BY THOMAS P. LUCAS, M.R.C.S., ENG., ETC. 99 



enlarge a formerly dug-out water-hole, but now dry. After 

 passing through some feet of surface humus and washed (flood) 

 matter he came upon a soft, plastic, black, marly, clayey deposit. 

 In the twelve or fourteen feet of this deposit that were passed 

 through, four bands of shell conglomerates were found. The three 

 higher beds are eighteen to twenty inches apart, but the lowest one 

 is quite four feet from the one above it. The shells are mostly an 

 estuarine recent species of bivalve with an occasional piece of 

 worn coral, now and then a stray oyster-shell and very rarely a 

 solitary shell of another species. I am informed that in driving 

 the piles for the railway bridge over the creek near by similar 

 shelly beds were met with and, if I am correct, at a depth of 

 twenty-eight feet fresh water. 



Do not geologists tell us that in former times the Brisbane 

 River was a very much larger and probably differently distributed 

 water channel ? It appears to me that both instances which I 

 have recorded go to support this view. To-day the estuarine 

 portion of the river appears to be much further out than for- 

 merly. In the floods of the nineties, oyster beds a distance 

 beyond the present mouth of the river were destroyed by the 

 sudden freshes of the Brisbane River. It takes four years for 

 oyster spawn to form new beds, and the supply of such spawn 

 is under other conditions. The shell beds at Hemmant do not 

 certainly suggest local oyster habitats, but they do prove the 

 occurrence of such at the time, at no great distance. But these 

 beds appear most conclusively to prove that that the shell colo- 

 nies were established near to the mouth of the river and in the 

 flux of the salt water tides ; for when in floods the fresh water 

 poured in hyperabundantly the estuarine salt water shell-fish 

 were killed, and did not appear again until deposits to 16 or 18 

 inches had been laid down. And in the section laid open this 

 evidences as having occurred four times. Doubtless by deeper 

 sinking more such and on a larger scale would be proved. 



Another point is worthy of notice. If these shells had been 

 buried as they died and immediately covered over with the flood 

 water muds, they ought largely to be found bedded in pairs 

 (bivalves). Instead of this they are mostly found singly or 

 forced into irregular conglomerates in all ways and fashions, as 

 they would be if long exposed after death to the tides and on a 

 mud bottom. ♦ 



If then my deductions are correct, the present Doughboy 

 Creek must in pre-historic human age (post-pleistocene) have 



