The enormous amount and peculiar character of the deposits of carbonate of lime, found in all parts of the globe, give the question of the formation of these deposits a peculiar interest, consisting, as these deposits do, of fossilised remains of lime-secreting animals, and bearing witness in themselves as to their origin. It is beyond question that the great mass of carbonate of lime found in the later geological epochs has, primarily, been absorbed by the marine fauna and flora from the ocean, and secreted by them in the form of coral, shells, or calcareous plants. From this may be realised the important function which lime salts play in respect to the economy of marine life.