not really in any way resemble a true epitheca, and the 

 presence or absence of a central dark line in section can 

 leave no doubt as to its homologies. 



Where an epitheca is present, there can be no budding 

 from outside the same, no external tissues existing. If buds 

 are found, as are stated to exist in Blastofrochus, they must be 

 due to the epitheca being imperfectly formed, so as to allow 

 the tissues of the polyp to project freely at certain parts of 

 the surface. 



The "columella" may be " essential " or " parietal," true 

 or false. In the first case, it arises on the basal plate as a 

 central deposit, to which the septal edges may secondarily be 

 attached. A " parietal columella" has no such basal deposit, 

 but is formed by the tissues which cover the larger septa, 

 fusing across the coelenteric cavity and joining them by tra- 

 beculae of corallum. The two modes of formation are mor- 

 phologically quite distinct from one another. I, hence, apply 

 the name only to the "essential " or true columella. In many 

 genera, the development being unknown, it is not clear 

 whether there is a true columella or not. In such, as the 

 deposition of a central pillar of carbonate of lime must be 

 regarded as the more primitive mode of formation, I assume 

 the presence of a true columella. 



" Pali " also are of two kinds, true and false. The former 

 arise as deposits on the basal plate, while the latter are the 

 mere thickened edges of the septa, or formed by trabeculae 

 from the same. The true pali are often, and indeed generally, 

 secondarily joined to the septal edges either by trabeculae or 

 along their whole length. Where a coral is truncated, it 

 follows that true pali can only be present in front of those 

 septa which are primarily formed on the basal plate. 

 Additional orders of septa, added during growth, can have 

 no pali, unless (as is conceivably the case in some of the 

 Astraeidae) the original pali become branched. 



3. The Genus FLABELLUM. 



Flabelhim Lesson, Illustr. de Zool., 183 1. 



Flabelliiin Milne Edwards et Haime, Ann. des Sc. nat., 3e 

 sen, t. IX., p. 256 (1848J and Coralliaires, t. II., p. 79 (1857). 



Blastofrochus Milne Edwards et Haime, Ann. des Sc. nat.» 

 3e ser., t. IX, p. 284 (1848) and Coralliaires, t. II., p. 99 

 (1857). Semper, Zeit. fiir. wiss. Zool., Bd. XXII., p. 237 



('^72). 



Rhizotrochus Milne Edwards et Haime, Ann. des Sc. nat.> 

 ^e ser., t. IX., p. 281 (I848: and Coralliaires, t. II., p. 97 

 (i?57). 



