241 



the series, T. ingalli, seychellensis, Jiiaza, and japonica, the last 

 three of which Sollas is incHned to regard as varietal modifica- 

 tions of a single species. 



The megascleres of the Natal species are much larger than 

 those of the other forms ; also the spherasters are larger. The 

 measurements are given below in microns : — 



T. magna. T. ingalli. T. seychellensis. T. maza. T. japonica. 



Strongyloxeas 4805x75 1700x32 1910x23 1680x32 1510x26 



Spherasters 120 85 95 55 67 



Genus Trachya (Carter.) 



Tracliya nuda, sp. n. 



Plate v., Fig. 7. Plate VI., Fig. 7a, b. 



Sponge massive ; without a cortex ; surface partly smooth, 

 partly finely papillate ; pores not visible ; a few minute oscules 

 at the ends of small conical papillae. 



Colour, in spirit, pale brown, lighter in the interior ; the 

 ground-substance tough-gelatinous, semi-transparent. Con- 

 sistence rather hard, but sponge easy to cut with a knife. 



Skeleton formed of long ill-defined bundles of oxeas radiating 

 from the attached base to the surface. 



Spicules. — Oxea, 1700 x 45 m, curved at the centre, gradually 

 attenuating to sharp points. 



Locality E. — Cone Point, Natal, 34 fms. ; bottom, broken 

 shells. 



The single specimen forms a rounded mass rising from a 

 broad base ; it is 5 cm. in height, 6 cm. in thickness, and 6 cm. 

 in length. 



The new species differs from Trachya pernucleata Cr. and 

 T. honida Cr. in being devoid of a cortical palisade of diactinal 

 microscleres. 



Both in outward appearance, in section, and skeletal arrange- 

 ment this sponge bears a remarkable resemblance to Trachya 

 durissima, Carter, from the Cape ; the latter, moreover, becomes 

 comparatively soft on immersion in water, while T. nuda 

 becomes very hard on drying. There is, however, a great 

 difference in the spiculation, Carter's species having styles — 

 but not tylostyles — and coming under the Suberitid family of 

 the Clavulida [Topsent, 18, p. iii]. 



Genus Hymeniacidon (Bowerbank). 

 Hymeniacidon caliculatum, sp. n. 

 Plate v., Fig. 8. Plate VI., Fig. 12. 

 Sponge stipitate, sub-caliculate. Surfaces slightly rough from 



