NATURAL MINERAL SPRING AT BUNGONIA. 55 



still forming. Near the Bungonia spring there are three separate 

 patches of the limestone marked on the accompanying map A, B, 

 and C. The C deposit is nearly half-a-mile up the creek from 

 the spring. At one time the waters reached the surface at 

 this point. At present I could detect neither water nor gas 

 escaping. 



Referring to the tufa generally, many varieties can be dis- 

 tinguished. The more compact kinds might at first sight be 

 easily mistaken for Silurian limestone, particularly on weathered 

 surfaces, but its dull sound under the hammer reveals its true 

 nature. One interesting variety is a granular limestone and 

 crystallised calcite in alternate layers, the calcite being stained a 

 bright red colour by iron oxide. Much of the rock is spongy in 

 texture, the cavities being filled with black mud. Near the spring 

 the tufa is in the bed of the creek as seen in the foreground of 

 the photograph I exhibit. At the point marked C, it is somewhat 

 above the present water level, and is honeycombed in a more or 

 less vertical direction by holes like annelid bores. These I take 

 to be cavities caused by escaping gases v while the rock was yet 

 forming. 



I have found the following shells as fossils in the limestone or 

 tufa : — Endodonta f venerea, Cox, Sphcerium macgillivrayi, Smith, 

 Bulinus carinatus, H. Adams, var. cumingii, H. Adams, Limnea 

 lessoni, Deshayes, Bulinus gibbosus, Gould. The shells were 

 identified for me by Mr. Charles Heclley of the Australian 

 Museum. They are all living species, as we should expect to find 

 in a rock now forming. The Limnea and Bulinus can be found 

 in great numbers, in calcareous nodules embedded in a black clay 

 on the " point " formed by the junction of Abel's Gully and 

 Lumley Creek. 



Silurian fossils are found at many places in the sandstones, 

 chiefly casts of a coral near Cyathophyllum. The limestone shown 

 contains spirifers, but I could find no specimens of the coral or 

 the brachiopod perfect enough for specific identification. 



