noun
apex of a shell; umbo
Zoological term for the pointed tip or earliest part of a mollusk shell, often used in descriptions of bivalves and gastropods.
二枚貝の殻頂は、成長の起点となる部分です。
The umbo of a bivalve is the part that serves as the starting point of growth.
この巻貝の殻頂は鋭く尖っている。
The apex of this gastropod shell is sharply pointed.