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CHAPTER XL 



RUGOSA AND ALCYONARIA. 



ORDER II. RUGOSA. 



THE order of the Rugosa includes an enormous number of 

 fossil corals, the vast majority of which are confined to the 

 Palaeozoic period. Throughout the Lower and Upper Silu- 

 rian, the Devonian, the Carboniferous, and the Permian, the 

 Rugosa, are the principal representatives of the Ocelenterata ; 

 but the order is not known to be represented at all during 

 the Triassic or Jurassic periods rich as the latter is in the 

 remains of corals and in the Cretaceous we find only the 

 singular little Holocystis of the Lower Greensand. In the 

 great series of the Tertiary deposits, again, there has been 

 discovered but one Rugose genus viz., the Conosmilia of the 

 later Tertiaries of Australia. Lastly, at the present day we 

 find only two living genera (HaplopJiyllia and Guynia) which 

 have any title to be regarded as Rugose Corals. While, 

 therefore, we may well admit that our knowledge of the 

 history of the Rugose Corals since the close of the Permian 

 period is extremely imperfect and fragmentary, still it re- 

 mains certain that the group is an essentially Palaeozoic 

 one, and that it underwent a very marked diminution before 

 the commencement of Mesozoic time. 



As regards their general characters, the Rugosa agree with 

 the Zoantharia sclerodermata in possessing a well-developed 

 sclerodermic corallum, with a true tkeca, and generally pre- 

 senting well-developed septa, though these are usually com- 



