Cerithium repandum Monterosato, 1878
Mediterranean. The species was previously considered as endemic to the Gulf of Gabes, living there in very shallow water on sandy-muddy substrate in lagunar areas. This is a very polymorphic species, hardly distinguishable from the common morph of C. vulgatum vulgatum. The unusual colours aside, the only way to separate these two species in specimens showing a morphological convergence are: 1- molecular analysis; 2- the study of the protoconch. In fact, the protoconch of vulgatum vulgatum is divided in two sectors: the first one is smooth, the following one finely striated. In repandum, the protoconch shows a rather weak sculpture on its entire surface (Garilli & al., 2017). Grazer and detritus feeder; larva non-planktotrophic.

50cm deep, in sand, Kerkennah islands, Tunisia. 24-29mm.
Shallow water, Ayrolles lagoon, Gruissan, Occitania, S. France. 26-28mm. R. Huet legit (FR).
The species seems attached to lagunar environments. Scultpure and colour variations: 1m deep, on mud, Stagno di Santa Gilla, Cagliari, S. Sardinia. 25-26mm.
Melanism in Chioggia area, southern corner of the Venice lagoon, Veneto, NE. Italy. 26mm. To be compared with the melanistic shells of vulgatum in Kerkennah.

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