Carychium nannodes

Carychium nannodes G.H. Clapp, 1905
Pygmy Thorn

  • Carychium nannodes G. H. Clapp 1905: 91, pl. 3, figs 7–9.

Identification. Shell elongate. Spire tapering. Whorls ca 5. Surface with nearly smooth and incremental striae very faint; with exceedingly tiny punctae at least 20× magnification. Aperture subovate, ca 1/3 of shell height, with a parietal fold, continuing internally around the columella, and a smaller columellar fold below. Palatal lip expanded but little thickened. Shell shining, translucent and colourless when fresh; dead shells become white and opaque. Shell to 1.3–1.5 mm high (higher than wide).

Animal presumably as in other Carychium species.

Carychium nannodes is the smallest of the Carychium species in Canada. It is recognized by its diminutive size (≤1.4 mm), smooth shell without any trace of striae, and thin, although recurved, palatal lip. The internal lamella is smoothly curved.

Habitat. Mesic upland forests, such as along the Niagara Escarpment; in leaf litter. A rare species, most Ontario records are from stream drift.

Canadian range. Ontario only; restricted to areas along the north shore of Lake Ontario. First reported by Oughton (1948) from stream drift of the Green, Rouge, Don, and Humber rivers. On the Niagara Escarpment at Crawford Lake, Halton Regional Municipality (Nekola & Barthel 2002). A rare species (although perceived rarity may be due to its small size and confusion with other Carychium species). Oughton (1948) first recorded this species in Canada; Burch & Van Devender (1978) and Nekola & Barthel (2002) figured shells from Ontario.

Etymology. Greek, nanos, “a dwarf”.