498 " THETIS " SCIENTIFIC RESULTS. 



Megascleres :— (1) Straight, fusiform, minutely spined styli ; 

 these not only echinate the fibres, but in many instances they 

 are incorporated and arranged parallel to the large smooth 

 styli ; frequentl)^ they are enveloped in horny matter at their 

 bases or apices forming triangular meshes, which are in keeping 

 with the length of the spicules; size 0-1 by 0*008 to 001 mm. 



(2) Stout, slightly curved smooth styli, with a thick well- 

 rounded base, and gi'adnally tapering to the acute apex ; these 

 occur in the fibres and form tufts at the surface ; size 0"3 by 

 0-014 mm. 



(3) Long straight cylindrical subtylostyli, with an abrupt acute 

 point and a slightly spiny base ; size 0'3 by O'OOi mm. This 

 form of spicule occurs chiefly in the dermal layer, but is also 

 found in the fibres and scattered throughout the sponge. 



Microscleres :— have not been observed. 



CLATHRIA FAVOSA, sp. nov. 

 Station 44. 



Sponge consisting of a series of irregular subcylindrical 

 branches ; the longest is 170 mm in length and from 3 to 7 mm. 

 in diameter. The smaller branches exhibit a few branchlets, 

 some of which are lateral and others dichotomous, but without 

 any coalescence. Surface minutely honeycombed ; the cells are 

 from 1 to 2 mm. in diameter, and often covered by a white 

 porous membrane ; the walls are thin, prominent, and finely 

 hispid. 



Texture rather inelastic and somewhat bi^ittle ; colour, when 

 the dermal surface is intact, white, elsewhere yellowish-grey. 



Skeleton : — the primary fibres consist of densely packed styli, 

 enclosed in a thin sheath of spongin ; they are about O'l mm. 

 more or less in diameter ; the secondaries have usually three or 

 four spicules in a row, and the connecting fibres are 0*5 in 

 diameter and frequently aspiculous ; both the smooth and spined 

 styli are often limited to one or two. The mesh is reticulate but 

 very loose and irregular, varying from oblong to rhomboidal, and 

 from 0"4 to 0'5 mm. in diameter. 



Megascleres : — (1) Short, stout, spined, echinating styli, very 

 few in number and widely scattered or absent altogether in some 

 parts of the skeleton ; near the ends of the fibres they are, how- 

 ever, more frequent, and often occur in tufts of three or more ; 

 they are cylindrical to within about two diameters or the 

 abruptly pointed, conical apex. The base has three or four 

 irregular spines ; the middle third of the shaft is smooth, and 

 the distal — less the acute conical point — bears a few long stoutish 

 spines, some of which almost equal half the diameter of the 

 spicule ; size 06 to 0'7 by O'Ol mm. 



