Smooth Duck Clam or Yellow Clam (Labellona laevigata / Labellona undulata)
Phylum: Mollusca, Class: Bivalvia, Order: Venerida, Family: Mactridae, Genus: Labellona, Species: L. laevigata · Mactridae (Trough shell / Surf clam family) · Bivalve (two-shelled clam), whole shell, elongate-oval fan shape
Species
Labellona laevigata
Shell Type
Bivalve (two-shelled clam), whole shell, elongate-oval fan shape
Family
Mactridae (Trough shell / Surf clam family)
Size
Approximately 3 to 4 inches in length, which is a standard adult size for this species. Typical adults range from 2.5 to 5 inches.
Color & Pattern
The exterior features a glossy, smooth porcelain-like surface with a distinct gradient. The umbo (beak) and upper region are a warm, buttery cream or soft yellow, fading gracefully into brilliant white toward the ventral margin. Concentric growth rings provide subtle texture without heavy ribbing. The colors are entirely natural and possess a vitreous luster.
Rarity
Common, frequently discovered by beachcombers in its native Indo-Pacific range, though specimens in pristine, gem-grade condition with unbroken margins are prized.
Habitat
Inhabits shallow marine waters, primarily buried in sandy or muddy-sandy substrates of intertidal and subtidal zones along coastal beaches and protected bays.
Geographic Range
Indo-Pacific region, widely distributed across tropical and subtropical shallow waters, commonly found along Southeast Asian coastlines and Australian shores.
Description
An exceptionally smooth and aesthetically pleasing bivalve shell with an elongated, oval-to-triangular silhouette. The surface is polished by natural wave action and time, displaying fine concentric growth lines. The prominent, yellowish umbo draws the eye, transitioning cleanly into crisp bands of porcelain white. The margins are tightly sealed, and the overall form is streamlined for burrowing in shifting coastal sands.
Key Features
Elongate oval shape, smooth glossy texture, lack of heavy external ribs or deep grooves, distinct yellowish umbo sharply contrasting with white margins, and a robust yet streamlined valve structure.
Collector Value
Low to moderate commercial value due to commonality, but highly valued by casual beachcombers and decorators for its striking color gradient and flawless symmetry. Typically valued between $5 to $15 depending on exact size and polish.
Condition Notes
Gem condition. The shell is fully intact with no chips, cracks, or boring sponge holes. The original natural gloss and coloration are exceptionally well-preserved, showing zero signs of sun-bleaching or severe erosion.
Interesting Facts
Mactrid clams are remarkably fast burrowers, utilizing a strong muscular foot to dig themselves back into the sand within seconds if exposed by shifting tides. Their smooth exterior reduces drag in turbulent surf zones.
Ecological Role
Serves as an important link in the coastal marine food web, filtering microscopic plankton from the water column and providing a crucial food source for carnivorous gastropods, rays, shorebirds, and crabs.
Similar Species
Other members of the Mactridae family such as Spisula solidissima (Atlantic surf clam), which tends to be larger, chalkier in texture, and lacks the distinct yellow-to-white gradient of Labellona laevigata.
Beach Finding Tips
Search sandy beaches at low tide, particularly after storms or heavy wave action when shifting sands uncover buried bivalves. Look along the high tide drift lines where lightweight intact shells are deposited.