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Carychium occidentale Pilsbry, 1891
Western Thorn
Family: Ellobiidae
Species account author: Robert Forsyth.


© 3CDSG DND     (Photo ID #16500)


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Distribution of Carychium occidentale in British Columbia in British Columbia

Species Information


Among BC species of Carychium, this is the largest species (mature height to 2.7 mm), further distinguished by its clearly tapering spire and thin, but expanded, palatal lip.


Minute (mature shell height, 2.0–2.7 mm); growth determinate; rather broadly fusiform, thin-shelled; translucent. Whorls: about 5–5½; spire whorls convex. Spire: elongate; sides usually more-or-less straight; apex bluntly rounded. Suture: deep. Last whorl: not descending at the aperture; no crest. Protoconch: smooth. Teleoconch sculpture: smooth, with weak colabral striae. Periostracum: inconspicuous. Umbilicus: chink-like. Aperture: subovate; ca 1/3 of shell height. Peristome: incomplete. Apertural dentition: 1 (larger) parietal lamella that continues internally around columella a smooth curve; 1 weakly formed lamella at base of columella that may be lacking. Palatal lip: expanded, edge thin, recurved; seldom with a low, medial callus on inside. Peristome, viewed from side: prosocline; more-or-less straight; belly of last whorl not projecting beyond the plane of peristome. Parietal callus: glazed, transparent, inconspicuous. Colour (periostracum): colourless or white; with a slightly silken sheen/shining.


Body white with dark eyespots.


In relatively undisturbed low elevation (≤ 80 m a.s.l.) deciduous and mixedwood forests. Bigleaf Maples are usually present. Colonies are found sporadically in deep litter areas, and nearly always in moist hollows, near seeps or along riparian zones.


Global range

BC to northern California where it occurs in the coastal counties of Del Norte, Humboldt and Mendocino (Roth and Sadeghian 2003); east through northern Washington to Idaho (Frest and Johannes 2001).

BC Range

Northern Vancouver Island, British Columbia (Forsyth 2004), south on Vancouver Island, the Gulf Islands, and on the mainland coast to the US border. Currently known in British Columbia from the west side of the Coast and Cascade ranges, it should be expected in the wet southern interior parts of the province. Spotty distribution.


Pacific Maritime; possible for the Montane Cordillera.



Genus name from the Greek, karyx (κάρυξ), "a herald", signifying the ancient use of a shell as a trumpet; the gender is neuter. Latin, "occidentale", "western”.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
NativeS3BlueNot Listed

BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

General References