26 



C. HEDLEY. 



tropical and temperate plants ; several Japanese species 

 extending thus far. 



Changes of Climate and Time. 

 It was noticed by Darwin how the organisms of the 

 beach leave the scantiest record in geological history. 

 Inhabitants of the river, the lake, or the continental shelf 

 are frequently preserved as fossils, but of the barnacles, 

 limpets, chitons, or whelks of the intertidal zone there is 

 hardly a trace. "The explanation, no doubt, is that the 

 littoral and sublittoral deposits are continually worn away,, 

 as soon as they are brought up by the slow and gradual 

 rising of the land within the grinding action of the coast 

 waters." 1 



A rare and interesting exception to this rule of destruc- 

 tion is a raised beach which occurs at the apex of the 

 Hunter delta, near Maitland. On investigation by David 

 and Etheridge it proved to contain thirty-two species of 

 mollusca, and one cirrhipede. 2 The interest of the collec- 

 tion centres on the four following shells : — Beaten strangei, 

 Brachyodontes erosus, ( = Mytilus menkeanus), Euchelus 

 atratus and Arcularia dorsata (=Nassa livkla). All these 

 have now disappeared from New South Wales. The mussel 

 B. erosus has even vanished from East Australia, though 

 it persists as a dwarf form in Tasmania. But large speci- 

 mens like the Maitland fossils still occur in the corres- 

 ponding latitudes of Western Australia. 



Arcularia dorsata (fig. 1) inhabits estuaries from Torres 

 Strait to Port Curtis, while the other two reach Moreton 

 Bay. That so large a proportion as one-tenth of this fauna 

 should have now gone from New South Wales shows not 

 only an appreciable geological antiquity, but also a change 

 of climate. Such exact criteria do these fossils afford 



1 Darwin, Origin of Species, 1860, pp. 289, 291. 



2 David and Etheridge, Kec. Geol. Surv. N.S. Wales, ii, 1890, pp. 37 - 52. 



