PROBLEM OF THE MONTICULIPOROIDEA 25 



as such they can be compared exactly with the inflections 

 produced by acanthopores in many Monticuliporoids, if the 

 small difference in calcareousness of skeleton be considered. 

 More calcareous ones have sharper processes. A lunarium is 

 wanting in Heliporidce, but this structure is absent in Fistuli- 

 pora in part, and in most Trepostomata. Any structural differ- 

 ences between Heliopora and Fistidipora are found further in 

 some genus or other closely related to the former, except the 

 monticules or maculae of the latter. 



If one places all Trepostomata and the Tabulata (Alcyo- 

 naria) together, they are compared as follows : The largest 

 cells of the former are scarcely equal the smallest autocells 

 of the latter. Growth habit is alike. Cells, monomorphic or 

 dimorphic, are alike ; except that distinct pseudosepta in auto- 

 cells are common in Tabulata, being absent in few cases and 

 these when the walls are very similar in structure to that of 

 Trepostomata, i. e., when crystalline radiate striping is absent, — 

 except also that mural pores cross the walls of many Tabulata, 

 not, however, in dimorphic forms nor in monomorphic ones with 

 small cells, — except again, the lunarium of Fistuliporidae and 

 the so-called dorsal septum of Alveolitidae. Notably, the two 

 lunarial angles, forming two pseudosepta, are on the upper side in 

 the former, the single " septum," pseudoseptum, is on the lower 

 side in the latter; the structures therefore not corresponding. If, 

 however, they be ascribed respectively to the double ventral 

 folds and the single dorsal fold of certain Alcyonarian Recent 

 corals, 1 one finds them all represented in Ccenites, a Paleozoic 

 tabulate coral. They are rarely indicated in skeletal structure 

 of either Monticuliporoidea or Tabulata, but argue Alcyoranian 

 affinities. 



Cell increase is not unlike. In the Tabulata (Alcyonaria) it 

 is by fission, unequal fission, stolonal gemmation, and intermural 

 gemmation, which are probably degrees of transformation. 2 

 Intermural gemmation is the rule in Trepostomata. The peculiar 



'See further, Neues Jahrb. Minn. Geol. and Pal. Beilb. X, pp. 316, 320. 

 2 See op. cit., pp. 281, 359. 



