What is a Crinoid? Crinoids, also known as "sea lilies" or "feather-stars", are marine animals. Crinoids are characterized by a mouth on the top surface that is surrounded by feeding arms. I have never seen such a wide variety of colors in crinoids. They look like a feathered plant. On one coral head I found 18 different color crinoids. There were many more colors and patterns around the world.