382 - ACALEPHA. 
merely invested with a thin membrane that projects beyond its the 
inferior is covered with a great number of tentacula, the exterior 
of which are the longest, and furnished with little cilia each termi- 
nated by a globule. They sometimes contain air; those in the mid- 
dle are the shortest, simplest and most fleshy. In the centre of all 
these tentacula is the mouth, in the form of a little salient proboscis. 
It leads to a simple stomath surrounded by a sort of glandular sub- 
tance. 
One species is known of a beautiful blue colour, that inhabits 
the Mediterranean and seas of hot climates(1). 
VELELLA, Lam. 
Where, as in Porpita, there is a mouth in the inferior surface in the 
form of a proboscis, surrounded with innumerable tentacula, the ex- 
terior of which is the longest, but the latter are not ciliated, and a 
still more important character is, that the cartilage, which is oval, 
has on its superior surface a vertical and tolerably elevated crest. 
This cartilage is diaphanous, and is merely marked with concentric 
striz. 
A species of this genus also is known, of the same colour as 
thé Porpita and inhabiting the same seas. It is eaten fried(2). 
(1) It is the Med. umbella, Mill., Natur. of Berl., Besch., II, ix, 2, 3; Holothuria 
nuda, Gm.; Forsk., XXVI, 1, i; and Encyc., XC, 6, 7; Porpita gigantea, Pér., 
Voy., XXXI, 6. 
The Medusa porpita, L., is merely its cartilage divested of the gelatine and ten- 
tacula. 
The Porpite appendiculée, Bosc., Vers, 1, xviii, 5, 6, if not an altered individual 
of the same, should constitute a separate subgenus. Itis the genus PotyBRacar- 
ont, Guilding., Zool. Journ., XI. 
(2) It is the Medusa velella and the Holothuria spirans, Gm.; Forsk., XXVI, k; 
Encyc., XC, 1,2. The Vélella scaphidia, Pér. Voy., XXX, 6, is nowise generically 
different; it appears that there are several species, such as the V. oblonga, V. 
sinistra, V. lata, Chamiss. and Eisenh., Ac. Cur. Nat., X, p. I, pl. xxxii. 
