Fauna of the Morrow Group 
121 
width of only 0.2 or 0.25 mm.; 6 V 2 or 7 occur in a centimeter. 
Dissepiments of the same shape and nearly or quite as strong 
as the branches, 1.1 or 1.2 mm. in width on the obverse side 
and only 0.25 or 0.3 mm. long between the zooecial ranges of the 
adjacent branches. Zooecia in 4 or 5 ranges increasing to 6 or 
7 before bifurcation and decreasing to 3 immediately thereafter ; 
apertures rather large, circular, about IV 2 diameters apart in 
the rows, 15 or 16 occurring in the space of 5 mm. ; peristomes 
prominent. 
Remarks. The strong carinate branches and dissepiments, 
which give the fenestrules, as observed from the reverse face of 
the zoarium, the appearance of deep, funnel-shaped pits con- 
stricted below, serve readily to distinguish this species from 
others of the genus. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). Brentwood limestone: Maple 
Street, Fayetteville, Arkansas (Station 148). Morrow forma- 
tion: near Ft. Gibson (Station 296), and Hulbert (Station 299), 
Oklahoma. 
Polypora halensis n. sp. 
Plate VI, figures 3, 3a. 
Description. Zoarium an undulating, fan-shaped, reticulating 
expansion composed of comparatively delicate, bifurcating 
branches united at regular intervals by slender dissepiments. 
Branches somewhat flexuous, especially as viewed from the 
reverse side, where they are about 0.2 mm. wide midway between 
dissepiments and broader at the points of union, ornamented by 
small rounded nodes irregularly placed along the sub-carinate, 
non-poriferous face and varjdng in number from 0 to 4 to the 
fenestrule; obverse face of the branches broadly convex, from 
0.5 to 1.0 mm. in width, 7 or 8 branches occurring in 1 cm. 
Fenestrules sub-polygonal on the reverse where their diameters 
are from 0.9 to 1.1 by 0.6 to 0.9 mm.; smaller and sub-oval, 0.7* 
to 1.0 by 0.3 to 0.6 mm. on the obverse face of the frond ; usually 
7 to the centimeter longitudinally, not arranged in oblique rows. 
Dissepiments shaped the same as the branches but somewhat 
more slender. Zooecia in 4 or 5 ranges, increasing to 7 before 
bifurcation ; apertures circular, about two diameters apart in the 
rows, 20 or 22 occurring in 5 mm. 
