XIV ZOANTHARIA MADREPORARIA 397 



section the limits of the calices are not well defined. The septa 

 are represented by twelve trabeculae. The zooids are small and 

 are usually provided with twelve tentacles. The most important 

 genus is Porites, which is so abundant on many reefs that it 

 may be said to rival Madrepora itself in the luxuriance of its 

 growth. On the Australian barrier reef a species of Porites 

 builds up coralla over twenty feet in length and as many in 

 height. According to Saville Kent they are usually found on 

 the outer side of the reef and form a basis of support for the 

 high-level Madreporas and other corals.^ 



The colours of Porites are very variable and often beautiful. 

 In Jamaica ^ the prevailing colours are bright blue, pale yellow, 

 and yellowish green. In Australia the colours are less brilliant 

 perhaps, but among the prevailing tints are light or bright lilac, 

 a delicate pink, dark yellow, and brown. The genus Porites 

 occurs in Eocene and Miocene deposits, and is now found on all 

 the more important coral reefs of the world. 



The genus Alveopora is usually placed with the Poritidae. 

 According to Bernard,^ however, its affinities with this family are 

 remote, and it is more closely related to the Favositidae (see 

 p. 344). The walls of the calices are contiguous and the septa 

 are reduced to rows of spines, as in the Favositidae. It is found 

 in shallow water in the Pacific, the Indian Ocean, and the Eed 

 Sea. 



Sub-Order 2. Cyclocnemaria. 



Madreporaria forming perforate or imperforate coralla. Solitary 

 or colonial. The zooids have usually a large number of mesenteries 

 arranged in two or more cycles. The mesenteries beyond the 

 protocnemic pairs arise in unilateral pairs in chambers other 

 than those between the directives. 



Sect. 1. Aporosa. — Cyclocnemaria in which tlie theca and 

 septa are not perforated. The zooids of the colonial forms may 

 communicate by means of superficial canals of the coenosarc, or 

 they may be in contact with one another only at their edges. 



Several ffimilies are included in this section, of which the 

 more important are : — 



^ Saville Kent, "Great Barrier Reef," 1893, p. 185. 



- Duerden, Mem. Ac. Washington, viii. 1902, p. 550. 



' H. M. Bernard, Journ. Linn. Soc. Zool. x.Kvi. 1897, p. -195. 



