484 CLASS ECHINODERMATA. 
Ixxvi. and lxxvil., acquires with age four long arms. Its 
umbrella is finely ciliated all around. Some reddish vessels 
pass from the stomach to the ‘circumference, subdividing in 
their course. 
Another, Med. chrysaora, Cuv., has the edges furnished 
with long tentacula, and some fulvous or brown lines or spots, 
disposed in radii in its convexity. It is also very common, 
and varies much as to the spots. 
We have given the general name of RHIZOSTOMA, to a 
portion of the great genus MEDUSA, comprehending the spe- 
cies which have no mouth open at the centre, and which ap- 
pear to be nourished through the suction of the ramifications 
of their pedicle, or of their tentacula. ‘They have four ovaries 
or more. 
RHIZOSTOMA, (proper) Cuv., 
Are those which have in the middle a pedicle, more or less 
ramified, according to the species. 
The vessels proceeding from the small ramifications of the 
pedicles, unite in a cavity of its base, from which branches 
proceed for all the parts of the umbrella. 
The most common is the Rhizostome bleu. Cuv. Jour. de 
Phys. tom. xlix. p. 436. Reaum. Acad. des Sc. 1710. pl. xi. 
f. 27, 28. Itis found every where on the sand of our coasts, 
when the sea retires, and its umbrella is sometimes nearly 
two feet in breadth. Its pedicle is divided into four pairs of 
arms, forked and denticulated almost ad infinitum, furnished 
each at the base with two corslets, equally denticulated. The 
umbrella has all around, in the thickness of its margins, a fine 
‘net-work of vessels. 
According to the observations of Messrs. Audouin, and 
Milne Edwards, these medusz live in society, or at least are 
always to be met with united in great numbers, and swimming 
in the same direction, the body being inclined obliquely. — 
