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, Strombus, Buccinum. 



III. No Head. 



Fam. iii. Acephales. 



* The mantle membranous or coriaceous, and naked. 

 Genera : Asciclia, 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. (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.-f- 



t The gene?~a of Cuvier arc the co-equals of the families of other natu- 

 ralists. 1 do not quote his nub-gcncru, for they were confessedly borrowed 

 Iii mi other authors. 



