American Paleozoic Bryozoa. 161 
larger than those in the intervening spaces, their diameter often 
exceeding jth of an inch, while that of the ordinary cells is about ;},5th 
of an inch. Cell-walls thin, with the angles of junction slightly 
_ elevated. . ioe 
In longitudinal sections (Pl. VI., fig. 4a) the tubes are thin-walled, 
and proceed abruptly from the attached epithecal membrane to the 
upper surface. Diaphragms may be absent or developed in limited 
numbers. The center of the walls is often traversed lengthwise by a 
delicate light line, indicating the central cavity of the spiniform tubuli. © 
Tangential sections (Pl. VI., fig. 4) often show a delicate dark line 
separating the thin walls of adjoining cells, which at nearly all their 
angles of junction, is enlarged so as to include a small. spiniform 
tubulus. Both these and longitudinal sections show, that with the 
exception of the larger cells already described, the cells consist of one 
kind only. 
This is a common species at the top of the hills back of Cincinnati, 
O., where over nine tenths of the specimens of Cyrtolites ornatus found 
are covered with it. The thin zoarium may sometimes be flaked off, 
so as to expose the beautifully cancellated shell of that gaste: opod. 
Formation and locality: Cincinnati group. At Cincinnati, O., and 
other localities where the strata marking the 420 ft. level above the 
Ohio river are exposed. 
LEPTOTRYPA CLAVIS, n. sp. (PI. VI., figs. 3 and 3a.) 
Zoarium growing parasitically, usually upon crinoid columns, but not 
infrequently upon the stems of small branching bryozoa. In thickness it 
varies from .02 to .15 of an inch, the largest specimen seen being about 
one inch in length. Those growing upon the crinoid columns usually 
become club-shaped or subfusiform, while those on other objects are 
variously and irregularly shaped. Surface presenting at intervals of .1 
inch, small clusters of cells a little larger than the average, which in a 
few specimens are slightly elevated above the general level of the sur- 
face. Cells of one kind only, rather unequal in size, and irregular in 
arrangement, with moderately thin walls, and an average diameter 
of ,4,th of an inch, while the diameter of those in the groups seldom 
exceeds ;1,th of an inch. When in a good state of preservation the 
spiniform tubuli are quite prominent and pointed, and being numerous, 
give the zoarium a characteristically hirsute appearance. 
Longitudinal sections (Pl. VI., fig. 3a) show a spiniform tubulus 
between nearly all of the thin and straight tube-walls. Their internal 
