frulicosa it differs in its much fewer bifurcations and more rigid appearance; 

 from S. incismrata, by its essentially parallel ranges of cell apertures. 



Formation and locality. Upper Helderberg group, Ontario, Canada. 



Stictopora rigida. 



PLATE XXVIII, FIGS. 18, 16. 



StUtopora riffida. Hall. Trans. Albany Institute, vol. x, abstract, p. 14. 1881. 



Report of State Geologist for 1882. Expl. pi. 25, figs. 15, 1(5. 1883. 



ZoABlUM consisting of a flattened, rigid, dichotomously branching stipe ; trans- 

 verse section lenticular ; width of branches from 2 to 3 mm., margins essen- 



