118 LIMNZAIDZ. 
This interesting species is local. It is found in ponds, 
ditches and sluggish streams. Its recorded range in 
England extends from Yorkshire to Kent, but it has not 
been authenticated for Ireland, Scotland or Wales. 
Var. albina (Taylor). Milk white and semi-transparent. 
Genus.—PLANORBIS Guettard. 
Quoit-shaped, dextral, circular. 
Sub-genus.—Hiprettis Hartmann. 
I. P. FONTANUS (22habiting springs) Lightfoot. Pl. VI., f. 2. 
[=P. Niripus Jeffreys.) 
Quoit-shaped ; thin, glossy, rufous horn colour; sharply keeled ;. 
whorls 4A—5 3; spire sunk ; wmbzlicus shallow. A. 13mm. B. 55mm. 
This may be distinguished from the last species by 
having no septa, being more depressed; the spire not being. 
so deeply sunk, and by having a shallower umbilicus. 
It is a common species, inhabiting mud and weeds, 
generally on the bottom. It is very partial to watercress. 
The crust of mud which frequently spoils its appearance 
is extremely hard to remove. 
Its distribution is general throughout the British Isles, 
though local in Scotland. 
Var. dlbida (Nelson). White. 
Sub-genus.—GVRAULUS Agassiz. 
2. P. NAUTILEUS (“ke a nautilus) Linné. Pl. VI., f. 3. 
Quoit-shaped, having the upper side flat and the under-side 
convex; dirty white or grey; striated in the line of growth by 
ridges of epidermis; whorls 3. A. £mm._ B. 23mm. 
