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Cystiscus angasi (Crosse, 1870)

Diagnosis: Shell minute or small, colourless transparent to opaque white; spire low; outer lip thickened internally, usually smooth, occasionally weakly denticulate centrally; external varix absent; siphonal notch absent; posterior notch absent; lacking collabral parietal callus ridge; columella multiplicate, with up to 8 plaits/lirae.

Size: Up to 3 mm in length.

Distribution:  Australian Museum collection: All of the Australian coastline including Tasmania, from intertidal down to 750 metres.  Common, but see remarks below.

Comparison: This species is the most triangular in outline of the family.  C. connectans resembles it, but is more elongate. (See Identification of beach specimens)

Synonymy: Synonyms given by Hewish in Wilson (1994) are Volvaria lubrica Petterd, 1884; Marginella shorehami Pritchard & Gatliff, 1899; Marginella simsoni Tate & May, 1900; Marginella ringens May 1919; Marginella erma Cotton 1944; Marginella amphora Laseron, 1948; and possibly Marginella angasi melania Laseron 1948

Remarks: This is by far the most common member of the family in NSW, frequently occurring in beach shell grit.  Coleman (1981) reported the species living in colonies around five metres depth on bryozoans.

As currently understood, the species has a circum-Australia distribution, occurring over a depth range from the intertidal to 750 metres.  Specimens sorted as this species in the Australian Museum collection vary in size from 1.7 to 3 mm, with considerable variation in shape and height of the lip.  This distribution, size range and shape variation strongly suggests that there is more than one species involved, so some or all of the synonyms listed above may represent valid species.  The subspecies Marginella angasi melania Lasereon, 1948 was described as having a black animal, so may be a different species. The species Marginella amphora Laseron, 1948 is based on a specimen of 2.8 mm in length with the outer lip rising above the spire, from 8-10 fathoms off Point Haliday, and may represent another species.

Hedley (1915) provided a figure of a specimen which he compared with the type of Marginella angasi Crosse in the British Museum .  The photographed specimen here (Fig. 1) is a specimen from Hedley’s lot (C.032422) which closely matches his figure.

Laseron (1957) provides a description and figure of the animal.

Fig. 1: Middle Harbour, NSW (C.032422)

Fig. 2: a. Syntype of Marginella amphora Laseron, 1948. Point Haliday, NSW, in 15-18 m (C.103371).  b. Syntype of Marginella angasi melania Laseron, 1948. Fairlight, North Harbour, NSW (C.103373)

Copyright Des Beechey 2004