TYPE C(ELENTERA. 117 



3. Order Cubomednscc. With the four radial primary tentacles 



transformed into sense-organs. Charybdea. 



4. Order DiscomeduscB.^Wiih all eight primary tentacles trans- 



formed into sense-organs. 



(a) Mouth-lobes not fused. Cyanea, Aurelia, Pelagia. 



(b) With mouth-lobes fused. Stomolophus. 



III. Class ANTHOZOA. Without medusoid forms. With ectodermal storna- 

 todoeum ; coelenteron divided into chambers by vertical mesenteries ; 

 reproductive organs developed in the endoderm. 



1. Order Alcyonaria. Colonial forms with eight mesenteries not 



arranged in pairs ; tentacles pinnate. 



(a) Without axial skeleton. Renilla, Alcyonium, Pennatula. 

 (6) With axial skeleton. Gorgonia, Leptogorgia, Isis, Coral- 

 Hum. 



(c) With tubular calcareous skeleton. Tubipora. 



2. Order Edwardsice. Simple forms with eight mesenteries not ar- 



ranged in pairs ; tentacles simple. Edwardsia. 



3. Order CenatttJiece. Simple forms with numerous mesenteries 



not arranged in pairs ; new mesenteries formed on each side of 

 dorsal mid-line. Cerianthus. 



4. Order Antipatharice. Colonial forms with axial horny support ; 



with six simple tentacles ; mesenteries not arranged in pairs. 

 Antipatharia. 



5. Order Protactinice. Simple forms \vith twelve primary mesenter- 



ies arranged in pairs, and in addition one unpaired mesentery 

 on each side, or one or two pairs. Scytophorus, Gonactinia, 

 Oractis. 



6. Order Zoanthece. Simple or colonial forms with twelve primary 



mesenteries arranged in pairs, and in addition a varying num- 

 ber of secondary pairs developed on each side of the primary 

 pair occupying the mid-ventral line. Zoanthus, Palythoa. 



7. Order Hexactinice. Simple or colonial forms with twelve pri- 



mary mesenteries arranged in pairs, and in addition a variable 

 number of secondary pairs arranged in cycles, the newer pairs 

 developing in the intervals between the pairs already present. 

 An external calcareous skeleton present in many forms. 



(a) Without calcareous skeleton (Malacodermata). Hal- 



campa, Aiptasia, Tealia, Metridiinn, Bunodes. 



(b) With a calcareous skeleton (Sclerodermata). Madrepora, 



Fungia, Manieina, Mceandrina, Astrangia. 



