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



Texture soft and spongy, coarsely fibrous ; the fibres becoming readily denuded of the soft 

 tissues so as to project freely beyond the surface. Surface, where intact, subglabrous but 

 conulose, with a minutely reticulate appearance. Dermal memhrane peeling off fairly 

 easily from the underlying tissues, not supported by any special skeleton, hence readily 

 tearing. Oscula small and scattered. Pores scattered through the dermal membrane. 



Skeleton. — There is no dermal skeleton, but the main skeleton is very strongly 

 developed. It consists of a system of stout fibres, branching and occasionally anasto- 

 mosing, and coming to the surface in tufts. The fibre itself is very characteristic, 

 consisting in the first place of a core of stylote spicules whose bases are, as a rule, in the 

 centre, and whose apices project more or less outwards and forwards; being thus arranged 

 in a fairly typical Axinellid manner. This spicular core is almost completely ensheathed 

 in spongin, beyond which the apices of only a few spicules project. At the surface each 

 branch of the fibre ends in a small, brush-like expansion. The average diameter of the 

 fibre is about 0-4 mm.; it is, of course, slenderer at the surface than in the deeper 

 parts of the sponge. 



Spicules. — Mcgasclera; of one form only, viz., smooth styli, slightly bent towards 

 the base and usually very gradually and sharply pointed at the apex ; size about 0-63 by 

 0015 mm. 



This species is peculiarly interesting on account of the unusually strong development 

 of spongin in the skeleton-fibre. It afibrds an additional good instance of the remarkable 

 fact that horny fibre may be developed in any group of sponges and is hence of very little 

 importance for purposes of classification. The massive form and the putty-like appear- 

 ance of the surface between the fibres are further points distinguishing the species from 

 its allies. 



Locality.— ^tatiow 313, January 20, 1876; lat. 52' 20' S., long. 67° 39' W.; east of 

 Strait of Magellan; dej^th, 55 fathoms; bottom, sand; bottom temperature, 47°"8. 

 One specimen. 



Axinella reticulata, Eidley and Dendy (PI. XXXVII. figs. 4, 4a). 



1886. Axinella reticulata, Ridley and Dendy, Ann. and Mag. JSfat. Hist., ser. 5, vol. xviii. p. 481. 



Sponge (PI. XXXVII. fig. 4) massive, sessile, with somewhat constricted base below, 

 and several short, thick-waUed oscular tubes above. Height 38 mm.; greatest breadth 

 44 mm.; breadth at base 29 mm. Colour in spirit very pale yellow. Texture firm, 

 almost incompressible. Surface very uneven, beset with numerous small conuli which 

 extend over the oscular tubes, but glabrous. Dermal membrane distinct, minutely 

 reticulate (PI. XXXVII. fig. 4a), but almost or quite without spicules. Pores in the 

 meshes of the dermal network; several in each mesh, reducing it to a secondary network. 

 Oscula, one at the summit of each oscular tube, about 4 mm. in diameter. 



