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Family: Helicodiscidae
Common name: Tight Coil
Discovery: Hubricht, 1962
Identification
Width: 3-4 mm
Height: 1.5-2.0 mm
Whorls: 5+
Helicodiscus notius has a shallow, open umbilicus, nearly half the diameter of its entire shell. Spiral lirae decorate the surface of the shell, including the embryonic whorl. Two cone-shaped teeth may usually be found on the basal wall of the final whorl and two on the outer wall. Sometimes a third pair of teeth may be present. As a juvenile, the disk-like shell of Helicodiscus notius is translucent; as a mature adult, it is opaque. The sutures are deep.
Ecology
Compared with Helicodiscus parallelus, H. notius prefers drier habitats. It may be found around logs and in the leaf litter of late-stage forests and occasionally in caves, but only where leaf litter has been washed or blown in (Hubricht, 1962). In Tennessee it has been noted in close association with limestone substrata (Coney et al, 1982).
Taxonomy
This species’ shell is not clearly distinguishable from Helicodiscus parallelus or H. shimeki and its described characters are so subtly different as to raise questions about its taxonomic validity. This species is also known as Helicodiscus notius notius.
Distribution
Helicodiscus notius is reported throughout the Southeastern and Central United States.
Conservation
NatureServe Global Rank: G5Q
