152 Cincinnati Society of Natural History. 
Longitudinal sections show that the tubes in the axial region of the 
zoarium have very thin and somewhat flexuous walls, and are crossed 
by diaphragms from two to four tube-diameters distant from each 
other. They bend into the peripheral region with a gentle curve, the 
walls at the same time becoming thickened, and the diaphragms much 
more numerous ; in the peripheral region the latter are placed at dis- 
tances apart of from one fourth to one tube diameter. An occasional 
small tube is met with, which, as it does not differ in its tabulation 
from the ordinary tubes, is to be regarded as young. The spiniform 
tubuli are large and readily enough detected in these sections.. They 
originate in the outer portion of the axial region. 
In tangential sections the cell-walls in their fully matured condition 
are of moderate thickness, and present a:median lucid line, on each 
side of which is a dark ring that immediately surrounds the cell-aper- 
ture. The latter represents the secondary deposit of sclerenchyma, 
while the lighter median line represents the original walls of the cells. 
The groups of larger cells are sometimes quite conspicuous on account 
of their size, and frequently a few small cells are incorporated within 
their limits. On account of the comparatively thick walls the spini- 
form tubuli are not so conspicuous, as they are when cut through a 
deeper level, where the cell-walls are thinner. They are isolated and 
occupy the point of junction between every three, four or five cells. 
This species is probably most nearly allied tq D. aspera, the surface 
characters of the two being very similar, D. trentonensis, however, is 
a smaller species, and more strictly dendroid. Internally they are 
distinguished by the thinner cell-walls, and much less numerous dia- 
phragms of D, aspera. 
Formation and locality : Collected by the author from the upper 
beds of the Trenton group, at Burgin, Ky., on the Cincinnati Southern 
Railroad. These strata I regard as equivalent to Safford’s Orthis bed. 
DEKAYIA APPRESSA, nh. sp. (FI. VI., figs. 7, 7a and 76). 
Zoarium in rare instances subfrondescent, usually ramose, aud from 
one to three inches in height. Branches flattened, dividing frequently, 
from .3 to .4 of an inch in width, and from .15 to .25 of an inch in 
thickness. Surface without monticules, but presenting groups of cells 
somewhat larger than the average, at intervals of about .075 inch, 
measuring from center to center. When the pellicle is preserved, and 
this is often the case, the spiniform tubuli are, though rather small 
and few, apparent enough. But when the pellicle is not preserved 
