Middle Cambrian
Jince Formation
Paradoxides gracilis Zone, Jince, Czech Republic.

40mm early Edrioasteroid on 115mm slab.

Edrioasteroid.

Stromatocystites is one of the earliest-known genera of the Class Edrioasterioidea, one of the earliest of all echinoderm groups. This genus is known from various sites of the Middle Cambrian of Europe.

Edrioasteroids survived into the Permian but died out before the end of the period.

See: Schuchert, Charles. A lower Cambrian edrioasterid, Stromatocystites walcotti:(with one plate). Vol. 70. Smithsonian Institution, 1919. (External Link)