BIVALVE SHELLS. 241 



obtuso circumscripto ; cardine lato, crasso, brevi, inaequaliter 

 tridentato, dentibus angustis, elongatis, parallelis, apice vix 

 canaliculatis ; dente laterali antico maximo, crasso, cardine 

 valde approximato, postico longiore, angusto, valde separato. 



Cyrena cyprinoides, Gray, Ann. Phil. 1825, p. 137. 



Velorita cyprinoides, Gray in Griff. Anim. Kingd. pl. 31. f. 5; 



Ann. Sf-^Mag. N. H. ser. 2. xi. 35^ 

 Venus cyprinoides, Gray in Wood, Ind. Test. Suppl. pl. 2. f. 11. 



Hab. Fluviis Japonicis. 



Genus 4. CYRENA. 



Aniraal ovatum, transversum; pallium ad margines simplex 

 vel fimbriatira, postice tracheis binis basi connatis, brevibus, ter- 

 minatura. Pes magnus, compressus, ovato-trigonus ; labiarum 

 appendices elongatae,ovatae, trigona), necnon conjunctffi ; branchise 

 inajqualissimae, interna major subquadrangularis, extema minima 

 subtrigona. 



Testa ovata vel subtrigona, crassa, solida, epidermide vestita, 

 cardo in utraque valva tridentatus, dentes paulo divergentes ; 

 dentes laterales duo, inaiquales ; autico breviore cardine approxi- 

 mato ; impressio pallii simplex. 



Venus, Chemn. (1/82) Conch. vi. 333. 



Cyclas (ex parte), Brug. (1792) Ency. Meth. pl. 301, 302. 



Lamk. (1802) Sysi. des An. s. Vert. 

 Cyrena (pro partel, Lamk. (1818) An. s. Vert. v. 551. 

 Cvrena /3, Gray (1847), Proc. Zool. Soc. p. 184. 

 Geloina, Gray (1840), Syn. Mus. Brit. 1844, p. 75. 

 Cyrena, Gray (1851), Aiin. Sf Mag. Nat. Hist. ser. 2. xi. 48. 

 Polymeroda, Rajin. Ann. Gen. Sci. Nat. Brux. 1820, v. 219. 



Synopsis Specierum. 

 I. Cyrence verce. 



A. Testa ovata, suborbicularis vel subtrigona, epidermide lamel- 



losa vel squamulosa. 



a. Testa subtrigona, 1-13. 



b. Testa ovata, 14-30. 



e. Testa suborbicularis, 31-34. 



B. Testa trigona, tumida, subcordiformi, epidermide nitente, 



35-41. 



11 



