CO^CHYLIA—DITHYBA. 23. 75 



Shell an inch and a quarter long, and nearly two broad, pale 

 yellowish-white, transparent, smooth except a few irregular ob- 

 scure transverse ridges, angular at the more produced side by a 

 rib which runs obliquely from the hinge to the margin : beaks 

 pointed not quite central, with a depression under them on the 

 shorter side : teeth as in this division. 



The discovery of tliis species, of which we have as yet found 

 only a few single valves, will we trust set at rest all doubts con- 

 cerning the two species of Chemnitz, the Mactra pellucida, and 

 the Mactra fragilis. 



Our specimens correspond exactly with his figure and descrip- 

 tion : testd ovali- oblong d, suhcompressd, albd, diaphand, Ifevi, 

 ctnnflexurd notabili et manifestd in parte anticd. " Shell oval- 

 oblong, flattish, white, transparent, smooth, with a singular and 

 evident flexure at the anterior side.'' He remarks also, that it 

 has the figure of a Tellina, but the hinge of a Mactra. 



Mactra testd subln'gond, striis transversis longitudinalibusque ladiaia. 



minutis. '^" 



Shell somewhat triangular, with transverse striae and minute lon- 

 gitudinal ones. 

 Mactra radiata. Donovan, British Shells, v. tab. 16L 

 Linn. Trans, viii. p. 61. 

 Turton, Britisii Fauna, p. 154. 

 Dillwyn, Descript. Catal. p. 138. 

 Turton, Conch. Diet. p. 80. 

 Cardium edentulum. Montagu, Test. Brit. Suppl. p. 29. 

 Found by Captain Laskey, at Portsmouth. 



l2 



