Apex (mollusc)
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In anatomy, an apex (
scaphopod, or cephalopod
.
The apex is used in end-blown conches.
Gastropods
The word "apex" is most often used to mean the tip of the
gastropod
. The apex is the first-formed, and therefore the oldest, part of the shell.
[1]
To be more precise, the apex would usually be where the tip of the embryonic shell or protoconch is situated, if that is still present in the adult shell (often it is lost or eroded away).
Coiled gastropod shells
The phrase apical whorls, or
teleoconch
.
Comparison of the apical part and the whole shell of Otukaia kiheiziebisu:
Limpet-like gastropod shells
Where this feature is present, the space under the apex of a patellate or patelliform (limpet-like) gastropod shell is called the apical cavity.
Scaphopods
The apex of
tusk shells
is the small, open posterior end, and the opening itself is usually called the apical aperture.
Cephalopods
In orthocone cephalopods, the pointed end of the shell is called the apex, and shell growth is away from the apex and toward the aperture. The first chamber of the apex is sometimes called the protoconch.
Bivalves
The apex of a valve of a
bivalve shell is the area around what is most commonly the umbo or beak. In some species the embryonic shell or prodissoconch
may be present at the apex of each of the two valves.
References
- ISBN 978-0-2415-1551-8.