| Alinda biplicata | |
|---|---|
|   | |
| Shell of Alinda biplicata | |
| Scientific classification   | |
| Kingdom: | Animalia | 
| Phylum: | Mollusca | 
| Class: | Gastropoda | 
| Order: | Stylommatophora | 
| Family: | Clausiliidae | 
| Genus: | Alinda | 
| Species: | A. biplicata | 
| Binomial name | |
| Alinda biplicata | |
| Synonyms | |
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Alinda biplicata, also known as Balea biplicata, common name the two-lipped door snail or Thames door snail, is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Clausiliidae, the door snails, all of which have a clausilium. [3] [4] [5]
This species is known to occur in several European countries and islands, including:
 
 This species is rare in Great Britain. In England, it is found mainly in the London area, almost exclusively along the River Thames, and is particularly preserved at Isleworth Ait. [6] There is also a colony at Purfleet in Essex. [7]
 
 Like all species in this family, this snail has a clausilium. This spoon-shaped "door" is supported by, and slides in, a series of internal shell folds, see the image below.
The weight of the adult live snail is 149±6 mg. [8]