What type of fish make sea shells?
Short Answer:
Fish do not make sea shells.
Long Answer:
Sea Shell: the hard protective outer case of a mollusk or
crustacean. That includes the calcium carbonate shells made by
clams and snails and the chitin/calcium shell of crabs and lobsters
and the like.
Fish: fish are a catch-all group that includes species with
backbones, fins but no limbs, get oxygen through gills, and live in
water. This includes hagfishes, sharks, bony fishes and more.
If you consider a sea shell to be anything hard you'd find
washed up on the shore, perhaps you might consider fish bones to be
a sea shell, but this would be wrong, because a shell is usually on
the outside of an organism. Many animals are called fish which
aren't fish, like starfish and jellyfish, but they are not true
fish.
In the Devonian era, around 400 million years ago, fish with
bony armored plates called placoderms swam the sea. This is
probably the closest to sea shells you can get from a fish, since
it's outside the body and hard, but they aren't alive today.
Therefore, since fish are vertebrates, and sea shells come from
invertebrates, fish do not make sea shells.