88 Cincinnati Society of Natural History. 
have one specimen of a nearly allied species or variety, which was 
collected near Waynesville, O., about 250 feet higher in the series. 
HETEROTRYPA SOLITARIA, n. sp. (PI. IL, figs. 3, 3a, 30.) 
Zoarium consisting of thin undulated, or somewhat palmated ex- 
pansions, from one to two tenths of an inch in thickness, and one inch 
or more in height. The surface is not raised into monticules, but at 
intervals of .15 inch, one may observe, on careful examination, small 
clusters of cells which are slightly larger than the average. The cells 
are polygonal and thin-walled, and those of the ordinary size have a 
diameter of about 1-100th of an inch, while that of the cells in the 
clusters mentioned, varies from 1-70th to 1-80th of an inch. The 
interstitial cells are almost entirely absent, and it is only rarely that 
I have been able to detect them at the surface. Occasionally the 
elevated points of small spiniform tubuli may be observed at the 
angles of the cells. 
Tangential sections (Pl. I., fig. 3a) show that the cells are angular, 
and rather unequal, with moderately thin walls. The interstitial cells 
are very few in number; being almost entirely absent in some sections. 
The figure of a tangential section referred to at the beginning of this 
paragraph represents more of these small cells than is usual. The 
spiniform tubuli are small, but quite numerous, and generally de- 
veloped only at the angles of junction of the cells. The walls of ad- 
joining tubes appear to be amalgamated one with another, as no dis- 
tinct line of demarcation can be detected between them. 
Longitudinal sections (Pl. I., fig. 3b) show that the walls of the tubes 
in the axial region are very thin, and that diaphragms are not de- 
veloped in this portion of the zoarium, these structures appearing only 
near the surface, where they are about one half a tube-diameter apart. 
The curvature of the tubes from the axial into the peripheral region is 
not abrupt but gradual. In the latter portion of the zoarium the tube- 
walls are but slightly thickened, and occasionally show one of the 
spiniform tubuli. The interstitial tubes, on account of their rarity, 
are easily overluoked. Those noticed were crossed by diaphragms, a 
little more crowded than in the larger tubes. 
This species might be confounded with Peronopora uniformis, 
Ulrich, a species in which also the cell walls are thin, and the inter- 
stitial cells few in numbers. However, even without the potent aid of 
thin sections they can readily be distinguished by one character: 
namely, P. uniformis belongs to the double-leaved species, and, by 
