Polydorichnus subapicalis Ishikawa et Kase, 2007

Diagnosis.⎯Very small hole (usually less than 2 mm) with circular to elliptical outer opening, suggested to be commensal in origin and present only in subapical whorls of gastropod shells. Axis of hole usually slightly oblique to substrate surface (mostly toward clockwise coiling direction of whorl). Boring associated with detrital mud tube, if preserved, in anterior two or three whorls of gastropod, and small abraded area on columella just beneath bore-hole opening.