27 



local till beck. Inland, where these objects are seen in section 

 in the cliff faces, they exhibit a. ring in relief. At Encounter 

 Bay, the waves in cutting their way through the sandy till 

 have truncated these spherical bodies, and as the outer and 

 inner portions of the matrix are softer than the spherical crust, 

 the former are denuded, leaving the indurated investment 

 as a circle in relief. 



This gives us the explanation desired. The hard and 

 raised circles give better holding-support to the Serpulae than 

 the softer ground around, the annelids become attached to 

 the stony circles, and from such a foundation build up their 

 colonies, the calcareous ring offering a certain likeness, in a 

 small way, to the coralline atolls, while the water, filling the 

 depressed centres, gives the similitude to the central lagoon 

 in such islands. 



II. Pseudo-Cryptozoon Structure. 



Bef. Howchin, "The Occurrence of the Genus Oryptozoon 

 in the (?) Cambrian of Australia," Trans. Roy. Soc. S. Austr., 

 vol. xxxviii., 1914, pp. 1-10, pis. 1-5. 



At the Ordinary Meeting of the Society, held on April 11, 

 1918, some rock specimens were exhibited by Mr. L. K. 

 Ward, Government Geologist, that had been collected by 

 Mr. Winton from the New Burra Mine.< 2 > The specimens 

 were obtained in limestone and contained certain wavy and 

 concentric structures that have, in some instances, a close 

 resemblance to those of the supposed fossil known as 

 Cryptozoon. I have recently visited the locality and now 

 offer a few remarks on the nature of the specimens and the 

 geological conditions under which they occur. 



The journey was made down the Burra Creek which 

 takes its rise about a mile above Kooringa, but the proper 

 watershed is in the ranges to the north of the township. The 

 creek flows in a south-easterly direction and finds its outlet, 

 when heavy rains occur, in the River Murray, at the Nor'- 

 west Bend. The creek below Kooringa follows a moderately 

 straight course and is heavily charged with alluvial sedi- 

 ments. A course was followed down the creek for nine miles. 

 A series of whale-back limestone ridges follow the western 

 side of the creek, with the main ranges visible beyond. The 

 limestone belongs to the Brighton Series, while the eastern 

 side of the creek consists of the underlying Tapley Hill 

 banded slates. The strike of the beds is roughly parallel with 

 the Burra Creek. At about nine miles from Kooringa, the 



(2) Trans. Roy. Soc. S. Austr., vol. xlii., 1918, p 297. 

 b2 



