About Vallonia costata (O.F.Müller, 1774)
This is a description of the gastropod species Vallonia costata (O.F.Müller, 1774). Its shell measures 1.1-1.6 mm by 2.2-2.7 mm and has 3.2-3.3 whorls. The whorls are slightly angular at the periphery, with deep sutures. The shell itself is flat, with regular, widely spaced ribs, and is striated between these ribs. The last whorl descends toward the aperture. The almost circular aperture is oblique, meaning it slopes downwards, and is broadly reflected in adult specimens. The lip of the aperture is thickened and reflected. Like all other species in the genus Vallonia, Vallonia costata has a very wide umbilicus. The shell is an ivory-white color. To see differences between this species and Vallonia pulchella, refer to the description of Vallonia pulchella. This species occurs in many countries and islands, including Great Britain, Ireland, the Czech Republic, Slovakia, Poland, the Netherlands, Latvia, Ukraine, Canada, the United States, and other areas.
