279 



pbytes by the mass of animals being supported bya continuous axis. 

 The axis is generally formed of one (or rarely of many elongated) 

 siliceous, calcareous, or horny body, extending from the base to the 

 apex of the coral mass. The axis, whether consisting of honiy, 

 Stony, or siliceous matter, is always formed of numerous concentric, 

 very thin laminas, more or less intermixed with mineral matter. 

 Those which have a horny or calcareous axis are generally branched, 

 and are uniformly fixed by an expanded base to some marine body. 



The single known kind which has a siliceous axis : the axis is 

 formed of many twisted fibres, and its ]ower end, instead of being 

 expanded, is gradually tapering and is parasitically imbedded in a 

 fixed sponge, and thus kept in its erect position. 



These corals have sometiraes been confouuded with some of the 

 more branched or tree-like Alcyoniens, or fleshy zoophytes. But 

 the coral mass of these animals has no distiuct continuous axis, being 

 only strengthened by more or less numerous spicula imbedded in 

 the flesh of the mass, as is the case in the animal part of these 

 zoophytes that covers the axis. 



In some genera, as Briareus, these spicula are more crowded 

 together in the centre of the mass, forming a harder centre to the 

 stem and branches ; but this axis-like body, vvhich is formed of au 

 immense uumber of spicula, mušt not be confouuded with the con- 

 tinued axis of the true Barked Zoophytes, which may be regarded 

 as fleshy zoophytes, which are in addition furuished with a centrai 

 axis to support their more branched form. 



They may be best divided into three distinct subdivisions, aceord- 

 ing to the chemical composition of the axis, thus — 



1. Hyalophytes. 



2. Lithophytes. 



3. Ceratophytes. 



Axis siliceous. 



Suborder I. Hyalophyta. 



Family 1. Hyalonemad.«. 

 Coral subcylindrical, racher attenuated and immersed in a fixed 

 sponge. Axis in the form of numerous elongated, slender, filiform, 

 siliceous fibres, extending from eud to end of the coral, and slightly 

 twisted together likę a rope. Bark fleshy, granular, strengthened 

 with short cylindrical spicula ; polypiferous cells scattered, rather 

 produced, wart-like, with a flat radiated tip. 



1. Hyalonema, Gray. 

 The character of the family. 



1. Hyalonema mirabilis. (PI. IX.) B. M. 



Hyalonema mirabilis, Gray, Syn. B. M. 1830j 118. 

 Hyalonema Sieboldii, Gra>% Proc. Zool. Soc. 1835, 63 ; Dana, 

 Exped. 642. 



Japan {Sir Hans Sloane, Siebold) . 



