108 



the underlying stratum is abrupt. The only recorded fossils are 

 Echinus Woodsi and Cellepora liemispheerica. 



Eastward from Wilson's Bluff it increases in thickness, and 

 at the termination of the cliffs has an estimated thickness of 

 eighty feet, the overlying marble being thirty. 



The same band was passed through in the wells, and is exposed 

 in the caverns about Mallabie, in the latter under a cover of 

 thirty feet by estimate of marble ; as also in a cavern twenty- 

 one and a half miles north-north-west from Mallabie, where 

 Pecten Gambieriensis was noted. 



"White Polyzoal Limestone. — This, the piece de resistance of 

 the geology of the Bunda Plateau, has a thickness of 188 feet 

 at "Wilson's Bluff, where it attains its highest known altitude 

 above sea level. It is a white friable earthy limestone, coarser 

 and harder than chalk, and readily dissolving in acid, without 

 leaving any appreciable residue. On a cursory inspection one 

 is struck by its similarity to the chalk of England, heightened 

 by the presence of layers of black flints and fossils, with a 

 cretaceous facies such as Salenia, Cidaris, Gryphcea, like G. 

 vesiculosa, a Terebratula, barely distinguishable from T. carnea, 

 Terebratulina, &c, &c. 



In its origin it differs as the debris has been derived from 

 polyzoa ; foraminifera, though present, are not abundant. 



The section at Wilson's Bluff exhibits the position of the 

 flint layers and fossil bands. The upper part is a hard white 

 stone, ringing under the hammer, full of Waldheimia, stained 

 with glauconite, and does not graduate into the overlying 

 limestone. Prom Wilson's Bluff to the east this band declines 

 at the rate of 1*32 feet per mile, and at the Peelunibie end is 

 only twenty feet thick, by estimate, above sea level. About 

 due north it was reached in a well, 162 feet deep, but the 

 depth penetrated is not known. In no other inland locality is 

 it within view. 



This same horizon seems to be the one reached in the wells 

 to the eastward of the Bight, but has there* acquired much 

 silicious property. 



The fossils obtained at Wilson's Bluff, all in situ, are given 

 in the following table : — 



Name of Species. Occurrence Elsewhere. 



Gryphasa tarda ? Hutton. Lower Aldinga series, Aldinga. 



Upper Eocene, New Zealand. 

 Plicatula sigillata, Tate. Lower Aldinga series, Aldinga ; Yorke's 



Peninsula. 

 Lower Murravian, Mannum. 

 Lima armigera, Tate. 



Pecten Eyrei, Tate. Lower Aldinga series, Aldinga ; Yorke's 



Peninsula. 



*An analysis gave a grey pulverulent insoluble residue of 10-64 per cent. 



