PLATE IV. 
TO ILLUSTRATE THE STRUCTURE OF CORALS. 
Fic. 
1. 
bo 
Magnified view of part of a transverse section of the corallum of Antillia Walli.! The upright 
plates are septa, and the lowest structure at right angles to the septa, and which has its lower 
margin somewhat wavy, is part of the epitheca. The structure parallel with the epitheca, and 
separated from it by the short coste and intercostal spaces, is the true wall. Higher up 
are two transverse dense layers of sclerenchyma; they spread from septum to septum across 
the interseptal loculi and simulate secondary walls. They are highly developed masses of dissepi- 
ments, whose intercellular spaces have been filled up with carbonate of lime. 
A longitudinal section of part of a corallite of Lonsdaleia Bronni,? magnified. The columella has 
been removed. The tabule are seen stretching across, but not interfering with the growth 
of the septa; externally, the vesicular endotheca partly produces a false wall. The dense wall 
is shown. 
and 4. Examples of inner and outer walls in Rugose corals. 
The septa and the cut edges of oblique dissepiments in a large species of Zaphrentis, from 
nature. 
Part of a corallite of Zaphrentis gigantea,® showing the granular epitheca, the slight true wall, the 
septa, and the interseptal loculi, with dissepiments. 
Calices and coenenchyma of Lyellia Americana,* magnified. 
Calicinal gemmation in a Caryophyllia ; it is fatal to the parent, and is accidental. From nature. 
and 10. Calicinal gemmation in a Cyathophyllum. The normal and the budding corallites are 
shown. 
Calicinal gemmation close to the margin, in the genus Isastrea, magnified. 
Fissiparous division of calices in Dichocenia. 
Fissiparous division of calices in Leptastrea Roissyana,° magnified. 
A serial calice of the genus Thysanus. 
Calices (serial) of a Meandrina. 
An example of extracalicular gemmation, from nature. 
A corallum of Oculina Halensis. The centre is occupied by the parent stem, and the buds radiate 
from it.® 
A section of a branch of a species of MJadrepora, magnified. The parent corallite occupies 
the centre, and the younger arise from it more or less at right angles. The peculiar septal 
arrangement of the genus and the porose condition of the sclerenchyma are shown. From 
nature. 
| Duncan and Wall, op. cit., pl. ii. 
234 From ‘Polypiers Fossiles des Terr. Pal.,) MM. Milne-Edwards et Jules Haime. 
> Non .“Geks Se, Nat... tx, pl. ix. 
6 “ Foss. Corals from Sinde,” ‘Ann. and Mag. Nat. Hist.,’ &c., April, 1864. 
