noun
Pronodularia japanensis (freshwater mussel)
A species of freshwater mussel native to Japan. The name literally means 'pinecone shell' due to its appearance.
マツカサガイは日本の川や湖に生息する淡水二枚貝です。
The Pronodularia japanensis is a freshwater bivalve that inhabits rivers and lakes in Japan.
From 松毬 (matsukasa, 'pinecone') + 貝 (kai, 'shellfish'), referring to the pinecone-like shape of the shell.