THE VOYAGE OF H.M.S. CHALLENGEE. 



Halichondria sp. (6). 



We include under this head two fragmentary, massive, amorphous specimens and a 

 few small pieces from off Marion Island, all in a very bad state of preservation, to which 

 we are not prepared to assign any specific name. They are certainly not worthy of the 

 erection of a new species for their reception, and we know of no old one in which they 

 might be included. They are characterised chiefly by a coarse, brittle, dermal layer, 

 readUy shaling off, composed of the dermal membrane and a more or less close reticula- 

 tion of oxeote spicules supporting it. Texture brittle, cavernous. Main skeleton, an 

 irregular loose reticulation of oxeote spicules. Spicules, smooth, slightly curved oxea, 

 rather abruptly pointed; size, about 0*42 by 0'017 mm. 



Locality. — Off Marion Island, December 26, 1873; depth, 50 to 75 fathoms. 

 Fragments. 



Halichondria (?) sp. (c), (PI. II. fig. 4). 



Sponge apparently free, lobose. The single specimen consists of three short, stout 

 lobes, united together at their bases. All the lobes are hoUow and rather thin-waUed, 

 the large central cavities all communicatiag with one another.* 



The specimen is 37 mm. in greatest diameter (from apex to apex of two lobes), 

 and about 12 mm. thick in the middle. Colour in spirit pale greyish -yellow. 

 Texture rather brittle. Surface uneven, but smooth and slightly glabrous, with a 

 minutely reticulate appearance. Dermal membrane delicate and transparent, but with 

 a chitinous look. Oscula (?); there are several smaU round apertures which lead right 

 through from the exterior to the internal cavities, and one which seems to communicate 

 only with a canal system within the thickness of the wall. 



Skeleton. — (a) Dermal; an irreg-ular but very abundant reticulation of closely packed, 

 long oxeote spicules, (h) Main; very dense, composed of closely packed, long oxea, 

 not very regular, but stout fibres may be distinguished running towards the surface, and 

 others crossing them; separate spicules again are irregularly strewn throughout, so that 

 the whole thickness of the sponge-wall consists of little else but spicules. 



Spicules. — Very long, curved (often slightly crooked), fusiform oxea (PI. II. fig. 4), 

 gradually and finely pointed. Size variable, measuring up to about 0'87 by 0'022 mm. 



Considering that there is only a single specimen of this sponge, which may be 

 abnormal or injured, we have thought it better to describe it without creating a new 



1 In the blind end of one of the lobes were found two small Crustaceans, but it is hardly likely that these can 

 have caused the very extensive excavation of the interior, though the possibUity of their being concerned in it must be 

 borne in mind. 



