Orders: Gymnolaemata (Sub-orders: Tripostomata, Cryptostomata, Cyclostomata, Ctenostomata, Cheilostomata), Phylactolaemata.
The Ctenostomata are ill adapted for preservation as fossils, though remains referred to this group have been 1 Calcareous spicules have been described by Lomas in Alcyonidium gelatinosum.
Ctenostomata the colony is similarly constituted, a branched stolon giving off the zooids, which are not connected with one another.
9, C), while in the Ctenostomata it is guarded by a delicate membrane similar to a piece of paper rolled into a longitudinally creased cylinder.
The Cyphonautes type has been shown by Prouho (24) to occur in two or three widely different species of Cheilostomata and Ctenostomata in which the eggs are laid and develop in the external water.