51 BIVALVE SHELLS. 



Cytherea incerta, Sow. Thes. Conch, p. 617- pi. 128. f. 17. 

 Hab. S. Jo.ui. Coll. Cuming. 



IV. Species dubiee. 



2y. Tbigo.na nucula. 



T. testa cordato-ovata, transversim striata, striis antice argutis, 

 medio obsoletis, alba ; extreniitate utraque acutiuscula ; mar- 

 ginf (lorsali antico rectilineo, postico arcuato, anticum bis 

 a.'qiuuitf; lunula cordata, parum distincta ; area nulla; liga- 

 mento cxtus vix conspicuo ; dentibus in valva dextra quatuor, 

 "■eminatis, prsrter anticum internum ad foveam, in valva sinis- 

 tra tribus, antico remoto ; sinu palliai-i acutangulo, mediam 

 testani hand attingente. 



Trigoua nucula, Philippi, Zeits.fur Malac. 1848, p. 144.no. 89. 

 Hab. In mari Chiliensi vel Peruviano. 



30. Trigona dubia, Sow.jun. See "T. damaoides," p. 47. 

 Hab. China. 



Genus 6. DIONE. 



Animal ovato-oblongum, postcrius tracheis duabus coadu- 

 natis terminatum, ajjerturie trachearum ad marginem tentaeulatie, 

 tcntaculis simplicibus ; pallii margines antice inferneque dis- 

 junctiE, li)ba> ))licata;, posterius supra trachearum basin tentaeu- 

 latie ; ])es maximus, compressus, linguiformis ; labiarum appen- 

 dices trigone, angustae,acuminatae; branchiae elongatae, inseqiiales, 

 transversa;, posterids connects, acuminatae, exteriores angusti- 

 oros. 



Testa ovata, transversa, ina-quilateralis, clausa ; marginibus in- 

 tegris sa>pius obtusis ; cardine in utraque valva tridentato, dente 

 laterah antico, lunulari adjuncto ; impressio pallii postice sinu- 

 osa ; sinus profundus, latus, seraiovatus. 



Vulvaria, Klein (1744), Ostrac. p. 155. 



Venua (s])ec.), Linn. (1758) Syst. Naf. ed. 10. p. 684; (1764), 



Mtis. Uric. p. 497; Syst. Nat. ed. 12. p. 1128. 



Chemnit:,Schr'6ter, Murray, Bom, Barbut, Gmelin, Dillwyn, 

 IVood. 

 Pcctunculus, Da Costa (1778), Co7wh. Brit. p. 184. 

 <'idista. Cali<;toderma, Poli (1795), Test. Sicil. ii. 252. 

 .Mrrctrix (ex parte), Lamk. (1799) M6n. de la Soc. d'Hist. Nat. 



de Paris, y. 85 ; (1801), Syst. des An. s. Vert. p. 122. 

 Cythcrea (ex parte), Lamk., Roissy (1805), Moll. Buff. vi. 336; 



