18 LEUCANDRA. 



whicli bears a small, hardly perceptible fringe of spicules, or appears naked. 

 The outer and inner surfaces are pretty smooth. The sponge attains a length 

 of 30 millim., and a diameter of 12 millim. The gastral cavity is cylindrical 

 and rather narrow, measuring only a third of the diameter of the sponge. 

 The thick body-wall is lacunar ; wide canals, with a circular transverse 

 section, measuring from 0*2-5 millim. in diameter, traverse it in every 

 direction. Below the outer surface we meet with extensive anastomosing 

 subdermal cavities, from which comparatively narrow canals take their origin ; 

 these can be traced for some distance in a centripetal direction. The cylindrical 

 canals mentioned above belong to the exhalant canal-system, and are connected 

 with the gastral cavity by very wide (0*4 millim.) and irregular tubes, which 

 are not perpendicular to the gastral wall, but extend upwards towards the 

 osculum. The apertures in the gastral wall at their terminations are scattered 

 sparsely, and measure on an average 0-5 millim. across. The ciliated chambers 

 have a diameter of 0-06 millim. 



Spicules. — The skeleton consists mainly of triacts in the parenchyma. 

 The gastral tetracts are small and irregularly scattered ; the rays and angles 

 are all different. The rays vary from 0-028-0-08 x 0-004-0-007. The paren- 

 chymal triacts are very regular ; sometimes the rays are slightly bent, they 

 are conic and blunt, and measure 0-35x O'Ol.— Diacts of the parenchyma 

 more or less radially disposed, pointed at both ends, slightly protruding beyond 

 the surface, spindle-shaped, and measuring 1-5 x 0-035 miUim., rather rare. — 

 Minute diacts in a continuous layer in the outer surface, all parallel aud 

 situated radially, measuring 0-08 x 0-002. These spicules are rounded at 

 the proximal and pointed sharply at the distal end. Although forming 

 a continuous layer, they nevertheless do not produce a dense and hard 

 armour, as in those species which possess a " Stabchen-Mortel " {HaecM). 

 Diacts forming the frill round the osculum of the same appearance as the 

 former, measuring 0-3-0-5 x 0-002, often slightly bent ; thickest towards the 

 proximal rounded end, and tapering from there to the distal end, which is, 

 in specimens, generally broken off. 



Gteogbaphioal Distribution. — East coast of Australia : Port Jackson, 

 Laminarian zone (Lendenfdd). 



Leucandra aspera^ Haeckel. 



Grantia aspcra, J. E. Gray, Proceedings of the Zoological Society of London, 

 1867, p. 554 (1867). 



Gnintla aspera, O. Schmidt, Die Spongien des Adriatischen Meeres, ii. Supple- 

 ment, Seite 4 (1866), 



Leucandra aspera, E. Haeckel, Die Kalkschwamme ; eine Monographic, Band 

 ii. Seite 101 (1872). 



