spores are attached. et¢raspores zonately divided, imbedded in the peri- 
phery of the ramuli. The colour is a dull red-brown, becoming darker in 
drying. The substance is rigid ; and in drying, the frond very imperfectly 
adheres to paper. 
A small species with which I first became acquainted by a 
single specimen given to me in 1851 by Dr. Curdie, of Geelong, 
and which I then correctly referred to the genus Acanthococcus, 
and placed in the University Herbarium, under the name here 
adopted. Strange to say, when I myself collected this plant, in 
1854, at King George’s Sound, I mistook its affinities, and with- 
out careful examination placed it in the genus Dicranema, of 
which it has externally the aspect. More recently, when pre- 
paring the analysis for our figure, I found that my first analysis was 
valid; the generic characters are clearly those of Acanthococcus, 
and the first-given name is now restored. 
It is by much the smallest and least branching of the genus, 
never that I know of growing beyond the size represented in our 
Plate. Its favourite habitat is on the stems of Cymodocea, which 
it sometimes completely infests. 
Fig. 1. AcaNTHococcus PUSILLUS,—the natural size. 2. Portion of a frond, 
with conceptacles in the tips. 3. Section through a conceptacle. 4. Sec- 
tion of one of the loculi from the same, with spores in situ. 5. Portion of 
a frond, with tetraspores immersed in its periphery. 6. Portion of the 
periphery, showing the tetraspores in situ. 7. A tetraspore :—the latter 
figures variously maguified. 
