130 SPBC'IFIC 



Lister Conch, tab. 351. fig. 189. 



Specimen clear white ; gape of the posterior 

 slope lanceolate, the circumference of which is 

 tumid and crcnate ', margin of the shell deeply 

 crenate; hinge furnished with an anterior tootli 

 besides the usual callus. 



Inhabits the Indian Ocean. 



Fig. 3. Hinge of Arca grawo5a. 



Fig. 4. Arca tortuosa. 



Shell parallelopiped, striate; larger valve ob- 

 liquely carinate. 



D'Jrgenville Co?ich.tah. 19. fig. 1. 



Specimen white ; striated longitudinallv and 

 transversely; valves dissimilar, much twisted; mar- 

 gin subcrenate. 



Inhabits the Indian Ocean. 



Fig. 5. A. JSFoce. 



Shell oblong, striated, emarginate at tlie apex, 

 beaks remote, margin gaping. 

 Lister Conch, tab. 368. fig. 208. 

 Specimen white and brown, rhomboidal ; exter- 



