123 



MM. Edwards and Haime* have adopted a similar binary 

 division ; as the name Actinoidea had been previously employed 

 in another and more limited sense, they have proposed the 

 term COEALLAEIA for the first sub-class, and HYDRAEIA 

 for the second. The following is a condensed summary of their 

 classification : — 



Sub-class CORALLARIA. — The Polypi possess distinct 

 internal reproductive organs, and their gastric cavity or visceral 

 chamber is surrounded by vertical radiating membranaceous 

 lamellae. The corallum is in general calcareous, and may be 

 either tubular, cyathoid, discoidal, or basal. 



Sub-class HYDRAEIA. — The Polypi have a simple gastric 

 cavity without vertical lamellae, and internal reproductive 

 organs. This gi'oup, which affords curious examples of alternate 

 generations, now fonhs an important division of the Htdeozoa, 

 and is connected with the Acalephce by morphological relations 

 not as yet fully understood. 



The CORALLARIA, or true Polyps, present three principal 

 modifications of structure, and are, therefore, divisible into as 

 many orders: the Zoanthaeia, Alotonaeia, and Podactinaeia. 



1st Order. — Zoanthaeia. — Have conical tubular tentacula, 

 simple or arborescent, but not bipinnate, and with numerous 

 perigastric membranaceous laminae containing the reproductive 

 organs. They are in general coralligenous, and almost all the 

 known fossil Polypidoms belong to this order, which is divisible 

 into two sections ; in one the dermal tissue remains soft 

 and flexible, the Malacodermous Zoantharia, the type of which is 

 the Actinia or common Sea Anemone, — and the other, the 

 Sclerenehymatous Zoantharia, possessing a soHd skeleton or 

 Polypidom, formed by the calcification of the chorion — the type 

 of which is Turbinolia, Astrcea, &c., and other reef-building 

 Corals, living and fossil. 



2nd Order. — Alcyonaeia. — The Polypi, with eight bi-pinnate 

 tentacula, and eight perigastric lameUae, containing the 

 reproductive organs ; the dermal tissue is in general consolidated 

 by isolated spiculae or nodular concretions; the corallum in 



* Annales dea Sciences Naturelles, 3^ s^rie, torn. ix. 

 K 



