THE GENUS ALYEOPOEA WITH THE FAYOSITID.i;. 509 



septa but uniting them inter se. This would be the theca proper, 

 the 'eutheea' o£ v. Heider and Ortmann. I cannot decide this point 

 for want of direct evidence — the sections of Galaxea, Lophohelia, 

 and Turhinolia seem to require it. But thei'e is a possible ex- 

 planation of at least the two latter of these without imagining a 

 distinct circular thecal fold. It is as follows : — The soft polyp 

 growing faster than its rigid epithecal cup, teuds to overflow it. I 

 believe this to have been a very common occurrence in the earlier 

 coral ages, and it still occurs, as will be presently sbown. la 

 the meantime, let us suppose that in Turhinolia and Lopho- 

 helia the Bandplatte is no true Eandplatte — that is, a portion 

 of the coelenlJeron passively cut off by the upgrowth of a theca, 

 but that it is merely a lap of the soft parts bulging down 

 over the rim of the cup, above which rim the septa pro- 

 jected. This would give us all the appearances shown ia 

 Eowler's sections of Lophohelia^, Bourne's of Euphyllia^, and 

 Miss Ogilvie's of Turhinoliat- The "theca" would in this 

 case be really the rim of the primitive epithecal cup slightly 

 folded over ; and from it septa could be infolded (see Fowler's 

 fig. 5). As some confirmation of this I would call attention to 

 the fact that Ortmann' s figure of Flahellum § shows a circum- 

 ferential dark line, whereas no other recorded figure shows 

 anything of the kind. I venture to suggest that in Ortmann's 

 specimen the soft parts bulged somewhat over the lip of the 

 epithecal cup, and that this caused a slightly folded rim. 



"With regard to the section of Oalaxea, I do not see why the 

 same explanation should not apply, only, in this case, the lap of 

 the more rapidly growing soft parts has reached an extreme, and 

 bagging down has united with those of adjacent polyps to secrete 

 the " coenenchyma" which characterizes the genus. I should 

 not, then, be inclined to call these circular folds of epitheca 

 " thecae," for fear of confusing them morphologically with the 

 synapticular and dissepimental thecse, but by some term implying 

 that they are only the rims of the primitive epithecal cups folded 

 back close against their sides. Again, as already stated, I should 

 distinguish between this overflowing liandplatte and that due to 

 the upgrowth of a theca from the floor of the cup. 



With regard to the fate of the primitive epithecal cup shown 



* Quart. Journ. Micr. Sci. xxviii., 1888. t Ibid. 



\ Phil. Trans. 1896, p. i^48, fig. 73. 



§ Zool. Jahrb. iv. (Syst.) 1889, pi. xviii. fig. 9. 



