229 



On section of specimen A, tlie embedded Lithistid appears 

 more vitreous than the surrounchno- tissues of the Pachaslrclla. 



Family Stellettidae. 



Stelletta (Astrella) hori'ens, sp. n. 

 Plates II and III, fig. 6. 



Sponge vase-shaped with thick rounded rim and thick walls 

 of almost stony hardness. Outer or poral surface and inner or 

 oscular surface bristling with strong protriaenes and oxea. 



Small cribriform groups of oscules, about i mm. in diameter, 

 distributed over the whole inner surface slightly below the level 

 of the jungle of projecting spicules; each oscule about .2 nun- in 

 diameter. 



Colour of outer surface purplish black, of inner, rufous brown. 



Skeleton mainly formed of radiating bundles of protrirenes and 

 oxea. Pycnasters forming a layer in the ectosome, and distri- 

 buted through the choanosome. 



Spicules. Megascleres. — Oxea (Fig. 6a) 3900 X 80 /'. 



Protriaenes (Fig. 6b): rhabdome 3810 X 140 m; length of 

 cladus 440 to 620 fi, chorda varying from 200 /< to o /*, the cladi 

 sharp-pointed, daw-like, occasionally almost meeting. 



Microscleres. Pycnasters (Fig. 6, c, d) 6-5 /< in diameter with 

 short pyramidal spines ; rarely the pycnasters becoming asters 

 12 /( in diameter, by leng1:hening of the spines- 

 Locality. — Durnford Point, Natal, N.W. f W-, distant 12 miles; 

 depth 90 fathoms. Bottom — broken shells. 



The vase, which has been cut off sharp from its area of attach- 

 ment, expands upwards from a massive solid base ; the cut sur- 

 face is oval, 6X5 cm- in diameter and shows the skeleton fibres 

 radiating from the centre. 



The dimensions of the sponge are as follows: — Height 15 cm., 

 diameter of mouth of vase 15X6 cm., thickness of rim i cm., 

 depth of cavity of vase 6.5 cm. 



The cladi of the remarkable claw-like protriaenes are visible to 

 the naked eye, and their presence renders it advisable to handle 

 the specimen very cautiously. 



A massive specimen of a Trachya is firmly attached to one side 

 of the StcUcita, but has not been sho\\>n in the figure of the latter 

 on Plate IL 



