Balea perversa
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| Balea perversa | |
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| live Balea perversa | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Order: | Stylommatophora |
| Family: | Clausiliidae |
| Genus: | Balea |
| Species: | B. perversa |
| Binomial name | |
| Balea perversa | |
| Synonyms | |
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Balea perversa, also known as the wall snail or tree snail,[1] is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Clausiliidae, the door snails. The shell of this species is left-handed in coiling and it looks like a juvenile of a clausiliid.
Balea perversa (as its synonymous name Pupa fragilis) is the type species of the genus Balea.
Balea perversa is widely distributed in western and central Europe east to Ukraine and westernmost Russia:[1]
- British Isles:[3] Great Britain and Ireland
- Western Europe[3]
- Switzerland – lower concern in Switzerland[3]
- Portugal[3]
- Germany – vulnerable in Germany, endangered in Bavaria [3]
- Austria – vulnerable in Austria[3]
- Czech Republic[4]
- Slovakia[4]
- on an islet near Estonia[5]
- Sicilia[3]
- Sardinia[3]
- Iceland[3]
- in Scandinavia only coastal above 62° N[3]
It was referred from Crimea,[3] but it was probably Mentissa gracilicosta.[5]
Description
The shell is small and resembles that of a juvenile clausilid. The color is pale brownish and the surface is often silky shiny. The shell often has distinct riblets. The apical whorls are cylindrical. The shell has 8-9 whorls and (unlike many clausiliids) the last whorl has the largest diameter. It is densely ribbed. The cervix is almost without keel. Apart from a rudimentary parietal fold, there are no folds in the aperture. This species has no clausilium.[3]
The width of the shell is 2.5–2.7 mm; the height of the shell is 7–10 mm.[3]
Balea perversa differs from Balea sarsii in that it is a less slender and brownish rather than yellowish shell; the first whorl increases in diameter less rapidly, and the sculpture is more prominently striated (with what are usually distinct riblets rather than coarse growth lines).[3]
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