18 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Not only do geological deposits yield evidence of ancient 

 climates, but palaeo-meteorological indications are sometimes 

 obtained. An interesting case is provided by the veritable 

 cemeter} T of Pliocene whales, sharks, etc., which occurs on the 

 Belgian coast and has been described by M. Van den Broeck. 

 According to Mr. F. W. Harmer* these cetaceans and fish were 

 drifted by the north-westerly gales prevailing in Pliocene times 

 into land-locked bays on the eastern shores of the ancient 

 " North Sea," and were unable to escape ; hence the enormous 

 accumulation of vertebrate skeletons in the deposits there. 



Similarly, the extensive growth of the roots of Coal 

 Measure trees on one side, and their relatively slight 

 growth towards the other in the Upper Carboniferous has 

 been quoted as evidence of the direction of prevalent gales in 

 those early days. 



(4) Salt-, brackish- or fresh-water. At present the best 

 evidence of these conditions is provided by the fossils them- 

 selves, having regard to their similarity or otherwise to modern 

 marine, estuarine or fresh- water forms. But attempts are being 

 made to apply other lithological criteria to the deposits in order 

 that deductions may be made in the absence of fossils. 



Although the ocean has become progressively more and 

 more salt throughout geological ages, and is assumed to have 

 originated, presumably as a saltless hydrosphere, about 100 

 million years ago,t it is noteworthy that in the Devonian period 

 there lived a pelecypod Archanodon, so markedly similar to 

 the freshwater mussel of to-day that there is little doubt but 

 that its habitat was fresh- water ; under other conditions, 

 Cardiola, Murchisonia, Nucula, Pleurotomaria, and other 

 gastropods, are found, bearing general characters similar to 



* Proc. Geol. Assoc, Vol. 17 (1902), p. 421. 



f For a summary of the evidence and deductions relating to this matter, 

 see F. W. Clarke, "Data of Geochemistry," Bull. 695 (1920), U.S. Geol. 

 Survey. But on the evidence of the accumulation of helium and lead in 

 rocks bearing radio-active minerals, the Devonian is stated to have been 

 formed about 380 million years ago. 



