In anatomy, an apex (adjectival form: apical) is part of the shell of a mollusk.
The apex is the pointed tip (the oldest part) of the shell of a gastropod, scaphopod, or cephalopod.
The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod.
Comparison of the apical part and the whole shell of Otukaia kiheiziebisu: Where this feature is present, the space under the apex of a patellate or patelliform (limpet-like) gastropod shell is called the apical cavity.
The apex of a valve of a bivalve shell is the area around what is most commonly the umbo or beak.