416 POLYPI. i 
In the fourth tribe the animal rind or bark encloses a mere 
fleshy substance without an axis either osseous or horny. In 
Aucyonium, Lin. 
As in the Pennatulz, we observe Polypi with eight denticulated arms, 
and intestines prolonged into the common mass of the ovaries: but 
this mass is not supported by an osseous axis; it is always fixed to 
the body; and where it is drawn out into trunks and branches, no- 
thing is found internally, but a gelatinous substance traversed by 
numerous canals surrounded with fibrous membranes. The bark is 
harder and excavated by cells into which the Polypi withdraw more 
or less entirely. The 
A. digitatum, Ell., Corall., XXXII, which is divided into 
thick and short branches; and the 2. exos, where branches are 
more slender, of a beautiful red, &c., are very abundant in 
European seas. 
Linnzus and his successors have rather lightly united to the Al- 
cyonia various marine bodies of different tissues but always without 
any visible Polypi. Such are 
Tuetuya, Lam. 
Where we observe the interior roughened with long, siliceous, spi- 
ral lines, which unite on a similarly siliceous and central nucleus. 
The crust, as in Spongia, presents two sorts of holes; the first, 
closed by a sort of grating, must be for the intromission of water, 
and the second, which are gaping, for its exit(1). 
(1) See Messrs Audouin and Milne Edwards, Ann. des Sc. Nat., XV, p. 17. 
N.B. A great portion of the lcyonia of Lam. belong in reality to his The- 
thyz. 
Add the fossil genera, which M. Lamouroux thinks he can approximate to the 
Alcyonia or Thethyz: his Hatrrroz, and those which form his order of the Ac- 
Trntaria; his Caenonporora, Hirrarinm, Limnorex, Senex, &c,—all produc- 
tions of which the nature is more or less problematical. 
