I 



CORALS AND BRYOZOA. 95 



Stictopoka semistriata. 



PLATE XXVIII, FIGS. 17--20. 



Stietopora semigtriata. Hall. Trans. Albany In.stitute, vol. x, abstract, p. 14. 1881. 



" •' " Report of State Geolojjist for 1882. Expl. pi. 28, figs. 17-20. 1883. 



ZoARiCM consisting of dichotomously branching, flattened stipes ; transverse 

 section lenticular ; width of branches about 3 mm., margins divergent ; 

 greatest thickness .50 mm. ; bifurcations moderately frequent. Cell aper- 

 tures nearly or quite circular, diameter 30 mm.; marginal apertures slightly 

 larger than the others; more or less distinctly disposed in longitudinal rows, 

 which increase by interstitial siddition, the rows being sometimes separated 

 by narrow ridges, at other times the space between them is smooth and the 

 apertures appear irregularly disposed. Peristomes thin, sometimes equally 

 elevated, but usually the anterior portion is slightly and the posterior portion 

 more strongly elevated, frequently with slight denticulations. 



This species closely resembles S. Gilberti, but the fronds are somewhat nar- 

 rower, much thinner, the margins of the branches are more nearly parallel, the 

 cell apertures are circular, more irregularly disposed, and the branches are fre- 

 quently without longitudinal ridges. It mjiy perhaps be only a variety of 

 that species. 



Formation and locality. Upper Helderberg group, west of Le Roy, N. Y. 



Stictopora rhomboidea. 



PLATE XXIX, FIGS. 27, 28. 



Stictopora rhomboidea. Hall. Trans. Albany Institute, vol. x, abstract, p. 15. 1881. 



Reiwrt of State Geologist .for 188.5, advance sheets. Expl. pi. 29, ligs. 27, 

 28. 1886. 



Zoaricm consisting of a flattened, dichotomously bifurcating frond; width of 

 branches 2 mm., margins essentially parallel ; transverse section elliptical ; 

 greatest thickness 1 mm. Cell apertures oval, length .33 mm., width two- 

 thirds the length ; disposed in longitudinal rows, usually alternating. Ranges 

 of apertures separated by very sinuous ridges, which are frequently anasto- 

 mosing, giving to the aperture the appearance of being surrounded by a rhom- 



