Rocks near Heathcute. 345 



he has sho-nTi that cherts and jaspers associated with the serpen- 

 tine area of Mt. Wellington, Gippsland. contain Upper Ordo- 

 vician graptolites. 



Mr. Summers^ has also shown at Tatong that a series nf cherts 

 is interbedded with unaltered slates whose age is not definitely 

 fixed, hut is probably Ordovician. 



11. — Conclusion. 



With regard to the conclusions at which I have arrived in this 

 paper, I find myself only in partial aigreement with previous 

 workers. 



I am in agreement with Mr. Dunn in regarding the diabases 

 aa mainly effusive. V7ith Professor Gregory I agree that the 

 diabase is pre'-Silurian, and with Dc. Howitt that the Ordo- 

 vicians are altered along the contact \x\th the diabase, and that 

 the l)lack cherts are altered Ordovician rocks. On the other 

 hand, I disagree with Dr. Howitt, who regarded the diabase as a 

 rock intrusive in Devonian times. I regai-d it as mainly efi'usive 

 in origin and probably of Lower Ordovician age. With Professor 

 Gregory I am unable to agree in the interpretation of some of the 

 field evidence, and I differ from Kim in regarding the cherts as 

 altered Ordoviciana and the diabase as being probably Lower 

 Ordovician in age, and in his interpretation of the relations of 

 land and sea in Lower Ordovician times. 



The new evidence which is brought forward in this paper is 

 as follows : — 



1. Some alteration in the geological boundaries and con- 

 siderable alterations in interpretation of field evidence. 



2. The finding of Prfltospongia and of other minute organ- 

 isms in the Ordovician rocks, and the possible occurrence of 

 Radiolaria. ^ 



3. The evidence for regarding much of the diabase as con- 

 sisting of foliated diabase tuffs. 



4. The explanation of the original composition and mode of 

 silicification of the cherts. 



5. The diaibasic character of some of the Ordovician rocks. 



6. The origin of the jasperoids. 



