Gazelle : The Palestinian Biological Bulletin (ISSN 0178 – 6288) . Number 126, June 2015, pp. 1-16. | 页面 3

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enough that the soft parts can withdraw completely into it. Those gastropods
without a shell, and those with only a very reduced or internal shell, are usually
known as slugs (Wikipedia).
The marine shelled species of gastropod include edible species such
as abalone, conches, periwinkles, whelks, and numerous other sea snails that
produce seashells that are coiled in the adult stage—though in some, the coiling
may not be very visible, for example in cowries. In a number of families of
species, such as all the various limpets, the shell is coiled only in the larval stage,
and is a simple conical structure after that (Wikipedia).

Drawing showing an apertural view of a shell of Sphincterochila prophetarum
(Bourguignat, 1852).
https://en.wikipedia.org/wiki/Sphincterochila_prophetarum#mediaviewer/File:Sphinc
terochila_prophetarum_shell.jpg

Etymology
The word "gastropod" is derived from the Ancient Greek words γαστήρ
(gastér, stem: gastr-) "stomach", and πούς (poús, stem: pod-) "foot", hence stomachfoot. This is an anthropomorphic misnomer, based on the fact that to humans it
appears as if snails and slugs crawl on their bellies. In reality, snails and slugs
have their stomach, the rest of their digestive system, and all the rest of
their viscera in a hump on the opposite, dorsal side of the body. In most
gastropods, this visceral hump is covered by, and contained within, the shell
(Wikipedia).
In the scientific literature, gastropods were described under "gasteropodes"
by Georges Cuvier in 1795 (Wikipedia).
The earlier name univalve means "one valve" or shell, in contrast
to bivalve applied to mollusks such as clams and meaning that those animals
possess two valves or shells (Wikipedia).
Gazelle : The Palestinian Biological Bulletin – Number 126 – June 2015