88 



ANTHOZOA. ZOANTHARIA 



1. Rugose Corals. 



Cyathophyllum. (fig. 30.) Simple or compound 

 massive. Septa numerous, of 

 two sizes, alternating, the longer 

 reaching the centre where they 

 may give rise to a false columella. 

 Fossula often absent. Tabulae 

 rather small, occupying the 

 central part only of the visceral 

 chamber. Dissepiments form 

 an extensive peripheral zone of 

 vesicular tissue. Bala to Car- 

 boniferous. Ex. C. murchisoni, 

 C. regium, Carboniferous Lime- 

 stone. 



often 



Fig. 30. Cyathophyllum murchisoni, 

 Carboniferous Limestone. Por- 

 tion of a vertical section, d, 

 dissepiments ; t, tabulae. 



Acervularia. Compound, massive ; corallites with an outer 

 polygonal (frequently hexagonal) theca, and an inner circular wall 

 formed by the thickening of the septa. Septa well developed, the 

 longer reaching the centre. Columella absent. Tabulae extend 

 across the central part of the visceral chamber. Dissepiments 

 form a peripheral zone of vesicular tissue. Silurian to Devonian. 

 Ex. A. ananas, Silurian. 



A B 



Fig. 31. Lithostrotion basaltiforme, Carboniferous Limestone. A. Hori- 

 zontal section of a single corallite, x 2J. B. Vertical section, x 5. 

 c, columella ; t, tabulae ; d, dissepiments ; w, theca. 



Phillipsastraea (=Smitkia). Compound, massive. Septa 

 numerous, with oblique ridges : septa of adjacent corallites con- 



