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MANUAL OF ZOOLOGY. 



which is known as the "fossula" (fig. 86, B, f), and which 

 appears to take the place of one of the primitive four septa. 

 (3.) When the septa are well developed, they generally present 



Fig. 86. Morphology of the Rugosa. A, Fragment of Zaphrentis gigantea, showing 

 the septa (s) with the sparse dissepiments crossing the interseptal loculi, the epitheca 

 (e), and the thin proper wall (TV). B, Transverse section of Zaphrentis Guerangeri, 

 showing the septa and dissepiments, the central area occupied solely by the tabulae, 

 and the "fossula" {f). C, Longitudinal section of the last, showing the arrangement 

 of the tabulae. (A is after Edwards and Haime ; B and C are after James Thomson.) 



themselves in the adult as of two sizes only, a larger and a 

 smaller (fig. 75, B). (4.) Tabula are usually present, in con- 

 junction with the septa. (5.) The compound coralla possess 

 no true coenenchyma, and one of their commonest modes of 

 increase is by means of " calicular gemmation." 



Recently it has been shown that some very abnormal Rugose corals were 

 provided with a lid or operculum, closing the mouth of the calice. In the 

 genus Calceola (fig. 88), formerly referred to the Brachiopoda, and very 

 abundant in certain parts of the Devonian system, the operculum consisted 

 of a single valve or piece. In Goniophyllum four valves were present, and 

 in Cystiphyllum prismatictim there were four or more valves in the oper- 

 culum. It is worthy of notice that some recent corals (species of Primnoa, 

 Paramuricea, and others) exhibit also a more or less complete operculum. 

 The calices of Cryptohelia pudica (one of the Hydroid group of the Stylaster- 

 idee) are also protected by a calcareous lamina in front of each. 



According to Professor Agassiz, the Rugosa ought not to be 

 considered as belonging to the Actinozoa, but should be placed 

 amongst the Hydrozoa. This radical change cannot, however, 

 be accepted unless upon the production of much more evi- 

 dence than has yet been brought forward in its favour. One 



