



AMONGST THE CORALS OF THE PALAOZOIC PERLOD. 239 
distinguish the remains of the old cups from particularly strong and well-marked 
“ accretion-ridges.” There is, however, strong reason for believing that the 
production of accretion-ridges and the simple form of calicular gemmation just 
alluded to, are merely different degrees of the same physiological process. 
Simple calicular gemmation is also particularly well exhibited in many 
| examples of Heliophyllum Halh, Edw. and H.; though not as the only method 
of increase in this fine species. Sometimes the primitive corallite produces no 
more than one new cup, which it throws up from one side of the calice, and in 
such cases both the original and the secondary corallite usually attain consider- 
able dimensions. In other examples several cups are produced successively, 
till the corallum may be composed of six or eight shortened corallites, arranged 
in a vertical series, and each springing from some portion of the calice of its 
predecessor. This mode of growth causes a considerable irregularity of form, 
old examples looking like a succession of inverted cones inserted into one 
another, the curvature of the whole mass being often rendered irregular by the 
bending of the successively produced corallites in different directions. 
It seems extremely probable that the peculiar form of simple calicular gem- 
mation, which I have just noticed as occurring in Cystiphyllum vesiculosum and 
Heliophyllum Halli, may really be due to some peculiarity in their surrounding 
conditions. Thus, examples of these species collected from the calcareous 
deposits of the Corniferous Limestone exhibit “‘ acretion-ridges,” but do not, so far 
as I have seen, produce a vertical series of cups. This latter mode of growth, 
on the other hand, is very common in specimens collected from the argillaceous 
beds of the Hamilton Group. It may therefore be suggested that the stimulus 
to the production of calicine buds in this peculiar fashion is, perhaps, to be found 
in the slow but regular deposition of fine clayey sediment, which ultimately 
buries the original polype to the lips, and thus threatens its existence. 
B. Compound Calicular Gemmation—In the ordinary method of calicular 
gemmation, to which I would apply the name of “compound,” the primitive 
corallite throws up from its calicine surface two or more buds, which, after 
reaching a certain size, in most cases repeat the process. In the typical examples 
of this mode of growth, as exhibited in such a coral as Cyathophyllum trun- 
catum, Linn., the primordial corallite attains no great size before commencing 
to bud; the buds produced are two or more in number, and they repeat the 
process. The necessary result of this is, that the aged corallum assumes the 
form of an inverted pyramidal mass, the base of which is formed by the primitive 
corallite. From the calice of this the secondary corallites diverge, and the sur- 
face of the entire mass is flattened or slightly convex. The calices of the second- 
ary corallites, and the corallites themselves, may remain more or less com- 
pletely separate, as is usually the case in Cyathophyllum truncatum. At other 
times the corallites are more intimately united by their walls, and the corallum 
