<'l,('rt>< <in<l I)!al>nsf; Rovk>i. 245 



is X. 40 detr. W. Unfortunately these strikes are in areas fairly 

 widely separated from one another, and so have not much signi- 

 ficance ; still they certainly show no evidence of unconformity 

 between the Ordovician and the cherty series. In this area, 

 therefore, the most natural position in which to place the cherts 

 is the Upper Ordovician, what little evidence of age there is re- 

 corded being in favour of this view, and it is only com- 

 parison with the Heathcote district that makes one consider 

 the possibility of the cherts belonging to the pre-Ordovician. 



The relation of the cherts to the diabase is difficult to deter- 

 mine, as there is no exposiu"e of any sharp junction between the 

 two, the whole surface being generally covered vnth rich diabasic 

 soil. Mr. Howitt recorded . a hornblendic dyke traversing the 

 cherts, so that if this dyke be connected with the diabases, the 

 cherts must be the older series. 



In general the raetamorphism of the sediments seems to in- 

 crease towards the contact, but exceptions to this rule may be 

 observed. 



In allotment 6, Parish of Toombullup North, is an occur- 

 rence of Selwynite similar to that obtained from Heathcote ; 

 but its relation to the other rocks is obscure, as it is sur- 

 rounded by alluvial material. This is of considerable interest, 

 as it serves as a link to connect up the Tatong area with the 

 Heathcnte area. 



Petrolugy of the Rocks. 



As I have had no opportunity yet of sectioning and examin- 

 ing the rocks of this district microscopically, the petrological 

 description of the igneous and metamorphic rocks must be 

 deferred until some future time. 



Conclusions. 

 In the Tatong area the cherty series are interbedded with 

 fairly normal sediments, and there is a gradual passage from 

 normal sediments through all stages into cherts. This means 

 that if the Tatong and Heathcote series are contemporaneous, 

 then we must include in the Heathcotian, normal sediments as 

 well as cherts and diabases. If this be accepted, then the dis- 

 tinctive characteristics of the Heathcotian series lose their full 

 significance, and it becomes extremely difficult, if not impossible. 



