A threatened species is any species which is vulnerable to extinction in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of critical depensation, a mathematical measure of biomass related to population growth rate. This quantitative metric is one method of evaluating the degree of endangerment without direct reference to human activity.
Desmoulin's whorl snail is a species of minute air-breathing land snail, a terrestrial pulmonate gastropod mollusc or micromollusc in the family Vertiginidae, the whorl snails.
Vertigo genesii, common name the round-mouthed whorl snail, is a species of minute air-breathing land snail, a terrestrial pulmonate gastropod mollusc or micromollusc in the family Vertiginidae, the whorl snails.
Lithoglyphus naticoides, the gravel snail, is a species of small or minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Lithoglyphidae.
Theodoxus fluviatilis, common name the river nerite, is a species of small freshwater and brackish water snail with a gill and an operculum, an aquatic gastropod mollusk in the family Neritidae, the nerites.
Pupilla alpicola is a species of minute air-breathing land snail, a terrestrial pulmonate gastropod mollusk or micromollusk in the family Pupillidae.
Bithynia is a genus of small freshwater snails with an operculum, aquatic prosobranch gastropod mollusks in the family Bithyniidae.
Lamellidea novoseelandica, formerly Tornelasmias capricorni, is an extinct species of minute air-breathing land snail, a terrestrial pulmonate gastropod mollusk or micromollusk in the family Achatinellidae. This species was endemic to Blackburn Island, off the coast of Australia.
Vallonia enniensis is a species of minute land snail, a terrestrial pulmonate gastropod mollusk or micromollusk in the family Valloniidae.
Helicopsis striata is a species of air-breathing land snail, terrestrial pulmonate gastropod mollusk in the family Geomitridae.
Ruthenica filograna 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.
Valvata piscinalis, common name the European stream valvata or European valve snail, is a species of minute freshwater snail with gills and an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails. It is also known as Cincinna piscinalis.
Bythinella austriaca is a species of very small freshwater snail with an operculum, an aquatic gastropod mollusk in the family Amnicolidae.
Pseudotrichia rubiginosa, sometimes known as the "German hairy snail", is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies.
Marstoniopsis is a genus of minute freshwater snails with a gill and an operculum, aquatic gastropod mollusks or micromollusks in the family Amnicolidae.
Vertigo parcedentata is a species of minute, air-breathing land snail, terrestrial pulmonate gastropod molluscs or micromollusks in the family Vertiginidae, the whorl snails.
Xerocrassa geyeri is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Geomitridae. It is also known as Trochoidea geyeri.
Zonites embolium is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Zonitidae.
Orcula zilchi is a species of small air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Orculidae. This species is known from the type locality in Bulgaria and three localities in Turkey.
