154 Cincinnati Society of Natural History. 
ones having a diameter of about ;4,th of an inch. At intervals there 
are distinct groups of large cells, some of which have a diameter ex- 
ceeding ~,th of an inch. True interstitial cells are apparently want- 
9, the few small cells occasionally seen being doubtlessly young 
ones. The spiniform tubuli I have not been able to detect at the 
surface. Pellicle not observed. 
In longitudinal sections the excessively thin-walled tubes in the 
axial region are seen to be crossed by few remote diaphragms. The 
tubes approach the surface with a gentle curve, the thickening of the 
walls that usually takes place as they enter the peripheral region, is 
scarcely perceptible in this species. The diaghragms are quite 
numerous in the “mature” or peripheral region, being about one 
tube diameter distant from each other. When the section passes 
through the spiniform tabuli they are, despite their small size, 
readily detected by the thickened appearance they give to the cell- 
walls between which they are placed. I have not been able to find any 
traces of interstitial tubes. 
Tangential sections of this species are remarkable for excessively 
thin-walled angular cells, between every five or-six of which the 
spiniform tubuli, which are smalier than in any other species of the 
genus, and inconspicuously isolated. The groups of large cells, men- 
tioned in the description of the surface characters, are of course, quite 
distinct in this kind of section. 
This species is closely allied to D. appressa in its growth and 
general features. Under the hand glass that species is seen to have 
somewhat smaller cells, less conspicuous clusters of large cells, and 
thicker tube-walls. Internally the much smaller spiniioes tubuli of 
D. paupera will serve to distinguish them. 
Formation and locality : Cincinnati group. Quite rare near the 
tops of the hills back of Cincinnati, O., where it appears to be re- 
stricted to a vertical range of only a few feet, somewhere between 375 
and 400 feet above low water mark. | 
DEKAYIA MULTISPINOSA, n. sp. (Plate VI., figs. 8 and 8a. ) 
Zoarium dendroid, branches somewhat flattened, from .25 to .6 inch 
in diameter. Surface not raised into monticules. Cell apertures often 
covered by a pellicle, upon the surface of which, and over the angles 
of junction of the cells, the numerous, but comparatively small spini- 
form tubuli are sharply elevated. Even when the pellicle is absent 
these spines are very readily detected under a hand glass. At inter- 
vals of about .1 of an inch, measuring from center to center, are clus- 
