Duchesne Record | 1915-06-12 | Page 4 | Magnesia in Sea Shells

Magnesia In Sea Shells Chemical analysis of starfishes sea urchins and crinoids collected from all parts of the world show that the skeletons of these animals contain I much magnesia The amount present Is found to vary with the temperature of the water in which the creatures lived The percentage of magnesia is highest in those specimens that lived in tropical waters and lowest In forms from the icy seas of Greenland and the Antarctic with a regular gradation gradation gradation grada grada- tion between which even shows the local effect of cold ocean currents upon life at the sea bottom The investigations investigations investigations in in- suggest that the skeletons skeletons skeletons tons of these animals have the compo compo- of ot the manganese limestone or dolo dolomite ife and it is possible that they furnish furnish clues not only as to the climatic conditions under which are now formed but also as to the temperatures of ot the oceans in different regions of the earth where during different periods of ot geologic history great deposits of limestone were formed