A Field Guide to the Snails of Lord Howe Island

138 Semilaoma costata Family Punctidae (Pinhead or Dot Snails) Semilaoma costata Shea & Griffiths, 2010 Coarse-ribbed Pinhead Snail Shell. Size: H = 0.7-0.8 mm, D = 1.3-1.5 mm. Colour: Pale yellow to white. Shape: Subdiscoidal with a low to flat spire; sutures impressed; whorl profile rounded to shouldered. Sculpture: Protoconch with spiral lirae; teleoconch with moderately closely spaced, fine radial ribs, interspersed with microsculpture of relatively strong radial and spiral threads. Aperture: Ovately lunate (width greater than height). Umbilicus: Moderately wide. Animal. Not known. Key distinguishing features. Minute size, relatively flat shape, distinct radial sculpture, moderately wide umbilicus. Habitat and occurrence. North Bay and Settlement areas, living in leaf litter. Common and widespread. Remarks. Differs from congeners in its flatter shape, more rounded whorl profile, more distinct radial sculpture and wider umbilicus.