CORALS FROM THE CORAL RAG. 85 
the name of Zhecosmilia trilobata,' is one of the varieties. Sometimes the young corallites, 
produced by a simple parent polyp, instead of forming a fascicular group, arrange them- 
selves so as to constitute a short row, and do not separate immediately from each other ; it 
may even happen that a few of these small series of corallites remain in contact laterally, 
and thus assume the form of Symphyllia. But these variations in the general form are 
only met with in young specimens, and have never been met with in the older, large 
Corals. 
The epitheca is well developed, and extends from the basis of the corallum almost to 
the edge of the calices, but the septa are exsert. Sometimes this coating continues to 
envelop two neighbouring corallites after these have become quite distinct internally, and 
it presents numerous strong circular wrinkles or folds, which are closely set and very 
unequally developed. When the epitheca has been in part, or totally, worn away, as is 
often the case, the costee or outer edge of the seyfa become visible, and appear delicately 
denticulated, not very closely set, and alternatively somewhat more or less thick. ‘There 
does not appear to be any true walls, and the spaces situated between the costo-septal 
laminze are occupied by dissepiments. 
The calices are seldom circular, (as in fig. 1, Tab. XIII ;) they usually become very soon 
oval, subtriangular, or lobated, and it often happens that two fossulz become perfectly 
distinct some time before any corresponding change takes place im the margin, and are 
united by common septa. The fossulee are small and rather shallow ; there is no appearance 
of a columella, and the septa meet in the centre of the visceral chamber at a very short 
distance from the surface of the calice. 
The number of the septa is extremely variable, and differs most especially according 
as the calice belongs to a newly-formed corallite, or is more or less ready to multiply by 
a fissiparous development. Similar modifications are always met with in fissiparous corals, 
and renders it very difficult to come at the knowledge of the real specific characters of the 
septal apparatus. But as far as that can be made out by the examination of the most 
perfectly circular calices which must be supposed to belong to individuals that have not 
begun to multiply in this way, it appears that the normal number of cycla is five ; the last 
cyclum being more or less imperfect. ‘The septa are thin, closely set, straight or slightly 
flexuous, exsert, and terminated by an oblique arched edge, which is armed with delicate, 
nearly equally developed, denticulations. ‘Those of the first three cycla are almost of the 
same size; those of the fourth cyclum not as thick towards their mner edge, and those of 
the fifth cyclum are very thin; all present on their sides slight granulations, arranged in 
radiate series, 
This fine coral often forms large arborescent masses, one or two feet in height. The 
specimen figured in PI. 13 is eight inches high, and Mr, Charlesworth showed us in the 
Museum of York a specimen, which, although incomplete, was more than one foot and a half 
1 Milne Edw. and J. Haime, Ann. Se. Nat., s. iii, vol. x, p. 272. 
