102 NAYADES. 



It is considerably more inflated than the ordinary form of 

 Anatmus, and is of a small size. Its length is one inch and 

 three-quarters ; its breadth three inches and a quarter ; and its 

 thickness one inch and one-eighth. 



Found at Southport, Lancashire; Loch Leven, Kim-ossshire ; 

 Prestwick Carr, Northumberland, where we obtained the beau- 

 tiful and highly characteristic specimen from which our figure 

 was taken ; and also in the rivers Shannon and Bresna, and the 

 Grand Canal, Ireland. 



Variety 4. Stagnalis, pi. XIV. 



Mytilus stagnalis, Sowerby, Brit. Miscell., pi. 16; Mijtilns 

 Cygneus, Maton and Rackett, Linn. Tr., VIII, p. 109; Mon- 

 tagu, Test. Brit., p. 171 ; Anodon stagnalis, Brown, Illust. 

 Conch., p. 79, pi. 28, f. 2. 



Shell thin, much inflated; umbones subcentral; anterior side 

 rounded, with a slight angle above; hinge line arcuated; poste- 

 rior side slightly hollowed, and terminating in a subacute beak ; 

 basal line nearly semicircular ; outer surface with an olivaceous, 

 shining epidermis ; very pearlaceous and iridescent internally. 



In the younger condition, the colour is of a bright yellowish- 

 green. 



Found in the pond of Kew Garden ; in the Canal Wharf at 

 Bolton Bridge, Lancashire ; and in the canal at Keighley. 



Variety 5. Intermedia, pi. XXX, f. 5, 6. 



Anoclonta intermedia, Lamarck, Hist. An. San. Vert., VI, p. 

 86; Pfeitfer, I, p. 113, pi. 6, f. 3; Alder, Mag. Zool. and Bot., 

 II, p. 118; Brown, Illust. Conch., p. 79, pi. 30, f. 5, 6. 



Shell very thin, with the hinge line almost straight, and, 

 ascending, forming an angle, from whence it descends in nearly 

 a parallel direction, assuming an obtuse point ; anterior side 

 slightly angulated; the basal line arcuated, and descending con- 

 siderably, in consequence of which the posterior side is very 

 deep, being a third more than the anterior one; surface covered 

 with a very bright yellowish-green epidermis, frequently with 

 divergent rays of a deeper hue; ligament not protruding beyond 

 the margin of the hinge line. 



Found in the canal, near Keighley. 



Variety 6. Complanata, pi. XII, f. 3, 4. 



Anodonta complanata, Ziegler Museum ; Rossmassler, I, p. 

 1 12, pi. 3, f. 68, a; Anodonta compressa, Menke, Syn., p. 106; 



