658 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



elaboration of shells, may be correlated with the special enriching of the ocean 

 in calcium salts during the Permian and following pre-Triassic time. In that 

 long period the land areas were of extraordinary siz.e and were largely covered 

 with thick Paleozoic limestones exposed for the first time. The impoverishment 

 and final extinction of the ammonites may have been largely caused by the 

 partial exhaustion of the calcium content of the ocean during the long and 

 remarkably extensive submergence of the continental plateaus during the Cre- 

 taceous. To such geographical and chemical changes, the ammonites, most of 

 which were possibly pelagic species (all of them needed abundant supplies of 

 calcium salts), must have been peculiarly sensitive, while the coastal species, 

 being nearer the sources of calcium-supply (the river-mouths), would be living 

 under more equable conditions. 



Tests of the Suggested Hypothesis. 



The rearrangement in the chemical constituents of pre-Cambrian ocean 

 water through the decay of animal matter is the fundamental premise of the 

 hypothesis and it deserves special examination and illustration. The tests of 

 the premise are at least threefold : laboratory experiment, observations on exist- 

 ing seas, and the witness of pre-Cambrian deposits, particularly of the carbonates. 



corroborative experiments. 



Murray, Woodhead, and Irvine have made a number of valuable observa- 

 tions on the chemical, modification of sea water exposed to the emanations of 

 putrefying animal matter and to the effete substances derived from living 

 animals.* 



In one experiment four small crabs weighing 90-72 grams were placed in 

 sea water absolutely free from carbonate of lime. After twelve months they 

 produced an alkalinity in the water equal to the production of 45-36 grams of 

 calcium carbonate. This effect was due to the decomposition of calcium sul- 

 phate by the uric acid, urea, and other effete matter. 



In a second experiment it was found that in seventeen days and at tempera- 

 tures ranging from sixty to eighty degrees Fahrenheit, the decomposition of 

 urine mixed with sea water had precipitated practically all the sulphate of lime 

 present. A similarly complete precipitation of all the sulphate in a solution of 

 pure water and calcium sulphate present in the proportion of average sea water, 

 was effected in eleven days by the decomposition of urine added to the solution. 



In a fourth experiment, nine small crabs were placed in two liters of water, 

 where they died. Complete putrefaction set in and continued at temperatures 

 varying from seventy to eighty degrees Pahr. Analysis showed that all the 

 lime salts were precipitated in the form of the carbonate. 



* Proc. Royal Society Edinburgh, Vol. 17, 1889, p. 79. 



