An ocean-going critter that looks like a squid stuck tail-first inside
a flat snail shell. The shells are beautifully colored in a very nice
blend of pastels. The fossil shells can be wildly patterened.
BRBR

Also the subject of a now rather obscure poem that begins,

"This is the ship of pearl, that, poets feign,
Sails the uncharted main..."

Actually, CN's do "sail"--fill some interior bladders with air and coast along
in a fleet, which must be am interesting sight. If they feel endangered, they
expel the air and sink.
zemedelec