American Paleozoic Bryozoa. 91 
like those of Heterotrypa, Amplexopora, and other genera of the Monti- 
culiporide, in which these structures exist, and in none of these do 
they appear before the zoarium has become fully matured. 
Dekayella obscura is readily distinguised from all the slender ramose 
Bryozoa of the Cincinnati group, by the thin membranaceous covering 
of the cell apertures. When worn its cellular structure resembles that 
of Dekayella ulricht (Heterotrypa ulrichi, Nicholson), but the larger 
size of the zoarium of that species will always serve to distinguish 
them. 
Formation and iocality: Cincinnati group. Not uncommon at 
Cincinnati, O., at an elevation of 150 feet above low water mark in the 
Ohio river. The best locality known to me is on Brown street, where 
the base of the hill has been graded for building purposes. 
CALLOPORELLA HARRISI, n. gen. et. sp. (PI. L, figs. 5, 5a, 50, 5c.) 
Gen. char., ante vol. V., p. 154. 
-Zoarium discoidal, consisting of a concavo-convex, thin, circular ex- 
pansion, different examples varying in diameter from .3 of an inch to 
1.0 inch, and in thickness from .02 to .05 of an inch. The upper or 
convex side is smooth, and covered by the cell-apertures, while the 
lower concave side is lined with an epithecal membrane, which is 
marked with faint concentric wrinkles, and sometimes with obscure 
radiating strie. The height of a specimen having a diameter of .8 of 
an inch, is about .25 inch. The cell-apertures are circular, and 
arranged in regular decussating series, the continuity of which ig 
sometimes interrupted by groups of cells slightly larger than the 
average. Theseclusters occur at intervals of .15 inch, and the diameter 
of the apertures of the cells composing them, varies from 1-125th to 
1-100th of an inch. They are further distinguished from the ordinary 
cells, the diameter of whose apertures is about 1-160th of an inch, by 
being separated from one another by interstitial spaces wider than usual, 
Measuring along one of the series, eleven or twelve of the ordinary 
cells may be counted in the space of .l inch. The interstitial spaces 
in most specimens, under an ordinary hand glass, appear to be solid. 
But when well preserved, and viewed under a higher magnifying 
power, they are seen to be occupied by a single, occasionally a double 
row of angular depressions, representing the apertures of the numerous 
interstitial cells. (Pl. I, fig. 5.) 
In tangential or transverse sections (Pl. I. fig. 5a) the proper 
zooecia are suboval or circular, and their visceral cavities are enclosed 
