52 MOLLUSCA. 
Les Ammonées. 
Gen. Ammonite, Orbulite, Ammonocérate, Turrilite, Ba- 
culite. 
2. DIVISION. —cEPHALOPODES MONOTHALAMES, 
Coquille uniloculaire, tout-a-fait extérieure, et enveloppant l’animal. 
Gen. Argonaute. 
3. DIVISION. —CEPHALOPODES SEPIAIRES. 
Point de coquille, soit intérieure, soit exterieure. Un corps solide, 
libre, erétacé ou corné, contenu dans l’intérieur de la plupart de ces 
animaux. 
Gen. Poulpe, Calmaret, Calmer, Séche. 
V. Orper.—Les H&TEROPEDES. 
Corps libre, allongé, nageant horizontalement. Téte distincte ; 
deux yeux. Point de bras en couronne sur la téte; point de pied 
sous le ventre ou sous la gorge pour ramper. Une ou plusieurs na- 
geoires, sans ordre régulier et non disposées par paires. 
GEN. Carinaire, Firole, Phylliroé. 
The authors of the first class of conchologists which we 
have mentioned, employ exclusively the characters furnish- 
ed by the shell, and scarcely deign to tell us that there is 
an animal attached to that shell. The authors of our third 
class are anxious to keep the shell out of view, and draw 
their distinctions from the animal; but they have failed in 
the attempt. In extreme cases, the characters of the shell 
are resorted to in the absence of distinctions furnished by 
the animal. 
Lamark perceived the inconvenience of separating these 
two modes of examining molluscous animals, and fortunate- 
ly formed a very natural combination. We shall give his 
character of the genus Patella, as a specimen of this mixed 
system. 
