146 



CCELENTERATA 



Division 1. PERFORATA. 



Corals wholly or i3artly porous or reiiciilate; zooids small with not 

 more than 12 septa (Fig. 239), whicli a»e sometimes indistinct: 2 



families, wliich include many important 







reef-building corals. 



-Cups of Porites 

 showing septa 

 (Vaughan). 



Family 1. ACROPORIDAE. 



Colony usually branched, the coral 

 being porous and containing canals con- 

 necting the polyps, which are usually small 

 and crowded; mesenteries in bilateral pairs; 

 cup small, deep, without columella and with 

 6 or 12 septa: about 8 genera and over 150 

 species. 



ACROPORA L. {Madrepora L.). Colony 

 branched, being either flabellate, radiate or 

 thick and little branched except towards the periphery; zooids project- 

 ing; terminal polyps with 6, lateral polyps with 12 tentacles; color 

 usually due to symbiotic algae: many species, in most tropical seas; 1 

 species in the West Indies. 



A. muricata L. Colony large (1 m. by 50 cm.), and usually spread- 

 ing, with 3 common varieties; A. cervicornis Lamarck, which is loosely 

 branched, A. prolifera Lam. (Fig. 240), in which 

 the branches are more crowded and often fused 

 together, and A. palmata Lam., made up of large 

 fan-shaped masses: West Indies and Florida. 



Family 2. POEITIDAE. 



Colony with a variety of forms, usually in- 

 crusting and massive, often forming thick 

 branches, but rarely dendritic; zooids small and 

 close together; coral porous and made up of a 

 system of trabeculae and cross bars: about 12 

 genera and 100 species, many of which are reef- 

 building. 



Porites* Lamarck. Cup with about 12 

 short septa; columella present but often indistinct: many species, 2 

 West Indian; often forming very large colonies. 



P. porites (Pallas). Colony more or less branching, there being 

 3 well-marked varieties; P. clavaria Lam., consisting of very thick 



Fig. 240 



Acropora muricata 

 (Vaughan). 



* See "On the Genus Porites," by R. Rathbun, Proc. U. S. Nat. Mus., Vol. 10, 

 p. 354, 1887. 



