1 2 2 Tntroducfion to A mmal Morphology. 



cylindrical papillae (Muricea). In Primnoa, the operculum 

 consists of three-pointed scales, and the axis consists of con-" 

 centric, calcified, horny lamellse, surrounded by alternate, 

 non-spiculigerous rings of horny and crystalline calcareous 

 matter. 



2. Gorgonidse — coenenchyma smooth ; axis horny, some- 

 times flat, leaf-like, with anastomosing branches forming 

 small (Xiphigorgia) or large interstices, whose meshes are 

 either open (Rhipidogorgia) or filled with soft coenenchyma. 

 In this case the sclerobase may be expanded into thin 

 lamellag (Phycogorgia) ; or round, with netted branches in 

 the leaf-like coenenchyma (Phyllogorgia*). In others, the 

 branches are tree-like, not anastomosing ; and the zooids are 

 disposed either regularly on both sides of the coenosarc 

 (Pterogorgia), or irregularly over its whole surface, which 

 may be fan-like or tasseled (Lophogorgia). The zooids are 

 either sunk into the thick, corky (Plexaura), or skin-like 

 (Leptogorgia) coenenchyma, or project on warts, with rounded 

 (Gorgonia) or bilabiate calyces (Eunicea). Plexaurella has 

 spicules in laminas between layers of horny matter. Sclero- 

 gorgia has an uncalcified, horny, spiculigerous axis. 



3. Gorgonellidae — axis corneo-calcareous, either straight, 

 unilaterally comb-like (Ctenocella), or rod-like (Juncella), in 

 structure like Plexaurella, but with spicules in the horny 

 laminae ; or branched, with (Vermicella) or without projecting 

 zooids (Gorgonella). In the last, the horny lamellae are con- 

 centric, calcified. 



Order 5. Isidaceae. — The axis consists of alternate^ 

 soft, and calcareous joints. 



This includes two families: — Melithaeidae — soft joints,, 

 suberose, concentrically laminated ; hard joints made of 

 cemented spicules ; branches arising sometimes from the 

 horny joints, which may be traversed by tubular canals 

 (Melithaea) ; Isididae — hard joints of concentrically laminated, 

 calcified membrane, traversed by radial lamellae, but without 

 spicules ; soft joints horny, like the axis in Gorgonidae ;. 



* Hymenogorgia differs in having free branches. 



