112 
Kirtley F. Mather 
with from 15 to 18 occurring in the space of 5 mm. ; interspaces 
thin. The zooecial tubes are comparatively short, prostrate 
below but soon becoming erect and proceeding directly to the 
surface of the layer ; diaphragms numerous, ordinarily less than 
their diameter apart, perforated. Mesopores rarely present; 
acanthopores moderately large, generally present at the junction 
angles of the zooecial walls. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville, Arkansas (Station 134). Morrow formation: near Ft. 
Gibson, Oklahoma (Stations 296 and 301). 
Stenopora sp. 
Plate IV, figure 6. 
A single, well-preserved specimen of another species of Sten- 
opora was found in association with the form just described. 
It consists of a laminar expansion about a millimeter in thick- 
ness and apparently free. The surface is smooth except tor the 
presence of low pyramidal spines at the junctions of the zooecial 
walls which are very thin. Apertures large, somewhat irregular 
in size and shape but commonly hexagonal or pentagonal, with 
angles very little rounded, and with only 11 or 12 zooecia occur- 
ring in the space of 5 mm. Zooecial tubes short, prostrate below 
but curving rapidly upward and proceeding directly to the sur- 
face of the zoarium ; diaphragms apparently rare ; mesopores 
exceptional; acanthopores commonly present at the junction 
angles of the walls. 
The specimen is evidently representative of an undescribed 
species and is characterized by the large apertures accompanied 
by very thin zooecial walls. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville, Arkansas (Station 134). 
Genus ANISOTRYPA Ulrich 
Anisotrypa sp. 
Plate IV, figures 7, 8. 
Description. Zoarium a curved laminar expansion, probably 
a fragment of a large hollow branch, composed of several layers 
intergrown and lined with a thin epitheca. Apertures sub-cir- 
cular, without conspicuous variation in size, 13 or 14 occurring 
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