Halisarca australiensis

Hab. Marine. Apparently extending itself over every ­ thing with which it comes in contact.

Thin and spreading, or contracted, sessile and massive. Consistence soft, elastic, and tough, but yielding like dough to the slightest pressure. Colour cream or pinkish yellow. Surface even, smooth, covered uniformly with a meshed fibro-reticulation, which contrasts strongly by its whiteness with the darker colour of the interstices, but is sometimes in the opposite condition, and sometimes so delicate as to be only seen well under the microscope, if even then. Pores in the interstices of the reticulation. Vents sparse, projecting here and there. Parenchyma consisting of a fibrous reticulation connected with that on the surface, which thus dips down into the interior, holding together the ampul! aceous sacs (Geisselkammern); the whole traversed by the branches of the excretory canal-systems. Fibre throughout consisting of delicate transparent filaments twisted together rope-like. Size variable. Largest spreading specimen about 2 in. in diameter by 1 - Sth in. in its greatest thickness, thinning towards the advancing circumference; largest massive speci ­ men, which is subglobular with crevices on the surface, about 3 - 4 ths in. each way.

Obs. As this species becomes hard by contraction in alcohol, so in pure water it becomes flaccid, hence the specimens vary in size a little when subjected to these conditions respectively. The most striking]> ai t about it is the fi bro-reticulated struc ­ ture of the surface, which, when well developed, is very beauti ­ ful. It appears to be particularly prone to extend itself over a species of Boltenia (stalked Ascidian).

Loc. Port Phillip Heads, South Australia. Depth 20 fath.