The smooth scallop Flexopecten glaber is an endemic species of the Mediterranean Sea. From the Roman Period onwards, populations of Narbonnese Gaul made it one of the most consumed marine species. The species was harvested from lagoons along the Mediterranean coast and shipped to consumers up to a hundred kilometres from the seashore. After a short break in the altomedieval distribution of shellfish, it appeared regularly in sites close to the coast in the 10th-12th centuries. The species subsequently almost disappeared from archaeological contexts and has been extremely rare on French Mediterranean shores since the 20th century. In this study, we aim to determine the ways and means by which the commercial networks managed to supply the hinterland populations with fresh products. We followed the morphological diversity of scallops through Antiquity and the Middle Ages (1st-12th centuries AD) of inland and coastal populations using geometric morphometrics through outline analysis of the shells using Elliptic Fourier Transforms. Smooth scallops differ morphometrically between the various lagoons of southern France suggesting either their reproductive isolation or ecological adaptation to the geographical fragmentation of their respective habitats. Thanks to this geographical structuring, we estimated the geographical origin of valves discovered in the hinterland. Most of these valves were associated with the nearest lagoon, suggesting a generally opportunistic supply. However, two different origins have been identified in the Roman town of Nîmes, suggesting that the demands of the large urban populations may have required supplies from further away. This work is part of the DEMETER research project (ERC Starting Grant; PI A. Evin).