348 



MOLLUSCA. 



Sub-order 3. VENERACEA. 



Gills slightly folded ; foot compressed ; siphons generally short. 



Fain. 13. Veneridae. Foot tongue-shaped ; siphons more or less united. 

 Venus L. ; Tapes Megerle ; Dosinia Scop. ; Cytherea Lam. ; Ludnopsis Forb. ; 

 Veiwrupis Lam. The Petricolidae (rock-borers) are allied here. 



Sub-order 4. CARDIACEA. 



Gills much folded ; foot cylindrical, more or less elongated; generally without 

 siphons. 



Fam. 14. Cardiidae. Cockles. Foot long, bent, without byssus ; pallial 

 orifices contiguous, with short siphons surrounded by papillae. Cardium L. 

 (Figs. 255, 259) ; Hemicardium Cuv. 



Fam. 15. Tridacnidae. Foot short, byssiferous ; pallial 

 orifices apart; posterior adductor only. Hippopus Lam.; 

 Tridacna Bruguiere. 



Fam. 16. Chamidae. Foot short, without byssus ; two 

 adductors ; shell fixed, asymmetrical ; pallial orifices sepa- 

 rated. Chama Bruguiere. 



Sub-order 5. MYACEA. 



Branchiae much folded ; foot compressed, more or less 

 reduced ; pedal orifice generally small ; siphons well de- 

 veloped. 



Fam. 17. Psammobiidae. Siphons separated, elongated ; 

 foot large, tongue-shaped. Psammdbia 

 Lamarck ; Sanguinolaria Lam. 



Fam. 18. Myidae. Siphons united ; 

 foot reduced, without byssus. Mija 

 L. ; Lutrariii Lamarck ; Corbula Brug. 

 Fam. 19. Solenidae. Foot strong, 

 elongated, often cylindrical, without 

 byssus ; siphons more or less short. 

 Solenocurtus Blain. ; Solen L. (razor 

 shell). 



Fam. 20. Saxicavidae. Rock-borers. 

 Foot small, byssiferous ; pedal orifice 

 very short. Saxicava Fleuriau. 



Fam. 21. Gastrochaenidae. Foot 

 cylindrical, very small, without bys- 

 sus ; gills narrow. The thin shell is 

 sometimes contained in a calcareous 

 tube secreted by the mantle. Gastro- 

 chaena Spengler. 



FIG. 2TO. Shell of 

 Pholas dactylus (after 

 Q ua tre fage s). f ' u m - 

 bonal plates ; I) dor- 

 sal plate. 



Sub-order 6. 



FIG. 271. Teredo 

 namlis removed 

 from its calca- 

 reous tube, with 

 elongated si- 

 phons (after 



Quatrefages). 



PHOLADACEA (Boring Mussels). 

 Foot very short, truncated ; siphons long, united ; without shell-ligament. 

 Fam. 22. Pholadidae. Organs contained in the shell ; with one or several 

 accessory shell-pieces. Gills prolonged into branchial siphon. Pholas L. 

 (Fig. 270), P. dactyl us L., mantle and siphons phosphorescent; Pholadul -u 

 Gooclall ; Jouannetia des Moulins. 



