SP0XGES FROM THE MERGUI ARCHIPELAGO. 



79 



its greatest dimensions, while that of Stelletta bacillifera is not 

 more than 4-6000ths inch long with proportionate thickness. 



Tethta cranium, Johnst., var. robitsta, nov. 

 This appears to be nothing more than a coarse form of 

 T. cranium, wherein the radiating spicular mass, separating into 

 bundles as it advances from the centre to the circumference, 

 leaveslarge interspaces (excretory interspaces) . These spaces open 

 by equally large vents all over the surface, but more especially 

 towards the lower part of this sponge, which is globular with 

 the exception that it is more or less tangentially cut by its sessile 

 attachment to the rock or object on which it may be growing. 

 Typical specimens of T. cranium are more compact and the vents 

 are at the summit (Ann. & Mag. Nat. Hist. 1872, vol. ix. p. 419, 

 pi. xxii. fig. 9 a). The specimens, of which there are two of about 

 the same size, are 2| inches high and 2| inches in their greatest 

 horizontal diameter, which is midway between the summit and the 

 base, that is somewhat contracted on account of the natural ten- 

 dency to a globular form ; while the centre of the sponge, from 

 which the large spicules radiate, is midway between the summit 

 and the base. The spicules of the interior, which project so 

 abundantly as to produce a hispid condition of the surface, are so 

 matted together by the mud in which the sponge has grown on 

 the subjacent rock that, in taking off this crust, the " forks " and 

 " anchors," together with the projecting ends of the " body- 

 spicules," ail come away with it. As the sponge generally is 

 very robust in habit, the spicules are correspondingly large ; in 

 fact the body-spicules are \ inch long by l-450th inch in 

 thickness, and the bihamateflesh-spicules, which, as usual, are Cl- 

 aud S-shaped and contort, are 5-6000ths inch long. 



Tethta dactyloidea, Carter. 



"With the exception of the colour being lightish grey or leaden 



white, the present specimen agrees with those of the S.E. coast 



of Arabia, where its colour is purple-red ; while at Bombay, 



where it grows in the sands of the Mahim Estuary, the species is 



strikingly yellow. Indeed the specimen from King Island, 



which I have divided vertically in order to study its structure, 



still presents a reddish tint in the centre, so that the grey colour, 



like that of many of the other sponges of this collection, seems 



7# 



