140 
Kirtley F. Mather 
Genus PRISMOPORA Hall 
Prismopora concava n. sp. 
Plate VII, figures 7, 7a. 
Description. Zoarium consisting of triangular branching 
stems, the faces of which are sub-equal in width and trans- 
versely concave. The width of the faces varies between 3.5 
and 4.0 mm. and the margins are very slightly sinuous and 
essentially parallel. Zooecia occupy the middle portion of each 
face over a space about 1 mm. in width and extend in a pinnate 
arrangement from this central strip to the lateral margins of 
the zoarium, leaving crescentic maculae curving inward from 
the margins. Between the non-poriferous and slightly de- 
pressed maculae, about 5 of which occur in 1 cm., there are 
4 or 5 curving ranges of apertures with 5 or 6 zooecia in 2 
mm. along the rows. Apertures circular, 1.5 to 2 diameters 
apart, directed obliquely to the face of the stem; peristomes 
faint and incomplete. 
Remarks. The pinnate arrangement of the zooecia of this 
species suggests that of Phractopora trifolia of the Keokuk 
stage, but the generally smaller dimensions and structures of ' 
the zoarium make it evident that the material at hand repre- 
sents the genus Prismopora. From P. triangulata, the common 
Pennsylvanian species, it is sharply distinguished by the orderly I 
arrangement of the apertures and from P. sereata by its nearly 
straight margins. 
Horizon and locality. Kessler limestone: East Mountain, , 
Fayetteville, Arkansas (Station 209). 
Genus GLYPTOPORA Ulrich 
Glyptopora crassistoma n, sp. 
Plate VII, figures 2, 2a. " 
Description. Zoarium consisting of thin bifoliate expansions 
known only from fragments, the largest of which is 16 by 12 
mm. in size. Surface marked by numerous lanceolate non- 
poriferous maculae or dimples irregularly placed but with a 
suggestion of a pinnate arrange xnoii t/ ^ diiiiples variable in size | 
but ordinarily between 4 and 6 mm. in length and about 1 mm. 
in greatest width, depressed somewhat below the surface of 
the frond, adjacent ones about 3 mm. apart, measuring between f 
