134 THE VOYAGE OF H.M.S. CHALLENGER. 



into consideration in the varying character of the deep-sea Actiniae, the position of the 

 septa being equally important. The arrangement of the septa typical of the Hex- 

 actiniae is only present in thirteen genera, among which I reckon Ophiodiscus and Poly- 

 domidium, in which we meet with the differentiation of muscular and genital septa which 

 is otherwise unknown, and the genera Steiihanactis and Amphianthus, in which we find 

 some approach to the Antipatharia. The other four genera differ from one another as 

 well as from the Hexactiniaj in the arrangement of the septa. They swell the number 

 of the varying forms represented in shallow water by the Zoantheae, Cerianthese, and 

 Edwardsise, and therefore seem to indicate that the diversity in the structure of the 

 Anthozoa was formerly much greater than it is at present, and that the remains of this 

 diversity have been more extensively preserved in the depths of the sea than in the 

 shallow waters. In this way we can recognise peculiarities in deep-sea Actiniae which 

 arc common to the whole deep-sea fauna. 



