TETRAXONIDA 



269 



have here definite evidence of the transition from a chahnoid to a pachychalinoid 

 skeleton in one and the same species. 



The species is very Hke Haliclona flaccida (Topsent), but this has spicules measuring 

 0-56 to 0-57 by o-oiy mm. As recorded above, however, there is considerable variation 

 in the size of the spicules of//, bi/amellata, and it is conceivable that the new species and 

 //. flaccida may even yet prove to be identical ; and possibly also synonymous with 

 H. dancoi. 



There are also four specimens, from Sts. WS 27, WS 86 and WS 99, which have oxea 

 measuring 0-35 by 0-009 "^™- ^^^ ^ skeleton, composed of primary lines 8-12 spicules 

 thick and secondary lines 2-4 spicules thick, which gives a more fibrous appearance to 

 the sponge (cf. Plate XLIX, figs. 2, 3). In external form, however, they show the same 

 transitions from tubular to infundibular. One specimen in particular is worth attention, 

 from St. WS 86. This is sub-infundibular, rather like a cup with a cut extending from 

 rim to base (Fig. 6 d). 



Haliclona stephensi, sp.n. 



Holotype. B.M. 28. 2. 15. 102. 



Occurrence. Saldanha Bay (beach). 



Diagnosis. Sponge thinly encrusting (always ?) ; surface smooth, even, minutely 

 hispid ; texture friable ; colour, in spirit, yellow ; skeleton an irregular network of single 

 spicules, perhaps quadratic in places, with ill-defined polyspicular bundles usually 

 running towards surface of sponge; oxea slightly curved, abruptly pointed, o-i2 by 

 o-oo6 mm. 



Remarks. The single specimen, an incrustation several square centimetres in area, 

 on a pebble, appears to agree closely with Reniera sp. from Reit's Bay described by 

 Stephens (1915, p. 464). 



Haliclona petrosioides, sp.n. (Fig. 7). 



Holotype. B.M. 28. 2. 15. 434. 



Occurrence. St. 6: Tristan da Cunha, 

 80-140 m. 



Diagnosis. Sponge encrusting to 

 massive and spreading ; surface uneven, 

 minutely hispid ; texture friable ; oscules 

 and pores not apparent; colour, in 

 spirit, white; skeleton a regular iso- 

 dictyal network with primary and 

 secondary lines five spicules thick, 

 and with numerous isolated spicules , 



scattered between meshes of main ^.^ ^ Haliclona petrosioides, sp.n. a, section at righ 

 skeleton; spongin not apparent; oxea angles to surface, showing structure of main skeleton 



slightly curved, 0-154 by 0-007 "^'^- ^ ^°' *' ^" oxeote, x 400. 



