PERMO-CARBONIFEROUS FENESTELLIDE. 185 
to McCoy’s original description,* I have little hesitation in 
referring the other three to Polypora. If the Australian 
species alone might be considered, the differences between 
the two generic types are distinct, and are as follows:— 
In Protoretepora, the colony is cup-shaped or infundi- 
buliform, with the cells upon the inside; in Polypora it is 
fan-shaped or flat, and while only one surface is cellulifer- 
ous, this can hardly be said to be either upon the interior 
orexterior. In connection with this last character, McCoy 
particularly remarks upon it when he says, “‘the species of 
the present genus (Polypora) do not appear to assume an 
infundibuliform or cup-shaped figure, but are usually flat 
and fan-shaped.’’* 
The branches of Protoretepora are more massive, the 
non-celluliferous layer is much thickened, particularly in 
older specimens, and instead of being vertically striated, 
the striz are in the nature of concentric plications sur- 
rounding the fenestrules. 
The cross-bars are nct prominent, nor as distinct as in 
Polypora, and there is a tendency for the fenestrules to be 
formed by an angulation of the branches as in Phyllopora. 
The cells of Protoretepora are rhomboidal in section with 
thin partition walls, though the mouths themselves are 
circular or oval, but the position of the cell walls is marked 
on the surface by a slight ridge, so that the cell mouths 
appear as circular dots each in the centre of the mesh of 
a rhomboidal pattern. 
On the other hand, in Polypora proper, the branches are 
straight, with distinct, often rod-like cross-bars, and the 
non-celluliferous surface is vertically striated. 
Referring to the presence or absence of cells upon the 
cross-bars, in allthe specimens of Protoretepora examined, 
* McCoy, (8) p. 206 
