53 



the beds at Sellick's Hill are on the same horizon as those at 

 Aldinga, the slight palgeontological contrasts between the two 

 localities is not exceptional, as the nature of the Cainozoic 

 sediments along the borders of Gulf St. Vincent frequently 

 vary within short distances to a very extraordinary degree. 

 The triturated condition and uniform grade of the material 

 which make up these limestones are suggestive of a littoral 

 deposit and the sorting action of the waves. On the southern 

 side of the Sellick's Hill section the limestones become less 

 fragmental and whole forms may be seen, particularly the 

 fronds of Retepora, which at some horizons is so abundant 

 that the stone might be classed as a Retepora limestone. 



Mr. Claris in his paper (loc. cit.J has supplied the follow- 

 ing list of fossils from these beds, which, he informs me, were 

 identified by the late Professor Ralph Tate : — 

 Crinoidea — Antedon pertusa, Tate, M.S. 

 Echinoidea — Cidaris, sp. 



Echinus woodsii, Laube. 



Lovcnia forbesi, Ten. -Woods. 



Echinola?npas posterocrassus, Gregory. 



Scutellina patella, Tate. 



Fibularia gregata, Tate. 



Brachiopoda— Waldh a mi a , sp . (indet . ) . 

 Lamellibranchiata — Pecten consobrinus, Tate. 

 To the above list I may add : — 

 Polyzoa — Cellepora, sp. 

 Retepora, sp. 



Lamellibranchiata — Ostrea hyotidoidea, Tate. 



Gasteropoda — Conus, sp. (Cast.). 



Turrit ella aldingce, Tate. 



Tectonic Considerations. 



The juxtaposition of two series of beds, of distinct ages 

 and stratigraphically uncomformable (as occurs in the dis- 

 trict under discussion), is a fortunate circumstance, as it sup- 

 plies data on which certain great tectonic movements in the 

 building up of South Australia may be recognized. 



Many questions are suggested by this unique example of 

 diastrophism in the Cainozoic rocks of our State, as, for 

 example, What was the nature of the earth movements that 

 produced this great distortion of the crust ? When did it 

 take place ? Was it an isolated movement or an incident 

 connected with a much wider field of disturbance ? Has the 

 disturbed area reached the stage of a stable equilibrium, or, 

 are further crust al adjustments likely to occur in the future ? 



