LIMN^A. 63 



full-grown specimens ; inner lip broadly and thickly spread on 

 the base of the penultimate whorl ; fold strong and very much 

 curved. 



Inhabits sluggish streams and stagnant water 

 throughout Great Britain. In form this is one of the 

 most elegant of our freshwater shells. It is an in- 

 dolent species, and adheres very firmly to the objects 

 to which it has attached itself. It frequently floats 

 on the surface of the water. Owing to the sluggish 

 nature of this species its shell is very frequently 

 incrusted with a mineral or vegetable deposit. The 

 eggs, which vary in number from forty to one hundred 

 and twenty, are deposited in oblong or roundish cap- 

 sules, and the fry are excluded in from twenty to 

 thirty days. The young shell is extremely slender 

 and fragile, and strongly resembles the variety fra- 

 gilis. In the ' Quarterly Journal of Conchology,' 

 May, 1877, p. 216, Mr. W. Nelson remarks, "This 

 species has the power (occasionally at any rate), when 

 irritated, of discharging a pale violet-coloured liquid. 

 Having observed many times that in scalding the 

 animal of this species, previous to cleaning out the 

 shells, the water was tinged with violet, I was led to 

 pay particular attention to them in the living state, 

 and found that they discharged this coloured liquid 

 sometimes at once upon being lifted out of the pond, 

 but more often if irritated." 



Var. I. fragilis. — Shell smaller, more fragile, slender, and 

 tapering. Kennet and Avon Junction Canal, Wilts, Surrey and 

 Croydon Canal, River Cam at Cambridge, Grand Canal, Dublin, 

 B.C. Near Birmingham (G. Sherriff Tye), near Wakefield 

 (J. Hebden), J.C. Near Colchester (Laver). 



Var. 2. albida. — Shell white. Grand Canal, Dublin, B.C. 



