316 SUPPLEMENT 
a kind of small tentaculum at its external side. The mouth is 
altogether terminal and vertical; the eyes almost superior ; 
and there is a sort of sucker under the neck. These characters 
are established upon the most common species of the genus, 
namely, the clio borealis of Linneus, a very small animal, 
almost entirely gelatinous, which is found in great abundance 
in the northern seas, where it is said to be known under the 
denomination of food for the whale, because it is allowed to 
constitute a considerable portion of the nourishment of that 
vast animal. 
With regard to the habits and manners of the next two 
genera of pteropods (Cymbulia and pneumodermon), we know 
nothing whatsoever. The same may be said of the limacine, 
except that the species which is known (clio helicina, Gm.) 
is scarcely less abundant than the clio borealis in the northern 
seas, and is also considered to constitute one of the principal 
aliments of the whale. 
There are certain peculiarities in the organization of the 
HyALZ#A, which, as they have been so briefly touched on in 
the text, it may be necessary concisely to notice here. 
M. de Lamarck was the first who established under this 
denomination a very distinct genus of the mollusca, though 
little was then known concerning it, except the shell, which 
Forskahl, and subsequently Gmelin ranged in the section of 
the terebratule. The first of these authors, indeed, has men- 
tioned something concerning the animal, which he observed 
in the living state. But he has spoken of it in a manner so 
obscure as to place it, as we have seen, among the bivalves, 
in which he was imitated by MM. Cuvier and de Lamarck, 
in their earlier works. Lamartiniere, who was the naturalist 
on the expedition of La Peyrouse, as well as Forster, who 
belonged to that of Captain Cook, was disposed to place it 
with clio. After M. Cuvier had published the comparative 
anatomy of this animal, no other variations took place, and 
