The deposits of this region are almost wholly calcareous. The sand sizes predominate in most of the sediments but in a few small areas fine-grained muds cover the bottom. The coarser parts of the deposits consist, in order of abundance, of the remains of calcareous algae, mollusks, coral, foraminifera, and 9 kinds of other easily recognized constituents. In addition small crystals of aragonite, ellipsoidal pellets, and indurated oolites are present in many of the fine-grained muds of the Great Bahama Bank and some flats of the Florida Keys. These substances, with exception of the fecal pellets, point to a certain amount of precipitation from saturated sea water. The physico-chemical factors connected with it are complex and little understood but precipitation probably tak s place whenever the delicate equilibrium is disturbed. Bacteria as a factor in causing precipitation are considered to be of minor importance. Waves and currents are very effective in transporting and sorting the sediments.