122 
Kirtley F, Mather 
Remarks. The approximate equality between the number of 
branches transversely and of fenestrules longitudinally in a unit 
distance and the presence of nodes along the reverse side of the 
branches are the distinguishing features of this species. In 
comparison with P. ulrichi of the Coal Measures the greater 
number of zooecial apertures in a unit space along the branches 
is also noteworthy. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). 
Polypora magna n. sp. 
Plate V, figures 1, la. 
Description. Zoarium an undulating, fan-shaped expansion 
attaining a length of at least 9 cm. and a width of 7 cm., com- 
posed of rigid, bifurcating branches united at regular intervals 
by strong dissepiments. Branches somewhat flattened on the 
reverse face and hence moderately sub-angular at either side; 
coarsely granulose, about 0.7 or 0.8 mm. in width but increasing 
to 1.4 mm. below a bifurcation and decreasing to 0.5 mm. imme- 
diately thereafter, as observed on the non-poriferous face of the 
frond ; typically 6 in a centimeter ; obverse face of the branches 
broadly convex, the branches a little wider there than on the 
other side. Fenestrules sub-oval in outline, 41/2 to 5 occurring 
in a centimeter, somewhat larger, 0.8 to 1.2 by 1.2 to 1.4 mm., on 
the reverse face than on the obverse, 0.6 to 0.7 by 1.0 to 1.2 mm., 
but shaped much the same on either side of the frond. Dis- 
sepiments nearly as wide as the branches and similarly shaped 
on the non-poriferous face of the zoarium but not increasing 
in width toward the opposite side as do the branches. Zooecia 
arranged in 6 or 7 rows increasing to as many as 10 below bifur- 
cations and decreasing to 5 immediately thereafter; apertures 
circular, separated by a space of 2 or more diameters in the 
ranges, about 16 or 17 occurring in 5 mm. 
Remarks. This, the largest of the Morrow Polyporas, is quite 
distinct from the others here described and may be compared 
with only one of the previously known members of the genus, 
P. submarginata. From that species it is readily distinguished 
by its less elongated fenestrules and the absence of spines be- 
tween the zooecial apertures. The large number of zooecial 
