Echinoderms - Blastoids

The Echinoderms include the Echinoids (Sea Urchins), Holothuroids (Sea Cucumber), Asteroids (Starfish ), Crinoids (Sea Lilies), as well as the extinct Blastoids, Cycstoids, and Carpoids.

Blastoids:
The Blastoids are a small, well-defined group of Echinoderms, which in life were attached to the substrate by a thin stem, and in which the compact theca is shaped like a rosebud. The theca is made up of three circles of five plates, known as basals, radials, and deltoid. The five columns of ambulacral plates are V-shaped, bearing short brachioles used for filtering food from the water. These fossils are locally common from the Silurian to the Permian, in marine shales and limestone.