LAMARCK. 525 



2. Shell univalve unilocular 



spiral sheathing the ani- 

 mal. 



* Aperture emarginate, or channelled at its base. Gen. : 

 Conus, Cypraea, Ovula, Terebellum, Oliva, An- 

 cillaria, Voluta, Mitra, Columbella, Marginella, 

 Cancellaria, Nassa, Purpura, Buccinum, Eburna, 

 Terebra, Dolium, Harpa, Cassis, Strombus, Ptero- 

 cera, Rostellaria, Murex, Fusus, Pyrula, Fascio- 

 laria, Turbinella, Pleurotoma, Clavatula, Cerithium. 

 ** Aperture entire and without a canal at its base. 

 Gen. : Trochus, Solarium, Turbo, Monodonta, 

 Cyclostoma, Scalaria, Pupa, Turritella, lanthina, 

 Bulla, Bulimus, Agathina, Limnaea, Melania, Pyra- 

 midella, Auricula, Valvata, Ampullaria, Planorbis, 

 Helix, Helicina, Nerita, Natica, Testacella, Sto- 

 matia, Haliotis, Vermicularia, Siliquaria, Aspergil- 

 lum, Carinaria, Argonauta. 



/Gen.: Nautilus, Orbulites, 



3. Shell univalve multilocu- Ammonites, Planulites, 



lar sheathing or enclo-| Nummulites, Spirula, Tur- 

 sing the animal. rulites, Baculites, Orthocera, 



^Hippurites, Belemnites. 



II. ACEPHALOUS MOLLUSCA. 



(Gen. : Ascidia, Biphores. 

 NAKED - tMammaria. 



CONCHIFEROUS. 



Gen. : Pinna, Mytilus, Mo- 

 diola, Anodonta, Unio, Nu- 

 cula. Pectunculus, Area, 

 Cucullasa, Trigonia, Tridac- 



1. Shell equivalve with or 

 without accessary pieces. 



na, Hippopus, Cardita, Iso- 

 cardia, Cardium, Crassatella, 

 Paphia, Lutraria, Mactra, 

 Petricola, Donax, Meretrix, 

 Venus, Venericardia, Cyclas, 

 Lucina, Tellina, Capsa, San- 

 guinolaria, Solen, Glycime- 

 ris, Mya, Pholas. 

 Shell inequivalve of two] 



or more valves, of which I 



the principal are un- 1 



equal. 

 * Principal valve tubular. Gen, : Teredo, Fistulana. 



