TETRAXONIDA 273 



little doubt that it is congeneric with HetnigeUhis nidis (Topsent), but whether it is con- 

 specific is not so certain, and it is perhaps preferable to recognize it as a distinct species. 

 Distribution. Graham Land; Victoria Land; Wilhelm Land. 



Hemigellius pachyderma, sp.n. (Plate XLVIII, fig. 4; Fig. 11). 

 Holotype. B.M. 28. 2. 15. 723. 

 Occurrence. St. WS 210: Falkland Islands, i6i m. 



Diagnosis. Sponge consisting of massive cylindrical branches ; surface even, minutely 

 hispid; texture friable; oscules conspicuous, 3-4 mm. in diameter, scattered irregularly 



Fig. II. Hemigellius pachyderma, sp.n. a, section at right angles to surface, showing 

 structure of main skeleton, x 30; b, oxeote, x 400. 



over surface ; pores apparently evenly distributed ; subdermal cavities large ; colour, in 

 spirit, greyish yellow; skeleton a reticulation consisting of stout spicule bundles, 5-7 

 spicules thick, running towards surface and anastomosing slightly, connected by 

 isolated spicules set at varying angles; main vertical fibres ending immediately beneath 

 surface in a dense subdermal palisade ; oxea slightly curved, measuring 0-28 by o-oi4mm. 



