348 COELENTERATA ANTHOZOA chap. 



consistency, of a green, brown, or yellow colour. On some reefs 

 the colonies of Sarcophytum form a very conspicuous feature, and 

 from their very slimy, slippery surface, add to the minor dangers of 

 wading in these regions. Both genera are dimorphic. Some species 

 of the genus Sclerophytum} which occur in the Indian Ocean, are 

 so hard and brittle that they might readily be mistaken for a 

 Zoantharian coral. This character is due to the enormous 

 number of tightly packed spicules borne by the coenenchym. 

 Some of these spicules in ;S'. querciforme are 7 mm. x 1'7 mm. ; 

 the largest, though not the longest {vide p. 335) of any spicules 

 occurring in the order. 



Another very important genus occurring on coral reefs, and 

 of very wide distribution, is Spongocles. This genus forms bushy 

 and rather brittle colonies of an endless variety of beautiful 

 shapes and colours. Arising from the neck of each anthocodia 

 there are one or two long, sharp, projecting spicules, which give 

 the surface a very spiny or prickly character. 



The genera Siphonogorgia and Cliironephthya form large 

 brittle, branching colonies which might readily be mistaken for 

 Gorgonians. The strength of the branches, however, is mainly 

 due to the large, densely packed, spindle-shaped spicules at the 

 surface of the coenenchym, the long coelenteric cavities of the 

 zooids penetrating the axis of both stem and branches. 

 Siphonogorgia is usually uniformly red or yellow in colour. 

 Cliironephthya, on the other hand, exhibits a great variety of 

 colour in specimens from the same reef, and indeed in different 

 branches of the same colony. 



Fam. 1. Xeniidae. — Alcyonacea with non- retractile zooids. 

 Spicules very small discs, usually containing a relatively small 

 proportion of lime. 



Xenia, Savigny ; Indian Ocean and Torres Straits. Hetero- 

 xenia, KoUiker ; Eed Sea, Cape of Good Hope, and Torres Straits. 



Fam. 2. Telestidae. — Colonies arising from an encrusting 

 membranous or branching stolon. The erect stem and branches 

 are formed by the body-walls of two or three zooids only, from 

 which secondary zooids and branches of the next order arise. 



Telesto, Lamouroux, widely distributed in warm waters of the 

 Atlantic, Pacific, and Indian Oceans. The genus Fascicularia, 

 Viguier, from the coast of Algiers, seems to be related to Telesto, 



' E. M. Pratt, Fauna and Geogr. Maldive Archip. ii. pt. i. 1903, p. 516. 



