CORALS AND BRYOZOA. 
271 
Ptilodictya plumea, n. sp. 
PLATE LXI, FIGS. 9-12. 
Zoarium consisting of a flattened stipe, base conically truncated, distal extremity 
of frond rounded. One well-preserved frond, immediately above the trun¬ 
cated basal apex, is cylindrical, having a diameter of 1 mm., very gradually 
enlarging and becoming flattened for the distance of 6 mm., where it expands 
much more rapidly and becomes very thin; at a point 7 mm. above the base 
the frond is 17 mm. in width, above that point the margins are sub-parallel, 
the frond very slightly expanding; on other examples the margins are parallel 
and the frond continues of uniform width’; transverse section flattened-lenticu- 
lar, greatest thickness .30 mm.; non-celluliferous marginal space obsolete. Cells 
tubular, oblique for the greater portion of their length, but usually opening 
directly outward. The cylindrical basal portion of the frond is striated; 
striae conspicuous, sharp, interrupted, granulose. Cell apertures circular or 
broadly oval, immersed, diameter about .18 mm., separated by from one- 
third to one-half the diameter of an aperture, generally irregularly disposed, 
but sometimes forming sub-regular intersecting rows oblique to the axis 
of the frond. Near the margins the cell apertures are oblique to the axis 
and present a confused appearance. Peristomes obsolete. Interapertural 
space elevated, convex or angulated, granulose, usually only one series of 
granules between adjacent apertures, but occasionally two, sometimes, where 
the apertures are disposed in intersecting rows there are more prominent 
nodes at the angles of the interapertural ridges. The surface is marked by 
low convex monticules, the centers of which are distant about 2 mm.; the 
apertures on these are a little larger than the others, and sometimes present 
a slightly confused arrangement. 
-V- -V- 
*3v*W7f , ’7r‘7f , 7rW7SW 
Formation and locality. Hamburg-on-the-Lake, Erie county, N. Y. 
