Anostoma, common name the up-mouth snails, is a genus of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Odontostomidae. Snails in this genus are found in Brazil.Adult snails in this genus have an extremely unusual shell morphology: the aperture of the adult shell faces directly "upwards", in other words, in the same direction as the spire. This seemingly impossible arrangement is made possible because the adult shell is carried upside down.