OF DENISON UNIVERSITY. 
75 
in the midrib ; in the lateral branches they are wedge-shaped and form 
a single series only. Apertures small, circular, in two ranges, one 
situated at the base of each lateral branch and two or three between. 
As near as can be determined, there are about twenty on each side of 
the midrib in 5 mm 
In having the longer lateral branches united by dissepiments this 
species approaches Ptilopora, but the general aspect and growth of the 
zoarium is so much like Pinnatoponi that it has seemed advisable to* 
place the species as above rather than under the former genus. If,, 
however, possession of non-celluliferous dissepiments is insisted upon 
as being the only point of difference between the two groups, then the 
species will have to stand as Ptilopora intermedia. In any event the 
specific name will indicate the intermediate character of the form. 
Compared with other species P. intermedia will be found to differ 
from Ptilopora vaLida, Ulrich,* from an equivalent horizon in Illinois, 
in being much more delicate, and from the associated Pinnatopora 
tenuiramosa, Ulrich,* in having the lateral branches less numerous in 
a given space and directed much more toward the distal extremity of 
the zoarium. In the last species the pinnae form an angle of nearly 
80° with the midrib. 
Formation and locality : — Cuyahoga shales of the Waverly series,, 
at Richfield, O. 
PINNATOPORA SIMULATRIX, n. sp. 
(Plate XIV, Fig. 3.) 
Zoarium pinnate, the reverse only seen. Midrib comparatively 
strong, about 0.6 mm. wide, somewhat flattened or broadly rounded 
and very finely striated longitudinally. Lateral branches (pinnae) de- 
pressed, slender, about 0.2 mm. wide, i to 2 mm. long, with fifteen 
given off on each side, in 10 mm.; they form an angle of about 70° 
with the midrib and the longer ones are occassionally united to each 
other by exceedingly thin dissepiments. 
This is another species that simulates Ptilopora in having some of 
the longer lateral branches united by dissepiments. I am, however, 
inclined to hold that species of the type of this and the preceeding ones 
cannot be removed from Pinnatopora if we propose to make natural 
affinity the primary disideratum of our classifications. P. simulatnx 
