BIVALVE SHELLS. 113 



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



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



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



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



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

 Gemma, Desh. Proc. Zool. Soc. 1853. 



1. Gemma gemma. B.M. 



G. testa parva, ovato-trigona, subsequilaterali, 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. pl. 15. f. 45. 

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

 Sow.jun. Thes. Conch. p. 737. pl. 158. f. 141. 



Hab. Status Uniti Americae septentrionalis. 



Genus 10. MERCENARIA. 



Animal ignotum. 



Testa triangidari-cordiformis, aequivalvis, ventricosa, globosa. 

 Cardo in utraque valva dentes tres compressi, erecti, subdivergen- 

 tes ; anteriores valvse sinistrse et posteriores valvae dextrse vali- 

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

 prominentes ; intus obHque sulcato-crenatse ; crenis undulatis 

 [Schumacher), impressio pallii margine inferiore remota, postice 

 sinu brevi, angusto, triangulari terminata, marginibus crebre 

 crenulatis. 



Pectunculus, Lister (1685), Co7ich. pl. 271. 

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

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

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

 ed. 10. (1758) p. &%&; (1767) 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 ssepius 

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

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



