LETTCANDRA. 17 



Spicules. — The skeleton chiefly consists of large tetracts, to which minute 

 diacts are added in the cortex, and tangential triacts in the gastral walL 

 The outer surface is covered with a smooth cortex of a brilliant white 

 colour, which is chiefly composed of a cement of minute diacts of peculiar 

 shape ; these consist of a longer, conic, and pointed centripetal part, 

 and, originating from the distal thick end of this, in an oblique direction, a 

 shorter, also pointed, centrifugal part, which has the shape of a triangular 

 pyramid. From the edges of this pyramid strong spines take their origin, 

 which are as long or longer than the spicule is thick, and give to the edges of 

 the pyramid a strongly serrated appearance ; these minute spicules measure 

 0-06 X 0-004 millim. In the cortex we meet here and there with middle-sized 

 triacts and large tetracts. The largest tetracts are regularly disposed ; 

 their rays are sagittally developed ; three of them extend tangeutially in 

 the outer surface and lie in one plane, the fourth extends centripetally, and 

 is exactly radial in its posirion, standing vertical on the plane of the other 

 three; this centripetal ray is 1-1-5 millim. long, and straight. The tangential 

 rays are 0*5-1 millim. long, and curved inward at the base ; all rays are 

 0*06-0'08 millim. thick. These spicules are very regularly situated at equal 

 intervals. Below the cortex a layer of tetracts is met with, the sagittal rays of 

 which are situated centrifugally and meet the centripetal rays of the dermal 

 tetracts.— Parenchymal smaller triacts regular, with rays measuring 0'2~ 

 0-5x0-002-0-004 millim. Parenchymal larger triacts with rays measuring 

 0-6-0-8 X 0-006-0-008 millim. Between these regular spicules a few irregular 

 triacts are uiet with. — Parenchymal tetracts irregular and variable, slightly 

 smaller than the dermal ones described above. Gastral and canal-walls (ex- 

 halant) are coated by a layer of sagittal triacts, which are situated tangentially. 

 The surface of the stomach and exhalant canals is consequently perfectly 

 smooth. The lateral rays enclose an angle of 160°, and measure 0-3x0-024 

 millim., the basal sagittal ray measures only 0'07 x 0-012 millim. Below the 

 outer surface groups of spindle-shaped cells are met with, which are mesodermal, 

 and which I regard as sensitive elements. 



Geogeaphical Distribution. — South coast of Australia : Bass's Straits 

 (Haechel). East coast of Australia: Port Jackson (Eamsa;/, Lemlevfdd), Port 

 Deuison (Bamsaij). 



Leucandra conica, Lendenfeld. 



Leucandra conica, R. von Lendenfeld, "A Monograph of the Australian 

 Sponges. — Part III.," Proceedings of the Liimean Society of New South 

 Wales, vol. ix. part 4, p. 1126 (1885). 



A small, solitary, irregular, more or less cylindrical sponge, with an osciilum 



c 



