1881.] THE SURVEY OF H.M.S. 'ALERT.' 1 iS 



an external framework, which is the main agent in giving the Sponge 

 its firmness. Arising from this subdermal network, and generally 

 closely enveloping it, is a much finer ("dermal") network or veil 

 (corresponding in relations to the veil on which Schmidt based his 

 genus Ditela, afterwards reunited to Spongia) ; its fibres are derived 

 from the upper surface of the subdermal fibres by smaller branches, 

 which branching out horizontally become much finer ; the finest 

 form the finer part of the network, of which the coarser form the 

 supporting ribs ; the diameter varies from '02534 millim. for the 

 coarsest to •00475 millim. for the finest fibres. The "veil," how- 

 ever, at the free end and at the lower edge of tlie Sponge projects 

 beyond it as a loose envelope. The fibres are very transparent, of a 

 pale amber-colour of various shades, and are delicately laminated. 

 The vertical and smaller subdermal fibres are cored by a uni- 

 serial row of fine acerate spicules, placed end to end. In the freely 

 projecting parts of the veil the stouter dermal fibres may be cored by 

 spicules quinqueserially arranged ; the finer dermal fibres are cored by 

 uniserial acerates, although these are often wanting for considerable 

 tracts, or only present at intervals. Parenchyma transparent. The 

 spicules apparently sometimes occur singly or in groups in the 

 stout subdermal fibres ; possibly others have been present and 

 been absorbed. Skeleton-spicules smooth, fine, acerate, tapering 

 somewhat gradually to sharp points, nearly straight ; size "076 by 

 •001267 millim. ; many of them have undergone more or less absorp- 

 tion. Flesh-spicules same as of skeleton. 



Examined. In the dried state and by mounting in balsam. 

 Hah. Hotspur Bank, off east coast of Brazil (lat. 17" 32' S,, 

 long. 35° 46' W.), 35 fathoms, on piece of calcareous rock. 



Obs. iis Schmidt's account is very short, and as the specimen is well 

 preserved, the characters of the Sponge are given fully. The chief 

 differences between this specimen and Schmidt's appear to be : — (1) 

 the superficial (not axial) position in the stout subdermal fibre of the 

 spicules in the former ; (2) the inferior diameter of that fibre as 

 compared with the present specimen (being as 3 to 5) ; (3) the 

 branching of Schmidt's specimen, and (4) its bearing (as appears 

 from his referring to Duch. de Fontbressin and Michelotti's species) 

 small spinous processes on its surface ; and (5), lastly, the superior 

 proportions of the spicules of Schmidt's specimen, which measure 

 •0887 by 0021 1 millim. These differences justify the separation of 

 this form at least as a well-marked variety, although our acquaintance 

 with the Chaliuidae appears to be too limited and their characters too 

 few to admit of distinguishing it as a species at present. Attention 

 is particularly called to the beauty and complexity of the arrange- 

 ment of the skeleton. 



The above differences may be thus tabulated ; — 



PROC. ZooL. Soc— 1881, No. VIII. 



