Coffee Bean Shell (also known as Coffee Bean Snail)
Phylum: Mollusca, Class: Gastropoda, Order: Ellobiida, Family: Ellobiidae, Genus: Melampus, Species: Melampus olivaceus · Ellobiidae (Marsh snail and coffee bean snail family) · Gastropod (univalve snail), whole shell, ovate or biconical shape
Species
Melampus olivaceus
Shell Type
Gastropod (univalve snail), whole shell, ovate or biconical shape
Family
Ellobiidae (Marsh snail and coffee bean snail family)
Size
Approximately 10 to 12 millimeters in length, which is average for a mature adult of this species. Adults typically range from 8 to 15 millimeters.
Color & Pattern
Glossy, smooth exterior featuring a creamy white or pale yellowish-tan base color with subtle brownish or reddish spiral banding. The aperture shows distinct reddish-brown inner denticles and folds.
Rarity
Common in appropriate marsh and estuary habitats, though frequently overlooked due to their small size.
Habitat
Found in upper intertidal zones, salt marshes, mudflats, and among coastal succulent vegetation such as pickleweed. They are semi-terrestrial air-breathing marine snails (pulmonates) that prefer brackish and sheltered coastal environments.
Geographic Range
Eastern Pacific coast, ranging from Central California down through Baja California and the Gulf of California, commonly encountered in protected bays and estuaries around Southern California like San Diego.
Description
A small, highly polished, ovate shell with a pointed spire and a long, narrow aperture. The outer lip is thickened and typically features internal white teeth, while the columella has two distinct oblique folds. Its porcelain-like finish and distinct coffee bean shape make it a delightful miniature find.
Key Features
Ovately biconical shape resembling a coffee bean, glossy surface, small flattened spire, narrow aperture with internal denticles, and characteristic folds on the columella.
Collector Value
Low commercial value due to abundance, but highly appreciated by micro-mollusk collectors and local beachcombers building regional collections.
Condition Notes
The specimen appears to be in very good, intact condition with a glossy surface and natural coloration intact, grading as Fine to Gem quality for its tiny size class.
Interesting Facts
Despite being marine-adjacent inhabitants, Melampus snails are pulmonate gastropods that breathe air using a primitive lung rather than gills. They climb up marsh plants during high tides to avoid submergence.
Ecological Role
Plays an important role in coastal detrital food webs, feeding on microalgae, decaying plant matter, and detritus, while serving as a food source for shorebirds and small marsh predators.
Similar Species
Other Melampus species such as Melampus bidentatus found on the Atlantic coast, which are differentiated primarily by geographic distribution and subtle differences in columellar fold arrangement.
Beach Finding Tips
Look near the high tide line in Southern California salt marshes and estuaries, specifically sifting through damp marsh debris, decaying vegetation, and under coastal succulents at low tide.
Notes
San Diego