148 THE VOYAGE OF H.M.S. CHALLENGER. 



Clathria decumhens, Ridley. 



1884. Clathria decumhens, Eidley, Zool. Coll. H.M.S. "Alert," Brit. Mus., p. 612, pL liii. fig. k ; 



pi. liv. figs, g, g'. 



With this species we identify a washed out skeleton from Torres Strait ; it differs 

 slightly from the type in external form and in the proportions of the spicules, and the 

 spines at the base of the smooth stjdus are very rarely seen. It much resembles 

 in external appearance specimens of Acarnus ternatus obtained by the " Alert " 

 from the same locality, forming " a clathrous structure of round soft anastomosing 

 trabeculse."^ 



Locality. — Cape York, Torres Strait; August 7, 1874; depth, 3 to 11 fathoms. 

 One specimen. 



Habitat. — Boudeuse and Etoile Islands, Amirante Group, 10 to 13 fathoms (Ridley, 

 " Alert") ; Torres Strait (Challenger). 



Clathria lendenfeldi, Ridley and Dendy (PI. XXVIII. fig. 5 ; PI. XXIX. fig. 6 ; 

 PI. XLVII. fig. 5). 



1886. Clathria Lendenfeldi, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 474. 



Sponge (PI. XXVIII. fig. 5) based upon a slender Gorgonia axis, which it encrusts. 

 From the encrusting portion arise several straight, cylincbical, unbranched processes 

 about 8 mm. in diameter, the longest of which is 94 mm. high. Colour in spirit light 

 yellow. Texture soft, fibrous, elastic. Surface hispid, with a reticulate ajapearance 

 due to the reticulate main skeleton (the specimen appears, however, to be a good deal 

 worn). Oscula small and scattered. 



Skeleton. — (a) Dermal; consisting of very slender, irregularly scattered, stylote 

 spicules, often found in loose, irregular brushes. (&) Main ; a reticulation of stout, 

 well-developed horny fibre, cored in places (chiefly at the ends of the primary lines) 

 by smooth stylote spicules. These spicules project freely from the ends of the j^rimary 

 fibres and thus give rise to the hispidation of the surface. The fibre (PI. XLVII. fig. 5) 

 abundantly is very echinated by spined stylote spicules, which are most abundant on 

 the secondary fibres. The secondary fibres are, also, almost or entirely without an 

 axial core of spicules. 



Spicules. — (a) Megasclera ; (1) long, straight, very slender, smooth styli or subtylo- 

 styli, very sharply and gradually pointed at the apex, sometimes faintly and minutely 

 spined at the base, measuring about 0'35 by 0"005 mm.; dermal. (2) Much larger, stouter, 

 smooth, very gradually and sharply pointed styli, slightly curved and measuring about 

 0"6 by 0*02 mm. ; in the main skeleton. Much smaller styli also occur as constituents 



» Eidley, Zool. Coll. H.M.S. " Altrt," Brit. Mus., 1884, p. 453. 



