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and diverging a little above. A lateral tooth distant from the hinge, placed 

 on the anterior side, sometimes obsolete. The callosities of the nymphae 

 large, arched, terminated near the beaks by a pit. Ligament external, sunk 

 in part under the beaks. 



C. tenuistria, C. Islandica, G fossil species. 



Cytherea. Shell equivalve, inequilateral, suborbicular, triangular, or 

 transverse; four cardinal teeth in the right valve, three of which diverge and 

 approximate at their base, and one quite insulated, situated under the lunula; 

 three diverging cardinal teeth in the other valve, and a pit rather distant par- 

 allel to the margin. No lateral teeth. 

 C. 



C. lusoria, 

 petechialis, 

 impudica, 

 castanea, 

 zonaria, 

 meretrix, 

 graphica, 

 morphina, 

 purpurata, 

 casta, 

 corbicula, 

 tripla, 

 gigantea, 

 erycina, 

 lilacina, 

 impa, 

 erycinella, 

 pectoralis, 

 planatella, 

 florida, 

 nitidula, 



chione, 



maculata, 



citrina, 



albina, 



lata, 



mactroides, 



trigonella, 



sulcatina, 



hebrsea, 



castrensis, 



ornata, 



picta, 



trigrina, 



Venetiana, 



juvenilis, 



rufa, 



Guiniensis, 



Dione, 



Arabica, 



trimaculata, 



C. immaculata, 

 pellucida, 

 lupatica, 

 lucinalis, 

 lunaris, 

 lactea, 

 exoleta, 

 lincta, 

 concentrica, 

 prostrata, 

 interrupta, 

 tigerina, 

 punctata, 

 umbonella, 

 unitatina, 

 scripta, 

 numulina, 

 muscaria, 

 pulicaris, 

 mixta, 



abbreviata, 

 pectinata, 

 gibbia, 

 ranella, 

 divaricata, 

 testudinalis, 

 cuneata, 

 placunella, 

 rugifera, 

 plicatina, 

 flexuosa, 

 macrodon, 

 linularis, 

 squamosa, 

 cardilla, 

 cygnus, 

 dentaria, 

 hians, 

 subrugosa, 

 9 fossil species. 



Venus. Shell equivalve, inequilateral, 

 approximate, cardinal teeth in each valve, 

 summit. Ligament external, covering the 



transverse or suborbicular; three 

 the lateral ones diverging at the 

 scutcheon. 



V. puerpera, 

 reticulata, 

 pygmea, 

 corbis, 

 crenulata, 

 discina, 

 verrucosa, 

 rugosa, 

 casina, 

 crebrisulca, 

 plicata, 

 cancellata, 



V. subrostrata, 

 granulata, 

 pectorina, 

 marie a, 

 cingulata, 

 cardioides, 

 grisea, 

 elliptica, 

 Dombeii, 

 mercenaria, 

 lagopus, 

 gallina, 



V. 



gallinula, 



pectinula, 



sulcata, 



exalbida, 



rufa, 



dorsata, 



hiantina, 



crassisulca, 



corrugata, 



Malabarica, 



papilionacea, 



adspersa, 



V. punctifera, 

 ' turgida, 

 ' literata, 

 ' sulcaria, 

 ' textile, 

 ' texturata, 

 ' geographica, 

 ' rariflamma, 

 ' decussata, 

 ' pullastra, 

 ' glandina, 

 ' truncata, 



