120 
Kirtley F. Mather 
ularly 0.7 by 0.8 mm. in lateral dimensions ; sub-circular to sub- 
oval in outline on the obverse face, 0.3 to 0.4 mm. by 0.2 to 0.3 
mm. in longitudinal and transverse diameter; quite constantly 
9 to the centimeter longitudinally. Zooecia arranged in four 
rows increasing to five or six before bifurcations and for short 
distances thereafter decreased to three ; apertures circular, fairly 
closely spaced, separated by one to one and a half diameters in 
the ranges, 21 or 22 occurring in a space of 5 mm. ; ranges prob- 
ably not separated by ridges or rows of tubercles. 
Remarks, This species displays a close affinity to P. nodo- 
carinata of the Upper Coal Measures but is distinguished from 
it by the more strongly carinate branches as seen on the reverse 
side and by the absence of the rows of tubercles on the obverse 
face between the zooecial ranges. In the shape of the branches 
it is comparable to P. triangularis but is sharply differentiated 
from that form by the shape of the fenestrules and the absence 
of the nodes on the reverse face. 
Hoidzon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). Brentwood limestone: East 
Mountain, Fayetteville, Arkansas (Station 150). Morrow for- 
mation: near Ft. Gibson, Oklahoma (Station 301). 
Polypora constricta n. sp. 
Plate IV, figures 16-17. 
Description. Zoarium a funnel-shaped or foliar undulating 
expansion composed of strongly carinate, nearly rigid branches 
united at regular intervals by dissepiments sub-equal to the 
branches in shape and width. Branches triangular in cross-sec- 
tion, 8 or 9 in a centimeter, carinate, 0.3 to 0.5 mm. wide on the 
reverse face with an occasional small, rounded tubercle which 
is situated at the point of junction with the dissepiments ; broadly 
convex and wider, 0.8 to 1.1 mm., on the poriferous side where 
the surface is finely rugose and a row of small spines, 0.3 to 
0.4 mm. apart, is present along the median line of many of the 
branches. Fenestrules sub-quadrate or sub-polygonal, with 
rounded corners on the reverse where their dimensions are close 
to 1.0 mm. in either direction; constricted toward the obverse 
side of the frond by the widening of branches and dissepiments 
so that they have a circular or sub-oval outline and a length and 
