112 FroccediiHj.s of the Royal, Society of Victoria. 



iiidixiduals vaiy in size, and, owing to their peculiar colonial 

 and bi-ancliing habit, it is difficult to give exact measure- 

 ments, but we may put down the average adult size as 

 about 20 mm. long and 5 mm. in diameter. A large colony 

 contains dozens of such individuals united together in a 

 complicated and irregular manner. The outer surface is 

 smooth, except for a slight unevenness due to the presence 

 of large triradiates, visible to the naked eye. The colour of 

 spirit specimens varies from pure white to pale brown, but 

 one specimen which I observed as it came out of the dredge 

 was then of a violet purple colour. 



The gastral cavity is wide and cylindrical and the wall is 

 about 2'5 ram. thick. There is a dense, thick coi'tex on both 

 gastral and dermal surfaces. 



The irdialant pores are thickly scattered over the surface 

 of the sponge ; each leads separately into a .shoi't, narrow, 

 cylind]-ical canal, situate in the outer portion of the dense 

 dermal cortex ; these canals soon unite to form lai'ger, but 

 still very well-detined, cylindrical canals, which anastomose 

 with one another by cross-branches and finally lead down to 

 the chamber layer between the dermal and gastral cortex, 

 where the canal system becomes more or less lacunar. The 

 flagellated chambers are thickly scattered through the meso- 

 derm of the chamber layer ; they vary much in shape and 

 size, from approximately spherical and only about 0"072 mm. 

 in diameter to elongatedly sac-shaped and as much as O'oT 

 by 013 mm.* The exhalant canals unite together into 

 tolerably large trunks, which penetrate the gastral cortex 

 and open into the gastral cavity. 



The skeleton is divisible into four portions, that of the 

 gasti'al cortex, that of the chamber layer, that of the dermal 

 cortex and that of the osculum. The gastral cortex is about 

 0'3 mm. thick and its skeleton consists entirely of a 

 dense feltwork of medium-sized triradiate spicules, arranged 

 irregularly but parallel to the gastral surface. These 

 spicules are sagittal, the oral angle being rather wider than 

 the paired angles and the oral rays rather longer than the 

 basal; oral rays straight or very slightly curved towards one 

 another, conical and gradually sharp-pointed, measuring 

 about 03 by 0'024 mm. ; basal ray straight, conical, 

 graduall}^ sharp-pointed, a little shorter than the orals. The 



* These measurements were taken from different specimens, but it would be 

 difficult to make a mistake as to the species in this particular case, and we 

 also find considerable variation in the chambers even in the same section. 



