1902.] SPONGES OF THE " SKEAT EXPEDITION." 217 



The identification has been made on the evidence of spicules alone. 

 If it should be correct, the specimen affords yet another example 

 of the extraoi'dinary variety in outward form of this species. 

 The sponge is a simple tube attached below to a small pebble, 

 with the single osculum at its free end. The surface is even. 



The skeleton is formed of stout fibres of tylostyles running 

 obliquely to sinaller tylostyles projecting vertically to the suiface. 

 In the ectosome spirasters are sparsely distributed : they are not 

 present in the interior of the sponge. 



Tylostyles of the main skeleton 0-570 x 0-025 to 0-30 x 0-01 mm. 



Tylostyles of the ectosome 0-24 x 0-01 mm. 



Spirasters : length 0-02-0-03 mm. ; average number of bends 3 ; 

 number of spines to each bend 3-5. 



Pulau Bidang. 



19. SUBERITES LAXOSUBERITES, n. sp. (Plate XV. fig. 4.) 

 Sponge encrusting, 1-4 mm. in thickness. Oscula not visible. 



Colour in spii'it whitish. Surface even, slightly hispid. 



The skeleton consists of short ascending and divei-ging fibres of 

 styles and of small styles in the ectosome projecting at the surface. 



Thus this species combines the fibrous arrangement of the styles of 

 the main skeleton — an arrangement characteristic of Laxosuherites 

 Topsent (Arch, de Zool. Exp. ser. 3, t. viii. p. 184) — with the 

 possession of an ectosomal skeleton of small styles like that of 

 Suherites. Occasional tylostyles are to be found among the styles 

 of the main skeleton. 



Styles 0-70x0-026 to M2x0-04 mm., the breadth measiued 

 being the gi-eatest breadth. 



Styles of the ectosome 0-25 x 0-004 mm. 



Tylostyles 0-70 x 0-02 ; breadth of head 0-01 mm. 



Pulau Bidang. 



20. PsEUDOSUBERiTES CAVA, n. sp. (Plate XIV. fig. 6.) 

 Sponge encrusting, with a few outlying free lobes ; transpai'ent ; 



rusty-brown in spirit. 



The subdermal cavities are large, and as the sponge forms only 

 a thin crust, they traverse almost its whole thickness ; the sponge 

 thus consists of two lamellae, one attached to the substratum, the 

 other being the dermal membrane, while colunnis containing 

 bundles of spicules stretch vertically between them. 



The spicules in the dermal membrane lie parallel to the surface, 

 those in the columns on reaching the surface spread out and just 

 extend beyond the dermal membrane. 



Spicules : Styles (not tylote as in the other species of the 

 genus), the largest measuring 0*54 X 0*012 mm. 



21. Terpios pugax Duchassaing & Michelotti. 



Terpios ftujax Keller, Zeitschr. f, wiss. Zool. Hi. p. 319 ; Topsent, 

 Arch, de Zool. Exp. (3) viii. p. 193. 



Sponge growing on a lamellibranch shell together with Amor- 

 phina sp. and Hymedesmia hallezi. 



