NIAGARA GROUP. 
167 
Genus POLYPORA (M‘Coy). 
This genus includes Bryozoa having the characters of Fenestella in every respect, except 
that they have more than two rows of cells on the branches. The carinate branches of Fene¬ 
stella, with a single row of cells on each side, are shown at the origin of the branches in 
the following species of Polypora ; but the number increases from two rows to four rows of 
cells on each branch, and there is a slight striation or carina between each row of cells. In the 
same example, also, the transverse dissepiments have in many cases a single cell at each ex¬ 
tremity as in some species of Fenestella. The character and habit of the animal, mode of 
growth, structure, and form of its habitation are precisely similar in both. 
The following is the only species that has fallen under my observation in this geological 
period, and its characters are probably more analogous to those of Fenestella than are those 
of the Carboniferous period. The one before us probably shows the first departure from the 
characters of true Fenestellae. 
562. 1. POLYPORA INCEPTA. 
Pl. XL D. Fig. 5 a-/. 
Frond expanded, flabellate, originally cyathiform or funnel-shaped; branches dividing 
somewhat regularly, sometimes anastomosing; transverse bars arranged at regular intervals, 
slender, scarcely thickened at their junction with the branches; fenestrules oblong quadran¬ 
gular, scarcely oval ; non-poriferous face with the branches regularly striated longitudinally, 
the stria extending into and running in the same direction as the transverse bars ; celluliferous 
side with the branches rounded, and marked by three or four rows of cells ; cells oval, alter¬ 
nating ; transverse bars thinner than on the non-poriferous side, sometimes expanded at ‘the 
junction with the branch, and bearing a single cell at each extremity. 
Fenestrules 4 to 41 in the space of three lines longitudinally, and 7 to 10 transversely in the 
same space. 
The inner or non-celluliferous face of this coral is undistinguishable from Fenestella; but 
the branches on the celluliferous side are not strongly carinated, and the surface is marked by 
three rows of cells. One of the specimens is flat and fan-shaped, but another has been clearly 
cup-form or funnel-shaped in its original condition. The branches are broader on the non- 
celluliferous face than any species of Fenestella in this group, except the F. tenuiceps , which 
has decidedly oval fenestrules. 
Fig. 5 a. The inner surface of a part of a large frond. 
Fig. 5 b. A portion of the same enlarged, showing the striated surface of the branches and the? 
transverse bars. 
