I/O MANUAL OF ZOOLOGY. 



In the typical Gorgonm the sclerobasis is horny, and more 

 or less arborescent, and the same is the case in the "Fan 

 Corals " (Rhipidogorgia), in which the corallum has the form 



Fig. 83. Red Coral (Corallium rubrum) of the natural size, and a portion enlarged. 



of a regularly reticulate fan-shaped expansion. The soft tissues 

 of the Gorgonida are abundantly supplied with sclerodermic 

 secretions in the form of calcareous spicules of very various 

 shapes, and often of very brilliant colours, which are in many 

 instances of such characteristic figures that they can be em- 

 ployed as a ground of generic distinction. These spicules 

 (" sclerites ") are very generally buried in the soft tissues, but 

 they may project beyond the surface of the coenosarc in such 

 numbers as to render the integument rough and prickly. 



FAMILY V. HELIOPORID^E. The Alcyonarians of this group 

 possess a well-developed sclerodermic corallum, composed of tabu- 

 late tubes of two sizes, the larger ones being furnished with rudi- 

 mentary septal lamina. 



The family Helioporida has been recently founded by Mr Mose- 

 ley for the reception of the living Heliopora ccerulea (fig. 84), and 

 of a number of extinct corals previously placed in the " Tabu- 

 late" section of the Zoantharia sderodermata. In Heliopora 

 the corallum is composite and sclerodermic, and composed 

 of corallites united by what has usually been regarded as a 

 " coenenchyma." The corallites are tubular, crossed by well- 



