SPONGES. 1 87 



cun ; or the top of the sponge-body may be flattened, with several irregular, shallow 

 depressions. Surface minutely and uniformly conulose ; the conuli barely 0'5 millim. 

 in diameter and separated from one another by deep but narrow, meandering grooves. 

 In the depression at the top the conuli may be covered over by a thin translucent 

 membrane containing small circular vents. Consistence compressible, resilient. 

 Colour (in spirit) pale yellowish-grey. A typical specimen (R.N. 163, not quite the 

 largest) gave the following measurements : total height 25 millims. ; length of stalk 

 8 millims. ; diameter of stalk 13 millims. ; longer diameter of body 31 millims. ; 

 shorter diameter 21 millims. 



The skeleton is arranged in a typical axinellid manner, consisting chiefly of plumose 

 columns of spicules running at right angles to the surface and ending in the conuli. 

 These columns lie pretty close together and are connected with one another crosswise 

 by occasional groups of spicules, or by single spicules, running across at right angles 

 from one to the other ; there are also numerous irregularly scattered spicules in the 

 interspaces. The spicules are cemented together in the columns, and sometimes also 

 in the cross connections, by a large amount of very pale-coloured spongin. There is 

 no special dermal skeleton, but the surface may be rendered slightly hispid by the 

 projection of the terminal spicules of the columns. 



Spicules. (1.) Short styli (Plate XII., fig. 6, b, c); fairly stout and more or less 

 curved, especially towards the base, which is broadly rounded off; with gradually and 

 finely pointed apex ; size about 0'268 millim. by O'Ol millim., but variable. 



(2.) Oxea (Plate XII., fig. 6, d, e) ; usually gently and evenly curved and sharply 

 pointed, but often irregularly ended ; of about the same size as the short styli, and 

 very numerous. 



(3.) Very long and slender, setaceous styli (Plate XII., fig. 6, a) (sometimes oxea), 

 measuring, say, about 075 millim. by O'OOS millim., but variable. These spicules are 

 found lying lengthwise in the interspaces between the plumose columns. 



(4.) Trichodragmata (Plate XII., fig. 6, /) ; bundles of short and very slender, 

 hair-like microscleres, slightly curved, the whole bundle measuring, say, about 

 0'032 millim. by O'OOS millim., but variable. These occur scattered quite irregularly 

 between the spicular columns. 



This beautiful and well-characterised little sponge is represented in the collection 

 by seven specimens. It differs widely from any of its known congeners in external 

 form, and spirit specimens are easily mistaken, at first sight, for young examples of 

 Phakellia donnani, though readily distinguished on closer inspection by their paler 

 colour, more finely conulose surface, &c. It is apparently common and may be looked 

 upon as one of the most characteristic species of the Ceylon Sponge-Fauna. 



E.N. 160A; 160B; 163; 163A ; 314; 332; 356 (all from Ceylon seas). 



Thrinacophora durissima, n. sp. Plate XII. , fig. 5. 



Sponge sessile, cushion-shaped, very strongly convex above and somewhat con- 



2 B 2 



