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DescriptionA tall shell, up to 15 cm high and 5 cm broad, with up to 9 moderately tumid whorls that form a spire with a concave profile. Protoconch bulbous, often of greater diameter than the next whorl and set more obliquely on the spire. Numerous pronounced spiral ridges present. Outer lip arises between spiral ridges 10-12 on last whorl. Shell white with a pale-yellow horny layer overlying the calcareous matter of the shell (periostracum).Similar to Colus gracilis but the spiral ridges are more pronounced, especially towards the apex, and the siphonal canal does not incline markedly to the left as it does in Colus gracilis. Occurrence in Britain may be adversely affected by seawater warming.