BPONaiiJDA. 473 



101. Stelletta purpurea. 

 (Plate XL. fig. E ; Plate XLIII. flgs.^,/.) 



Free, subspherical or suboval. A single circular vent (about 2 

 millim. in diameter in moderate-sized specimens) often present ; it 

 leads deeply into the sponge. Surface subpapillose, i. e. embossed 

 •with small semiglobular elevations, visible most readily under a 

 lateral light. Colour purple in spirit, when well preserved. A 

 distinct cortical layer with sarcode of the same consistency as that 

 of the central part of the sponge, about "7 millim. broad, containing 

 the subcortical crypts, and formed (in adult specimens) by the space 

 intervening between the heads of the superficial zone-spicules j 

 a subcortical zone of anchors and smaller zone-spicules. Deep 

 sarcode transparent, brownish yeUowj that of surface purplish 

 red, rather granular. 



Spicules : — (1) Zone-spicule ; shaft stout, tapering gradually to 

 sharp point, 1-4 to 1-6 by "045 to -06 millim. ; arms strong, 

 tapering gradually to sharp points, projecting somewhat forward 

 at the commencement, and then curving backwards slightly, '27 

 by •043 to -06 millim. in length and breadth respectively, (2) 

 Anchor, long, tapering to sharp point ; head almost flat above ; 

 arms turning rather abruptly back to form an angle of about 45° 

 with shaft, tapering to sharp points ; expanse of arms at their 

 points "1 millim. ; diameter of shaft about -035 miUSm. ; length of 

 shaft about 2 millim., of arms about -07 miUim. Head usually lying 

 below the zone of " chones. " (3) Body acerate, long, slender, 

 tapering very gradually from centre to sharp points ; size about 1*5 

 to 2 by -037 millim. (4) Minute stellate of flesh; about 7 to 

 10 arms ; no perceptible body ; arms straight, very slender, viz. 

 about "0008 millim. in diameter, apparently smooth, terminated 

 by minute head; diameter of spicule across arms '02 to "025 

 millim. : distributed throughout aU parts of the sarcode. 



Sah. Prince of Wales Channel, Thursday Island, and West 

 Island, Torres Straits, 4-9 fms. ; bottom sand or sand and coral. 

 Port Darwin, 7-12 fms. ; bottom sand and mud. Arafura Sea off 

 N.W. coast of Australia, 32-36 fms. ; sand, mud, and shells. 



Specimens not abundant at any of the stations. The single 

 specimen from West Island is remarkable for being half covered 

 by specimens of lotrochota purpurea, BMzochalina sirigaporensis, 

 Cladochalina nuda, and a coralline. 



Stelletta purpurea, var. retroflexa. (Plate XLIII. fig. Jc.) 



This name may be applied to a specimen which has the expanse 

 of the arms of the zone-spicule somewhat greater than in the typical 

 form, while their diameter is less, and one or more of the arms 

 generally has the point bent backwards abruptly, so as to form an 

 angle of about 135° with the rest of the arm. The specimen is 

 globular, and has a vent about 1'5 millim. in diameter. The bend 



