Prof. NicJiolson on Classification of "Tabulate Corals" 95 



With the abandonment of the " tabulae " as structures of 

 classificatory significance, the "Tabulata" of Edwards and 

 Haime must necessarily be broken up and redistributed. It 

 remains for consideration, however, what groups are really 

 included under the old name of " Zoantharia TahUata," and 

 whether or not this name may be still retained, in a restricted 

 sense, for any of the forms originally included under it. 

 By the investigations of Agassiz, Yerrill, Lindstrom, Duncan, 

 Moseley, Eominger, and others, we have been made ac- 

 quainted with the true structure and relationship of several 

 of the groups which constituted the old division of the 

 " Tabulata," and my own researches upon the varied and 

 numerous Palaeozoic types have enabled me to throw more 

 light upon the nature and affinities of some of the others. 

 Our present knowledge is admittedly imperfect, but it would 

 appear that the division of the Zoantharia tahulata, as 

 until very recently understood, comprised about twelve dis- 

 tinct groups of animals. What these groups are, and what is 

 their ascertained or probable position in the zoological series, 

 will appear from the following very brief synopsis : 



I. MiLLEPORlD^. — The corallum of Millepora, the type of 

 this group, has long been well known. Its form is usually 

 foliaceous or lobate, and it is composed of an extremely 

 porous coenenchyma, traversed in every direction by tubular 

 canals, which freely communicate with one another and also 

 with the visceral chambers of the polypites themselves. The 

 surface exhibits two sets of openings, one large, the other 

 small, the latter much the most numerous. The large open- 

 ings (the true " calices ") are the mouths of tubes which are 

 crossed by well-developed transverse partitions or " tabulae," 

 the smaller tubes being similarly and more closely tabulate. 

 From the researches of Mr Moseley, we now know that these 

 two sets of tubes are occupied by two sets of zooids of cor- 

 respondingly different sizes. In the large tubes are contained 

 large zooids (" gastrozooids "), which are short, with four 

 tentacles, a distinct mouth, and a digestive cavity, and which 

 carry on all the work of digestion and assimilation. The 

 small tubes enclose smaller zooids (" dactylozooids "), which 

 are long and slender, carry numerous clavate tentacles in 



