188 C. F. LASERON. 
the non-celluliferous layer occasionally much thickened. 
Cell-bearing surface flattened, the external surface ridged 
and angular, and covered with fine striations which are not 
longitudinal, but tend to surround the oval, but often nearly 
circular fenestrules. Cross-bars not. prominent and sunk 
beneath the general level of the main branches. These 
are much thickened opposite the dissepiments, and there is 
a marked tendency for the cross-bars to be thus suppressed, 
the main branches bending and forming the fenestrules by 
uniting with the adjacent branches. 
No perfect celluliferous surface is yet known, but speci- 
mens as a general rule, so readily split along the line 
between the two layers of the colony, that the base of the 
cells are often visible. By this it is seen, that the cells 
are rhomboidal in section, packed closely together, their 
thin walls running diagonally across the branch, from 7 to 
10 rows upon each branch, and 3 or possibly 4 in the length 
of each fenestrule, and an additional 1 or 2 in the breadth 
of each dissepiment. So far, though several well preserved 
specimens have been examined, no cells have been actually 
detected on the cross-bars, though there is a tendency for 
the cells to encroach upon their borders. 
Measurements :—Average length of fenestrule, 1 to 1°2 
-mm., width °5 to ‘75 mm., widtb of branches up to 1°5 
mm.; and in a space of 10 mm. measured longitudinally 
there are present on an average 6 cross-bars. 
Horizon and Locality:—Branxton (Upper Marine Series). 
Relations and differences: — Protoretepora montuosa is 
undoubtedly closely related to Polypora Koninckiana 
Waagen and Pichl,* from the Carboniferous formation of 
India, this species showing similar concentric striations on 
the non-celluliferous side, the same thickening in older 
1 Waagen and Pichl, (8) pl. 90, fig. 1. 
