>Latitudinal trends in the shell characteristics of marine gastropods

Species of shallow water, marine gastropods along the Atlantic coast of the United States exhibit latitudinal trends in shell characteristics that reflect the efficiency of calcium carbonate utilization. Thew are interprcted as direct responses - both genetic and ecopheno-typic - to the availability of calcium carbonate, which in near surface marine environments is primarily a function of the planetary temperature gradient. Mot-phological differences between marine and non-marine gastropods can be explained similarly, although the causative factor is probably salinity rather than temperature. Potential geolcgic applications of the rcsults are location of the paleopole and paleoequator, discovei-y of the temperature boundaries between ancient surface currents, estimation of the earth's palcotemperature gradient, and determination of absolute paleotemperature.