CLASSIFICATION. 27 



which are twelve in number as a rule. The septa are thus 

 seen to be pseudo-septa, and they cannot be regarded as being 

 homologous with the septa of the Zoantharia sclerodcrmata. 

 The so-called ccenenchymal tubes are occupied by sacs lined 

 by the endoderm, which are closed externally, but communi- 

 cate freely with the body-cavities of the polypes by means 

 of transverse canals ; and Mr Moseley suggests, with great 

 probability, that these are really of the nature of rudimentary 

 sexless polypes. 



XI. CHyETETiD.E. — This group is almost certainly made up 

 of very heterogeneous materials, and will undergo disintegra- 

 tion when subjected to a sufficiently searching investigation. 

 As it is even, the lines along which this disintegration will take 

 place can be to some extent discerned. Taking the miscella- 

 neous assemblage of forms at present included in it, no other 

 general definition of the group seems possible than that it com- 

 prises very variably -formed corals, composed of contiguous, 

 thin-walled, mostly prismatic corallites, which have imperfor- 

 ate walls, are intersected by well-developed tabulae, and are 

 destitute of septal laminae or spines. 



Taking the typical members of the Chcztetida: — viz. , Chcstetes 

 radians, Fischer, and its few immediate allies — we find that we 

 have to deal with corals in most essential respects similar to 

 those of the typical Favositidcs, except that " mural pores " or 

 other openings in the walls are wanting, while there are (in 

 reality) no traces of septa, and the walls of the corallites are 

 completely amalgamated. These diff"erences are of course such 

 as to show that the place of Chcstetes in the system must be far 

 removed from that of Favosites. I am nevertheless satisfied 

 that CImtetes radians, Fischer, and the forms immediately 

 related to it, are genuine Actinozoa, though I am not able to 

 assign to them any certain place in this class. So far as one 

 can judge, they seem to have more affinities with the Alcyo- 

 naria than with any other group. 



The position of the numerous forms referred to Monticuli- 

 pora, Fistulipora, and other allied types (which I shall provi- 



