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Limacina (Limacina) retroversa (Fleming, 1823) subsp. retroversa (Fleming, 1823) forma balea Möller, 1841a


This is a small, shelled, pelagic thecosomatous pteropod with a left-coiled shell, 0.3 cm in diameter. The spire is highly coiled. It has 9 transparent whorls with a brown to purple hue. There is no umbilical keel. Faint transverse striae are present. It is found in temperate waters of the North Atlantic where it feeds on phytoplankton, it is a mucus feeder (Limacina r. balea shell).

Taxonomic Description

The thin transparent shell is light rose. It has a higher coil than in the forma retroversa (Limacina spp.) with a smaller top angle, the number of whorls is larger, up to 9. The whole shell shows a rather coarse spiral striation and numerous transverse growth lines. The suture is clear. The shell aperture is not so very large and not regularly rounded, but somewhat oblique. Umbilicus is narrow and deep. A wing protrusion is present (Limacina r. balea soft parts). The Limacina r. balea radula formula is 1-1-1 and it is composed of about 8 transverse rows.
Shell measurements: height to 7 mm, average maximum diameter 2.4 mm.


The juveniles have a small left coiled shell. A special description is not available.


The form is a protandric hermaphrodite.


This form is phytophagous and epipelagic, the temperature range is (3)11-18°C and the salinity range is 3.18-3.5%S


This form is found in cold waters of N-Atlantic between 30° and 75°N. See also under forma retroversa, see the Limacina r. balea map.

Geological Record

This form is found in the Pleistocene of the Mediterranean, it disappeared again in the Boreal period.


Limacina balea (non Munthe, 1888) Möller, 1841: 489.
Types could not be located.

Limacina retroversa balea