AN ALGA, FORMING A PSEUDOMORPH OP A SILICIOUS SPONGES, 



AN ALGA, FORMING A PSEUDOMORPH OF A 

 SILICIOUS SPONGE, 



R. V. Lendenpeld, Ph.D. 



(Plate XLVIIL, Fig. 5.) 



(From the Australian Museum Laboratory.) 



The sponge in question is a new species of Dactylochalina, and 

 I will give a short description of it here, before entering on the 

 subject proper of this paper. 



Dactylocpialina australis. Nova species. 



The outer appearance of the sponge is very similar to that of 

 Dactylochalina reticulata, R. v. Lendenfeld, described ina previous 

 paper in this number of the Proceedings. 



The whole sponge in Dactylochalina australis, is formed of 

 cylindrical elongate parts, 8-10 mm. in diameter, with a circular 

 transverse section and numerous large oscula. These are circular, 

 and have an average diameter of 3 mm. The surface of these 

 digitate structures is not smooth and regular as in other species, 

 but appears rather rough and irregular in consequence of the 

 presence of irregular protuberances and numerous sharp curves. 

 The oscula are slightly raised. The length of these digitate pro- 

 cesses is 150-250 mm. 



A number, 6-20, of such cylindrical digitates grow out from a 

 common base. They never form anastomoses. 



