SPONGES FROM THE MERGUI ARCHIPELAGO. 



69 



Order VI. HOLOKHAPHIDOTA. 



HALICHOXDRIA TAXICEi, Jollliston. 



Growing by itself and over other sponges. This world-wide 

 species (Schmidt's " Amorpliina "), by possessing one form of 

 spicule only, viz. acerate, curved, fusiform, smooth, gradually 

 attenuated to sharpness at both ends, and very variable in size, 

 and by its white colour, is easily recognized as being present in 

 several instances at King Island. 



Phlceodictyox isodicttiforme, Carter, Ann. Sf May. Xat. 

 Hist. 1882, vol. x. p. 122. 



In this specimen the tubulate prolongations which grow from 

 a common base, spreading over shell-detritus, are about 2| 

 inches long and g of an inch in transverse diameter. They are 

 sometimes bifurcated or polychotomously divided, but they are 

 unfortunately all frayed out and rendered thus imperfect at 

 their free ends. The consistence is fragile and delicate. Colour 

 white. Structure isodictyal externally, supported internally by 

 reticulate fibre with meshes vertical to the surface, which seems 

 to me to be the same structure as that described and illustrated by 

 Johnston and Bowerbank in the species u Haliclwndria albescens" 

 and u Hymeniacidon albescens " respectively. 



Isodictta smr/LAXs, Bowerb. (Plate VI. figs. 1 & 2.) 



There are eight specimens of Isodictya, all characterized by 

 the symmetrical arrangement of their spicules, which are small 

 acerates, and by the absence of skeletal fibre, as laid down by Dr. 

 Bowerbank for the diagnosis of this genus. Moreover, although 

 of different forms they all appear, like the British varieties of this 

 sponge, as stated by Dr. Johnston, to belong to one species only, 

 viz. his Halichondria simulans (Hist. Brit. Sponges, p. 109),= 

 Isodictya, Bowerb. Four, which are small specimens that have 

 grown on oyster-shells, are massive and cancellated ; three of them 

 are of a dark brown colour, and the other, viz. No. 8, much lighter. 

 Prom its appearance this variety might be termed " cancellata" 

 whence the subvarieties, after their colour, might be called "fusca " 

 and " alb i da" respectively. No. 71 grows over a rock to the 

 extent of several square inches, and, consisting of a thin stratum 

 of a light brown colour with single, well-marked vents, some way 



