Class Crinoidea

1. Possess a cup like body form.
2. Their body position is in an upwardly erect direction.
3. Has branched tentacles better known as tube feet.
4. Branching nervous system.
5. Five or more feathery arms.
6. Water vascular system.
7. Contains an aboral stock.

Crinoids are mostly sedentary creatures living in aquatic environments. They have five or more feathery arms extending from their cup shaped body. Its arms are edged with feathery projections called pinnules. These pinnules contain numerous tube feet with sensory organs branching into each one of them . With its arms it can sweep food toward its mouth for feeding. The organism can also use its tentacular arms for swimming. As the organism's aboral stockis released from its anchored substrate it acheives locomotion by beating its arms. Even when the crinoids are not anchored, the mouth upward posture is still in effect.

• As the sessile animal views a particle of food floating in the water medium, the tube feet are extended. This is done by hydraulic pressure from within the animal by causing them to extend considerabe lengths compared to the invertebrate. The tentacle then clings on to the food and brings it towards the mouth for ingestion.
• There are usually only five arms present in an Crinoid. These arms although can divide to form up to 200 arms, each with numerous side branches.

1. Banister, Dr. Keith and Dr. Andrew Campbell. 1985. The Encyclopedia of Aquatic Life. New York: Facts on File.
2. Bertin, Leon. 1967. Larousse Encyclopedia of Animal Life. New York: The Hamlyn Publishing Group Limited.