CORALS AND BRYOZOA. 
89 
COSCINOTRYPA, Hall. 1886. 
COSCINOTRYPA CRIBRIFORMIS, Vai'. CARINATA. 
PLATE XXIX, FIGS. 29-35 ; AND PLATE XXXIII, FIGS. 22-25. 
Cosciniam cribriformis. Prout. Trans. St. Louis Acad. Sci., vol. 1, No. 2, p. 269, pi. 16, fig-s. 1. 1 a. 1858. 
Clathropora carinata, Hall Report of State Geologist for 1882. Expl. pi. 26, figs. 22-25. 1883. 
Coscinotrypa “ “ Report of State Geologist for 1885, advance sheets. Expl. pi. 29, figs. 29-35. 
1S86. 
Zoarium consisting of explanate 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 a mesotheca. 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 radiate 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 1.50 
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 Keyserlingi 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. 
