250 



core to the spongin fibres. If a core is present at all it is 

 formed of spined styles or foreign bodies. 



Toxas also are apparently absent. 



The solitary specimen, which apparently has been cut in 

 half, expands upwards from a contracted base to a height of 

 27 cm, the width of the piece being 20 cm., and the thickness 

 of the wall 1.5 cm. Near the base the wall is perforated by 

 a large hole. 



Genus Stylostichon (Topscnt). 



Stylostichon involutum, sp. n. 



Plate v., P^ig. 16. Plate VI., Fig. ija-e. 



Sponge forming a thick, firm but flexible, plate, growing 

 from a narrow base and with its lateral edges coiled inwards. 

 Surface presenting a finely hispid woolly appearance, this being 

 due to plumose dermal tufts of oxeas and included foreign 

 particles. Pores and oscules not visible. 



Colour (in spirit) brown. 



Skeleton composed of branching plumose columns diverging 

 obliquely from the central plane, and composed of spined 

 styles echinated by smaller spined styles. Dermal skeleton 

 composed of fan-shaped tufts of oxeas at the summits of the 

 plumose columns. 



Spicules. Megascleres. — Large style, 360x24/1, slightly 

 curved near the base, spined at the lower third, the thorn-like 

 spines pointing backwards. 



Small echinating style, 120 x 6 //, with a marked bend at an 

 angle of 45^ at the basal end, spined at the lower half. 



Oxea of dermal skeleton, loio x 8 /.t, straight, slender, fusi- 

 form. 



Microscleres. — Large sigma, 120 x 4 yu. 



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

 shells. 



The specimen representing the new species is 8 cm. high, 

 and 8 cm. wide, the wall being 2 cm. thick. 



The species is distinguished by its peculiarly arranged ecto- 

 somal skeleton. 



Genus Histoderma (Carter). 



Histoderma natal ense, sp. n. 



Plate v., Fig. 17. Plate VI., Fig. i8a-e. 



Sponge small, bulbous, free or attached, with cylindrical 

 tubular oscules, with a smooth and firm cortex inclosing a 

 soft pith. Colour, white. 



