CORALS AND BRYOZOA. 
221 
and the absence of comparatively strong conical nodes between the cell 
apertures: from F. multaculeata by the more delicate appearance of the surface 
of the frond, the smaller and more broadly oval cell apertures, and the absence 
of minute spines on the peristomes and at the angles of the margins of the 
mesopores: from F. minuta by the smaller cell apertures, the much smaller 
mesopores, and the difference in the arrangement of the cell apertures, which, 
in that species, are disposed so as to give a striated appearance to the surface: 
from F. intercellata, of the Upper Helderberg group, by the finer appearance of 
the surface of the frond, the smaller cell apertures, and the much thinner 
walled -mesopores; in manner of growth, habit and general appearance it most 
nearly resembles F. tegens of this geological formation, but the cell apertures 
are slightly larger and more oval, the mesopores are larger, and generally only 
one series between adjacent apertures, while in that species there are usually 
two and sometimes three series : from F. densa it is distinguished by the smaller 
and more distant cell apertures, and the absence of maculae composed of larger 
apertures: from F. decipiens by the smaller, more regularly oval cell apertures, 
and the much smaller mesopores. 
Formation and locality. Hamilton group, Eighteen-Mile creek, Erie county, 
New York. 
Fistulipoha involvens, n. sp. 
PLATE LIX, FIG. 2. 
Zoarium consisting of thin foliaceous expansions, incrusting other objects; 
greatest observed thickness less than .50 mm. Cell apertures nearly cir¬ 
cular or broadly oval, diameter about .15 mm., irregularly disposed, usually 
separated by more than the diameter of an aperture. Peristomes thin, not 
elevated above the surrounding surface, the apertures frequently appearing 
immersed. Mesopores very minute, from two to four ranges between adja¬ 
cent apertures; margins equal to or higher than the peristomes. 
This species most nearly resembles F. micropora , but may be distinguished 
by the more nearly circular cell apertures, their wider separation, the more 
minute mesopores, and the greater number of series between adjacent cell 
