FAMILY NAIADES. 



215 



% 



1. Anodonta cygnea. Swan Anodon. 



Shell ; obliquely ovate or oblong, varying from compressed to ven- 

 tricosely gibbous, anterior side rounded, a little gaping in the 

 region of the foot, posterior side obliquely produced, slightly 

 auriculated towards the seat of the ligament, valves roughly 

 concentrically ridged at irregular intervals by additions of 

 growth, upon which the epidermis lodges in fibrous wrinkles, 

 bright verdigris green passing with age into fulvous olive, 

 flesh-tinged towards the umboes, umboes compressed, plicately 

 wrinkled, wrinkles few, obsolete or eroded with age, hinge 

 toothless, in the centre, on the posterior side furnished with 

 a rudimentary lateral tooth, in the form of a faintly developed 

 elongated ridge. 



Mytilus cygneus and anatinus, Linnaeus (1758), Syst. Nat. ed. 10. p. 706. 



Mytilus radiatus, Miiller (1774), Hist. Verm, part ii. p. 209. 



Mytilus Zellensis, Gmelin (1788), Syst. Wat. p. 3262. 



Anodontites cygncea and anatina, Poiret (1801), Coq. de I'Aisne, p. 109. 



Anodonta variabilis, Draparnaud (1801), Tabl. Moll. p. 108. 



Mytilus Avonensis, Montagu (1803), Test. Brit. p. 172. 



Anodonta cygncea and anatina, Draparnaud (1805), Hist. Moll. p. 133. 

 pi. xii. f. 1, 2. 



