Calliostoma occidentale

(Mighels & Adams, 1842)

Description (shell):
The shell is a slightly transparent straight-sided cone with seven whorls. Last whorl is keeled and occupies 55 % of shell height. Ornament of prominent, rather well-spaced spiral ridges of which the most adapical on the last whorl is nodose, though higher in the spire nodosities occur on other ridges too. The spiral ridges are narrow, that at the periphery of the last whorl sharp-edged and forming the keel; there are four or five on the last whorl above the keel, four on the next two, gradually reducing up the spire. They are less prominent on the base and may be absent there except marginally and centrally. Prosocline growth lines are present but are not obvious. The protoconch has a reticulated pattern but this is commonly lost by erosion. Aperture occupies 40 % of shell height. Outer lip rather acutely angulated. There is little or no bulge on the columella; a small umbilicus is present.

Up to 12 x 11 mm.

Shell with reddish opalescent lustre. The spiral ridges are often yellowish.

Cephalic lappets minute or absent; three pairs of epipodial tentacles. The body is cream with purplish brown markings.

Lives on stones 19-1000 m deep and feeds on alcyonarians and hydroids.

A northern species found from the British Isles and Scandinavia to Iceland and also off eastern American coasts. (Distr. C. occidentale).