104 
A lig. F. Foerste 
row tubes in the interior of the fronds, approaching the surface at 
a very oblique angle, rapidly widening at the surface; the upper 
wall thin, moderately convex, with a convex anterior outline; the 
lower wall formed by the general surface of the frond, concave for 
a short distance anterior to the margin of the upper wall; the cav- 
ity thus formed at the aperture is filled usually with clay, produc- 
ing a semilunate border to the anterior edge of the upper wall, 
very similar to that of Alveolites platys. Apertures about 4 in a 
width of 5 mm. 
Associated with these specimens are thin expansions similar to 
those of Alveolites platysjhxxt with corallites equal in size and form 
of aperture to those of Platyaxum pegramensis . The lower surface 
of these expansions is covered by a wrinkled epitheca. The largest 
specimen has a width of ii cm. The free edges of the expansions 
have a thickness of I to 2 mm. The anterior outline of the upper 
wall of many of the corallites of one specimen is concave or even, 
V-shaped owing to the weathering back of the raised median part 
of the wall; at some apertures this median part of the upper wall 
is raised as distinctly as in Platyaxum platys. In another specimen 
the anterior part of the upper wall is only slightly convex, but the 
anterior outline is distinctly convex. The form of the anterior out- 
line of the upper wall appears to be determined in part by the 
general curvature of the wall; where theupperwallis very depressed 
even along the median part the outline is more strongly convex, 
where the median part is distinctly raised the outline is nearly 
straight or moderately concave; when the median part is sharply 
raised the median part of the outline is often distinctly indented, , 
and the adjacent parts project slightly. These flat expansions 
with a basal epitheca, which we shall call Alveolites pegramensis 
temporarily, are believed to be identical specifically with Platy- 
axum pegramensis. Although no specimens showing the mode of i 
origin of the frondose forms are at hand, it is believed that they 
originate locally from parts of the flat expansions. 
Brownsport bed: bridge two miles west of Pegram, Tennessee. 
Pachypora (Platyaxum) platys, sp. nov. 
{Plate I, Figs. 16, A, B, C.) 
Corallum forming flat, thin fronds, i to 3 mm. thick, irregularly 
lobate, with corallites on both sides. The interior of the frond is 
