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.

Distribution

This species is known to occur in a number of 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. There is also a colony at Purfleet in Essex.

[The internal shell anatomy of the body whorl of Alinda biplicata

1 - Lamella superior 2 - Lamella inferior 3 - Lamella subcolumellaris 4 - Lunella 5 - Clausilium 6 - Plica medialis 7 - Plica principalis 8 - Lamella spiralis | upload.wikimedia.org/wikipedia/commons/5/57/Alinda///biplicata///anatomy.jpg]

Description

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.