### **Common Saddle Oyster (*Anomia ephippium*)**
Identification
Often called the "Jingle Shell," this bivalve is a master of disguise. Reaching up to 6cm, its shells are remarkably thin, translucent, and possess a stunning pearly luster. While the upper valve is convex and often ripples with shades of silver, rose-pink, or golden-yellow, the lower valve is flat and hidden. Look for the defining field mark: a distinct, circular hole (the foramen) in the lower valve through which a calcified "plug" passes to anchor the animal. Unlike the symmetrical Edible Oyster, the Saddle Oyster is highly irregular; it is "xenomorphic," meaning it grows to perfectly mimic the texture and shape of the rock or shell beneath it.
Habitat & Range
You’ll find these glittering treasures along the coasts of the Northeastern Atlantic, from Norway down to the Mediterranean and North Africa. They thrive from the low intertidal zone down to depths of 150 meters. Look for them firmly cemented to hard substrates—rocks, shipwrecks, or even the shells of living crabs and larger mollusks like Great Scallops.
Behaviour
The Saddle Oyster is a sessile homebody. Once the larvae settle, they secrete a liquid that hardens into a permanent, bone-like anchor. An observer beachcombing after a storm might find the empty, translucent upper valves washed ashore; when several are shaken together in your hand, they produce a metallic, melodic tinkling—hence the name "Jingle Shell."
Diet
As a dedicated suspension feeder, *A. ephippium* relies on the rhythm of the tides. It draws seawater in through its mantle, using specialized, mesh-like gills to trap microscopic phytoplankton and organic detritus. Cilia then transport this "marine snow" directly to the mouth in a continuous, silent feast.
Fascinating Fact
The "plug" that anchors the oyster to a rock isn't just a sticky thread like a mussel’s; it is a permanent, calcified extension of the animal’s own body. It is so strong that when the oyster dies, the shell often breaks away, leaving the white, stony plug behind on the rock like a ghostly fingerprint.