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 Gastropods - Snails, Periwinkles,
Cowrie, Limpets & Whelks
Snails are common in all levels of the rocky intertidal zones.
They feed mainly on algae and decaying matter. Some carnivorous
snails have radulae that bore holes through the shells of other
mollusks to eat them. Many species are hermaphroditic and capable
of reproduction asexually.
The tissue layer of a snail which overlies the body and secretes
the shell is known as the mantle. Any disturbance causes the
mantle to slide around and disappear into the shell.
 Snails
Wavy Top Snail - Astraea undosa
White Slipper Snail - Crepodila nummaria
Western White Slipper Snail - Crepodila perforans
Perwinkle
Perwinkle have a radula which is used to scrape algae, diatoms,
and organic debris from rocks or other hard surfaces. They must
live near the ocean and spend time underwater but they prefer
to be partially exposed to air.
Eroded Periwinkle - Littorina planaxis
Melarhaphe neritoides
Littorina saxatilis
Cowrie
When a Chestnut Cowrie is undisturbed, the mantle is extended
to almost cover the entire shell. The enamel, which covers the
entire exterior of the shell, is secreted by glands in the edge
of the mantle. This polishing action of the sliding of the mantle
in and out, aides in giving the Cowrie its high gloss.
Chestnut Cowrie - Zonaria spadicea
Limpets
This limpet gets its name from the keyhole appearance in
the top of the shell. Water is drawn under the shell and secreted
through the hole along with the limpets waste. The animal is
too large to completely fit into its shell and extends beyond
on all sides. The length of the shell can get up to four inches.
Keyhole limpets primarily feed on algae at night and often return
to the same resting spot after a journey of six to thirty six
inches.
Giant Keyhole Limpet - Megathura crenulata
Ribbed Limpet - Collisella digitalis
White-Cap Limpet - Acmaea mitra
Rough Limpet - Collisella scabra
Southern Keyhole Limpet - Lucapinella callomargonata
Whelks
Thais lamellosa
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