Read the poem and answer the question.

I found a shell, a curly one;
Lying on the sand.
I picked it up and took it home,
Held tightly in my hand.

Mommy looked at it and then,
She held it to my ear,
And from the shell there came a song
Soft and sweet and clear.

I was surprised, I listened hard,
And it was really true:
If you can find a nice big shell,
You’ll hear the singing too.

--Unknown

What did mommy do with the shell?