155 



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

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

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

 in part under the beaks. 



C. tenuistria, C . Islandica, Q 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. lusoria, 

 ' petechialis, 

 ' impudica, 

 ' castanea, 

 ' zonaria, 

 ' meretrix, 

 1 graphica, 

 ' morphina, 

 ' purpurata, 

 ' casta, 

 ' corbicula, 



' tripla, 



' gigantea, 



' erycina, 



' lilacina, 



' impa, 



' erycinella, 



' pectoralis, 



' planatella, 



' florida, 



' nitidula, 



C. chione, 

 ' maculata, 

 ' citrina, 

 ' albina, 

 ' lata, 



' mactroides, 

 ' trigonella, 

 ' sulcatina, 

 ' hebrasa, 

 1 castrensis, 

 ' ornata, 

 ' picta, 

 ' trigrina, 

 ' Venetiana, 

 ' juvenilis, 

 ' rufa, 



' Guiniensis, 

 ' Dione, 

 ' Arabica, 

 1 trimaculata, 



C. immaculata, 

 ' pellucida, 

 ' lupatica, 

 ' lucinalis, 

 ' lunaris, 

 ' lactea, 

 ' exoleta, 

 ' lincta, 

 ' concentrica, 

 ' prostrata, 

 ' interrupta, 

 ' tigerina, 

 ' punctata, 

 ' umbonella, 

 ' unitatina, 

 ' scripta, 

 ' numulina, 

 ' muscaria, 

 ' pulicaris, 

 ' mixta, 



C. 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, 

 Ligament external, covering the 



V. 



summit. 



V. puerpera, 

 ' reticulata, 

 ' pygmea, 

 ' corbis, 

 ' crenulata, 

 ' discina, 

 ' verrucosa, 

 ' rugosa, 

 ' casina, 

 ' crebrisulca, 

 ' plicata, 

 ' cancellata, 



V. subrostrata, 

 granulata, 

 pectorina, 

 marica, 

 cingulata, 

 cardioides, 

 grisea, 

 elliptica, 

 Dombeii, 

 mercenaria, 

 lagopus, 

 gallina, 



transverse 

 the lateral 

 scutcheon. 



gallinula, 



pectinula, 



sulcata, 



exalbida, 



rufa, 



dorsata, 



hiantina, 



crassisulca, 



corrugata, 



Malabarica, 



papilionacea, 



adspersa, 



or suborbicular; three 

 ones diverging at the 



V. punctifera, 

 ' turgida, 

 ' literata, 

 ' sulcaria, 

 ' textile, 

 ' texturata, 

 ' geographica, 

 ' rariflamma, 

 1 decussata, 

 ' pullastra, 

 ' glandina, 

 ' truncata, 



