TETRAXONIDA 3" 



therefore appears to correspond fairly closely with that described by Topsent {he. cit.), 

 but is more complete and better preserved than any yet recorded. It is pyriform and 

 pedunculate, 70 mm. high, and 60 mm. by 25 mm. across the top. Several small oscules 

 are situated on the upper surface. The general surface of the sponge is even, glistening 

 when removed from the alcohol, and very minutely conulose. 



The dimensions of the spicules are the smallest on record. Those of the previously 

 described specimens range as follows: styli o-495-o-9 by o-02-o-028 mm., tornota 

 0-285-0-4 by o-ooy-o-oi mm., chelae o-04-o-o75 mm. Those of the present specimen 

 are: styh 0-3 by 0-009 mm., tornota o-i8 by o-oo6 mm., chelae o-03-o-o63 mm. The 

 most noticeable feature of this variation in spicule size is that although the two categories 

 of megascleres vary considerably in size, the chelae are almost constant. This holds true 

 for most species of sponges, that while the microscleres may be almost constant in size, 

 the megascleres may be subject to very large ranges of variation. 



Distribution. Graham Land ; Victoria Land ; Wilhelm Land. 



Myxilla chilensis, Thiele (Plate LIV, fig. 10). 



M. chilensis, Thiele, 1905, p. 443, figs. 22, 62. 

 Occurrence. St. 58: Falkland Islands, 0-5 m. 



Remarks. The single example is growing in intimate association with an alga, the 

 sponge tissues forming a thin coating on the branches of the alga. The skeleton is quite 

 typical except that the acanthostyh are smaller than those of the holotype and are more 

 tapering at the distal end, resembling more the acanthostyli of Hymedesmia laevis, 

 Thiele (loc. cit., pi. xxxi, fig. 69 b). 



Distribution. Chile. 



Myxilla elongata, Topsent. 



M. elongata, Topsent, 1916, p. 168; 1917, p. 54, pi. iv, fig. 3, pi. vi, fig. 11; Burton, 1929 

 P- 435- 

 Occurrence. St. 158: South Georgia, 401-41 1 m.; St. 160: Shag Rocks, 177 m. 



Remarks. The two specimens agree closely in all respects, the larger being irregularly 

 lobose and white in colour, with smooth but even surface. Both difl^er from the type in 

 size, the arrangement of the tornota, the more feeble spining of the tornota, and in the 

 presence of echinating acanthostyli (see Burton, loc. cit.). 



Distribution. Graham Land; Victoria Land. 



Myxilla basimucronata, sp.n. (Fig. 26). 



Holotype. B.M. 28. 2. 15. 462. 



Occurrence. St. 42: South Georgia, 120-204 m.; St. WS27: South Georgia, 106-109 m.; St. 

 WS 42: South Georgia, 198 m. 



Diagnosis. Sponge of small size, sub-ramose with cylindrical branches or forming 

 dorso-ventrally flattened lobes; surface smooth, even; dermal membrane readily 

 separable; sub-dermal cavities spacious; pores and oscules not apparent; colour, in 

 spirit, pale brown ; main skeleton a regular reticulation of smooth styli, 0-47 by 0-017 mm.. 



