SIMPLICIA. 375 
convex, resembling the head of a mushroom, and called the wmbella. 
Its contractions and dilatations assist the locomotion of the animal. 
The edges of this umbella, as well as the mouth, or the suckers more 
or less prolonged into pedicles which supply the want of it, in the 
middle of the inferior surface, are furnished with tentacula of various 
forms and very different sizes. These various degrees of complica- 
tion have given rise to numerous divisions(1). 
We will designate by the general name of 
Mepusa, 
Or Medusa proper, those which have a true mouth in the middle 
of the inferior surface, either simply open at the surface or pro- 
longed into a pedicle. 
Under the name of 
JEQUOREA, 
We may reunite those in which this mouth is simple and not 
prolonged, nor furnished with arms. 
When there are no tentacula round the umbella they constitute 
the Puoroynia of Lamarck(2). 
When the circumference of the umbella is furnished with tentacu- 
la we have the Aquorea proper—quorea of Péron—one of the 
most numerous of all the subgenera, particularly in the seas of hot 
climates(3). 
Certain species are remarkable for having their inferior surface 
(1) For this genus, see the Prodromus of Péron and Lesueur, Ann. du Mus., 
XIV, and XV; it is well to remember that their genera are frequently founded on 
bad figures, such as those of Baster and Borlasse and without haying seen the 
animals; and that they have increased the number of species beyond all bounds. 
(2) The Phoreint and Eulimenes of Péron. 
(3) Medusa xquorea, Gm.; Forsk., XXXI; Encyc., Vers, XCV, 1; quorea 
mesonema, Péron; Forsk., XXVIII, B;—Med. mucilaginosa, Chamiss., and Kisenh., 
Ac. Nat. Cur., X, part I, pl. xxx, f. 2, and the species engraved by M. Lesueur and 
indicated by Péron, Ann. du Mus., XV, and by M. de Lamarck, Hist., des Anim. 
sans vert., II, 498, et seq. Itis to be regretted that these plates are not to be 
purchased. Ialso add to them the Preasra, and Meurrea of Péron. 
