ORDER POLYPI POLYPIFERI. 507 
ACETABULUM, Lain. 
A slender and hollow stem, supports a round and thin plate, 
like a parasol, striated in radii, crenulated at the edge, and 
having at the centre a small smooth disk surrounded with 
pores. No polypi are perceptible in it. ‘The radii of its disk 
are hollow, and contain greenish grains, which has caused it 
to be regarded as a plant by Carolini. 
There is one of them in the Mediterranean. (Tubularia 
acetabulum, Gm. Donat. Adri. iii. Tournef. Inst. ccecxviii.) 
PoLYPHYSA, Lam., 
Have, like the preceding, a slender and hollow stem, but 
which supports at its summit, a packet of small closed vesi- 
cles, instead of a disk formed of tubes. (Pol. aspergillum, 
Lamour.) 
The third family, 
POLYFPI corticati, 
Comprehends the genera in which the polypi are all attached 
by a common, thick, fleshy, or gelatinous substance, in the 
cavities of which they are received and which envelopes an 
axis of variable form and substance. The polypi of those 
which have been observed, are a little more complex than 
the preceding, and approach more to the actinie. In their 
interior a stomach is distinguishable, from which proceed eight 
intestines, two of which are prolonged into the common mass, 
and the others terminating sooner, appear to fill the place of 
ovaries. 
They are subdivided into four tribes. 
The first is that of 
CERATOPHYTA, 
In which the interior axis has the appearance of wood or horn, 
and is fixed. Two genera are known, both very numerous. 
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