16 Proceedings of the Royal Society of Victoria. 



latter, if really youngei' than the mesozoic strata, which I 

 doubt, must have covered them in some part of the area. 

 Certainly, volcanic rocks, as widely spread as these have been 

 shewn to be, cannot have consisted of dykes only, but must also 

 have flowed out in sheets. In certain places, as at Nareen, 

 Wando Dale, Grit Jurk, Carapook, and Ivilliecrankie, the 

 underlying rocks are of course visible, and consist either of 

 granite or the fundamental crystalline schists of the area. 



EXPLANATION OF PLATE I. 



Fig. \. — A slice from Little Piock, Brit Brit, shewing a mass of 

 small sanidine crystals with large macroscopic ones 

 in the centre of the field. Polarized light, nicols 

 crossed. 



Fig. 2. — Typical trachytic rock from Carapook with a por- 

 phyritic twin crystal of sanidine. Polarized light, 

 nicols crossed. 



Fig. 3. — Typical trachytic rock from Carapook. The main mass 

 of the I'ock is sanidine, and scattered through it 

 are columnar crystals of probably augite. Ordinary 

 light. 



Fig. 4, — Trachytic rock from Phoines, near Cai^apook, with 

 sanidine and Ijrown augite. Ordinary liglit. 

 All magnified 28 diameters. 



