SPONGES. 147 



R.N. 67 (Gulf of Manaar); 96 (Gulf of Mannar, dry); 141 ?, 142 (both from deep 

 water off Galle and onwards up West Coast) ; 249 (Stat. XV., Periya Paar). 



Trachyopsis, n. gen. 



Renierina? in which the main skeleton is composed of a dense, irregular network of 

 oxea, while the surface is protected by similar (or perhaps more slender) spicules 

 arranged in dense vertical brushes, which support the pore-bearing dermal 

 membrane. 



This genus is of somewhat doubtful systematic position ; in certain features it 

 recalls the genera Trachya and Spongosoritcs, and it differs from typical Renierhw 

 in the replacement of the reticulate dermal skeleton characteristic of that group by 

 radially arranged brushes of oxea. 



Trachyopsis halichondrioides, n. sp. Plate X., fig. 10. 



Sponge massive (or thickly encrusting ?) ; upper surface slightly convex, rising up 

 at irregular intervals into a few short, thick-walled, cylindrical, tubular processes, 

 each terminated by a single circular vent. General surface smooth and almost 

 glabrous, but uneven ; very minutely reticulate as seen under a lens. Inhalant pores 

 minute and scattered. Colour in spirit, pale yellowish-grey. Texture of body hard 

 and compact, penetrated by numerous narrow vertical canals. Greatest diameter of 

 specimen, which is irregular in outline, 44 millims. ; thickness about the middle 

 15 millims. (but the specimen has evidently been cut off from its base). Height of 

 largest projection about 8 millims.; diameter in the middle about 5 '5 millims.; 

 diameter of the vent at its apex 2'5 millims. 



The main skeleton is an extremely dense and very irregular reticulation of stout 

 oxea, with a tendency to arrange themselves in ill-defined tracts running towards the 

 surface. Immediately beneath the surface the oxea, here perhaps somewhat more 

 slender than usual, are arranged in dense brushes perpendicularly to the dermal 

 membrane, beyond which their apices may project very slightly. 



Spicules. Oxea (Plate X., fig. 10); short, usually stout, sub-fusiform, gently 

 curved or (often) biangulate, fairly gradually and sharply jjointed at each end ; size, 

 when fully developed, about - 64 millim. by 0'0328 millim. ; frequently more slender. 



R.N. 147 (deep water off Galle and onwards up West Coast of Ceylon). 



Sub-family : CHALININ.K. 



Haplosclerida? without microscleres and with diactinal megascleres. Skeleton a 



network of more or less strongly developed horny fibre cored by megascleres. 



It is highly probable that this sub-family is of polyphyletic origin, being derived 



from several genera of Gelliinre and Renierina? by loss of microscleres and strong 



development of spongin. Some species have probably been derived from Toxochalina 



2 



