Fauna of the Morrow Group 
123 
ranges is in keeping with the generally robust nature of the 
zoarium. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). Brentwood limestone: near 
Brentwood, Arkansas (Station 145). 
Polypora kesslerensis n. sp. 
Plate y, figures 6, 6a. 
Description. Zoarium an undulating, reticulated expansion 
composed of bifurcating branches united by short, broad dissepi- 
ments at regularly alternating intervals. Branches broadly con- 
vex on the obverse face, slightly flexuous; 0.8 to 1.0 mm. in 
width, increasing to 1.3 mm. below a bifurcation; ordinarily 7 
in the space of a centimeter. Fenestrules oval, 0.6 to 0.7 by 0.9 
to 1.0 mm. in size, 51/2 to 6 occurring in a centimeter longi- 
tudinally, arranged also in oblique rows where about 41/2 are 
found in the same distance. Dissepiments slightly depressed 
below the poriferous surface, comparatively short and broad, 
gently convex longitudinally, slightly concave transversely; 0.7 
to 1.6 mm. in width and 0.2 to 0.5 mm. long between the ranges 
of zooecia which in many cases encroach somewhat from the 
adjacent branches upon the ends of the dissepiments. Zooecia 
in five or six, or even as many as seven ranges, 18 or 19 in the 
space of 5 mm. longitudinally, the ranges distinctly sinuous, 
apertures circular, 1% to 2 diameters apart in the longitudinal 
rows. Eeverse not known. 
Remarks. Like that of P, complanata, the zoarium of this 
species has more the appearance of a ‘‘rhythmically perforated 
plate’^ than of a network with distinct branches.* From that 
form P. kesslerensis is distinguished by its comparatively larger 
fenestrules and more slender branches. It is, perhaps, inter- 
mediate between P. complanata and the two species to be next 
described which approach in characteristics the members of the 
genus Phyllopora. 
Horizon and locality. Kessler limestone: East Mountain, Fay- 
etteville, Arkansas (Station 209). 
