SPONGES — WHITELEGGE. 503 



(2) Small isochelfe rather abundant especially in the dermal 

 region ; size 16 mm. 



The species described above is closely allied to R. filifer, 

 Ridley and Dendy, but differs in wanting the thick dermal crust, 

 as well as in habit and a slight ditference in the spicular charac- 

 ters. It also differs from R. seriatus, Theile, in habit and in the 

 size of the spicules. R. topsenti, Theile, is allied in general 

 features as to surface and mode of branching, but here again the 

 spicules differ in size, and ia R. topsenti the peculiar toxa are 

 absent ("?). 



RH APHID OPHLUS BISPINOSUS, sp. nov. 

 Station 45. 



Sponge arising from a well defined discoidal ba.se, with a short 

 peduncle, and two primary and four short secondary branches. 

 The total height is 50 mm., and the diameter of the somewhat 

 angular stem and branches is from 4 to 5 mm. The surface is 

 minutely honeycombed and densely hispid, with projecting, 

 smooth, stylote spicules. The dermal meoibrane is finely porous 

 and here and there forms a tympanic covering over the apices 

 of the cells. Oscula apparently absent. Texture highly elastic, 

 reticulate, and rather tough ; colour yellowish-grey. 



The skeleton consists of an open network of fibres with a 

 moderate amount of spongin ; the primaries are cored with stout 

 and also with slender smooth styli, intermixed with which are a 

 number of spined styli ; these are fairly uniform in length, but 

 vary greatly in diameter. The spicules in the primary fibres are 

 arranged in compact bundles, about 0*2 mm. in diameter ; in the 

 secondaries they are more diffused and generally divergent at 

 their apices ; the connecting fibres consist of one or two rows of 

 spicules, but as a rule they are ill defined, and the mesh is 

 occupied with scattered spicules. All the fibres are echinated 

 by spined styli, and also by long smooth styli ; the latter are 

 arranged at right angles and are fairly abundant centrally ; at 

 the ends of the fibres they are densely packed and project through 

 the dermis, thus giving the surface its hispid appearance. The 

 mesh is usually elongate and about 0-25 to 0'5 mm. in its narrow 

 diameter. 



Megascleres : — (1) Curved, gradually tapering, and wholly 

 spined styli ; the base is somewhat swollen, the apex acute, and 

 the longer spines are recurved ; these chiefly echinate the fibres ; 

 size 0-17 to 0-2 by 0-01 mm. 



(2) Slender, straight, spined styli; these occur in the fibres 

 and scattered in the choanosome ; size 0-2 by 0-002 mm. or le.ss. 



