CORALLIFERI, 413 
In the third tribe, or the 
- NATANTES, 
The axis is stony but not fixed. 
PennaTuua, Lin. 
A common body, free from all adhesion(1), of a regular and con- 
stant form, and susceptible of locomotion by the contractions of its 
fleshy portion and the combined action of its Polypi. This body is 
fleshy, and contracts or dilates in its various parts by means of the 
fibrous layers that enter into its composition; its axis encloses a sim- 
ple stony stem; the Polypi have generally eight dentated arms. 
Most of the species diffuse a vivid phosphorescent light. 
Whatever be the general form of the Pennatule, one of their ex- 
tremities is always destitute of Polypi, and has been compared to 
the tubular portion of a bird’s feather. 
PENNATULA, Cuy. 
The Pennatule, properly so called, have given their name to the 
whole genus, which name has been derived from their own resem- 
blance to a quill. The portion destitute of Polypi is cylindrical 
and terminates in an obtuse point. The other part is furnished on 
each side with wings or laminz, more or less long and broad, sup- 
ported by spines or rigid sete which arise from their interior and 
roughen one of their edges, without, however, being articulated with 
the stony stem of the axis; it is from between their laminz that the 
Polypi protrude. 
P. rubra, P. phosphorea, Gm.(2); Albinus, Annot. Acad., I, 
vi, 3, 4. . Where the stem between the laminz is extremely 
scabrous posteriorly, with the exception of a longitudinal line. 
In the Atlantic ocean and Mediterranean. 
(1) Certain species penetrate into the sand or become entangled in the folds of 
yarious marine bodies, but never form any durable adhesion. 
(2) Both are red. The P. rubra only differs from the other in having a little 
spine at the base of each posterior lamina. It is perhaps a mere variety. 
