FAMILIES AJTD GENERA OF THE MABHEPORARIA. 



7 



Description of the Section Madreporaria Aporosa. 



Section I. MADREPORARIA APOROSA, Milne-Edwards 

 and Jules Haime, Hist. Nat. des Corall. vol. ii. p. 3 

 (1857-60). 



The diagnosis given by these authors is positive and negative 

 in its characters, aod this was necessary, for the sections Tabulata 

 and Tubulosa were defined at that time. 



They state : — " The corals of this section are of all the Madre- 

 poraria those in which the corallum is the most perfect. A 

 complete wall is always associated in them with a well-developed 

 septal apparatus. The sclerenchyma which composes the coral- 

 lum grows in a continuous manner, and forms laminae of a 

 compact tissue, in which the points corresponding with elemen- 

 tary nodules often project more than the rest, but are hardly ever 

 separated by spaces even of the narrowest kind. The calices are 

 distinctly stellate, and only present six septa when young. 

 During development the rays formed by the upper edges of the 

 septa become twelve in number, subsequently twenty-four, &c. ; 

 but the hexameral type remains almost always recognizable by 

 the predominant size of the early or first septa over those of later 

 age. The interseptal loculi are either open down their whole 

 depth or more or less completely closed by synapticula and 

 ' traverses.' These last may subdivide and form a series of 

 superimposed loculi, but each one is independent of the others 

 and they never unite to form disk -shaped laminae, which may extend 

 across the visceral cavity and shut it off in a series of stories as 

 in the Madreporaria Tabulata and Rugosa " *. 



Now it is evident that in some genera of this section, the se]3ta 

 are cribriform, and that the calices of many are polygonal or 

 serial, or unsymmetrical in shape. Moreover the hexameral 

 arrangement of the septa is not constant ; it may be pentameral, 

 heptameral, octameral, or decameral. It is true that tabulae are 

 found in a few species and genera, and that synapticula exist iu 

 genera which were not thought to have them by Edwards k Haime. 



The following is the diagnosis of the Madreporaria Aporosa 

 as now limited : — 



Madreporaria with simple or colonial forms. Hard structures 



* Hist. Nat. des Oorall. vol. ii. p. 5, 



