MOLLUSCA. 39 
relle de Paris. ‘These papers, with some additional obser- 
vations, were at last published ina separate form, under the 
title Mémoires pour servir a Vhistoire et a Vv Anatomie des 
Mollusques, Paris, 1816. In the following year he published 
Le Regne Animal, distribué dapreés son organisation, in 
which he arranged the mollusca according to his peculiar 
views, from characters drawn exclusively from the animal. 
In the third volume, of what may be termed the third edi- 
tion of that invaluable work, published in 1830, the same 
arrangement, with the exception of a few modifications, was 
adhered to. 
He divides the mollusca into six classes, which he terms 
Cephalopoda, Pteropoda, Gasteropoda, Acephala, Brachi- 
opoda, and Cirrhipoda. 
In the class CepHALOPODA, the body is in the form of a 
sack, open above, containing the branchiz, with a distinct 
head, surrounded by fleshy elongations or arms, adapted for 
moving the body or seizing prey. Into this class, along with 
the Sepia of Linnzeus, Cuvier has inserted the multilocular 
shells of his genus auéilus and the genus Argonauta. But 
it is to be feared, that our knowledge of the testaceous mol- 
lusca which inhabit the numerous multilocular shells, is too 
limited to enable us to assign to all of them their true place 
in a natural arrangement of animals. 
In the second class, termed Prrroropa, the body is 
closed, the head is destitute of the long fleshy arms which 
distinguish the animals of the preceding division; two fin- 
like membranes, situate on the sides of the neck, and on 
which the branchial tissue is in general spread, serve as or- 
gans of motion. There is only one shelly mollusca belong- 
ing to this class, viz., the anomia tridentata of Forskaehl, 
now forming a part of the genus Hyalcea. 
