Metacrinus rotundus, the Japanese sea lily, is a species of stalked crinoid in the family Isselicrinidae.

It is a species found off the west coast of Japan, near the edge of the continental shelf at a depth of around 100 to 150 metres (330 to 490 ft) deep.

The stalk continues lengthening during the animal's life and may reach 40 centimetres (16 in) and the arms can grow to half that length.

[5] In favorable locations, there may be a dense bed of sea lilies and it may form part of a rich micro-habitat with bivalve mollusks and brittle stars.

After fertilization the eggs hatch into barrel-shaped larvae that are planktonic for a few days before settling on the seabed, cementing themselves to hard surfaces, undergoing metamorphosis and developing into juvenile sea lilies[6]