30 DENDBILLA. BAJALUS. 



covered with irregular couuli, 2-4 millim. high and, on an average, 8 

 millim. apart. The oscula are scattered, 3 millim. wide. The whole sponge 

 appears perfectly hollow. The digitate processes are tubular, with walls 

 about 3 millim. thick ; the cavities of these tubes join below ia the basal mass 

 of the sponge, from which the digitate processes grow up, to a lai'ge hollow 

 space. This cavity opens outward at the termini of the digitate processes by 

 large circular pseudoscula, which are covered with perforated membranes ; 

 the pores of which can be contracted or dilated, and are surrounded by rings 

 of sensitive cells. 



The final ramifications of the skeleton-Bhves are 0"14 millim. thick, and 

 nearly straight ; they anastomose here and there. The pith-cylinders have a 

 thickness equal to about half the thickness of the fibres. 



Geographical DiSTRiBUTioN.^East coast of Australia : Port Jackson 



{Lendenfeld). 



Familia HALISARCID^. 

 Hexaceratina without horn-fibres and without horn-spicules. 



Genus BAJALtJS. 



Halisarcidae with simple, sac-shaped, not ramifying, cihated 

 chambers ; without a reticulation of supporting-threads ; and with 

 large and complicated subdermal cavities. 



Bajalus laxus, Lendenfeld. 



Bajalus laxiis, E. von Lendenfeld, "A Monograph of the Australian Sponges. — 

 Part IV. The Myxospongiae," Proceedings of the Linnean Society New 

 South Wales, vol. x. p. 5 (188.5). 



Our sponge represents an irregularly ramified or lobose mass of a dull purple 

 colour. The separate processes are either digitate and slender, or short, 

 broad, and lobular ; they measure to 18 millim. in length and from 2 to 

 10 millim. in breadth. The long and slender processes are cylindrical; the 

 truncate ones generally more or less flattened. Both kinds of processes never 

 occur on the same specimen ; so that one might distinguish two varieties of 

 this species — one with broad, the other with slender ramifications. The whole 

 sponge never seems to attain a large size : the finest specimen I have seen 

 measured 50 x 40 x 20 millim. It is always more or less expanded in one 



