W. J. SOLLAS ON PHARETROSPONGIA STRAHANI. 255 



Fig. 9. Individual spicules of fig. 8 ( X 435). 



10. Transverse sections of spicules ( X435). 



11. Spicule from a recent Australian sponge, for comparison with fig. 9 



(X435). 



12. Section of fibre of Australian sponge ( X 140). 



13. Fragments of spicules containing small spherules of an unknown 



nature ( X 140). 



14. Isolated spherule from the infilling chalk-marl of an intermesh 



(X140). 



15. Outlines of spheroidal bodies composed of the same material as the 



preceding spherules ( X 140). 



16. Section of the preceding, showing component spherules (xl40). 



Discussion. 



Rev. T. G. Bonnet remarked that the question of fossilization 

 was one of great difficulty, but it seemed to him to be rather an 

 unusual process for silica to be replaced by carbonate of lime. 



The President thought it was more probable that tbe sponge de- 

 scribed was one of the Calcispongise. The spherules observed by 

 the author were exceedingly interesting to him, as he had observed 

 in silicified corals what seemed to him to be similar bodies, which, 

 however, he regarded as being dusty innllings of minute cavities ; 

 at least the appearance presented by them when carefully examined 

 under polarized light seemed to justify such a conclusion. 



