■10 AUSTRALIAN QUATERNARY CLIMATES AND MIGRATION 



bonna east of Lake Eyre, and is well represented in the warmer 

 rivers of Queensland ; Hale and Tindale suggest that its distribu- 

 tion in the layers at Devon Downs implies climatic change "in the 

 direction of the semi-arid conditions of the lower watershed of 

 the present time. ' ' The author is of the opinion that the arid con- 

 ditions at the time of the Postglacial Optimum are indicated. 

 Bulinus is a fresh- water genus most abundant in Layer XI (Pre- 

 Pirrian) and its distribution is taken to suggest the cooler climate 

 of the Postglacial that prevailed previous to 8,000 years ago. The 

 relative abundance of the three molluscs seems, therefore, to sup- 

 port the Postglacial climatic changes emphasized here. If the 

 chelonian in Layer X was actually CheJodina expansa, such 

 would be inconsistent with them, for that species is only found in 

 northern Australia ; it is, however, only compared with (■. expansa. 

 It would seem from the physiography of the Lower Murray that 

 all the industries and cultures of Tartanga and Devon Downs 

 belong to the Postglacial period. They have certainly been 

 deposited during a period of accumulation succeeding a period of 

 removal, presumably the vertical erosion accompanying the lower- 

 ing of sea-level during the last glacial period. That being so, they 

 are certainly Postglacial. 



B. Artefacts Associated with Dimes. 



Altona Bay is on the north-west shore of Port Phillip Bay, the 

 dune area, there extending 3 or 4 miles south-west along the 

 shore from the Kororoit Creek and 1J miles inland. It has been 

 described and mapped in detail by ~ Hills (1940). Extending 

 along the shoreline is a beach ridge and inland behind this are 

 ridges (referred to here as the inner ridges) of intercalated dune- 

 sand and shell-beds 4 to 5 feet above the floors of the intervening 

 swales. The contained shells are all living species and well pre- 

 served ; some of them have paired valves. The shell-bed showing 

 in the cutting on the Altona railway line about 200 yards west of 

 the Kororoit Creek, is 8 feet thick and its upper surface is about 9} 

 feet above L.W.M. (low-water mark at Hobson's Bay— the datum 

 usual in Victoria) ; it rests on the lava-plain-Newer Volcanic 

 Basalt (Middle Pleistocene). Some layers in it are almost entirely 

 composed of shells, others of fine, loose sand with shells and 

 travertine. Pritchard (1909) states that "there is no hesitation in 

 saying that the shells are marine but occasionally a layer of 

 brackish water shells composed of such genera as Truncatella, 

 Coxiella, Assiminea, Salinator and Ophicardelus make their 

 appearance." The water in which the beds were laid down was, 

 seemingly, in close proximity to a shoreline. 



