34 C(ELENTERATA. 



Subclass II. ALCYONAKIA. 



ASTEROIDA. OCTACTINIA. OCTOCORALLA. 



Polypes with eight pinnately fringed tentacles in one series. 

 Corallum, when present, external, spicular, or with a sclerobasic 

 axis, but occasionally thecal or tubular. 



The polypes are connected by the coenosarc, through which per- 

 meates prolongations of the body-cavity of each, thus permitting 

 a free circulation of fluids. There is sometimes an outer skeleton, 

 either with or without a central sclerobasic axis. The corallum 

 is rarely thecal, " never presenting traces of septa." 



These composite organisms are, with few exceptions, fixed ; 

 they are only found in deep water. 



Adherent to some foreign body. 



Ectoderm leathery, contractile ALCYONIACE^E. 



Ectoderm hard, not contractile. 

 Branched. 



Calcareous or horny G-ORGONIACB.E. 



Alternately calcareous or horny . . . ISIDACEJE. 



Tubular TUBIPORACE^E. 



Not adherent . .. PENNATULACEJS. 



Order I. ALCYONIACE^E. 



Ectoderm leathery, slightly contractile, with calcareous spicules 

 in tissues. No sclerobasis. Permanently rooted. 



Alcywiium digitatum, a lobed, spongy-looking body, pellucid 

 when distended with water, and covered with stellate apertures for 

 the polypes, is well known under the name of " Dead men's 

 fingers. Telesto is a tree-like organism, with a tubular, subcal- 

 careous corallum. 



Alcyoniida. Cornularndce. 



Alcyonium=Lobularia. Cornularia. 



Nephthya. Anthelia. 



Sarcophyton. Sarcodictyon. 



Tekstida. 

 Telesto. 



Order II. GOEGONIACE^. 



Axis branched, erect, sclerobasic, either horny or calcareous : 

 permanently rooted. Ccenenchyma smooth. 



