Ceratostoma foliatum (Gmelin, 1791)

(Ceratostoma foliatum)
(Ceratostoma foliatum)

(juvenile specimen showing cancellate sculpture - 15mm.)


Purpura foliata
Common Name:
Leafy Hornmouth, Leafy or Foliate Thorn Purpura
To about 85mm (3.5in), but has reached 100mm or so.
This large shell should not be confused with any other in our region. It is distinguished by the three wing-like varices on each whorl; these vary in size, and can be large and frilly. Between these varices, the shell has strong chord-like spiral ridges. Very young specimens look cancellate due to smaller, more numerous longitudinal ribs and stronger, more numerous spiral ridges. The siphon canal is closed and upturned. There is one large tooth on the anterior end of the outer lip (thus "hornmouth"). Color: white to brown (dark chocolate or yellowish), usually with spiral banding.
Sitka, Alaska to San Pedro, California, but uncommon south of Point Conception.
This snail lives in the low intertidal and subtidal zones to 65m or more. In northern areas C. foliatum lives in shallower water than in the more southern part of its range. It lives in rocky areas, especially where there are barnacles and bivalves, it primary food sources.
A very interesting description of this species' sculpture and its transition from juvenile to adult can be found in the following book:

Morris, R.H., D.P. Abbott and E.C. Haderlie, 1980. Intertidal Invertebrates of California. Stanford CA: Stanford University Press.

A number of theories have be proposed as reasons for the large varices on this snail's shell; they may provide protection from predators or may act as stabilizers to keep the shell aperture-down if the snail is dislodged and falls through the water.

Like other murexes, the Leafy Hornmouth is a predator. It feeds mainly on barnacles and bivalves, such as clams and scallops. It does so by boring through the prey's shell. Spawning occurs in late February-March, when clusters of yellowish vase-like egg capsules may be found under rocks. Each case contains 30-80 eggs.

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