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. 



TI. The Head distinct, the animal gasteropod. 

 Fam. ii. Gasteropodes. 



* Shelless, or the Shell intemal.—Genern : Doris, Phyl- 

 lidia, Thetis, Liniax, 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. (6) 

 Aperture emarginate or effuse. Genera : Voluta, 

 Ovula, Cypra?a, Conus, Terebellum. (c) Aperture 

 canaliculate. Genera: Murex, Strombus, Buccinuni. 



III. No Head. 



Fam. iii. Acephales. 



* The mantle memhranous or coriaceous, and naJced. 

 Genera : Ascidia, Biphores, Firoles, Thalia. 



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

 in front ; no articulated tentacula nor ciliated arms. 

 {a) Inequivalve. Genera : Ostrea, Lazare, Spondylus, 

 Placuna, Anomia, Peloris. {h) 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 : Tcrebratula, 

 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.f 



t 1\\c genera of Cuvier are tlie co-equals of the families of other natu- 

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 I do not quote his sub-genera, for they were confessedly borrowed 

 from otiicr authors. 



