Page:The Scientific Monthly vol. 3.djvu/310

 304 THE SCIENTIFIC MONTHLY

bacteria, developed the massive limestones of the Tetons. Clarke

observes :

We are now begimiiiig to fee where the magnesia of the limeatODes cornea from and the al|^ arp probabi; the moet important (Contributors of that con- (titaeat.

��FtO. B. A. Foasll nlipe (KeirlaniUt cancnlrica, f/ticlandio froNilata) from til* AIsodIiIbii Bell S^rlea ot Montana. Walcolt. B. PobbII c^akareoos alse (Crgftouon proUftrunK) from the Cambrian llmatooe of L«ster Park near Saratoga Sprlngi, Ntw York. C. An algnl pool near the Great l^JUDtaln Geyser. YellowitODe Park. WalMIt Photographed by II. P. Cushlng.

Thus representatives of the Rhodophyceas contribute as high as 87 per cent, of calcium carbonate and 25 per cent, of magnesium carbonate.

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