tusk shell
A marine mollusk with a long, tubular, tusk-shaped shell. Also known as a scaphopod.
Tusk shells live buried in the sand.
I picked up a tusk shell on the beach.
Compound of 角 (tsuno, 'horn') and 貝 (kai, 'shell'), referring to the shell's horn-like shape. The reading つのがい is a straightforward combination of the kun'yomi readings of the two kanji.