436 JANE STEPHENS : ATLANTIC SPONGES 



Carter), and at Mozambique (S. punctulata Ridley). The Scotia specimens come 

 much nearer to the Madeira specimens in spiculation than to these, as the 

 Port Elizabeth sponge possesses robust spinispirae, while the sponge from 

 Mozambique possesses a dermal crust of spinispirae and a large proportion of 

 slender tylostyli. 



Family Polymastiid^e. 

 Polymastia littoralis n. sp. (Plate XXXVIII, fig. 4 ; Plate XL, fig. 3.) 



Station 482. Houtjes Bay, Saldanha Bay, shore. 19th May 1904. 



Several pieces, which are probably parts of the same specimen, are preserved. 

 The largest piece measures about 14 cm. by 10 cm. The sponge, which has been 

 cut off from its support, is in the form of an encrustation, from 10 to 15 mm. 

 in thickness. It possesses a very well-marked cortex about 3 mm. thick, which 

 adheres closely to the choanosome. The upper surface of the sponge bears 

 numerous papillae, which have a maximum diameter of about 4 mm. Among 

 these are scattered a few larger papillae with a diameter of about 8 to 12 mm. 

 The papillae are very short and rigid, and are probably in a much contracted state. 

 The surface is even and is apparently smooth, but under the lens it is seen to 

 be very minutely hispid. 



The colour in spirit is pale greyish yellow. 



The skeleton of the choanosome is formed of thick fibres, consisting of closely 

 packed styli. These fibres run vertically from the base of the sponge to the 

 cortex. At the base they may be as much as 1 mm. in diameter, but they soon 

 divide into finer strands which fan out beneath the cortex. The ends of the fibres 

 penetrate into the cortex, but do not project beyond the surface of the sponge. 

 Small subtylostyli, similar to those of the outermost layer of the cortex, occur 

 in little bundles scattered throughout the choanosome between the main fibres, 

 and are found in special abundance immediately below the cortex. 



The cortical skeleton is made up of two layers of spicules. The outermost layer 

 consists of closely set vertical brushes of small subtylostyli, the tips of which 

 project slightly above the surface of the sponge. Beneath this is a thick, dense 

 layer of large tylostyli and subtylostyli, which are placed for the most part vertically 

 to the surface, but many of which lie quite irregularly. 



The arrangement of the spicules in the papillae is quite similar to that in the 

 main body of the sponge. Towards the centre are strong fibres of large styli 

 running longitudinally through the papilla, with scattered bundles of small 

 subtylostyli lying between them. At the surface are closely set vertical brushes 

 of small subtylostyli, and beneath them is a thick layer of densely packed tylostyli 

 and subtylostyli. 



Spicules. — (l) Large styli of the skeletal fibres. — Shaft fusiform, straight. 



