Some native (C. integra, A. limosa) and invasive (B. tentaculata, P. antipodarum) species that are hard to tell apart. Shells are not identical in scale.

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Bithynia tentaculata

Cincinnatia integra

Amnicola limosa

Potamopyrgus antipodarum

Potamopgyrus antipodarum Operculum


















Comparison of Fontigens nickliniana and Potamopyrgus antipodarum

Fontigens nickliniana Potamopyrgus antipodarum
drawing of Fontigens nickliniana
  • Whorls are more rounded, almost shouldered, sutures more deeply incised, resulting in a bigger “gap.

  • Spire is more rounded, less pointed

  • Aperture is oval

  • Aperture lip is reflected only slightly at base of lip.

  • Whorls are less rounded, sutures less incised, resulting in a smaller “gap.”

  • Spire is more pointed

  • Aperture is not perfectly oval, it is drawn up to a point forming an angle, resulting in almost a teardrop shape

  • Aperture is reflected around most of the lip except at the very top.

  • Usually a brown-reddish rim of periostracum around the whitish color of the apertural lip.

Image on the Left from the Encyclopedia of life. Image on the R from Burch 1980. Image on the L from report to US Army by Daniell Cosier, Daniel Molloy (NY State Museum) and David Richards (Montana State University). Report includes many excellent images including dissections.