190 Cc. F. LASERON. 
POLYPORA PERTINAX sp. nov. 
(Plates V, VI, VIII, fig. 1, X, fig. 1.) 
Description:—Nature of colony uncertain, but probably 
fan-shaped. The largest specimen is about two inches in 
length, but this is evidently part of a much larger colony. 
Branches moderately coarse, very straight and rigid, bifur- 
cating at rare intervals, and thickened slightly opposite the 
cross-bars. The celluliferous surface is flat, and owing to 
the matrix filling the fenestrules, the branches appear 
broader, and the fenestrules smaller, on the non-celluliferous 
side. The non-celluliferous layer is rounded externally, 
but is slightly concave on the interior surface, that on 
which rests the bases of the cells. Both surfaces of this 
layer are covered with longitudinal striations, more pro- 
minent however on the internal surface. The branches are 
separated from each other by slightly more than their own 
width on the non-celluliferous surface and slightly less on 
the celluliferous side. Cross-bars thinner than the branches, 
distinct, rounded on the one side and flattened on the other, 
to conform to the shape of the branches, and faintly 
striated. The fenestrules are oval, about twice as long as 
broad. 
The cells are rounded, the apertures slightly restricted, 
with exserted rims, and separated from each other by a 
little more than their own diameter. The celluliferous 
surface is flat, or even slightly concave, and there are 
typically three rows of alternating cells on each branch. 
Previous to bifurcating, the branches generally broaden 
very much, and the number of cells increases typically to 
six. There are usually two cells longitudinally in the 
length of one fenestrule, with an additional one in the width 
_ of the cross-bar. 
Measurements:—In the space of 10 mm., measured 
longitudinally, 8 cross-bars were counted. Length of 
fenestrule °75 to 1 mm., width °*4 mm. 
Locality and Horizon :—Allandale (Lower Marine Series). 
