4 • THE VOYAGE OF H.M.S. CHALLENGER. 



in both, and in the arrangement of the fibre, though this is rather more definite in the 

 main skeleton in Bowerbank's sponge. 



Locality. — Off the south-west coast of Patagonia. One specimen. 



Habitat. — British seas (Bowerbank); off south-west coast of Patagonia (Challenger). 



Halichondria solida, Eidley and Dendy (PI. II. figs. 5, 5a). 



1886. Halichondria solida, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. 



p. 326. 



Sponge massive, sessile, encrusting, growing over a mass of nuUipore. The single 

 specimen in the collection is about 62 mm. long by 37 mm. broad and 31 mm. thick. 

 Colour in spirit greyish -yellow.^ Texture extremely compact ; firm, but slightly 

 compressible. Surface uneven, rather rough to the touch ; may be minutely hispid 

 in places. Dermal membrane difficult to make out, inseparable from the underlying 

 tissues. Oscula doubtful ; few if any ; possibly the sponge is Hpostomous. 



Skeleton. — There is no special dermal reticulation distinguishable as such from the 

 main skeleton. The main skeleton consists of a densely felted mass of long oxeote 

 spicules, densely packed, but without order and without discernible fibres. Hence there 

 is no great difi"erence in appearance between a surface section and a section taken at 

 right angles to the surface. 



Sjncules. — More or less curved, large, smooth, fusiform oxea (PI. II. figs. 5, 5a), 

 almost invariably rounded off instead of jDointed at each end (thus becoming strongylote), 

 and with the end often rather wrinkled or roughened in appearance. Size extremely 

 variable, both as regards length and thickness. The largest spicules are by no means 

 the thickest ; length up to about 1"1 mm., thickness up to about 0*038 mm.; the degree 

 of curvature also varies very much. 



This species may be distinguished by its very dense and compact structure, the 

 absence of any skeleton fibres, and the rounding off of the ends of the spicules. If it 

 were not for the absence of a definite skeletal fibre, it would be rather referable to 

 Petrosia, especially considering the tendency of its spicules to become blunted (c/l 

 Petrosia truncata, infra). 



Locality. — Reefs, Tahiti ; September 28, 1875 ; depth, 30 to 70 fathoms. One 

 specimen. 



Halichondria solida, var. rugosa. 



We propose the above name for a single, large, massive, sub-columnar, sub-lobose 

 specimen of a dark chocolate-brown colour. It differs from the type of the species 

 (1) in its dark colour; (2) in the nature of the surface, which is roughened by little 



' Tinged with violet owing to the presence of a darkly-coloured horny sponge on the same mass. 



