^ 170. THR ACEPIIALA. 185 



Genera : Orbicula, Terebratula, Lingvla. 



ORDER III LAMELLIBRANCHIA. 



Animals which are symmetrical and bivalved, and whose more or less 

 closed mantle encloses two pairs of lamelliform tentacles and branchiae. 



SUB-ORDER I. MONOMYA. 



Family : Ostracea. 

 Genera : Ostrea, Anomia. 



Family : Pectinea. 

 Genera : Pecten, Spondylus, Lima. 



Family : Malleacea. 

 Genera : Malleus, Perna, Crenatida. 



SUB-ORDER II. DIMYA. 



Family : Aviculacea, 

 Genera : Aviada, Meleagrina, Pinna. 



Family : Akcacea. 

 Genera : Area, Pechinculus, Trigonia, Nucula. 



Family : Naiades. 

 Genera : Anodonta, Unio. 



Family : Mytilacea. 

 Genera : Mytilus, Modiola, Lithodomus, Tichogonia. 



Family : Chamacea. • • 



Genera : Chama, Isocardia. 



Family : Cardiacea. 



Genera : Cardium, Lucina, Hiatella, Cyclas, Piscidium, Tellina, Psam- 

 mobia, Yenus, Cytherea, Venei-upis, Mactra, Lutraria, Ungidina. 



Family : Pyloridae. 

 Genera : Mya, Solen, Solenomya, Panopaea. 



SUB-ORDER III. INCLUSA. 



Family : Teredina. 



Genera : Pholas, Teredo. 

 16* 



