52 CO^CHYLIA—DITHYRA. 16. 



16. AMPKIDESMPl— LAMARCK. 



Tata ovata, eequivalvis, subclausa. Cardo dente covMeari'- 



formi cum denticuUs adjeetisy et lateralihus. higamentum 



externum. 

 Shell oval, equi valve, mostly closed. Hinge with a spoon-shaped 



tooth and adjacent denticles, and lateral teeth. Ligament 



external. 



All the British species, hitherto discovered of this genus, have 

 a lateral tooth on each side in one of the valves only. 



prismaticum. Amphioesma testd ovato-oblongd, latere antico attenuato, valrd 

 alterd denticulo simpUci et dentibus lateralihus. 

 Shell oval-oblong, tapering at the anterior side, with a plain 

 denticle and lateral teeth in one of the valves. 

 Tab. nost. 5, fig. 3. 

 Ligula prismatica. Montagu, Suppl. p. 23, tab. 26, fig. 3. 



Penna/nt, Brit. Zool. iv. p. 169. 

 Mya prismatica. Wood, Conch, p. 101. 



Dillwyn, Descript. Catal. p. 47. 

 Turton, Conch. Diet. p. 103. 

 Mu», nost. Western coasts, British Channel, Scotland. 



Shell nearly half an inch long, and t^ice as broad, thin^ 

 transparent, glossy white reflecting metallic colors, elegantly 

 tapering to a point at one end and rounded at the other : beaks 

 SKiall, pointing towards the longer side: inside smooth, glossy. 



