12 TABULATE CORALS. 



With the abandonment of the "tabulae" as structures of 

 classificatory significance, the "Tabulata" of Milne -Edwards 

 and Haime must necessarily be broken up and undergo 

 redistribution. It remains, however, for consideration, what 

 groups are really included under the old name of " Zoatitharia 

 Tabulata" and whether or not this name may still be retained, 

 in a restricted sense, for any of the forms originally placed 

 under it. By the investigations of Agassiz, Verrill, Lindstrom, 

 Duncan, Moseley, Rominger, and others, we have been made 

 acquainted with the true structure and relationships of several 

 of the groups which constituted the old division of the Tabti- 

 lata, and my own researches upon the varied and numerous 

 Palaeozoic types have enabled me to throw some light upon 

 the nature and position of some of the others. Our present 

 knowledge is admittedly imperfect ; but it would appear that 

 the division of the Zoantharia Tabulata, as until very recently 

 understood, comprises about twelve distinct groups of animals. 

 Of these groups, the first two are not known (with any cer- 

 tainty, at any rate) to have had any Palaeozoic representatives, 

 and I shall therefore say here what appears to me to be 

 necessary concerning them ; while I shall merely summarise 

 the characters of the remaining groups, all of which I shall 

 have to treat of hereafter at greater length : — 



I. MiLLEPORiD.E. — The corallum in this group is usually 

 foliaceous, lobate, or sub-massive, and it is composed of an 

 extremely porous coenenchyma, traversed in every direction 

 by tubular canals, which freely communicate with one another, 

 and which also open into the visceral chambers of the polypites 

 themselves. The surface (fig. i, c) exhibits two sets of aper- 

 tures, one large and the other small, the larger ones beino- 

 much the fewest. The large openings (the true "calices") 

 are the mouths of tubes which are crossed by well-developed 

 transverse partitions or "tabula;" (fig. i, b), the livino- animal 

 inhabiting only the outermost of the chambers thus formed. 



in fact, would be to give another name to the structures in the two latter groups 

 which simulate the " tabulre " of the first group. 



