Mr Etheridge on Fossils from Boiven River Coalfield. 275 



specimens intermediate between it and the supposed F. 

 ampla referred to above. In point of texture the one now 

 under consideration compares most favourably with Lonsdale's 

 F. fossula. 



That one and all of these are a single variable species it is 

 difficult to believe, and I do not for one moment so assert it ; 

 but it is nevertheless quite clear that, taking certain well- 

 marked forms amongst these Australian Carboniferous Polyzoa 

 as fixed points, we then have a series of intermediate ex- 

 amples so varied and so numerous that it is exceedingly dif- 

 ficult, and at times I believe quite impossible, to draw a line 

 of demarcation where one species begins and the other ends — 

 what is one and what is another. Some observers would 

 doubtless endeavour to make every slight variation a specific 

 diff'erence ; but with this I do not agree, and were they to do 

 so in the present instance, a difficult and much obscured sub- 

 ject would become still more complex. 



Genus Protoretepora— Z^e Koninck, 1877. 



(Foss. Pal. Nouv-Galles du Sucl., pt. 3, p. 178.) 



Obs. — This genus was established by Professor De Koninck 

 for the reception of certain species hitherto placed in Fenestella, 

 Polypora, and other genera. According to the original defini- 

 tion of Fenestella, as laid down by Lonsdale, the celluliferous 

 face of the polyzoarium is external.* He says, " One row of 

 pores on each side of the branches externally;" and again 

 M'Coy, in describing the genus, adds, " two rows of prominent 

 pores on the external carinated face of each interstice." f By 

 the redefinition of M'Coy, and again of King,| the original 

 Fenestella of Lonsdale became restricted to those fan-like or 

 infundibuliform reticulate Palaeozoic Polyzoa in which the 

 vertical or radiating ribs (interstices) are alone poriferous, 

 and the connecting bars (dissepiments) not so. By this judi- 

 cious restriction there were eliminated from Fenestella (Lonsd.), 

 such colonies as Polypora (M'Coy), Ptylopora (Secular), Phyllo^ 

 pora (King), and the like. Polypora (M'Coy), includes those 



* Murcliison's "Silurian Syst.," 1839, p. 677. 



+ Synop. Carb. Limestone Foss. Ireland, 1844, p. 200., 



X Mon. Perm. Foss. England, 1850, p. 35. 



