262 PALEONTOLOGY OF OHIO. 



Ptilodictya flagellum, Mcholson. 



Plate 25, figs. 4, 46. 



Polyzoary consisting of a single, narrow, unbranched, two-edged, flat- 

 tened frond, which has an acutely elliptical section. The frond com- 

 mences at an attenuated base, and gradually expands till a width of one 

 line is reached, the total length in the only specimen examined being 

 eight lines. The general form of the frond is falciform, but towards the 

 base it is alternately bent from side to side in a flexuous manner. The 

 cells are arranged in longitudinal rows, about ten rows in the space of 

 one line, the cells of contiguous rows alternating with one another. The 

 cell-mouths, when most perfect, are narrow and long-oval ; when worn, 

 sub-circular; and the rows of cells are separated by strongly elevated 

 ridges. The non-celiuliferous margins of the frond are inconspicuous; 

 and the centi^al axis, though doubtless present, was not clearly deter- 

 mined. 



The species most nearly resembles Ptilodictya gladiola, Billings, from 

 which it is distinguished by its much smaller size and less width, and 

 by its flexuous form. From P. falciformis, Nich., it is separated not only 

 by the above characters, but also by the longitudinal arrangement of the 

 cells. 



Position and locality : Cincinnati group, Lebanon, Ohio. Collected by Prof. Edward 

 Orton and Mr. W. PI. Bean. 



Ptilodictya (?) aectipoka, Nicholson. 



Plate 25, figs. 9, 96. 



Polyzoary forming a cylindrical, slightly branched frond, which is not 

 sharp-edged, exhibits no non-celluliferous borders, and shows no traces 

 of a central laminar axis. Cells arranged in obscurely longitudinal, 

 alternating rows, apparently perpendicular to the surface, and radiating 

 in all directions from an imaginary axis. Cell-mouths very much com- 

 pressed, much longer than wide, expanded below, and attenuated superi- 

 orly, where they are often somewhat twisted and bent. Upon the whole, 

 the cells are pyriform in shape, with their narrow ends directed upwards, 

 about eight in the space of one line measured vertically, and twelve in 

 the same space measured diagonally. The cells are not always in con- 

 tact, especially in their upper portion, and their borders are always dis- 



