REPORT ON THE DEEP-SEA KERATOSA. 



5] 



contain the usual brown phgeodia-like contents, which fill up the hydrorhiza of the 

 symbiotic Tubularian (probably Stylactis or Stylactella, figs. 2, 3, h). I was, however, not 

 able to observe anywhere the hydranths or the gonophores of the Hydroid, which might 

 be due to the bad state of preservation. 



Xenophya. — The foreign bodies which compose the pseudo-skeleton of this species 

 are almost exclusively various siliceous spicules of sponges, belonging to very different 

 genera of Hexactinellida, Tetractinellida, and Monaxonida ; the quality and quantity of 

 different forms is very variable, according to the accidental composition of the ground 

 on which the sponge grows. The majority of the xenophya, and especially the larger 

 spicules, are not completely enclosed by the horny fibres, but only partially on the ends. 



Horny Skeleton (figs. 2-4, f). — The entire body of the foliaceous sponge is supported 

 and traversed by a very fine framework, composed of anastomosing horny fibres produced 

 by the sponge itself. Examined by a weak lens, this delicate network fills up all the 

 meshes of the coarser network of the polyp-corm (fig. 1). The yellow horny fibres are of 

 the usual Keratose structure, the broader with a distinct axial filament. The majority 

 of the fibres are 0'004 to 0"006 mm. broad, many finer, only O'OOl mm. or less ; rarely 

 there are larger fibres, 0*01 to 0*012 mm. in diameter, or even more. The stellate nodal 

 points of the Keratose network are 0'02 to 0'04 in diameter. 



Psammophyllum fiustraceum, n. sp. (PL IV. figs. 5-8 ; PL V. fig. 5). 



BaUtat.— North Pacific, Station 241; June 23, 1875; lat. 35° 41' N., long. 157° 

 42' E. ; depth, 2300 fathoms ; bottom, red clay. 



Sponge foliaceous, reniform, pedunculate, rather thick and soft, with lobulate distal 

 margin. Surface with branched ribs in the proximal part, with concentric zones in 

 the distal part. Framework of the spongin-fibres very dense and irregular, composed of 

 branched and anastomosing fibres of unequal thickness; these include numerous siliceous 

 spicules of sponges, Eadiolarian tests and other xenophya, which also fill up the maltha. 



Psammophyllum fiustraceum is of special interest as a connecting link between the 

 preceding and the following species. The single specimen observed (figured in PL IV. 

 fig. 5, natural size) is a broad fiabelliform leaf, similar to Stannophyllum venosum (PL I. 

 fig. 4). Its breadth is 105 mm., its height (without pedicle) 70 mm.; the slender pedicle, 

 which arises from the centre of the concave proximal margin, is inversely conical, 33 

 mm. long, 16 mm. broad at the distal insertion. The convex distal margin of the leaf is 

 lobulate, with twelve to fifteen large lobes, each of which is again divided into two to 

 four smaller lobules. 



The surface of the reniform leaf is felty, of a brown colour. The proximal part is 

 traversed by branched radiating ribs, which diverge from the attachment of the pedicle, 



