augite in a finely crystallised felspathic groundmass. The 

 inclusions are considerably decomposed. Tliey contain pale 

 rhombic and monoclinic pyroxene, intergrown in a curious 

 fashion, and unlike anything noticed in Dundas, together 

 with a considerable amount of the greenish substance, com- 

 posed of interlacing fibres and irregular areas which has 

 been taken to be talc pseudomorphous after olivine in the 

 Dundas rocks, though the birefringence seems rather low. 

 There is little doubt that the inclusion represents a plutonic 

 ultrabasie rock; but from its apparent association with 

 granitic rocks it does not seem certain that the inclusion 

 is of the same series as the Dundas rocks. 



This point must here be left undecided. Nor can we with 

 certainty correlate the Dundas inclusions with the nodules 

 of olivine, pyroxene, and spinel v> iiieh are abundant, in the 

 basalt flows of New England and the Darling Downs, 

 and which resemble those studied in detail in the basalt of 

 Mount Gambier. 1 These have not been studied at all, in 

 t ie preparation of this paper, and cannot therefore be dealt 

 with as perhaps they should be in this discussion. 



Outside Australia, though nodules of hornblende, pyroxene 

 or olivine, are common enough in basaltic rocks, gabbroid 

 inclusions are singularly uncommon. Lacroix divides in- 

 clusions in volcanic rocks into two main groups — enallo- 

 genous and homceogenous— (not homogeneous). The former 

 contains those inclusions which in origin and mineralogical 

 composition are in no way related to the including volcanic 

 rocks (as the fragments of sandstone and conglomerate in 

 the Dundas neck); the latter group comprises those inclus- 

 ions which in mineralogical composition and origin exhibit 

 a more or less marked analogy with the enclosing rock.' J 

 But it is in just such rocks as are here described, that lie 



1 E. R. Stanley. I'rans. n-M I'r.u?. Roy. Sor. South Austr, 1909, p. 66. 



