the foot of this snail are flapped up and down much in the manner of a bat in flight.
However, the pelagic habitat and the ability to swim are the exception among the snails. The intertidal zone which is intermittently flooded and drained by the moving tides is well stocked with many kinds of creeping snails. Many Nassarius Mud Snails live exclusively on the warm, flat mud-
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Figure 3. a, The Nassa Mud Snail, Nassarius, crawling under the sand with it’s siphon extended into the water above; b, cutaway view of a protobranch snail showing the direction of water currents (arrows) down the siphon, over the gills and out from the right side of the body. (After Ankel 1936.)
bars of quiet bays. Among the carnivorous snails, we find that their ecologic stations are determined by the location of the worms or bivalves upon which they feed. One or two species of Terebra and Polinices Moon Shell are found burrowing in the sand of beach slopes where they are able to find their favorite clams, but the majority of these snail genera are found from low-tide mark to a depth of several fathoms. Since most marine gastropods are nocturnal in habit and shun bright sunlight, many species spend their time hidden in crevices under rocks. This affords protection to themselves and their eggs from predators, bright sun and violent wave action.
A great number of species live in deep water, and frequently their vertical distribution is limited to relatively narrow ranges. From some 500 dredging samples taken off southeastern Florida by the late J. B. Henderson’s yacht “Eolis,” Bayer’s Dwarf Olive (Olivella bayeri) was found in depths ranging from 25 to 115 fathoms. On the other hand, the Greenland Moon Shell has been found from twelve feet to over two miles in depth.
In their experimental search for new living places, a few gastropods have evolved strange associations with other marine animals. The dwarf Cypho-
