BIVALVE SHELLS. 113 



Venus (species), Totten (183 ), Sill. Journ. xxvi. 367. 



Gould (1841), Rep. Inv. of Massac, p. 88. 



Hartley (1843), Descr. Cat. p. 126. 



DeKay (184 ), Zool. of New York, v. 218. 



Sow.jun. (1852), Thes. Conch, p. 737. 

 Gemma, Desk. Proc. Zool. Soc. 1853. 



1. Gemma gemma. B.M. 



G. testa pai-va, ovato-trigona, subaequilaterall, transversim striata, 

 nitida violaceo-amethystina ; cardine angusto, dentibus diva- 

 ricatis, mediano in utraque valva triangulari ; marginibus cre- 

 nulatis. 



Venus Gemma, Totten, Sill. Journ. xxvi. 367. f. 2. a-d. 

 Gould, Report Inv. of Massachus. p. 88. f. 51. 

 Hanley, Descr. Cat. p. 126 ; in Wood, Suppl. pi. 1 5. f. 45. 

 DeKay, Zool. de New York, v. 218. pi. 27. f. 277- 

 Sow.jun. Thes. Conch, p. 737. pi. 158. f. 141. 



Hab. Status Uniti Americae septentrionalis. 



Genus 10. MERCENARIA, 



Animal ignotum. 



Testa triangulari-cordiformis, ajquivalvis, ventricosa, globosa. 

 Cardo in uti-aque valva dentes tres compressi, erecti, subdivergen- 

 tes ; anteriores valvae sinistrse et posteriores valva3 dextrae vali- 

 diores, sub-bifidi ; reliqui simplices, lamellati. Njmphse intus 

 prominentes ; intus oblique sulcato-crenatae ; crenis undulatis 

 [Schumacher), impressio pallii margine inferiore remota, postice 

 sinu brevi, angusto, triangulari terminata, marginibus crebre 

 crenulatis. 



Pectunculus, Lister (1685), Conch, pi. 271. 

 Concha, Gualt. (1742), Ind. Test. pi. 88. 

 Chamelffia, Klein (1753), Tent. Ostrac. p. 155. 

 Venus (spec), Linn. (1761) Faun. Suec. ed. 2. p. 519 ; Syst. Nat. 

 ed. 10. (1758) p. 686; (1/67) ed. 12. p. 1128. 



Spengler (1789), Berl. Naturf vi. 307. 

 Mercenaria, Schumacher (1817), Essai d'une Meth. p. 135. 



Gray (1847), Proc. Zool. Soc. p. 183. 



1. Mercenaria violacea. B.M. 



M. testa ovato-trigona, cordata, crassa, ponderosa, antice latiore, 

 postice obtuse angulata, griseo squalida, in medio saepius 

 rufescente, transversim striato-lamellosa ; striis tenuibus, ele- 

 vatis, in medio evanidis, postice irregularibus; umbonibus mag- 



