444 POLYPI. 
PLEXAURES, 
Of which the thick bark, with non-salient cells, effervesces but 
slightly in acids *. - 
EunNIcEA, 
Where the bark, organized like that of the Plexaures, is furnished 
with projecting mammillie, from which the Polypi protrude f. 
Mouricka, 
Where the moderately thick bark is provided with projecting mam- 
millz, covered with imbricated and rough scales f. 
Primnoa, 
Where the elongated mammille become imbricated by hanging one 
over the other§. 
In the second tribe, that of the 
LirHopuyta, 
The internal axis is of astrong substance and fixed. In 
Isis, Ln.,. 
This axis is ramous, and has no cells or cavities on its surface. The 
animal bark which envelopes it is mixed with calcareous granules, as 
in the Gorgoniz. In the 
: Corauium, Lam., 
The axis is without articulations, and is merely striated on its surface. 
It is to this subgenus that belongs the 
Isis nobilis, L.; Esp., 1, VII, or Coral of commerce, so cele- 
brated for the beautiful red colour of its stony axis, and for the 
high polish of which it is susceptible. It constitutes the object 
of a lucrative fishery in several parts of the Mediterranean. Its 
bark is reddish and cretaceous. The Polypi, as in many other 
genera, have eight denticulated arms. 
Meuirms, Lam., 
Where the stony substance of the axis is interrupted by knots filled 
with a matter resembling cork ||. In 
Isis, Lam., 
Or Isis properly so called, it is interrupted by strangulations, of which 
* Gorgonia crassa, Gm., Ac. des Se., 1700, pl. ii; —G. suberosa, Ell., Corall., 
XXVI, f. p, q, r;—G. friabilis, Lamour., Sol. and Ell., XVIII, f. 3. 
+ Gorgonia antipathes, Seb.; TI1, civ, 2, evii, 4;—Hun. limiformis, Lamour., Sol. 
and Ell., XVIII, f. 1; —Zua. clavaria, Id., 1b., 2;—Hun. mammosa, Lamour., add to 
Sol. and Ell., LXX, f. 3. 
t M. spicifera, Lamour., or Gorg. muricata, Gm.; App. to Sol. and Ell., LXXI, 
f. 1, 2;—@M. elongata, Lamour., Id. f. 3, 4. 
§ Gorg. reseda, Gm.; Sol. and Ell., XIII, f. 1, 2. 
|| Lsts ocracea, Esper., I, iv;—ZIs. coccinea, Id., I11, A, 5. 
