ANODONTA. 17 



I. ANODONTA CYG'NEA,* LiNNfi. Pl. III. 



Body longish oval, compressed, grey, with sometimes a 

 yellowish or reddish tint ; foot dirty yellow, more or le,ss tinged 

 with orange or red ; mantle brownish at the edges ; gills (lower 

 orifice) grey, or reddish-grey, somewhat resembling gauze. 



Shell oblong, somewhat swollen, thin, rather glossy, greenish- 

 yellow, sometimes brown, with irregular grooves formed by the 

 lines of growth, strongly wrinkled on the posterior and lower 

 sides ; epidermis thin ; beaks straight, placed away from the 

 centre ; umbonal region strongly plaited, compressed ; ligament 

 long ; hinge lijie straight ; anterior side rounded, sloping 

 abruptly downwards, not gaping ; posterior side somewhat com- 

 pressed above, sloping gently, ending in a rounded wedge-shaped 

 point, gaping ; lower margin straightish ; inside white, pearly, 

 iridescent ; hinge small, sharply ridged in both valves on the 

 posterior side ; scars very indistinct. 



Inhabits sluggish rivers, canals, ponds, &c., in most 

 parts of Great Britain, as far north as the counties of 

 Banff and Perth. 



Var. I. radiata. — Shell larger, yellowish-green, beautifully 

 marked with longitudinal rays or streaks of the same colour ; 

 beaks placed at a distance of only one-third from the anterior 

 side. Bog of Allen, Ireland, Clumber Lake, Notts, B.C. Near 

 Birmingham (G. Sherriff Tye), near Wakefield (J. Hebden), J.C. 



Var. 2. incrassata. — Shell more swollen and solid, olive- 

 brown ; upper margin or hinge line rather curved on the pos- 

 terior side. Scarborough, Otterspool, Lancaster, Oxwich Marsh, 

 Swansea, ^.C. Near Birmingham (G. Sherriff Tye), J.C. River 

 Earn, Perthshire (F. Buchanan White), S.N. River Irvine, 

 Ayrshire (McMurtrie). 



Var. 3. Zellensis. — Shell broader, yelio wish-brown, having the 

 upper and lower sides nearly parallel ; posterior side much pro- 

 duced. Bog of Allen, Ireland, Clumber Lake, Notts, B.C. 

 Near Birmingham (G. Sherriff Tye), J.C. 



Var. 4. pallida. — Shell light yellow or fawn-colour ; hinge 



Of or belonging to swans, as those birds feed upon it. 



C 



