Cryptostomata

an order of fossil Bryozoa. The colonies of Cryptostomata are small (up to 15 cm), predominantly reticular; more rarely, they are branching or lamellar. The calcareous skeleton is permeated by a system of capillaries. There are three suborders, comprising ten families (approximately 150 genera). Widely distributed from the Ordovician to the beginning of the Triassic, they lived in seas and participated in the formation of reefs. They have great stratigraphic significance.