Astropecten scoparius (species of starfish)
A starfish species found in Japanese waters; the name literally means 'maple leaf shell' but refers to a starfish, not a shell.
I found an Astropecten scoparius on the sandy beach.
Kanji spelling exists but is rarely used; the word is usually written in kana.
Hiragana spelling is also common.
Compound of 紅葉 (もみじ, 'maple leaf') + 貝 (がい, 'shell'), from the starfish's shape resembling a maple leaf. The exact derivation is uncertain.