HALME, — STELOSPONGIA, 



163 



of the sponge). The oscula are about 0-5 millim. wide. The canals are wide, 

 and there is very little organized substance in the sponge compared with the 

 quantity of foreign bodies in the skeleton and the voluminous vestibular 

 lacunae. 



The skeleton consists of a rather irregular network of fibres, which vary in 

 thickness from 0-003-0-018 millim. At the points of junction of the fine 

 fibres, knots are formed. The longitudinal fibres, which are much thicker than 

 the others — on an average O'Olo millim. — can be regarded as main fibres. 

 Both the thick and slender fibres are charged with foreign bodies ; the former 

 to such an extent that they attain a knotty surface. Among these, foreign 

 siliceous spicules are particularly prevalent. Sand-grains, on an average 0*12 

 millim. in size, are abundant in the thick, but absent in the slender fibres. The 

 foreign bodies in the latter appear as an axial string of broken foreign siliceous 

 spicules. These fragments are very uniform in size and on an average 0-06 

 millim. long. Some spicules appear intact : none seem, however, to be proper 

 spicules. 



GrEOGEAPHiCAL DISTRIBUTION. — East coast of Australia: Port Jackson, 

 N. S. W. (Lendetifeld) ; Broughton Island (Bamsai/). 



Genus STELOSPONGIA. 



Spongidse with large ciliated chambers, wide subdermal cavities, 

 and a skeleton-net with wide meshes, which is generally streng- 

 thened by longitudinal trellis-like fascicles of closely approximated 

 fibres. 



Stelospongia serta, u. sp. 



Lobose, massive, irregular sponges, which attain a maximum diameter of 

 160 millim. The continuous surface is covered with very small couuli 0*4 

 millim. high and V2 millim. apart. The oscula, which measure 1*4 millim. in 

 width, are scattered chiefly over the prominent parts. Light brown colour, in 

 spirit. 



The skeleton consists of a network of fibres 0'018-0"03 millim. thick ; these 

 approximate here and there to form rather indistinct fascicles in which the 

 meshes are 0'3 millim. wide. In the interstitial network the meshes average 

 1 millim. in width. At the joining-points of the fibres in the fascicles occa- 

 sionally very large sand-grains are observed, which measure on an average 0-5 

 millim. in diameter ; they may be single, or there may be two or three together 

 in a cluster. The whole structure is exceedingly similar to the skeleton of 

 certain species of Ualme. 



m2 



