CUVIER. 527 



MOLLUSCA. 

 I. THE HEAD ENCIRCLED WITH TENTACULA WHICH SERVE 



THE PURPOSES OF FEET. 



Fam. I. CEPHALOPODES. 



* Naked Genus: Sepia. ** Testaceous Genera: 

 Argonauta, Nautilus. 



II. THE HEAD DISTINCT, THE ANIMAL GASTEROPOD. 



Fam. ii. GASTEROPODES. 



* Shelless, or the Shell internal. Genera : Doris, Phyl- 

 lidia, Thetis, Limax, Testacella, Sigaretus, Aplysia. 

 ** Shelled. Shell multivalve. Genus: Chiton. 

 Shell conical. Genus : Patella. Shell tur- 

 binate. (a) Aperture entire. Genera : Haliotis, Ne- 

 rita, Turbo, Vermetus, Trochus, Bulla, Helix, (b) 

 Aperture emarginate or effuse. Genera : Voluta, 

 Ovula, Cypraea, Conus, Terebellum. (c) Aperture 

 canaliculate. Genera: Murex, S trombus, Buccinuin. 



III. No HEAD. 



Fam. iii. ACEPHALES. 



* The mantle membranous or coriaceous, and naked. 

 Genera : Ascidia, Biphores, Firoles, Thalia. 



** The mantle furnished with a shell: . Mantle open 

 in front ; no articulated tentacula nor ciliated arms. 

 () Inequivalve. Genera : Ostrea, Lazare, Spondylus, 

 Placuna, Anomia, Peloris. (b) Equivalve, a foot for 

 creeping, no siphons. Genera : Anodonta, Unio. 

 (c) Equivalve, a foot for spinning, no siphons. 

 Genera : Lima, Perna, Avicula, Mytilus, Pinna, (d) 

 Siphons to the mantle for a vent and respiration. 

 The foot often fitted for spinning. Genera : Tellina, 

 Cardium, Mactra, Venus, Donax, Chama, Area. 

 Mantle open at one end for the passage of the foot 

 and prolonged into a double siphon at the other. 

 Genera : Solen, Mya, Pholas, Teredo. Mantle 

 open in front, but neither foot nor siphons ; two 

 ciliated spirally coiled arms. Genera : Terebratula, 

 Lingula, Orbicula. Mantle open in front ; no 

 foot nor siphons. A tube proceeding from the body, 

 and horny articulated tentacula arranged in pairs. 

 Genera : Anatifa, Balanus.-)- 



t The genera of Cuviev are the co-equals of the families of other natu- 

 ralists. I do not quote his sub-genera, for they were confessedly borrowed 

 from other authors. 



