MADREPORARIAN CORALS 



51 



Oken's genus Favia was established in 1815 for a section 

 of the older genus Astrea of Lamarck, and it includes species 

 of corals that have been described under the generic names 

 Orbicella, Heliastraea, Plesiastraea, etc., etc. 



The corals of this genus are usually hemispherical or 

 almost spherical in shape, without lobes or branches but 



Fig. 17. — Favia. A small specimen. Xat. size. 



sometimes encrusting in habit. The surface of the coral 

 consists of a large number of close-set calices about 10 mm. 

 in diameter which project but slightly above the general 

 level of the scanty peritheca between them. The calices 

 are usually circular in outline, but in many specimens where 

 they seem to be more crowded together than in others they 

 become angular and distorted, but never regularly hexagonal. 

 The septa vary greatly in number, but in a typical calyx 



