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depressions occupying the bottom of the calyx, and assuming 

 a crucial appearance ; in other cases only one of these primary 

 septa is well developed, and in others no trace of the septal 

 groups can be seen ; the whole apparatus is represented by 

 numerous equally developed radiate strise rising on the surface 

 of the tabulae, and extending up the inner side of its walls. 



The Corallites are always perfectly distinct, and never united 

 by means of a coenenchyma; nor do they ever form a Hnear 

 series, as is often the case in the preceding groups. They 

 multiply by gemmation, and the reproductive buds are in general 

 developed on the surface of the calices of the parents; this 

 often arrests the growth of the latter, and gives rise to a 

 super-position of generations. The septa, although in general 

 very incomplete, are never porous, nor bear synapticulse, but the 

 visceral chamber is in general filled up from the bottom by a 

 series of transverse tabulae, or by a vesicular structm-e, which 

 often constitutes the principal part of the corallum. We 

 divide this sub-order into three families — the Statjrid^, the 

 Cyathaxonid^, the Cyathophyllid^. 



The Stattrid-e have a simple or compound corallum, with 

 well-developed septa extending, without interruption, from the 

 bottom to the top of the visceral chamber, and arranged in 

 four systems by an equal number of primary septa. 



The Cyathaxonid^ have a simple corallum, with the septa 

 complete, and well developed; extending from the bottom to the 

 top of the visceral chamber, and not forming a regular radiate 

 circle ; there are no dessepiments nor tabulse. 



The Cyathophyllid^ have a corallum with incomplete septa, 

 that do not extend from the bottom to the top of the visceral 

 chamber in the form of uninterrupted laminae : the visceral 

 chamber is divided by a series of super-imposed tabulae. 



All the genera composing this sub-order, with one exception, 

 are special to the Palaeozoic epoch ; the Holocystis belonging to 

 the family STAUKiDiE has been found in the Lower Greensand. 

 Of the forty other genera comprised in the group Rugosa, 

 seventeen date from the Silurian period, and six are special 

 to it; six extend into the Devonian period, and four into 



