British Ordovician Cystoids

In part 3, 4 genera (including one new subgenus) and 16 species (3 new, 5 unnamed) of fistuliporite Rhombifera, and 3 newly discovered diploporite cystoids (1 new genus, 2 new species), are described. British fistuliporite cystoids are confined to the Caradoc and Ashgill series. Fistuliporites had meric stems and were medium to high-level suspension feeders. They lack an organized plate arrangement in the theca and passed body fluids through their rhombs for respiratory gas exchange.