IV] MEANING OF THE TERM 'FOSSIL.' 67 



was impossible to say where the river came to an end and the 

 sea began. The Creek is described as a long tortuous arm of 

 the sea, 10 to 15 miles long, with the side walls covered with 

 orchids and Platycerium. The ferns and palms were abundant 

 in the lateral shady glens ; marine and inland animals lived in 

 close proximity. 



" Here is a narrow strip of the sea water, twenty miles distant from 

 the open sea ; on a sandy shallow flat close to its head are to be seen 



basking in the sun numbers of sting-rays All over these flats, and 



throughout the whole stretch of the creek, shoals of Grey Mullet are to be 

 met with ; numerous other marine fish inhabit the creek. Porpoises 

 chase the mullet right up to the commencement of the sand-flat. At the 

 shores of the creek the rocks are covered with masses of excellent oysters 

 and mussel, and other shell-bearing molluscs are abundant, whilst a small 

 crab is to be found in numbers in every crevice. On the other hand the 

 water is overhung by numerous species of forest trees, by orchids and 

 ferns, and other vegetation of all kinds ; mangroves grow only in the 

 shallow bays. The gum trees lean over the water in which swim the 

 Trygon and mullet, just as willows hang over a pool of carp. The sandy 

 bottom is full of branches and stems of trees, and is covered in patches 

 here and there by their leaves. Insects constantly fall in the water, and 

 are devoured by the mullet. Land birds of all kinds fly to and fro across 

 the creek, and when wounded may easily be drowned in it. Wallabies 

 swiin across occasionally, and may add their bones to the debris at the 

 bottom. Hence here is being formed a sandy deposit, in which may be 

 found cetacean, marsupial, bird, fish, and insect remains, together with 

 land and sea shells, and fragments of a vast land flora ; yet how restricted 

 is the area occupied by this deposit, and how easily might surviving 

 fragments of such a record be missed by future geological explorers 'i" 



The term ' fossil ' suggests to the lay mind a petrifaction or 

 a replacement by mineral matter of the plant tissues. In the 

 scientific sense, a fossil plant, that is a plant or part of a plant 

 whether in the form of a true petrifaction or a structureless 

 mould or cast, which has been buried in the earth by natural 

 causes, may be indistinguishable from a piece of recent wood 

 lately fallen from the parent tree. In the geologically recent 

 peat beds such little altered fossils (or sub-fossils) are common 

 enough, and even in older rocks the more resistant parts of plant 

 fragments are often found in a practically unaltered state. In 

 the leaf impressions on an impervious clay, the brown-walled 

 1 Challenger (85), Narrative, vol. i. p. 459. 



5—2 



