162 Proceedings of the Royal Society of Victoria. 



between the diabase on the north and an intrusion of 

 aplite on the south-east. The unaltered ordovician is shown 

 as half a furlong in width, but the only part which is 

 represented as metamorphic is a circular patch at the 

 extreme head of this ordovician bay. Had the metamorphic 

 rocks been formed by the alteration of the ordoviciaiis owing to 

 the intrusion of the diabases and the aplites, then we should have 

 certainly expected the whole of this nari'ow band of the 

 ordovicians to have been altered. 



The map at the northern end of the Heathcote series is 

 equally difficult to explain on the view that the metamorphic 

 rocks have been formed by the alteration of the ordovicians 

 (PL XXIV., Figs. 3, 4). For instance, the plan of Crosbie 

 and Redcastle (Nos. A and B, opposite p. 4, in Mr. 

 Howitt's Monograph) shows one thin band of metamorphic 

 rock in the southern half of paddock 4C ; it lies between diabase 

 •on the east and the ordovician on the west ; but the ordovician 

 rocks at the northern end overlap the metamorphic and rest 

 directly on the diabases. Similarly on the western flanks of the 

 diabase range at the south-eastern corner in Crosbie and south- 

 western corner of Redcastle and north-western corner of Dargile. 

 Here for most of the way the ordovicians are separated from the 

 diabase by a band of metamorphic rocks ; but at the northern 

 half of paddock loaa in Redcastle, the ordovician rocks are 

 shown^ to overlap the metamorphic band and rest directly on the 

 diabases. 



I have not been able to confirm the mapping in these localities, 

 and have not visited the sections at the northern part of Crosbie. 

 But the evidence is of importance as it is inconsistent with the 

 view expressed in the memoir accompanying those maps. The 

 field relations show, according to the work of the surveyor, that 

 the ordovician rocks have been deposited unconformably on the 

 edge of an old series of metamorphic rocks and diabases. In 

 some cases the ordovicians were laid down upon the xuetamorphic 

 rocks and in other cases directly upon the diabase. Moreovei', 

 the metamorphic rocks occur in places where there are no igneous 

 rocks exposed in the immediate vicinity. Thus an exposure of 



1 Howitt, op. cit., Map facing p. 4 ; the part in (luostion is reproduced on pi xxiv. , fifr. 4. 



