ALCYONARIA. 



473 



3. MADREPORARIA or coral - producing polyps with a definite 

 number of tentacles in most cases in multiples of six (appar- 

 ently only four in the Cyatliopliylloid corals, all of which are 

 fossil) ; as Madrepores, Porites, Astraeas, Maeandrinas, etc. 



SUB-SECTION II. 



THE ORDER OF ALCYONARIA OR SEA-PENS, SEA-FANF 



ETC. 



THE Alcyonarians are polyps which have eight long- 

 fringed tentacles around a narrow disk, and which form 

 communities by budding. The " Sea-pens " and Renillas 



FIG. 709. 



Sea-fan, Gorgonia Jlabellum. 



