Abstract
Distribution of magnesium and strontium was determined between waters and calcites secreted by the oyster species Crassostrea virginica and C. rhizophorae in natural habitats at eight localities, from Maine to Puerto Rico. The concentration of strontium in the calcite shells increases with increasing temperature in the range 13° to 25°C, and also with increasing Sr++/Ca++ molal ratio in the water. The concentration of magnesium in the shells increases irregularly with temperature, and it is apparently independent of the Mg++/Ca++ ratio in the water. The greater variation with temperature in the distribution factor for magnesium may be related to genetic differences between semi-isolated populations.