S2^onges from South Australia. 127 



28. Leuconia Jistidosay var. australiensis. 



Individualized. Specimen long, straight, sacciform, and 

 so flatly compressed that the sides are in close approximation ; 

 suddenly contracted at the free end to 6-16ths inch, while the 

 rest of the body generally is 10-12ths inch in diameter; pro- 

 vided with a peristome (whose spicules are broken off so shortly 

 that the mouth looks as if it were naked) ; convex at the large 

 end, where it was attached by the most prominent part to the 

 object on which it grew. Colour sponge-brown. Surface con- 

 sisting of cribriform sarcode charged with sagittal triradiates 

 and densely traversed by more or less long flimsy acerates, 

 arranged in thin, broken, indistinct lines, apparently without 

 any uniformity. Pores, which are the holes of the cribriform 

 sarcode, comparatively small in size. Vent single, terminal, 

 occupying the free end of the specimen, which is truncate, 

 compressed to a narrow slit ; surrounded by a peristome ; 

 leading into a large cloacal cavity corresponding in shape 

 with that of the body, which is slightly contracted in the 

 centre ; scattered over with holes of different sizes and differ- 

 rent distances apart, some very large and deeply sunk into 

 the internal structure, others very small and shallow, all 

 showing inwardly a variable number of openings, which 

 belong to the excretory canals of the wall-structure ; surface 

 of the cloaca, its holes and deep depressions, all echinated 

 with the short and curved fourth ray of quadriradiates. 

 Structure of the wall, which, compared with the width of the 

 cloaca, is very thin (not being more than 3-24ths inch in 

 diameter), composed of cancellated sarcode traversed by the 

 canals of the excretory canal-system, which, repeatedly 

 branching, subdivide the whole almost infinitely : supported 

 on small triradiates, which appear to have no definite arrange- 

 ment. Spicules of three kinds, viz. acerate, triradiate, and 

 quadriradiate : — 1, acerates, of difierent lengths and different 

 sizes, the longest and finest chiefly confined to the peristome 

 (but for the most part broken off, so that their original length 

 cannot be ascertained) ; some, viz. the stoutest, which remain 

 entire, fusiform, bent at the extremity, and much shorter 

 than the rest, averaging 150 by 12-6000ths inch. 2, trira- 

 diates, regular and irregular, of different sizes and forms, 

 chiefly sagittal. 3, quadriradiates, of much the same size, 

 which is rather small. No. 1 in its finest and longest forms 

 chiefly characterizes the peristome, but is equally spread all 

 over the body together with the shorter and stouter ones, all 

 mixed up in a matted more or less shaggy mass, so that when 

 dry the whole surface glistens from the silky flimsy nature of 



