CORALS AND BRYOZOA. 249 



by about one-third the width of an aperture ; generally seven or eight longi- 

 tudinal rows on a branch ; the apertures of the marginal rows are not larger 

 than the others. Peristomes moderately thick, distinctly elevated, the 

 posterior portion the more prominent, oblique, not denticulated, and on the 

 specimens observed smooth. The narrow space between the ranges of aper- 

 tures is flat or slightly concave, with a thin, angular, sinuous striation along 

 the middle, usually continuous, but on portions of the frond sometimes inter- 

 rupted and tortuous, occasionally having the appearance of entirely surround- 

 ing an aperture. 



********* 



Formation and locality. Hamilton group, near the head of Canandaigua lake, 

 N. Y. 



Stictopora incrassata. 



PLATE I,XU, FIGS. 1-6. 



stictopora incrassata. Hall. Trans. Albany Institute, vol. x, p. 190. 1881. 

 " " " Report of State Geologist for 1883, p. 47. 1884. 



ZoARiUM consisting of a flattened, dichotomously branched frond, proceeding 

 from a spreading base attached to foreign bodies. Branches generally from 

 3 to 3.50 mm. in width : margins parallel, except for a short distance below 

 a bifurcation, where they are slightly expanded ; non-celluliferous mar- 

 ginal space a little more than .50 mm. in width; transverse section oval or 

 broadly lenticular, greatest thickness 1.60 mm., sometimes one face of the 

 branch is more convex than the other; bifurcations distant, occurring at 

 intervals of from .15 to .25 mm. on the specimens observed. Cells tubular, 

 short, arising obliquely from the mesotheca at an angle of about forty-five 

 degrees, curving and opening directly outward, gradually enlarging to the 

 apertures. Intercellular tissue vesiculose ; vesicles irregularly disposed. 

 Cell apertures ovate, the smaller end toward the base of the frond, length 

 .50 mm., width a little more than one-half the length ; frequently operculate, 

 the opercula consisting of thin, flat or slightly convex plates, extending 

 across the apertures, and having one or two very prominent, sub-conical 

 nodes, which are more frequently situated near the margin than at the 



