CORALS AND BRYOZOA. 89 



COSCINOTRYPA, Hall. 1886. 



COSCINOTRYPA CRIBRIFORMIS, Var. CARINATA. 



PLATE XXIX, KIGS. 29-35; AND PLATK XXXUI, FIGS, ii-ib. 



Cosciniam cribrifurmis. Prodt. Ti-ans. St. Louis Acad. Sci., vol. 1, No. 2, p. 2B9, pi. 16, fig-s. 1, la. 1858. 

 Clathrnpora carinata. Hall Report of State Geologist for 1882. Expl. pi. 26, figs. 22-25. 1883. 

 Coteinotrypa " " Report of State Geologist for 1§85, advance sheets. Expl. pi. 29, figs. 29-35. 



1886. 



ZoARiUM consisting of e.x;planate fronds, celluliferous on both faces, with perfora- 

 tions or fenestrules at varying distances from each other. At unequal intervals 

 the surface is raised into angular folds or plications, which continue growth in 

 the same manner, and in a direction at right angles to the parent frond; these in 

 turn giving rise to similar elevations. Cells tubular, very oblique, slightly 

 curved, arising from amesotheca. Cell apertures trilobate, diameter .20 mm.; 

 sometimes when macerated appearing arched or sub-triangular; very closely 

 and usually irregularly disposed, but sometimes alternating and sub-imbricat- 

 ing. The apertures adjacent to the fenestrules invariably r.adiate from them. 

 At the posterior margin of the apertures there are strong crescentic denticula- 

 tions, which in the course of growth form two parallel ridges along the 

 interior of the cell wall. Fenestrules circular or oval ; diameter from 1.60 

 to 2 mm., distant from each other from 2 to 5 mm. ; a space, .75 mm. wide, 

 around each fenestrule destitute of cell apertures. Intercellular space 

 vesiculose. The variation in the size and distance from each other of the 

 fenestrules is so great, that frequently the extremes have only a generic 

 resemblance. In some fronds the fenestrules are small, irregularly disposed, 

 distant 5 mm. or more ; in others they are large, closely disposed in regular 

 intersecting rows ; while in still others, or in portions of the fronds having 

 small fenestrules, they are represented by maculae destitute of cell apertures. 

 All gradations may occur. 



Two forms, from the Falls of the Ohio, have been described by Prout, as 

 Coscinium Keijserlingi and C. cribriformis ; the form here described is not C. Key- 

 serlingi, but has been identified with C. cribriformis, which was based upon one 

 of the many phases of the species as now recognized. 



Formation and locality. Upper Helderberg group. Falls of the Ohio river. 



