154 
BULLETIN OF THE LABORATORIES 
III. Clathropora frondosa, Hall. 
{Plate XV, Fig. 3; Plate XVII, Fig. 3.) 
Clathropora frondosa, Hall, 18S2, iith Indiana Geol. Report. 
Fronds flabellate, composed of branches which divide dichoto- 
mously at short intervals, forming short curves, which come in contact 
again, coalesce, and divide as before ; by this means a fenestrated 
frond is produced, which would alternately consist of a series of short 
free branches or a series of rings along the growing edge, if the growth 
were regular. In that case the fenestrules would be also arranged in 
a concentric series of rows, the rows containing one more fenestrule 
after each reunion of the branches. As a matter of fact, bifurcation 
does not proceed in so regular a manner, but still enough regularity 
exists to place the fenestrules in something like lines or curves, which 
are often very striking. The fronds expand rapidly above, the sides 
forming broad, outward curves, the anterior edge being broadly round- 
ed. The fenestrules are comparatively small, oval or even circular in 
shape. The cells are quadrangular, rhomboidal or hexagonal in form, 
never typically elongated. From 7 to 8 cells occupy a length of 2 
mm. The number of cell-rows on the branches varies from 8 to 17. 
The fenestrules are also variable in size, an average size being 2 mm, 
varying to 3 mm. The fronds frequently become very large, attaining 
a length and breadth of 200 mm. The base of the fronds in the two 
:specimens which alone preserved this portion was observed to be 
broadly rounded just beneath the first fenestrule, indicating that the 
frond was attached by the stipe to an articulating base ; the latter has 
not been identified in our collections. 
Locality and position. Soldiers’ Home Quarries, Centreville, Clin- 
ton Group. 
IV. Clathropora Clinton ensis. Hall and Whitfield. 
■{Plate XV, Fig. 4; Plate XVII, Fig. 4.) 
Clathropora Clintonensis, Hall and Whitfield, 1875 ; Ohio, Pal. Vol. H. 
Fronds very similar to the last, the fenestrules varying from 2 to 
5 mm. in length ; typically they are of larger size than those of C. 
frondosa^ and are more elongated and irregular in form, varying from oval 
to ovate, sub-rhomboidal,. or even irregular in outline, the upper part 
