Pomatiopsis - Walker Snails (Family Pomatiopsidae)
Slender Walker, Pomatiopsis lapidaria (Say, 1817)
Walker snails are amphibious snails, more often state-listed with aquatic species than with terrestrial. They are prosobranch snails, a large group of primarily aquatic snails, with a gill for breathing and a cover over the aperture called an operculum. Regardless of their affinity to truly aquatic snails, they may be found a short distance from water.
Oesch et al. (2013) note that the Slender Walker “lives in the water or on land, in wet to moist environments such as stream banks, fens, and lowlands.” The size range of these taller-than-wide conical snails is 5-7 mm and they are superficially similar to some Pupillids. The lip is slightly reflected according to Dourson (2010).
There are two Walker snails in Indiana: the Slender Walker, Pomatiopsis lapidaria (Say, 1817) and the Brown Walker, Pomatiopsis cincinnatiensis (I. Lea, 1840). The Slender Walker is the more common of the two and is distinguished (according to Dourson 2010) by its slightly larger size and more inflated profile as well as one addition whorl (6-7 for the Slender Walker compared to 5 for the Brown Walker.
The Slender Walker, Pomatiopsis lapidaria (Say, 1817)
Identification: This is the more common of the two Walker species in Indiana. The shell runs 6-7 mm diameter; elongate with tall conic spire; 7 whorls, and umbilicate. The apertural lip (peristome) is slightly thickened within; an operculum is present. The shell color has been described as light greenish brown, tan, or "rich brown".
Comparison: The Slender Walker is distinguished (according to Dourson 2010) by its slightly larger size and more inflated profile as well as one addition whorl (6-7 for the Slender Walker compared to 5 for the Brown Walker.
Habitat: Dourson (2010) describes the Slender Walker as a "calciphile snail often referred to as amphibious or even aquatic; common on wet limestone rock faces, in dripping seeps, and in mats of algae faces along small streams". Oesch et al. (2013) describe it as a snail that lives in the water or on land, in wet to moist environments such as stream banks, fens, and lowlands.
Status: Widely distributed in suitable habitat.
The Brown Walker, Pomatiopsis cincinnatiensis (I. Lea, 1840)
Identification and Comparison: The Brown Walker is the smaller species (~ 5 mm compared to 6-7 mm) with one less whorl (5 compared to 6-7 according to Dourson 2010).
Habitat: The Brown Walker, according to Dourson (2010) seems to prefer wetter sites than P. lapidaria, but they are sometimes found together.
Status: Distributed in central and northern part of the state in suitable habitat. Probably exists elsewhere.
