S])onges from South Australia. 129 



in Its thin form, is confined to the peristome, and in its stouter 

 one to the surface, where it is indistinctly grouped into tufts 

 between the cribriform areas ; no. 2 to the structure of the 

 wall generally ; and no. 3, the quadriradiates, to the surface 

 of the cloaca, wliere its fourth arm, wliich is long and curved, 

 thickly echinates the surface. Size of specimen 7-12ths inch 

 high, not includuig the peristome, by 5-12ths inch in its 

 greatest transverse diameter, being rather compressed, 



Obs. This species is closely allied to Leuconia Jistulosa, var. 

 australiensisj in most respects. 



30. Leuconia echinata. 



Individualized and social. Pyriform, wide above, narrow 

 below, where it is contracted and turned on one side towards 

 the point of attachment ; peristomed ; thickly echinated with 

 large, much curved aceratcs. Colour whitish yellow outside, 

 sponge-brown within. Surface composed of cribriform sar- 

 code in the midst of small radiates ; echinated with the ace- 

 rates mentioned. Pores, the holes in the cribriform sarcode, 

 most of which are comparatively small, while tlie rest, scat- 

 tered here and there, vary under 1 -166th inch in diameter. 

 Vent single, circular, terminal, surrounded by a peristome, 

 leading into a sacciform cloacal cavity corresponding in shape 

 to that of the specimen, a little wider in its widest part than 

 the thickness of tiie wall ; holes in the cloaca subcircular, 

 large and wide apart, each sphinctered by cribriform sarcode, 

 whose interstices are circular and in more or less plurality, 

 varying in diameter under half that of the subjacent hole ; sur- 

 face of the cloaca moderately covered with tliick curved spines, 

 viz. the fourth arms of quadriradiates. Structure of the wall 

 cancellous, supported on the rays of large triradiates, and 

 traversed by the canals of the excretory system. Spicules of 

 three kinds, viz. acerate, triradiate, and quadriradiate : — 

 1, acerates of two forms, viz. one long, straight, thin, cylin- 

 drical, silky, and the other thick, fusiform, much curved, and 

 very thick, the latter averaging 450 by 18-6000ths in. ; 2, tri- 

 radiates of ditierent sizes and different degrees of irregularity, 

 the smallest and most regular on the surface, the next in size 

 on the surface of the cloaca, and by far the largest of all, 

 whose shaft may be 102 by 18-6000ths and arms respectively 

 150 by 18-6000ths, confined to the wall-structure ; 3, quadri- 

 radiates, in which the fourth arm is thick and curved. No. 

 1 is confined to the peristome in its fine straight form, and in 

 its curved and stout one thickly echinates the sui'face, where 

 its outer part, which is the largest and most curved, ia directed 

 Ann. & Mag. N. Hist. Ser. 5. Vol xviii. 9 



