160 Cincinnati Society of Natural History. 
In longitudinal sections (Pl. VL., fig. 26), the tubes are seen to be at 
first somewhat prostrate, but they soon rise and proceed directly to 
the surface. Their walls are moderately thin, and quite straight. 
Diaphragms are usually absent, an isolated one is, however, occasion- 
ally met with. Excepting the point of size, no difference can be de- 
tected between the ordinary tubes and the small ones mentioned in 
describing the monticules. On account of the filling of the tubes 
with the surrounding shaly matrix, the minute characters, which 
under other circumstances would be distinct, are often much obscured, 
if not obliterated. 
Tangential sections (Pl. VL, fig. 2a), show that the angles of the cells 
are somewhat thickened and occupied by a small spiniform tabuli, 
which, if the section be taken from an inferiorly preserved example, 
may be overlooked. The cell-walls between the angles are thin, and 
in the state of preservation accessible to me, show no divisional line, 
those of adjoining cells being apparently amalgamated with one another. 
A variable though never large number of small cells, which our 
present information demands we should regard as either young or 
aborted, are irregularly interspersed among the ordinary cells, but 
oftener aggregated between the cells occupying the surface monticules. 
All the specimens of this species seen by me, and their number is 
not less than three hundred, are without an exception, attached to a 
small species of Orthoceras, from two to four inches in length, and 
from .3 to .6 of an inch in diameter, at the larger end. The small 
conical monticules, and flat interspaces of ZL. minima, will distinguish 
it from the other species of the genus, as well as from all the rest of 
the parasitic Monticuliporide of the Cincinnati group, with the ex- 
ception, perhaps, of some of the species of Atactopora. These are, 
however, readily distinguished by their spiniferous and inflected cell- 
walls. 
Formation and locality : Cincinnati group, Not uncommon in the 
shaly beds at Hamilton, Ohio, at an elevation equivalent to 350 feet 
above low water mark in the Ohio river, at Cincinnati, O. It is rare 
at the Cincinnati quarries. 
LEpToTRYPA ORNATA, n. sp. (Pl. VL, figs. 4 and 4a.) 
Zoarium parasitically attached to Cyrtolites ornatus, the entire shell 
of which it covers with a thin expansion, from .02 to .10 of an inch in 
thickness. Surface smooth, but presenting at intervals of .1 inch, 
measuring from center to center, groups of cells that are conspicuously 
