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BULLETIN OF THE LABORATORIES 
species are not in a very good state of preservation and better speci- 
mens may prove that my figures of them are defective in not showing 
a sloping area and in having the zooecia apertures too large. 
Formation and locality : — The Ohio specimens are from the Cuy- 
ahoga shales at Lodi ; the types of both 7 ?. incrassata and R. spiralis 
are from the Keokuk group at King’s Mountain, Ky. 
Collection of Prof. C. L. Herrick. 
RHOMBOPORA OHIOENSIS, n. sp. 
(Plate XIV, Fig.^.) 
Compare Rhombopora dichotoma, Ulrich. 111. Geol. Surv. vol. VIII, pi. LXX^ 
figs. 13, 13b. 
Zoarium ramose, bifurcation distant. Branches cylindrical, be- 
tween i.o and. 1.3 mm. in diameter. Zooecia apertures arranged in 
longitudinal and diagonally intersecting series, oval, small in the old 
state, longer when young, the diameter becoming smaller with age by 
an internal deposit of sclerenchyma. Interspaces ridge-shaped, more 
acute in the young than in the fully matured state. The interspaces 
form sinuous ridges, alternately approaching and diverging from each 
other ; rarely coalescing, usually leaving a narrow depression between 
the ends of the sloping areas that surround the zooecia apertures. 
Summit of ridges with a row of small tubercles (acanthopores ?). 
measuring longitudinally ten or eleven zooecia occur in 5 mm.; diag-. 
onally seven in 2 mm. The diagonal rows intersect each other at an 
angle of about 65°. 
The form briefly described above is so much like R. dichotoma^ 
Ulrich, from the Burlington limestone of Iowa that I am strongly in- 
clined to regard is as only a local variation of that species. The num- 
ber of zooecia in a given space and the general aspect of the surface is 
the same, the only differences observed being the greater frequency of 
the narrow sulcus between the ends of the ceils, the more acute angle 
at which the diagonal rows intersect each other and the smaller diam- 
eter of the branches. 
A still smaller form, with more frequently bifurcating branches, 
0.7 or 0.8 mm. in diameter, occurs at the Richfield, Lodi and Bur- 
bank exposures . Whether this should be separated from R. Ohioensis 
is as yet undetermined. It agrees very closely (so also does R. Ohio- 
ensis) with a common species of the Keokuk group of Iowa and Illi- 
