270 



DISCOVERY REPORTS 



Remarks. The species appears to differ from all other species of Haliclona in the 

 regularity and compactness of the skeleton, combined with the small size of the spicules. 

 It appears to be most closely related to several of the varieties of Petrosia similis, Ridley 

 and Dendy, from the Indian Ocean and the Kerguelen area. 



Genus Haliclonissa, gen.n. 



Genotype. H. verrucosa, sp.n. 



Diagnosis. Haploscleridae with skeleton composed of fibres running vertically to 

 surface, often anastomosing to form an irregular network, with numerous isolated 

 spicules scattered between ; without special dermal skeleton. 



Remarks. The genus appears to be intermediate between Haliclona and Microxina. 



Haliclonissa verrucosa, sp.n. (Plate LI, fig. 3 ; Fig. 8). 



Holotype. B.M. 28. 2. 15. 473." 



Occurrence. St. 180: Palmer Archipelago, 160 m. 



Diagnosis. Sponge composed of stout, irregularly cylindrical branches, bearing a 

 few conspicuous oscules 10 mm. in diameter ; oscules leading out from shallow, capacious 

 cloacae ; surface verrucose ; texture friable ; colour, in spirit, pale yellow ; skeleton com- 

 posed of diffuse fibres, 6-20 spicules thick, running vertically to surface and forming in 



Fig. 8. Haliclonissa verrucosa, sp.n. Section at right angles to 

 surface, to show structure of skeleton, x 10. 



places an irregular network, with numerous isolated spicules scattered between ; spongin 

 inconspicuous; oxea slightly curved, tapering gradually to a point at each end, 0-5 by 

 0-017 "-'i^- 



Remarks. The holotype measures 13 cm. long by approximately 5 cm. in diameter. 

 In places it is almost regularly cylindrical, but is mainly somewhat flattened laterally. 

 It resembles in appearance some of the Antarctic species of Isodiclya and also, to a lesser 

 extent, HemigelUus rudis (Topsent), but the structure of the skeleton shows that it be- 

 longs to a different genus. 



