TETRAXONIDA 271 



Haliclonissa sacciformis, sp.n. (Plate XLVIII, fig. 10; Fig. 9). 



Holotype. B.M. 28. 2. 15. 621. 



Occurrence. St. WS 223: Falkland Islands, 11401. 



Diagnosis. Sponge sacciform, sessile, erect; surface soft to touch, minutely pilose, 

 having an appearance of fine velvet; exhalant 

 apertures opening into a deep central cloaca ; tex- 

 ture very soft and compressible ; colour, in spirit, 

 yellowish grey; skeleton of stout multispicular 

 primary fibres running vertically to surface, con- 

 nected by diffuse and irregular secondary fibres, 

 with numerous isolated spicules scattered between ; 

 spicules slender oxea measuring 0-32 by 0-007 mm. 



Remarks. The single specimen is laterally 

 compressed, about 13 cm. high, 9 cm. across and 

 2-5 cm. wide, with a wide mouth at the apex 

 leading into a deep and capacious cloaca. It re- 

 sembles Chalina spoiigiosissima, Topsent closely 

 in texture, but differs in the external form and the 

 size of the spicules. The primary lines of the 

 skeleton, too, are multispicular instead of bi- or 

 trispicular. 



Genus Microxina, Topsent 



Microxina benedeni (Topsent) (Plate L, fig. i ; Fig. 10). 



Gellius benedeni, Topsent, 1901, p. 6; GelUodes benedeni, id., loc. cit., p. 16, pi. ii, fig. 3, pi. iii, 

 fig. 5; Microxina charcoti, Topsent, 1916, p. 170; id., 1917, p. 72, pi. i, fig. 3, pi. ii, fig. 3, pi. vi, 

 fig. 17; GelUodes benedeni, \z.x . fortior , id., 1917, p. 75, pi. ii, fig. i, pi. vi, fig. 22; G. benedeni. 

 Burton, 1929, p. 423; Microxina charcoti, id., loc. cit., p. 423. 



Occurrence. St. 39: South Georgia, 179-235 in.; St. 149: South Georgia, 200-234 m.; St. 190: 

 Palmer Archipelago, 315 m.; St. WS 81 : Falkland Islands, 81-82 m.; St. WS 99: Falkland Islands, 

 251-225 m.; St. WS 248: Falkland Islands, 210-242 m. 



Remarks. The British Museum 

 now possesses a considerable 

 number of specimens of GelUodes 

 benedeni and Microxina charcoti, 

 and from these it is clear that the 

 two species are alike in external 

 form and spiculation, except that 

 the first possesses sigmata only, 



with the addition of raphides in ^ 



the var.fortior, and the second has pig. 10. Microxina benedeni (Topsent), showing transition 

 microxea only. This being the from sigmata to microxea. 



5-2 



Fig. 9. Haliclonissa sacciformis, sp.n. Sec- 

 tion at right angles to surface, x 20. 



