The Sub-class Prosobranchia contains the marine snails and a few freshwater and terrestrial species. The characteristic used to spilt them is the operculum (a horny lid used to close the opening of the shell). If it has an operculum it is in the subclass Prosobranchia, if it doesn't it is in the Pulmonata. Also Prosobranchia have one pair of tentacles.
Above is Triton australis
Below is Strombus gigas, the Queen conch or the Great green conch. It is the largest North American mollusc, with some specimens reaching just over 30 cm. It is found in the Caribbean and surrounding waters; usually on sand.
Below is Cassis madagascariensis which is often used by jewellers for carving cameos. It is a possible predator of invasive sea urchins, and is found in tropical and temperate oceans from surface to 1000 m deep.
Lacinate conch, Strombus sinuatus, Sinustrombus sinuatus, below, is found in the South Pacific 30 - 40 m deep.
Above is the Shin-bone tibia, Tibia fusus fusus in the Strombidae family. It is found in the S. E. Pacific offshore in sandy waters. Its length is 23 cm when fully grown.
Chiagara spider conch, Lambis chiagra, in the Strombidae family, above, is found in the Indo-Pacific in the intertidal zone at depths of 1 - 30 m near the shore and on sand. It emerges to hunt at night and feeds on fish and worms.
Papal mitre shell, Mitra papalis, above, is found in the Indo-Pacific in coral reefs and under rocks. The average size is 10 cm.
The Sundial shell, Architectonica perspectiva, above and below is found in shallow waters on sand in the Indian Ocean and the Western Pacific. The whorls are flattened on one side rising to a steep spire on the other. There is a beautiful opening inside the spire that is wide and looks like a spiral staircase.