Sponges from South Australia. 513 



particularly defined by a cortex and Jilled with parenchymatous 

 structure, and that which is empty or hollow, to wliich I have 

 just alluded ; the former in communication with the surface, 

 the cloaca^ and the hollow spaces by pores situated in these 

 parts respectively, together with small holes, but much larger 

 than the pores, in the cortex here and there, also opening into 

 the hollow spaces. Hollow spaces or intervals communicating 

 externally through the infundibular holes of the surface and 

 internally with the cloaca through the holes in the surface of 

 this cavity. Structure of the parenchyma cancellous, traversed 

 by branched canal-systems which respectively open into the 

 hollow spaces through the " small holes " in the cortex just 

 mentioned ; canals more or less echinated by the fourth ray 

 of quadriradiates. Hollow spaces more or less smooth or 

 sparsely echinated, like the cloaca. Spicules of two kinds, 

 viz. triradiate and quadriradiate, both apparently equally 

 abundant : — 1, triradiate of two sizes, viz. large and small, 

 the former equiradiate and equiangled, a little raised in the 

 centre ; rays stout, irregular in their outline, becoming sud- 

 denly much diminished a little way from the end, about 

 52 by 13-6000ths in their greatest dimensions ; the latter or 

 smaller similar, but with the ray more regular in form, about 

 35 by 4-6000ths ; both forms variable in size between the 

 measurements given. 2, quadriradiate, the same as the 

 smaller triradiate in size, but with the fourth ray in addition 

 curved and somewhat shorter. The large triradiates appear 

 to be confined to the surface, where they are occasionally 

 provided with a fourth arm, and the quadriradiates, mixed 

 with the triradiates, to the interior generally, the former per- 

 haps most abounding on those surfaces •which are most echi- 

 nated. Size varying with that of the specimen, of which 

 there are upwards of a dozen, extending from that of a small 

 bean to one nearly 6 inches in its longest diameter. The 

 largest of all is the free or floating specimen, which is sub- 

 ovoid, 3 inches high, that is placing the large mouth upwards 

 (for there are several small ones about the body, each provided 

 with a lip), and 5| X 4f horizontally in its greatest diameters ; 

 the large mouth is 3 by ^ inch in its greatest diameters, and 

 the cloacal cavity much larger ; wall averaging an inch 

 thick. The rounded form combined with a compact, white, 

 even, homogeneous-looking structure on the surface indicates 

 that this specimen has for some time been free and floating ; 

 its parenchyma is abundantly charged with reproductive 

 bodies. The next largest specimen was attached by several 

 atteimated portions of the body, and, having been much less 

 exposed to friction, presents a much more perfect state of the 



