SUPPLEMENT 
ON THE 
SECOND CLASS OF THE MOLLUSCA. 
THE PTEROPODA. 
To the text on this small class we must add proportionally 
little. 
The first genus (CL10) was established in 1774, by Pallas. 
Brown, some years previously, had given the name to some 
other little animals, tolerably approximating, but which are 
contained in a gelatinous case. Pallas gave to this genus the 
name of Clione. But as Linneus and others had united all 
the pteropods under the general name of clio, MM. Peron and 
Lesueur thought fit to separate this genus anew, in their labours 
on the family, and to give the name of Cleodora to the true 
clio of Brown, and leave that of clio to the animal so called by 
Pallas. The characters of the genus clio thus circumscribed, 
are a free and naked body, more or less elongated, a little de- 
pressed, pointed behind, and without any other fins than the 
lateral appendages, considered as being branchiferous. The 
head is very distinct, provided with six tentacula, conical, 
retractile, separated into two groups of three each, capable of 
being entirely concealed in a sort of prepuce, which itself has 
