136 
Kirtley F. Mather 
typically 8 in number but increasing to 13 or 14 before a bifur- 
cation, the ranges slightly sinuous and rarely separated by a 
faint discontinuous ridge, 12 or 13 apertures occurring in 5 mm. ; 
in places an indefinite oblique arrangement ma,y be observed and 
still more rarely the apertures in the three lateral rows on either 
side are grouped into curving lines with a roughly pinnate 
arrangement ; non-poriferous margin comparatively wide. Aper- 
tures circular, peristomes complete, strongly elevated and thin 
when well-preserved, not so high and thicker on worn specimens. 
Remarks. Only two of the previously described American 
species of Cystoclictya are reported to have branches as 
broad as those of the individuals referred to this species. C. 
carbonaria of the Coal Measures is even more robust than the 
material at hand and has an appreciably larger number of zooecia 
in a unit distance. C. simulans of the Keokuk limestone is on 
the contrary more slender than C. hrentwooclensis and is further 
distinguished by its more widely separated zooecial apertures 
with strongly elevated and thick peristomes. The comparatively 
broad non-poriferous margins of the Brentwood form are also 
noteworthy. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). Brentwood limestone: vicin- 
ity of Fayetteville, Arkansas (Stations 135 and 148). 
Cystodictya sinuomarginata n. sp. 
Plate VII, figures 11, 11a. 
Description. Zoarium composed of ramose bifoliate branches 
with pinnate projections along the margins which in some in- 
stances develop into secondary branches. Branches from 2.0 to 
2.7 mm. in width, elongate sub-elliptical in cross-section ; lateral 
projections variable in outline but occurring quite regularly 4 to 
a centimeter on either side, varying from regular sinuosities in 
which the convex outline of the projection is the counterpart of 
the concave interspace and the whole projection is only 0.8 mm. 
in length, to small branchlets, 1.2 to 1.4 mm. in width and nearly 
2 mm., in length, directed somewhat obliquely outward from the 
primary stipe; the latter may develop into secondarjr branches 
nearly or quite as wide as the primary ones and having similar 
sinuous margins. Zooecia, in 6 to 8 ranges separated by fine 
