Littorines are the most common mollusks of the high shoreline where they are found in abundance throughout the tropics. Two species are the dominant mollusks of the rocky supratidal region in the islands, the animals feeding on algae and detritus which they rasp from the surface of rocks. Despite their supratidal habit, these mollusks are tied to the sea by their mode of development, for their eggs and larvae develop in the ocean. Fertilization is internal and the fertilized eggs are released into the ocean where development occurs. The Hawaiian littorines do not have distinct breeding seasons but breed continuously for 13 lunar months (Struhsaker, 1966). Littorine shells are of small to medium size, conical, thin or solid, and there is a small, horny operculum which completely fills the aperture when it is in place.