KALTKEXTERON. CLATHRISSA. 217 



pointed. The fibres are echinated by spined strongyla 0-09 millim. loDg, and 

 0-011 millim. thick at the stouter end, which is attached to the fibre, and 0"006 

 millim. thick at the free projecting end. Both ends are .slightly thickened. 

 The body of the spicule is nearly cylindrical and bears numerous short and 

 stout spines, so as to attain more a rough than a spined appearance. 



Geogkaphical Distribution. — West coast of Australia : Western Australia 

 (Baily). 



Kalykenteron silex, n. sp. 



The sponge consists of a meandriforni lamella which grows up from a small 

 base of attachment ; it is somewhat flower-shaped, often caliculate. The 

 whole sponge attains a height of 120 millim. The lamella is pretty uniformly 

 6 millim. thick and rounded at the margin. 



The skeleton consists of spicule-bundles 0'2 millim. thick, composed of large 

 and stout styli. There is hardly any spongin discernible. The fibres are 

 echinated by spined styli 0-09 millim. long and O'OOS millim. thick. 



G-EOGEAPHiCAL DISTRIBUTION. — East coast of Australia : Port Molle, Q. 

 (Ramsay). 



Genus CLATHRISSA, n. gen. 



Desmacidonidae with a skeleton composed of dense bundles of 

 slender oxea, with very little spongin ; echinated by spined styli. 



Clathrissa arbuscula, n. sp. 



(Plate V. fig. 2.) 



Small, irregular, lobose or digitate sponges, with erect processes, attaining a 

 height of 150 millim. The living .sponge is very soft and resilient, orange-red 

 in colour. Spirit-specimens are brownish grey. The whole of the surface is 

 covered with densely situated villous, distally rounded or thickened outgrowths, 

 which are about 1-5 millim. thick and from 2-8 millim. long. 



The skeleton consists of longitudinal, much-branched main fibres, 0*04 millim. 

 thick, and on an average 0-2 millim. apart, composed of dense masses of 

 spicules which are straight, cylindrical oxea, 0-18 millim. long and 0-007 

 thick. The horny substance which binds these spicules together is only very 

 slightly developed and difficult to observe. The fibres are echinated by spined 

 conic, mostly straight or slightly curved styli 0-12 milliui. long, and at their 



