Sjjonges from South Australia. 133 



33. Leuconia Johnstonii, var. australiensis. 



Individualized. Glohoconical, sessile, rather compressed, 

 open and conical above, convex and wide below, where the 

 most prominent part becomes the point of attachment ; no 

 peristome. Colour whitish outside, sponge-brown within. 

 Surface consisting of cribriform sarcode charged with trira- 

 diates, faced by comparatively large quadriradiates. Pores, 

 the holes of the cribriform sarcode, varying in size under 

 l-200th inch (? are the largest for fichalant purposes). Vent 

 single, terminal, naked, leading into a sacciform cylindrical 

 cloaca, corresponding in shape with that of the specimen, 

 about the same diameter in its widest part as the thickness of 

 the wall ; scantily overscattered with a few holes of widely 

 different sizes, viz. some very large (l-2J:th inch in diameter) 

 and others very small, situated at variable distances apart, 

 and the large ones so sunk into the internal structure that 

 they appear like diverticula of the cloaca, into which more or 

 less of the excretory canals of the internal structure open, and 

 thus pour out their contents before the latter enter the cavity 

 of the cloaca itself; surface of the cloaca, together with its 

 diverticula, entirely smooth and void of all echination, being 

 bound down by sagittal triradiates only. Wall comparatively 

 thick, consisting of cancellaied sarcodic structure traversed by 

 the canals of the excretory system, supported by a skeletal 

 structure composed of triradiates and quadriradiates of differ- 

 ent sizes, among which the sagittal form is most conspicuous. 

 Spicules of two kinds, viz. triradiate and quadriradiate : — 

 1, triradiates, of different sizes, chiefly irregular, among whicli 

 the sagittal is, as just stated, the most conspicuous ; 2, quadri- 

 radiates, of different sizes, which are again mostly sagittal, 

 that of the surface, which is by far the largest, averaging 135 

 by 12-6000ths in. in the shaft and a little less in the arms, 

 so that it has an eqaiarmed appearance ; the arms arching 

 upwards and outwards serve to bind down the dermal 

 structure, and the shaft descending perpendicularly to support 

 it from within ; while thus traversing the outer part of the 

 wall the shafts are accompanied by dilated portions in their 

 intervals which are identical in appearance with the " sub- 

 dermal cavities " of the non-calcareous sponges. No. 1 is 

 abundant in the skeletal structure of the wall and in its 

 limiting layers, viz. that of the surface or cortex and that of 

 the cloaca ; no. 2, the quadriradiate, is equally abundant with 

 the triradiates in the structure of the wall, and almost exclu- 

 sively on the surface of the body, but entirely absent on that 

 of the cloaca, on which a curved spine or fourth arm is not to 



