American Paleozoic Bryozoa. 89 
examining the edge of the zoarium, the tubes are seen to proceed at 
nearly aright angle from the distinct median laminz to each face ofthe 
expansion. On the other hand, H. solitaria is truly frondescent (as 
explained on page 123, vol. V., of this Journal ), and there being no me- 
dian lamina in such forms, the margin of the frond is uniformly occu- 
pied by the cell-apertures. When longitudinally fractured, the tubes 
are seen to approach the surface in precisely the same manner, as they 
do in any of the ramose Monticuliporide. Thesmall, thin, and smooth 
frond, as well as the extreme paucity of interstitial tubes, will distin- 
guish it from the species of Heterotrypa so far described. 
Formation and locality: Cincinnati group. Rare near the tops of 
the hills west of Covington, Ky., at a height of about 300 feet above 
low water mark in the Ohio river. 
(DEKAYELLA OBSCURA, n. gen. et. sp. (PI. I, figs, 4, 4a, 40.) 
Gen. char., ante vol. V., p. 155. 
Zoarium ramose, consisting of slender ramulets, .18 to .25 of an inch 
in diameter, dividing dichotomously at intervals of .4 inch or more. 
Monticules are not developed, the surface usually being smooth. 
Cells from 1-120th, to 1-110th of an inch in diameter, with moderate- 
ly thick walls, and subangular apertures. When in a good state of 
perservation, the cell-orifices over large patches of the surface are 
entirely covered, or only partially, by a very thin pellicle or membrane. 
It is developed from the margin of the aperture inwardly, and when 
not fully completed, an irregular opening is left in the center (PI. L, 
fig. 4). The boundary lines of the cells are now thin, and project but 
little above the-pellicle. The interstitial cells are numerous, and vary 
much in shape and size, but are always more or less angular. At in- 
tervals of about .1 inch, they are usually aggregated into unequal 
clusters. The spiniform tubuli are of two kinds, large and small, 
the former may be observed very readily at the surface, and they 
often show the minute orifice at their summits. About five may be 
counted in the spaceof.l inch. The latter are smaller and much more 
numerous, and can not be detected except on perfectly preserved ex- 
amples. They are developed in the cell-walls, and three or four 
surround each cell. 
In tangential sections (PI. L., fig. 4a) the proper cells are subcircular, 
and have thick walls. Each cell-cavity is encircled by a thin band or 
ring of dark sclerenchyma, the thinner original walls having a lighter 
color. The interstitial cells are numerous, unequal and angular, those 
