52 MOLLUSCA. 



Les Ammon'es. 



GEN. Ammonite, Orbulite, Ammonocerate, Turrilite, Ba- 

 culite. 



2. DIVISION. CEPHALOPODES MONOTHALAMES. 



Coquille uniloculaire, tout-a-fait exterieure, et enveloppant 1'animal. 

 GEN. Argonaute. 



3. DIVISION. CEPHALOPODES SEPIAIRES. 



Point de coquille, soit interieure, soit exterieure. Un corps solide, 

 libre, cretace ou come, contenu dans 1'interieur de la plupart de ces 

 animaux. 



GEN. Poulpe, Calmaret, Calmer, Seche. 



V. ORDRE. LES HETEROPEDES. 



Corps libre, allonge, nageant horizontalement. Tete distincte ; 

 deux yeux. Point de bras en couronne sur la tete ; point de pied 

 sous le ventre ou sous la gorge pour ramper. Une ou plusieurs na- 

 geoires, sans ordre regulier et non disposees par paires. 

 GEN. Carinaire, Firole, Phylliroe. 



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 eases, 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- 



