ORDER POLYPI POLYPIFERI. 509 
The second tribe, 
LITHOPHYTA, 
Has the interior axis of a stony substance and fixed. 
Isis, L., 
Have the axis branched, and without impressions or cellules, 
hollowed at its surface. ‘The animal bark which envelopes 
it, is mixed with calcareous grains, as in Gorgonia. 
CoRALIUM, Lam., 
Has its axis without articulations, and only striated at its 
surface. 
It is to this subgenus that belongs 
The coral of commerce. Isis nobilis, L. Esp. i. vii., cele- 
brated for the fine red colour of its stony axis, and the fine 
polish of which it is susceptible, which renders it particularly 
adapted for the composition of various trinkets. Its fishery 
is very productive in several parts of the Mediterranean. Its 
bark is cretaceous and reddish. Its polypi, as in many other 
genera, have eight denticulated arms. 
MELITE, Lam., 
Have the stony substance of their axis interrupted by inflated 
knots, of a substance similar to cork. (sts ocracea, Espern.) 
Isis, properly so called. Lam., 
Have it interrupted by strangulations, the substance of which 
resembles horn. Their bark, thick and soft, falls more easily 
than in the preceding. (Ls¢s hippuris, L., &c.) 
M. Lamouroux yet distinguishes from the Isis, properly so 
called, 
