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 Fenestellge. 



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 vnth the branches j fenestrules oblong quadran- 

 gular, scarcely oval ; non-poriferous face with the branches regularly striated longitudinally, 

 the striae 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 4 1 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. 



