PLATE IV. 



TO ILLUSTRATK THE STRUCTURE OF CORALS. 

 Fig. 



1. 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 costse 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. 



2. A longitudinal section of part of a cor.allite of Lonsdaleia Bronni,- magnified. The columella has 



been removed. The tabulae 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. 

 3 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, 

 (i. Part of a corallite of Zaphrentis gigantea,^ showing the granular epitheca, the slight true wall, the 



septa, and the interseptal loculi, with dissepiments. 

 7. Cahces and cccnenchyma of Lijellia Americana,^ magnified. 



S. Calicinal gemmation in a Caryophyllia ; it is fatal to the parent, and is accidental. From uature. 

 !) and 10. Calicinal gemmation in a Cyathophylhitn. The normal and the budding corallites are 



shown. 

 1 1 . Calicinal gemmation close to the margin, in the genus Isastrcea, magnified. 

 \i 

 13 

 N 



!.■; 

 ifi 



Fissiparous division of calices in Dichoeania. 



Fissiparous division of calices in Leptastrcea Roissyana,^ magnified. 



A serial calice of the genus Thysanus. 



Calices (serial) of a Mceandrina. 



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 Madrepora, 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., pi. ii. 



- ^ * From ' Polypiers Fossiles des Terr. Pal.,' MM. Milne-Edwards et Jules Haime. 



'" ' Ann. des. Sc. Nat.,' t. x, pi. ix. 



•* " Foss. Corals from Sinde," ' Ann. and Mag. Nat. Hist.,' &c., April, 18G4. 



