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DIVISION III. Oblong linear. 

 Family 1st. With a transverse lobe on each side of the hinge. 



Scientific name. Locality. Scientific name. Locality. 



Malleus, Pulo condore, So. Seas, 



Ceylon. 



Family 2d. With a slight beak on one side of the hinge. 

 Figurata, Nicobar Isles. 



Family 3d. Rounded at the hinge. 

 Regula, Red Sea. 



Family 4th. Valves diverging at the hinge, and the inside vaulted. 



Fornicata, Red Sea. 



v 



DIVISION IV. Parasitical, or attached to other substances. 

 Family 1st. Willi one valve produced at the summit. 



Cucullata, Africa, Arabia, S. Seas. Forskalii, Coast of Egypt. 



Virginea, Virginia. Cristata, 



Rostrata, Mediterranean. Sinensis, China. 



Family 2cZ. With the valves nearly equal. 



Orientalis, Indian Seas. Orbicularis, 



Folium, Amboyna, W. I., Med. Arborea, 



Plicata, W. I., Med., Spain. Senegalensis, 



Indian Ocean. 

 Atlan. & Ind. Seas. 

 Senegal. 



Crista Galli, 

 Hyotis, 



Family 3d. With the valves strongly plaited longitudinally. 

 Indian Ocean, China. Frons, West Indies. 



DIVISION V. With the hinge composed of transverse furrows in a straight 



line. 



Crenatula, Red Sea. Ephippium, 



Semiaurita, Mediterranean. Alata, 



Perna, E. & W. Indies, China. Picta, 



Isognomon, Amboyna. Legumen, 



Tranquebar, Africa. 

 West Indies. 

 Red Sea. 

 Nicobar Isles. 



