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tened in Flabellaria . In Jania the branches are room xt. 
simply forked and slender, with long cylindrical 
joints. In Amphiroa the branches are forked, 
and the joints compressed, and separated by 
longer spaces. In others, the stems are mem¬ 
branaceous, tubular, and covered with a chalky 
coat. Of these, some are furcately branched, 
as the Gulaxura , where the branches are jointed, 
whilst in Dichotomoria they are continuous. 
In Penicillus the forked branches arise from the 
end of a cylindrical stem, which is furnished 
below with a fibrous root. The genus Poly- 
physa is like Penicillus , but the head consists of 
eight or ten small ovate simple vesicles. 
The Umbrella Coralline ( Acetabulum ) has a 
slender stem, which supports a thin, round 
head resembling a parasol, radiately striated, 
crenate at the margin, with a little smooth disc 
in the centre, surrounded by pores. No polypi 
are perceptible ; the radii of the head are hollow 
and, when recent, contain greenish granules, 
which induced Cavolini to consider this pro¬ 
duction as a vegetable, and M. Rafinau, in a 
memoir lately presented to the Academy of 
Sciences of Paris, regards it as a conferva. 
The Corallines belonging to the third group 
resemble the Ulvce of the botanists, but are 
covered with a calcareous coat, have a very short 
stem, and an expanded fan-shaped frond, marked 
with curved concentric lines. 
r 
Lastly. 
