136 LIMNAID. 
throughout Great Britain and Ireland. Var. g7bdosa is 
usually found in swift clear streams. 
Var. I. cdpuloides (Jan.). Larger, apex near the centre. 
Var. II. gibbdsa (Bourg.). Smaller, with the hook over- 
hanging the posterior margin. 
Var. III. dlbida ( Jeff.). White, more finely striated. 
Var. IV stricta (Morel.). Much elevated, sides com- 
pressed. 
Genus.—VELLETIA Gray. 
Shell conical, compressed ; afex sub-central, sinistral. 
V. LACUSTRIS (zxhabiting ponds) Linné. Pl. VII., f. 10. 
Compressed, oblong, thin; afex acute, sinistral A. 63 mm. 
B. 23 mm. 
The ‘Pond Limpet’ is found in sluggish streams, 
canals, ponds, and marshes, on the stalks of flags, rushes, 
and other water plants, especially the Stratiofes ; and it 
may often be found adhering to other shells. Though 
almost as widely distributed as the last species, it is more 
local, especially in Ireland. Its compressed oblong form 
marks it off distinctly from A. fuviatilis. 
Var. I. compréssa ( Jeff). Broader and flatter. 
Var. II. dlbida ( Jeff:). White or colourless. 
Var. III. méguinidna (Bourg.). Elevated, compressed 
at the sides ; corresponding to var. stricta of A. fluviatilis. 
