# Romans see red! Updating our knowledge on dye extraction activities along the Atlantic coast of France through archaeomalacology

Catherine Dupont

► To cite this version:

Catherine Dupont. Romans see red! Updating our knowledge on dye extraction activities along the Atlantic coast of France through archaeomalacology. Catherine Dupont; Anna Baudry; Marie-Yvane Daire. Dupont C., Baudry A., Daire M.-Y. (dir.), 2025 – Archaeology Of Coastal Settlements And Human/Environment Interactions In The Atlantic North Of The Equator / Archéologie des peuplements littoraux et des interactions Homme/Milieu en Atlantique nord équateur. Proceedings of the International conference HOMER 2021, Île d'Oléron (France), 28/09/2021 - 02/10/2021. https://www sidestone com/books/archaeology-of-coastal-settlements, Sidestone, pp.543-560, 2025. hal-05520944

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ARCHAEOLOGY OF
COASTAL SETTLEMENTS

ARCHÉOLOGIE DES
PEUPLEMENTS LITTORAUX

HOMER 2021 Conference

CATHERINE DUPONT, ANNA BAUDRY & MARIE-YVANE DAIRE (EDS)
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sidestonepress

This is a free offprint – as with all our publications the entire book is freely accessible on our website, and is available in print or as PDF e-book.

www sidestone com
ARCHAEOLOGY OF COASTAL
SETTLEMENTS

ARCHÉOLOGIE DES PEUPLEMENTS
LITTORAUX

HOMER 2021 Conference

CATHERINE DUPONT, ANNA BAUDRY & MARIE-YVANE DAIRE (DIR.)
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MAIRIE
DE
LE CHÂTEAU-D'OLÉRON

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la
Charente
Maritime

+ Inrap +

Institut national
de recherches
archéologiques
préventives

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<figure><img src="image_7.png" /></figure>

MINISTÈRE
DE LA CULTURE

Liberté
Egalité
Fraternité

drassm
DEPARTMENT DES RECHERCHES ANALEDHIQUES
LIBERTÉ Egalité Fraternité

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

PRÉFET
DE LA RÉGION
NOUVELLE-AQUITAINE

Liberté
Egalité
Fraternité

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Terre, Écosystèmes et Sociétés

Observatoire
des Sciences de l'Univers
de Rennes
# Contents

11 **Introduction**

15 **CHAPTER 1. COASTAL AND MARITIME ARCHAEOLOGY: TODAY'S CHALLENGES** |
L'ARCHÉOLOGIE LITTORALE ET MARITIME : LES DÉFIS D'AUJOURD'HUI

17 Préserver les épaves métalliques contemporaines par protection cathodique :
caractérisation globale *in situ* et analyse multi-échelle des couches de corrosion
et de la biodiversité

Florence MERCIER-BION, Justine VERNET, Marine BAYLE, Clémentine CAUBISENS, Jean-Bernard MEMET, Laurent URIOS, Nathalie HUET, Lila REBOUL, Jean-Paul GALLIEN, Eddy FOY et Philippe DILLMANN

31 Cyclones et patrimoine archéologique littoral : apports des interventions menées après les ouragans Irma et Maria (2017) sur les îles caribéennes de Saint-Martin et de la Guadeloupe

Nathalie SERRAND, Christophe HÉNOCQ, Dominique BONNISSENT, Christian STOUVENOT, Fabrice CASAGRANDE, Pierre-Yves DEVILLERS, Jean-Georges FERRIÉ, Nathalie SELLIER-SÉGARD et Martijn VAN DEN BEL

45 Tic-tac, le compte à rebours a démarré : la perte du patrimoine archéologique
côtier des Petites Antilles françaises, entre urgence et stratégie

Christian STOUVENOT, Dominique BONNISSENT, Marie-Yvane DAIRE, Elías LÓPEZ-ROMERO et Nathalie SERRAND

57 Érosion côtière, et gestion des héritages du Néolithique à demain : Approche intégrée à la Gournaise (Île d'Yeu, Vendée)

Elsa CARIOU, Annabelle CHAUVITEAU-LACOSTE, Catherine MOREAU, Donatienne LEPAROUX et Adrien DUBOIS

69 La course contre la montre face à l'érosion : la stratégie développée en Médoc
(Gironde, France)

Florence VERDIN avec la collaboration de Frédérique EYNAUD, Elías LÓPEZ-ROMERO, Clément COUTELIER, Camille CULIOLI et Alizé HOFFMANN

81 Sea level rise as driver for the destruction of archaeological remains and immovable heritage from the Paleolithic to modern times: a new friendly vulnerability index applied to the Peniche coast (Lisbon, Portugal)

Luís RENDEIRO, Ana RAMOS-PEREIRA and Ana CATARINA SOUSA
97 **CHAPTER 2. UNLOCKING THE POTENTIAL OF SUBMERGED, INTERTIDAL AND COASTAL SITES: DEVELOPING METHODS FOR THEIR IDENTIFICATION AND STUDY** | LE POTENTIEL DES SITES LITTORAUX (IMMERGÉS, INTERTIDAUX, CÔTIERS), MÉTHODES ET TECHNIQUES D'IDENTIFICATION ET D'ÉTUDE

99 **Les vestiges archéologiques de l'Anse Bellay (Martinique) : Érosion littorale et transgressions marines anciennes et actuelles**
Thomas ROMON, Hervé GUY et Marie-Michelle MOREAU

111 **Menaces sur les sites archéologiques littoraux – L'exemple de la côte vendéenne prospectée depuis une dizaine d'années**
Jean-Marc LARGE

123 **Prospections archéologiques à Saint-Androny et Anglade (Gironde) : apports à la connaissance des marais de Saint-Ciers-sur-Gironde**
Richard LOPES

137 **Archaeological study as a last defense against erosion: methodology on protohistorical fortified sites from the Channel-Atlantic coasts**
Hervé DUVAL

151 **Sur l'intérêt des méthodes de prospection géophysique pour étudier les sites archéologiques sur l'estran. Exemples sur la façade atlantique française**
Vivien MATHÉ, Pierre-Emmanuel AUGÉ, Guillaume BRUNIAUX, Jean-Marc LARGE, François LÉVÊQUE, Ludovic SOLER et Thomas VIGNEAU

161 **Évolution de l'environnement autour d'un site du second âge de Fer en position d'estran à Plougasnou/Saint-Jean-du-Doigt (Finistère, France)**
David Aoustin, Chantal LEROYER, Cédric ROSSIGNOL, Dominique MARGUERIE, François LE GALL et Marie-Yvane DAIRE

183 **Approche croisée archéologique et géographique d'un territoire maritime :
L'exemple de la baie de la Bourgneuf (Atlantique, Pays de la Loire)**
Gaëlle DIEULEFET, Mohamed MAANAN et Pierre POUZET

195 **Un dolmen à la mer... Dolmen de la pointe des Chats à l'Île de Groix (Morbihan). Analyse architecturale du tumulus détérioré par l'érosion marine**
Philippe GOUÉZIN, Chloë MARTIN, Catherine ROBERT et Léa TRIFAULT

207 **Les conditions d'implantation de la citadelle littorale du Château d'Oléron (Charente-Maritime, France) : un état de la recherche**
Bastien GISSINGER

219 **CHAPTER 3. NAVIGATION, CIRCULATION AND PORT INSTALLATIONS** |
NAVIGATIONS, CIRCULATIONS ET INSTALLATIONS PORTUAIRES

221 **Les pirogues protohistoriques du lac de Sanguinet, des embarcations adaptées au cabotage ? (France, Landes, 40)**
Guillaume PARPAITE
239 Par-delà l'hypervisibilité des pirogues monoxyles, dans l'enregistrement archéologique des premières navigations européennes

Michel PHILIPPE

253 Moving across the Seascape-Landscape: site location patterns in the inland sea of Última Esperanza (Magallanes region, Chile) during the Late Holocene

Albert GARCÍA-PIQUER, Vanessa NAVARRETE, Raquel PIQUÉ and Alfredo PRIETO

267 Saint-Pierre de la Martinique, le bord de mer, entre attractivité et vulnérabilité (XVIIe-XXe siècles)

Annie BOLLE et Jeanne CAZASSUS-BÉRARD

281 Armature portuaire et réseaux d'échanges autour de Redon (Bretagne, Ille-et-Vilaine) du IXe au XVIe siècle

Julien BACHELIER

291 Disparaître ou s'adapter : les ports médiévaux de Beaugeay et d'Esnandes face au colmatage des marais charentais (Charente-Maritime)

Catherine VACHER avec la collaboration de Brigitte VÉQUAUD et de Jean-Claude BONNIN

303 Approches géographiques et premières réflexions sur l'emplacement des ports maritimes et fluvio-maritimes de Bretagne, de la Protohistoire à l'époque moderne

Julie REMY, Olivia HULOT, Carl CALONE-REBATEL, Jimmy MOUCHARD, Yves MÉNEZ, Thierry LORHO, Jean-Manuel CONILLEAU et Denis DÉGEZ

317 Belle-Île-en-Mer (Morbihan, France) or the Non-insularity: an Island-Continent from the Early Neolithic to the Late Iron Age

Gwenaëlle HAMON, Hervé DUVAL, Lorena AUDOUARD and Benjamin GEHRES

331 La circulation des céramiques par voie maritime : les produits d'origine lointaine en Bretagne du milieu du XIIIe à la fin du XVIIe siècle

Clément LE GUÉDARD et Yves HENIGFELD

345 Publication of the uncertain locations of French ports of eighteenth century in a gazetteer

Christine PLUMEJEAUD-PERREAU, Christian PFISTER, Thierry SAUZEAU and Silvia MARZAGALLI

357 Navires, barachois et chaffauds : Stratégies d'implantation et témoignages de l'aménagement du littoral à Saint-Pierre-et-Miquelon (XVIIe-XXe siècles)

Cécile SAUVAGE, Elise NECTOUX et Eric RIETH

375 La construction navale normande au service des expéditions atlantiques au xviᵉ siècle. L'exemple du commerce du bois-brésil illustré par un panneau sculpté de « l'isle du Brésil »

Michel DAEFFLER

389 L'épave Sables-d'Or-les-Pins 3, un chantier de démontage de navire au XVIIIe siècle sur l'estran (Fréhel, Côtes-d'Armor, France)

Marine JAOUEN, Olivia HULOT, Éric RIETH, Catherine LAVIER, Clément LE GUÉDARD et Philippe MIGAUD
401 L'épave Bloscon 1 perdue au large de Roscoff (Finistère, France) aux IIIe-IVe siècles de notre ère et sa cargaison de lingots d'étain et de plomb-étain

Olivia HULOT, Cécile LE CARLIER DE VESLUD, Francoise LABAUNE-JEAN et Philippe MIGAUD

415 État des lieux sur le cabotage aux Petites Antilles (Guadeloupe Martinique) à la période coloniale : Contribution d'archéologie historique

Jean-Sébastien GUIBERT

429 CHAPTER 4. THE ANTHROPIZATION OF THE COAST: INFRASTRUCTURE, TRANSFORMATION AND PRODUCTION TECHNIQUES | ANTHROPISATION DU LITTORAL : INFRASTRUCTURES, TRANSFORMATION ET TECHNIQUES DE PRODUCTION

431 Settlement pattern and subsistence strategies in the High Arctic: drone survey of an archaeological site at Ukaleqarteq (Kap-Höegh, North-Eastern Greenland)

Emilie GAUTHIER, Vincent BICHET, Hervé RICHARD, Edouard MASSON MACLEAN, Jérôme FORT and David GREMILLET

445 Une occupation littorale inédite à Saint-Martin (île de l'archipel guadeloupéen) de la fin du XVIIe ou du début du XVIIIe siècle : preuves matérielles d'une occupation précoce d'une population marginale

Nathalie SELLIER et Alexandre COULAUD

455 Aménagement et exploitation du littoral de Rue et de l'estuaire de la Maye (Picardie) du XIe au XVIe siècle

Christophe CLOQUIER et Stéphane DESRUELLES

467 Les cisterciens et la mer sur le littoral nord de la Bretagne du XIIe au XVIIIe siècle

Fadila HAMELIN

479 L'édification et l'exploitation des pêcheries en pierre, d'origine médiévale, appelées « écluses » sur l'île de Ré (Charente-Maritime)

Jacques BOUCARD

493 Découverte récente de bassins d'affinage des huîtres (Ve-VIe siècle), à Soulac-sur-Mer (Gironde)

Florence VERDIN, Camille CULIOLI, Elsa CARIOU, avec la collaboration de Pierre STÉPHAN, Clément COUTELIER et Nicolas DICKÈS (†)

507 Prospections géophysiques et sondages archéologiques de deux sites à sel de la région de Rochefort-sur-Mer (Charente-Maritime, France) : caractérisation des structures et de la géométrie des dépôts

Vivien MATHÉ, Stéphane VACHER, François LÉVÊQUE, Guillaume BRUNIAUX, Guilhem LANDREAU, Antoine LAURENT, Frédéric POUGET et Vincent ARD

519 Sondages archéologiques sur deux sites à sel de la région de Rochefort (17), France : Nouvelles données sur l'organisation des sites et le mobilier

Stéphane VACHER, Guilhem LANDREAU, Vivien MATHÉ et François LÉVÊQUE
**533** "Shell middens" in Ireland: is it time for change in terminology?
Carolyn HOWLE OUTLAW

**543** Romans see red! Updating our knowledge on dye extraction activities along the Atlantic coast of France through archaeomalacology
Catherine DUPONT

**561** Hang up to the hook! Manufacture and fishing practices at Mesolithic Olsteinhelleren, Norway
Albane MAZET, David ÉVA, Knut Andreas BERGSVIK and Claire HOUMARD

**577** Approches lipidiques du contenu des céramiques pour appréhender l'utilisation des ressources naturelles sur la côte atlantique de la France à la fin du Néolithique et au début de l'âge du Bronze : Les Caltières, Beg ar Loued et Ors, trois cas en cours d'étude
Camielsa PRÉVOST, Akshyeta SURYANARAYAN, Nicolas FROMONT, Yvan PAILLER, Ludovic SOLER, Martine REGERT, Anne-Charlotte PHILIPPE-LELONG, Philippe FORRÉ, Vincent ARD et Thierry BLASCO

**595** An assessment of the potential of shell growth-checks in limpets (*Patella vulgata*) for estimating the season of archaeological deposits, using Iron Age limpets from Bornais, Western Isles, Scotland
Tim HEWSON and Julia BEST

**607** Ostéologie et ostéométrie de la sardine atlantique (Sardina pilchardus)
Océane CHARPENTIER, Yvon DRÉANO et Gaël PIQUÈS

**621** Commerce et consommation de poissons à Saintes (Charente-Maritime, France) entre le Ier et le XIIe siècle. L'exemple du site de la Providence (Rue Bernard)
Brice EPHREM et Benoît CLAVEL

**635** Acquisition and consumption of animal resources in a coastal context: The Late Neolithic 1 occupation of La Crapaudière in Sainte-Marie-de-Ré (Charente-Maritime, France)
Anna BAUDRY, Christophe MAITAY, Caroline MOUGNE, Camielsa PRÉVOST, Yvon DRÉANO et Catherine DUPONT

**647** Consumption of shells, crustaceans and vertebrates at the end of the Iron Age: the shell midden AC3 in the Aber Braz cove on the Île de Sein (Brittany, France)
Aurélia BORVON, Catherine DUPONT, Louis DUTOUQUET, ORIANE DIGARD et Aurélie CLAUDE

**661** Les invertébrés et vertébrés marins de Vaux-sur-Mer (Charente-Maritime, France). Une exploitation des ressources marines durant le haut Moyen Âge en Saintonge
Brice EPHREM, Catherine DUPONT, Caroline MOUGNE et Damien DELAGE

**679** La maison forte du Goust (Malville, Loire-Atlantique), l'alimentation d'habitants aisés du XVIe siècle
Justine VORENGER
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# Romans see red!
## Updating our knowledge on dye extraction activities along the Atlantic coast of France through archaeomalacology

Catherine DUPONT

**Abstract:** The extraction of dyes from marine shells is a universal activity. This paper is a synthesis of our knowledge of this activity along the Atlantic coast of France from shells at archaeological sites. It represents an update since the first HOMER conference. On the Atlantic coast of France this activity is no longer practiced. Despite this discontinuation and a historical reference during the 18th century, archaeology reveals an activity that may have spread all along the French Atlantic coast and over a long period of time. Archaeological sites with systematically broken dog whelks *Nucella lapillus* and oyster drills *Ocenebra erinaceus* are known from Protohistory to the Middle Ages. Ten new sites have been identified since our synthesis in 2013. New excavations offer the possibility of setting the chronology of this activity more precisely, calling into question whether its origin was linked to Mediterranean influences. On some archaeological sites, it is possible to describe the evolution of dye extraction from the first attempts to its abandonment. Structures and tools associated with this exploitation of the dog whelk are described. Some elements are missing, such as for, example, cooking or storage containers. That absence is perhaps not a coincidence but is linked to the organisation of this activity.

**Keywords:** dye, dog whelk, murex, oyster drill, France, shells, maritime archaeology, Atlantic, Mediterranean influences, macrolithic.

## Les Romains voient rouge ! Mise à jour des connaissances sur l'extraction de colorant via l'archéomalacologie sur le littoral atlantique français

**Résumé :** L'extraction de colorant pourpre à partir de coquillages est universelle. Seules deux espèces liées à cette utilisation ont été identifiées le long du littoral atlantique français : le pourpre *Nucella lapillus* et le murex *Ocenebra erinaceus*. Cet article a pour but
de faire un bilan des avancées, sur l'extraction de colorant à partir de ces coquillages, 10 ans après le premier colloque HOMER : extension chronologique et géographique, différentes étapes du processus d'extraction, localisation des concentrations de coquilles tinctoriales sur le site archéologique, composition des dépotoirs coquilliers, autres artefacts liés à l'extraction de colorant à partir de coquillages. Il se base sur les restes coquilliers découverts lors de fouilles. À la rédaction de cet article au moins 39 sites archéologiques ont été répertoriés. Ils se matérialisent par des concentrations de pourpres systématiquement cassés. Les nouveaux sites archéologiques découverts depuis le premier bilan seront présentés.

Bien qu'oubliée aujourd'hui sur les côtes françaises, l'extraction de colorant à partir de ces coquillages se révèle être une activité qui s'est établie sur une longue durée ; c'est-à-dire de la Protohistoire au XIVe siècle AD. Un texte révèle la persistance de la connaissance des propriétés colorantes du pourpre au moins jusqu'à la moitié du XVIIIe siècle sur les côtes charentaises. Un sondage archéologique témoigne de cette activité dès le Bronze ancien (IIIe millénaire BC) sur notre zone d'étude. Une fouille programmée de plus grande ampleur permet de caler l'activité dès la Tène moyenne (IIIe siècle BC). Des hypothèses y seront proposées pour savoir sous quelles influences cette activité a pu se développer. Certains lieux semblent également en conserver la mémoire et la pratiquent sur plusieurs siècles. Les différentes étapes du traitement des coquillages pour extraire le colorant (de leur collecte sur l'estran à leur abandon dans les fossés) y

sont interrogées pour savoir si celles-ci ont été modifiées dans le temps. Malgré les changements techniques et socio-économiques qui ont pu intervenir sur ces sites, force est de constater une continuité dans les savoir-faire techniques utilisés.

Les artefacts qui sont liés à cette activité, autres que coquilliers, sont également interrogés. Les avancées sur ce sujet concernent entre autres, les outils utilisés pour cassés les coquillages. Ils correspondent soit à des galets, soit à des grands blocs de roche associés à des meules. Des foyers semblent également intervenir dans la production de colorant. Leur particularité est la présence d'un système permettant une chauffe indirecte du produit. La participation de l'eau douce et donc la présence d'un puits a aussi été identifiée sur au moins un des sites dédiés à cette activité. De petits instruments comme une pince à épiler ou une navette servant à repriser les filets ont été découverts dans les concentrations de coquilles. Ils restent anecdotiques. Leur rareté tout comme l'absence de récipients identifiés en lien avec cette activité n'est sans doute pas un hasard. Tous ont sans doute été récupérés voire réutilisés dans d'autres localités.

Bien que secondaire dans l'activité, le murex, similaire de par son aspect à ses cousins méditerranéens, peut être un témoin clé d'une influence extérieure en tant que catalyseur de cette activité.

Mots-clés : teinture, pourpre, murex, France, archéologie maritime, atlantique, influences méditerranéennes, marco-outillages, archéomalacologie.

## Introduction

Worldwide, more than thirty molluscs can produce purple dye (Haubrichs, 2004), and about fifteen are known to have been used by humans for their colouring properties (Cardon, 2007). Two species are found along the Atlantic coast of France: the dog whelk *Nucella lapillus* and the oyster drill also known as murex *Ocenebra erinaceus*. The term murex is generic and applies to several species worldwide, while the term oyster drill is used to specify the species *O. erinaceus*. Whilst both species *N. lapillus* and *O. erinaceus* have wide distribution ranges (Poppe and Goto, 1991), their use in dye production can be archaeologically documented in Ireland, England and France (Dupont, 2013).

Although the dyeing properties of these two shells, dog whelks and oyster drills, are known to biologists (Fretter and Graham, 1984) as well as historians (Cardon, 2007), their archaeological significance has remained unremarked in France for a long time. This is partly due to a collective amnesia, the difficulty of identifying this

activity at the time of excavation (Dupont, 2013) and the relatively recent development of archaeomalacofaunal analyses along the French Atlantic coast.

Despite the fact that the dyeing properties of these species have been forgotten by present-day coastal populations, at least two texts refer to them. One is by F. Henry (1952) who reports the correspondence of W. Cole (1685, p. 1288) in the late seventeenth century: "he heard of somebody living by the sea-side in some Port or creek in Ireland" who dyed linen kerchiefs with "some liquid substance taken out of a shell-fish". A more recent reference dating from the mid-18th century on the French coast was reported by F. Duhart (2019, p. 36). "On the coast of Lozières, a small whelk is collected, known by the common name of "burgau-morchou". Within this shell there is a small juice filled with a dark red liquor, which has a sort of relationship with the purple of the ancients; the inhabitants of Lozières mark their laundry with it "On ramaffe fur la côte de Lozieres, un petit buccin, connu par le vulgaire fous le
nom de burgau-morchou. Dans l'intérieur de ce coquillage, eft un petit fuc rempli d'une liqueur rouge foncé, laquelle a une forte de rapport avec la pourpre des anciens ; les habitans de Lozieres en marquent le linge" (Arcère, 1756, p. 8; fig. 1).

From the archaeologist's point of view, it is often
difficult to identify dog whelks and oyster drills shells
during excavation. They are often stained with sediment.
Their presence in the form of concentrations, evidence
for systematic breakage (fig. 2), and the low proportions
of the oyster drill compared to dog whelks are the key
criteria that make it possible to detect the extraction of dye
(Dupont, 2011).

The scarcity of analyses of molluscan purple-producing
sites was highlighted ten years ago (Dupont, 2013). The
aim of this article is to review the new archaeological
discoveries relating to this activity: geographical and
chronological extension, location in the archaeological
site of shell waste, composition of the shell middens, stages
of the dye extraction process, and the presence of other
artefacts related to the Mollusca in dye production.

1. Newly discovered sites

Ten new sites have been inventoried since the previous
synthesis (Dupont, 2013; fig. 1, n° 30-39; table 1). Several
shell deposits were discovered during surveys in the Îles
Chausey and on Île Dumet (fig. 3). Three others were
discovered during excavations undertaken to explore
research questions other than dye production: Fosses
Saint-Ursin, Mont-Castel and Le Dessous des Cotis. Dye
production was identified during the excavation itself
only for the last of these. The other five sites (Les Prés
Biard, Petit-Caux "Parc éolien Dieppe", Clos des Agneaux,
Le Parc, Bas-Verger), were the subject of excavations in
advance of development.

Among the challenges we set ourselves in 2013
(Dupont, 2013), there have been positive developments
in archaeomalacofaunal analyses (fig. 3). The average
time taken for these analyses to be completed after
excavation has reduced from 3 years 9 months during
the 2000s to 3 years since 2010. This delay in analysis has
resulted in the addition of new details and data on both
the chronology and the proportions of the species that are
present (table 1 and 2). Although the analysis of shells is
still not included in most archaeological research agendas,
the identification of dye extraction after an initial field
evaluation motivated the excavation of at least one site.
This was La Pouplinière, where the surface was littered
with dog whelk fragments (fig. 2, n° 1).

In terms of the geographical extension of dye
extraction, the main contribution in recent years has
been the discovery of eight sites on the north coast of
France (fig. 1, n° 32-39). This may be partly related to a
more systematic consideration of shells in excavations
in Normandy.

2. Purple extraction before the arrival of
the Romans

In the previous synthesis, we evidenced the broad
chronological extent of dye extraction, from Protohistory
to Middle Ages. The earliest excavated archaeological levels
dated from the Late La Tène period and new excavation,
at Les Prés-Biard, documents the extraction of dye as early
as Early La Tène. The upper chronological marker falls in
the 14th century. It is complemented by textual data that
attests to the sporadic use of the dyeing properties of dog
whelk south of the Loire in the mid-18th century.

Among the sites that preceded the Roman conquest,
Port-Blanc bears witness to shell accumulations as early as
the Middle La Tène period (Daire and Baudry, 2018). This
site is unique in the context of the French Atlantic coast with
extractive activities focused on the oyster drill (Ocenebra
erinaceus). On other sites, the oyster drill is always less
abundant than the dog whelk, with the species proportions
linked to their accessibility on the foreshore (Dupont,
2011). The oyster drill is less accessible as it is found on the
lowest levels of the foreshore and this generally reflected
in the more limited collection strategy for this species
compared to the dog whelk, i.e. the preferential selection
of large individuals (fig. 4, example of La Pouplinière). At
Port-Blanc, the exploitation pattern is different with both
dog whelks and oyster drills were collected regardless of
their size range (fig. 4). This deliberate search for oyster
drills on the lowest levels of the foreshore in the Middle
La Tène is unprecedented on the French Atlantic coast.
This strong pressure on the lowest foreshore is also
evident through the high proportion of a species of limpet
named *Patella aspera*. This unexpected focus on the oyster
drill may be a result of its physical resemblance to the
Mediterranean murex *Hexaplex trunculus*.

This larger size murex is the predominant species in
dye production in the Mediterranean region (Marzano,
2013) at this time across roman empire? Whilst the
Romans were not physically present in western Gaul
(Merlat, 1954; Galliou, 2016), in the Middle La Tène,
contacts existed across the Mediterranean area through
the transport of goods along the Atlantic coast. These long-
distance exports are documented from the early Iron Age
onwards, reaching as far as Ireland (Hill, 1995; Gibbons
and Gibbons, 2004). Sea-lanes, such as those proposed
for the first century AD, could already have been active
during the Middle La Tène period (Cunliffe, 1984). Thus, if
the production of purple dye was driven by Mediterranean
or Italian influences, they seem to predate the Roman
conquest (Dupont et al., 2023).

Mont-Castel provides evidence for the exploitation of
the dog whelk for its dyeing properties under the influence
of the Romans. The site was occupied from the Final
Bronze Age onwards, with evidence that the dog whelk
was eaten at that time. This species represented 10% of the
<figure><img src="image_14.png" /></figure>
malacofaunal assemblage (total MNI = 94) and the shells were not broken. In the Late La Tène, the proportion of dog whelk reaches 32% (table 2) and their shelly were being intentionally broken to extract the dye gland. This new practice at the end of the La Tène period was probably influenced by the arrival of Roman soldiers in north western France. The presence of Romans is also reflected in the consumption of flat oysters on this site.

Considering shellfish from the fieldwork stage onwards has also enabled significant progress in defining the chronology of dye extraction. At La Pouplinière, this process is evidenced from the second half of the 1st century AD to the end of the 1st century AD; at Le Dessous des Cotis, from the end of the 1st to the beginning of the 4th century; at Clos du Moulin, from the 5th to the 11th century; on Île Dumet, from the end of the 8th to the 10th century and at Le Parc, from the 6th to the 9th century.

The long-term duration of dye extraction at individual sites is therefore confirmed, even if that does not allow us to assume that this exploitation was continuous. Among the most striking examples of the longevity of these practices are the sites of Les Prés Biard (from Early La Tène to the Middle Ages) and Le Grand Essart (from Antiquity to the Middle Ages).

We can conclude that the use of dog whelk and oyster drill gastropods was practised not only over a wide geographical area, but also over a long period of time. According to the current state of research, there is a peak in this activity in the 1st century AD.

## 3. The stages of dye extraction

Several syntheses drawing on historical records describe the extraction of dye from marine molluscs, from the initial collection of shells to the use of the coloured pigments (e.g. Macheboeuf, 2020; Biggam, 2007; Cardon, 2007). What contribution to our understanding do these new archaeological results from the Atlantic coast of France make?

## 3.1. Shellfish gathering and storage

The very limited representation of oyster drill compared to dog whelk is a widespread feature in France (table 2). Three sites show percentages slightly higher than 1% of MNI: Port-Blanc, Les Prés Biard and La Pouplinière. At Port-Blanc, 1.5% of the oyster drills are linked to the oldest phase of occupation and possible Mediterranean influence. Unlike Port-Blanc, La Pouplinière does not show evidence for the collection of small-sized oyster drills (fig. 4). La Pouplinière and Les Prés Biard stand out from the other sites through the way in which the shells were broken. Is this particularity related to the high proportion of oyster drills in the dye extraction? It could be explained by the same external influences.

The management of the natural stock of dog whelk shellfish can be examined through metrical analysis of length. Port-Blanc has the highest levels of shellfish exploitation with 83% of individuals smaller than 20 mm (NMI = 5,798). The lowest average length falls in its last phase of occupation, and is evidence of very strong fishing pressure at this time. That may be the reason for the gradual disappearance of the resource, making dyeing activity at Port-Blanc unprofitable. Even if it was not the only cause for the final abandonment of the site, it may have been one of the catalysts. The Port-Blanc site is followed by ZA Pladreau (56% of individuals under 20 mm; N = 287), Clos du Moulin (44%; N = 2,065), Le Grand Essart (43%; N = 1,206), La Pouplinière (35%; N = 937) and Les Prés Biard (26%; N = 51).

Le Dessous des Cotis and Mont-Castel are exceptions despite a similar breakage pattern at most of sites. In the former, only 4.5% of the individuals are less than 20 mm long (N = 467) and for the latter 2.6% (N = 76). The selection of these tall sizes is in concordance with the selections observed for the food register. The selected mollusc are always superior to 20 mm from Prehistory to nowadays when shells are considered as food. This selection of large shells is also correlated with large hypobranchial glands with colouring properties.

(Opposite page) Fig. 1 – Location of archaeological sites with dog whelks *Nucella lapillus* associated with dyeing along the Atlantic coast of France: 1) La Plaine; 2) Sables-d'Or; 3) Granville; 4) Le Yaudet; 5) Pointe du Béron; 6) Prat; 7) Staol; 8) Tariec Vraz; 9) Borings 1 and 2, Île aux Moutons; 10) Île de Brunec; 11) Tréutan; 12) Port-Blanc; 13) Plage du Lomer; 14) Pen-Bé; 15) ZA du Pladreau; 16) Le Clos du Moulin; 17) La Cossonière-des-Rives; 18) La Pouplinière; 19) La Lucette; 20) Moulin Tillac; 21) Comtée; 22) La Cornillais; 23) ZAC des "Terres aux Moines"; 24) Les Missotières; 25) Le Grand Essart; 26) La Payré 2; 27) Champ du Bois; 28) Bel Air; 29) Les Plantes; 30) Le Dessous des Cotis; 31) Dumps C, E and H Île Dumet; 32) Les Prés Biard; 33) Petit-Caux "Parc éolien Dieppe"; 34) Île Chausey; 35) Fosse Saint-Ursin; 36) Clos des Agneaux; 37) Le Parc; 38) Bas-Verger; 39) Mont-Castel (CAD: C. Dupont).

(Page opposée) Fig. 1 – Localisation des sites archéologiques à pourpres *Nucella lapillus* utilisés à des fins tinctoriales sur le littoral atlantique français : 1) La Plaine ; 2) Sables-d'Or ; 3) Granville ; 4) Le Yaudet ; 5) Pointe du Béron ; 6) Prat ; 7) Staol ; 8) Tariec Vraz ; 9) Borings 1 et 2, Île aux Moutons ; 10) Île de Brunec ; 11) Tréutan ; 12) Port-Blanc ; 13) Plage du Lomer ; 14) Pen-Bé ; 15) ZA du Pladreau ; 16) Le Clos du Moulin ; 17) La Cossonière-des-Rives ; 18) La Pouplinière ; 19) La Lucette ; 20) Moulin Tillac ; 21) Comtée ; 22) La Cornillais ; 23) ZAC des « Terres aux Moines » ; 24) Les Missotières ; 25) Le Grand Essart ; 26) La Payré 2 ; 27) Champ du Bois ; 28) Bel Air ; 29) Les Plantes ; 30) Le Dessous des Cotis ; 31) Dumps C, E et H Île Dumet ; 32) Les Prés Biard ; 33) Petit-Caux « Parc éolien Dieppe » ; 34) Île Chausey ; 35) Fosse Saint-Ursin ; 36) Clos des Agneaux ; 37) Le Parc ; 38) Bas-Verger ; 39) Mont-Castel (DAO : C. Dupont).
<table><thead><tr><th>No. on the map</th><th>Sites</th><th>Town, administrative Department number</th><th>Level of archaeological intervention on shells</th><th>Chronology</th><th>Sources</th></tr></thead><tbody><tr><td>14</td><td>Pen-Bé</td><td>Assérac, 44</td><td>Survey</td><td>Unknown</td><td>Card 85.114.005 AP of the SRA Pays de la Loire in Dupont, 2013</td></tr><tr><td>13</td><td>Plage du Lomer</td><td>Pénestin, 56</td><td>Survey (surface collection)</td><td>Unknown</td><td>Jacquet, 2003; Dupont et al., 2018</td></tr><tr><td>11</td><td>Tréutan</td><td>Damgan, 56</td><td>Survey (surface collection)</td><td>Unknown</td><td>Y. Gruet in Dupont, 2013</td></tr><tr><td>5</td><td>Pointe du Béron</td><td>Roscoff, 29</td><td>Survey (surface collection)</td><td>Protohistory</td><td>Fischer, 1925</td></tr><tr><td>6</td><td>Prat</td><td>Santec, 29</td><td>Survey</td><td>Protohistory</td><td>Discovery J.-C. Le Goff and D. Roué; Cocaign, 1997</td></tr><tr><td>8</td><td>Tariec Vraz</td><td>Landéda, 29</td><td>Emergency survey (collection on sight)</td><td>Early Bronze Age</td><td>Pailler and Sparfel, 2008</td></tr><tr><td>32</td><td>Les Prés Biard</td><td>Erquy, 22</td><td>Excavation (sieving bulk soil samples)</td><td>Early La Tène; Late Antiquity; Early Middle Ages (7<sup>th</sup>-11<sup>th</sup>)</td><td>Excavation Inrap M. Levan in 2019; unpublished</td></tr><tr><td>12</td><td>Port-Blanc Île d'Hoedic</td><td>Quiberon, 56</td><td>Excavation (sieving bulk soil samples)</td><td>Middle La Tène to beginning of the Gallo-Roman period</td><td>Excavation M.-Y. Daire in 2005 / 2007-2010; Dupont in Daire and Baudry, 2018</td></tr><tr><td>9</td><td>Borings1 and 2 Île aux Moutons</td><td>Fouesnant, 29</td><td>Excavation (sieving bulk soil samples)</td><td>Late La Tène</td><td>Excavation G. Hamon in 2002; Dupont in Daire and Hamon, 2013</td></tr><tr><td>39</td><td>Mont-Castel</td><td>Port-en-Bessin, 14</td><td>Excavation (sieving bulk soil samples)</td><td>Late La Tène</td><td>Excavation Inrap C. Marcigny in 2015-2017; Dupont and Rupin, 2022</td></tr><tr><td>7</td><td>Staol</td><td>Santec, 29</td><td>Survey (surface collection)</td><td>La Tène to the Gallo-Roman period</td><td>Cocaign et al., 1995</td></tr><tr><td>15</td><td>ZA du Pladreau</td><td>Piriac-sur-Mer, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Late La Tène to the Gallo-Roman period</td><td>Excavation Inrap M.-L. Hervé in 2005; Hervé, 2007</td></tr><tr><td>27</td><td>Champ du Bois</td><td>Charron, 17</td><td>Excavation (sieving bulk soil samples)</td><td>La Tène to the Middle Ages</td><td>Excavation J. Guillement in 1973-1979; Y. Gruet in Guillement, 1978</td></tr><tr><td>28</td><td>Bel Air Île de Charron</td><td>Charron, 17</td><td>Survey</td><td>Gallo-Roman</td><td>Surveys Y. Gruet and Y. Bodeur in Dupont, 2013</td></tr><tr><td>3</td><td>Granville</td><td>Hillion, 22</td><td>Survey</td><td>Gallo-Roman</td><td>Cocaign, 1992</td></tr><tr><td>18</td><td>La Pouplinière</td><td>Saint-Michel-Chef-Chef, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Gallo-Roman (second half to the end of 1<sup>st</sup> AD)</td><td>Excavation Inrap D. Doyen in 2008/2009; Tessier, 2001; Dupont and Doyen, 2017</td></tr><tr><td>30</td><td>"Le Dessous des Cotis"</td><td>Commes, 14</td><td>Excavation (sieving bulk soil samples)</td><td>Gallo-Roman (end 1<sup>st</sup> AD to the beginning of the 4<sup>th</sup> AD)</td><td>Excavation C. Alline 2017; Dupont and Rupin, 2020</td></tr><tr><td>2</td><td>Sables-d'Or</td><td>Fréhel, 22</td><td>Survey</td><td>Gallo-Roman</td><td>Bizien-Jaglin, 2006</td></tr><tr><td>25</td><td>Le Grand Essart</td><td>Jard Sur Mer, 85</td><td>Excavation (sieving bulk soil samples)</td><td>Late Antiquity to the Middle Ages (5-10<sup>th</sup> AD)</td><td>Archaeological diagnostic Inrap X. Dubillot in 2006; Excavation Inrap D. Séris in 2007; Séris, 2009</td></tr><tr><td>16</td><td>Le Clos du Moulin</td><td>Piriac-sur-Mer, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Early Middle Ages (5<sup>th</sup>-11<sup>th</sup>)</td><td>Excavation Inrap M.-L. Hervé in 2011; Hervé-Monteil, 2014.</td></tr><tr><td>4</td><td>Le Yaudet</td><td>Ploulec'h, 22</td><td>Excavation (sieving bulk soil samples)</td><td>Early Middle Ages (666-775 AD)</td><td>Campbell, 2007, 2008</td></tr><tr><td>31</td><td>Dumps C, E et H de l'Île Dumet</td><td>Piriac-sur-Mer, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Early Middle Ages (end of the 8<sup>th</sup> to 10<sup>th</sup>)</td><td>Dupont and Rupin, 2018.</td></tr><tr><td>10</td><td>Île de Brunec, Archipel des Glénan</td><td>Fouesnant, 29</td><td>Excavation (sieving bulk soil samples)</td><td>Early Middle Ages</td><td>Le Goffic and Pichon, 1996</td></tr></tbody></table>

Table 1 – Geographical and chronological data for archaeological sites with dog whelks used in dyeing activity arranged according to chronological classification (in red: new since Dupont 2013).

Tabl. 1 – Données géographiques, chronologiques des sites archéologiques présentant des pourpres utilisés dans l'activité tinctoriale selon un classement chronologique (en rouge : nouveautés depuis Dupont 2013).
<table><thead><tr><th>No. on the map</th><th>Sites</th><th>Town, administrative Department number</th><th>Level of archaeological intervention on shells</th><th>Chronology</th><th>Sources</th></tr></thead><tbody><tr><td>23</td><td>ZAC des Terres aux Moines'</td><td>Pornic, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Early Middle Ages</td><td>Survey D. Joncheray in 1990; Gruet, 1993; Tessier, 2001</td></tr><tr><td>35</td><td>Fosses Saint-Ursin</td><td>Courseulles-sur-Mer, 14</td><td>Excavation</td><td>Early Middle Ages</td><td>Excavation C. Hanusse in 2015 unpublished</td></tr><tr><td>37</td><td>Le Parc</td><td>Colomby-Anguerny, 14</td><td>Excavation (sieving bulk soil samples)</td><td>Haut Moyen Âge (6<sup>th</sup>-9<sup>th</sup>)</td><td>Excavation Inrap V. Carpentier in 2016; Mougne, 2020</td></tr><tr><td>1</td><td>La Plaine Île de Tatihou</td><td>Saint-Vaast-La-Hougue, 50</td><td>Excavation (sieving bulk soil samples)</td><td>Middle Ages (11<sup>th</sup>-14<sup>th</sup>)</td><td>Excavation V. Carpentier in 2003; Carpentier, 2009</td></tr><tr><td>36</td><td>Clos des Agneaux</td><td>Clos des Agneaux, Préfailles, 44</td><td>Excavation (sieving bulk soil samples)</td><td>Late Middle Ages</td><td>Excavation Archeodenum J. Ménager in 2019; Mougne, 2021a</td></tr><tr><td>29</td><td>Les Plantes</td><td>Charron, 17</td><td>Excavation (sieving bulk soil samples)</td><td>Late Middle Ages (13<sup>th</sup>-14<sup>th</sup>)</td><td>Excavation E. Normand in 2002; Dupont 2013</td></tr><tr><td>26</td><td>La Payré 2</td><td>Jard Sur Mer, 85</td><td>Survey</td><td>Middle Ages</td><td>Card 85.114.005 AP of the SRA Pays de la Loire inventory; Dupont 2013</td></tr><tr><td>21</td><td>Comtée</td><td>La Plaine-sur-Mer, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001</td></tr><tr><td>22</td><td>La Cornillais</td><td>Pornic, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001</td></tr><tr><td>17</td><td>La Cossonière-des-Rives</td><td>Saint-Michel-Chef-Chef, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001</td></tr><tr><td>19</td><td>La Lucette</td><td>La Plaine, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001</td></tr><tr><td>24</td><td>Les Missotières</td><td>Bernerie-en-Retz, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001</td></tr><tr><td>20</td><td>Moulin Tillac</td><td>Préfailles, 44</td><td>Survey (sieving bulk soil samples)</td><td>Middle Ages</td><td>Tessier 2001, Survey Y. Gruet unpublished</td></tr><tr><td>33</td><td>Petit-Caux "Parc éolien Dieppe"</td><td>Le Tréport, 76</td><td>Excavation (sieving bulk soil samples)</td><td>In progress</td><td>Excavation Inrap C. Barbet in 2018-2019; unpublished</td></tr><tr><td>34</td><td>Île Chausey</td><td>Granville, 50</td><td>Survey (sieving bulk soil samples)</td><td>In progress</td><td>Survey H. Gandois in 2019-2020; Gandois et al. 2019</td></tr><tr><td>38</td><td>Bas-Verger</td><td>Maisons, 14</td><td>Excavation (sieving bulk soil samples)</td><td>In progress</td><td>Excavation Service archéologique du conseil général du Calvados A. Leffet in 2020; Mougne 2021b</td></tr></tbody></table>

Table 1 – Continued.

Tabl. 1 – Suite.

Thus, with the exception of the protohistoric site of Mont-Castel and the Gallo-Roman site “Le Dessous des Cotis”, the populations who collected the dog whelks did not hesitate to gather the smallest individuals from the rocks.

Once collected, these shells were either processed directly or stored so as to accumulate a large stock. Structures may have existed on the foreshore for the storage of live shellfish (Macheboeuf, 2020). They could be have been present on the Plage du Lomer (personal communication, L. Pirault). Prolonged storage of dog whelks and oyster drills can lead, if they are not fed, to them eating each other (Dupont, 2011). They attack their prey by piercing their shells leaving perforations. Complete and incomplete perforations have been systematically counted at La Pouplinière, Clos du Moulin and Le Dessous des Cotis. Overall they do not exceed 0.2%, and the proportions are lower than perforations observed on the mussels and oysters at the same sites. This does not indicate prolonged

storage of the dog whelks and oyster drills, unless they were fed during this period.

## 3.2. Dye extraction

In order to determine how the shells were broken to extract the dye, we have continued to apply the fragmentation typology described in Dupont (2011; fig. 5). This demonstrates, for all the analysed sites, that more than 96% of the dog whelks were broken by human action: 96% at Port-Blanc, 99% at Grand Essart, 99.1% at Saint-Ursin, 99.4% at Le Yaudet (Campbell, 2007), 99.5% at Île aux Moutons and on Île de Brunec (Le Goffic and Pichon, 1996), 99 to 99.6% on the Îles Chausey, 99.5 to 99.6% at ZA Pladreau, 97 to 99% on Le Dessous des Cotis, 97 to 100% on Île Dumet, 99.9% at Mont-Castel and 100% at La Plaine, Les Prés Biard, Le Clos du Moulin and 100% in most of the samples of La Pouplinière.

For most of the archaeological sites where the MNI of dog whelks exceeds 60, the breakage pattern is similar to that of Port-Blanc with the exception of La Pouplinière and Les Prés
<table><thead><tr><th rowspan="2">Number on the map</th><th rowspan="2">Sites</th><th colspan="3">Main other species</th><th colspan="2">Dog whelks N. et oyster drills O.</th><th rowspan="2">Sources</th></tr><tr><th>Name</th><th>%</th><th>MNI</th><th>%</th><th>MNI</th></tr></thead><tbody><tr><td>14</td><td>Pen-Bé</td><td></td><td>absence</td><td></td><td>100%</td><td>?</td><td>Card 85.114.005 AP of the SRA Pays de la Loire in Dupont, 2013</td></tr><tr><td>13</td><td>Plage du Lomer</td><td></td><td>absence</td><td></td><td>N. 100%</td><td>N. 12</td><td>Dupont et al., 2018</td></tr><tr><td>11</td><td>Tréutan</td><td>Patella sp.</td><td>presence</td><td></td><td>presence</td><td></td><td>Y. Gruet in Dupont, 2013</td></tr><tr><td>5</td><td>Pointe du Béron</td><td>Patella sp.</td><td>majority</td><td></td><td>minority</td><td></td><td>Fischer 1925</td></tr><tr><td>6</td><td>Prat</td><td>Patella sp.</td><td>majority</td><td></td><td>minority</td><td></td><td>J.-C. Le Goff and D. Roué cited in Cocaign, 1997</td></tr><tr><td rowspan="2">8</td><td rowspan="2">Tariec Vraz</td><td>Patella sp.</td><td>78%</td><td>91</td><td rowspan="2">N. 5%</td><td rowspan="2">N. 6</td><td rowspan="2">Dupont, 2013</td></tr><tr><td>Littorina obtusata</td><td>10%</td><td>12</td></tr><tr><td rowspan="12">32</td><td rowspan="12">Les Prés Biard</td><td>Fait 1066 Early La Tène</td><td>Patella sp.</td><td>36%</td><td>11</td><td rowspan="2">N. 38% O. 4%</td><td rowspan="2">N. 19 O. 4</td><td rowspan="12">Dupont and Rupin, 2021</td></tr><tr><td>Mytilius edulis</td><td>22%</td><td>18</td></tr><tr><td>Fait 1149 Late Antiquity or Early Middle Ages</td><td>Patella sp.</td><td>35%</td><td>14</td><td rowspan="2">N. 30% O. 3%</td><td rowspan="2">N. 12 O. 1</td></tr><tr><td>Mytilius edulis</td><td>18%</td><td>7</td></tr><tr><td>Fait 1210 Early Middle Ages</td><td>Patella sp.</td><td>19%</td><td>77</td><td rowspan="2">N. 36% O. 1%</td><td rowspan="2">N. 146 O. 4</td></tr><tr><td>Mytilius edulis</td><td>43%</td><td>174</td></tr><tr><td>Fait 1140 Early Middle Ages</td><td>Mytilius edulis</td><td>2%</td><td>20</td><td>N. 90% O. 7%</td><td>N. 1181 O. 90</td></tr><tr><td>Fait 1317 Early Middle Ages</td><td>Patella sp.</td><td>18%</td><td>370</td><td rowspan="2">N. 65% O. 3%</td><td rowspan="2">N. 1356 O. 58</td></tr><tr><td>Mytilius edulis</td><td>14%</td><td>292</td></tr><tr><td>Fait 1133 Early Middle Ages</td><td>Patella sp.</td><td>80%</td><td>375</td><td rowspan="2">N. 13% O. 0.2%</td><td rowspan="2">N. 62 O. 1</td></tr><tr><td>Mytilius edulis</td><td>6%</td><td>29</td></tr><tr><td rowspan="12">12</td><td rowspan="12">Port-Blanc</td><td>Phase 1 / Middle La Tène</td><td>Patella sp.</td><td>77.17%</td><td>514</td><td rowspan="2">N. 0.60% O. 1.50%</td><td rowspan="2">N. 4 O. 10</td><td rowspan="12">Daire and Baudry, 2018</td></tr><tr><td>Phorcus lineatus</td><td>3.15%</td><td>21</td></tr><tr><td>Phase 2 / Late La Tène</td><td>Patella sp.</td><td>88.02%</td><td>222062</td><td rowspan="2">N. 5% O. 0.10%</td><td rowspan="2">N. 3070 O. 56 X</td></tr><tr><td>Mytilius edulis</td><td>3.30%</td><td>1860</td></tr><tr><td>Phase 3 / Late La Tène</td><td>Patella sp.</td><td>84.46%</td><td>19635</td><td rowspan="2">N. 6% O. 0.25%</td><td rowspan="2">N. 1421 O. 59</td></tr><tr><td>Phorcus lineatus</td><td>5.15%</td><td>1198</td></tr><tr><td>Phase 3-4 / Late La Tène</td><td>Patella sp.</td><td>64.68%</td><td>9816</td><td rowspan="2">N. 26% O. 0.30%</td><td rowspan="2">N. 3951 O. 46</td></tr><tr><td>Mytilius edulis</td><td>6.89%</td><td>1046</td></tr><tr><td>Phase 4-5 / End 1<sup>st</sup> BC- Beginning 1<sup>st</sup> AD</td><td>Patella sp.</td><td>58.40%</td><td>8156</td><td rowspan="2">N. 37.74% O. 0.26%</td><td rowspan="2">N. 5270 O. 36</td></tr><tr><td>Phorcus lineatus</td><td>1.47</td><td>205</td></tr><tr><td rowspan="2">9</td><td rowspan="2">île aux Moutons</td><td>Sondage 1</td><td>Patella sp.</td><td>33%</td><td>39</td><td rowspan="2">N. 66% N. 79</td><td rowspan="2">Daire and Hamon, 2013</td></tr><tr><td>Sondage 2</td><td>Patella sp.</td><td>53%</td><td>288</td></tr><tr><td rowspan="3">39</td><td rowspan="3">Mont-Castel</td><td>Mytilius edulis</td><td>48%</td><td>1070</td><td rowspan="3">N. 32% O. 0.04%</td><td rowspan="3">N. 723 O. 1</td><td rowspan="3">Dupont and Rupin, 2022</td></tr><tr><td>Patella sp.</td><td>11%</td><td>245</td></tr><tr><td>Ostrea edulis</td><td>5%</td><td>56</td></tr><tr><td>7</td><td>Staol</td><td>Patella sp.</td><td>majority</td><td></td><td>minority</td><td></td><td>Cocaign, 1997</td></tr></tbody></table>

Table 2 – Composition of shell deposits with broken dog whelks and oyster drills (MNI: Minimum Number of Individuals; in red: new since Dupont 2013).

Tabl. 2 – Proportions des pourpres et les mureux par rapport aux espèces majorités découvertes (en rouge: nouveautés depuis Dupont 2013).
<table><thead><tr><th rowspan="2">Number on the map</th><th rowspan="2">Sites</th><th colspan="3">Main other species</th><th colspan="2">Dog whelks N. et oyster drills O.</th><th rowspan="2">Sources</th></tr><tr><th>Name</th><th>%</th><th>MNI</th><th>%</th><th>MNI</th></tr></thead><tbody><tr><td rowspan="4">15</td><td rowspan="4">ZA du Pladreau</td><td rowspan="2">FO1406</td><td>Patella sp.</td><td>30%</td><td>1057</td><td>N. 66%<br>O. 0.11%</td><td>N. 2314<br>O. 4</td><td rowspan="4">Dupont, 2013</td></tr><tr><td>Mytilius edulis</td><td>3%</td><td>107</td><td></td><td></td></tr><tr><td rowspan="2">US1246</td><td>Patella sp.</td><td>78%</td><td>585</td><td>N. 15%<br>O. 0.13%</td><td>N. 110<br>O. 1</td></tr><tr><td>Ostrea edulis</td><td>3%</td><td>21</td><td></td><td></td></tr><tr><td>27</td><td colspan="2">Champ du Bois</td><td colspan="2">presence</td><td colspan="2">presence</td><td>Y. Gruet; Dupont, 2013</td></tr><tr><td>28</td><td colspan="2">Bel Air Île de Charron</td><td colspan="2">Ostrea edulis</td><td colspan="2">minority</td><td>Y. Gruet and Y. Bodeur; Dupont, 2013</td></tr><tr><td>3</td><td colspan="2">Granville</td><td colspan="2">absence</td><td colspan="2">100%</td><td>Cocaign, 1992</td></tr><tr><td rowspan="2">18</td><td rowspan="2">La Pouplinière</td><td rowspan="2"></td><td>Patella sp.</td><td>15%</td><td>73</td><td>81%</td><td>385</td><td rowspan="2">Tessier, 2001</td></tr><tr><td>Patella sp.</td><td>1%</td><td>182</td><td>N. 94.90%<br>O. 2%</td><td>N. 17179<br>O. 378</td></tr><tr><td rowspan="2">30</td><td rowspan="2">"Le Dessous des Cotis"</td><td rowspan="2"></td><td>Patella sp.</td><td>37%</td><td>3 280</td><td>N. 18%<br>O. 0.1%</td><td>N. 1 582<br>O. 9</td><td rowspan="2">Dupont and Rupin, 2020</td></tr><tr><td>Mytilius edulis</td><td>36%</td><td>3 189</td><td></td><td></td></tr><tr><td>2</td><td colspan="2">Sables-d'Or</td><td colspan="2">absence</td><td colspan="2">100%</td><td>Bizien-Jaglin, 2006</td></tr><tr><td rowspan="4">25</td><td rowspan="4">Le Grand Essart</td><td rowspan="2">1<sup>st</sup> AD</td><td>Patella sp.</td><td>75%</td><td>555</td><td>N. 13%</td><td>N. 96</td><td rowspan="4">Séris, 2009</td></tr><tr><td>Cearstoderma edule</td><td>6%</td><td>44</td><td>O. 0%</td><td>O. 0</td></tr><tr><td rowspan="2">6<sup>th</sup>-10<sup>th</sup></td><td>Patella sp.</td><td>15%</td><td>1618</td><td>N. 72%</td><td>N. 7660</td></tr><tr><td>Cearstoderma edule</td><td>5%</td><td>504</td><td>O. 0.20%</td><td>O. 21</td></tr><tr><td rowspan="2">16</td><td rowspan="2">Le Clos du Moulin</td><td rowspan="2"></td><td>Patella sp.</td><td>32%</td><td>9 419</td><td>N. 61%</td><td>N. 17 764</td><td rowspan="2">Hervé-Monteil, 2014</td></tr><tr><td>Ruditapes decussatus</td><td>1.6%</td><td>477</td><td>O. 0.4%</td><td>O. 118</td></tr><tr><td rowspan="2">4</td><td rowspan="2">Le Yaudet (Us708)</td><td rowspan="2"></td><td>Patella sp.</td><td>84%</td><td>2623</td><td>5%</td><td>160</td><td rowspan="2">Campbell, 2008</td></tr><tr><td>Mytilius edulis</td><td>8%</td><td>233</td><td></td><td></td></tr><tr><td rowspan="4">31</td><td rowspan="2">Dump C, Île Dumet</td><td rowspan="2"></td><td>Patella sp.</td><td>73%</td><td>201</td><td>N. 13%</td><td>N. 37</td><td rowspan="4">Dupont and Rupin, 2018</td></tr><tr><td>Mytilius sp.</td><td>8%</td><td>23</td><td>O. 2%</td><td>O. 5</td></tr><tr><td rowspan="2">Dump r E, Île Dumet</td><td>Patella sp.</td><td>55%</td><td>343</td><td>N. 42%<br>O. 0%</td><td>N. 260<br>O. 0</td></tr><tr><td>Patella sp.</td><td>18%</td><td>28</td><td>N. 64%</td><td>N. 99</td></tr><tr><td>35</td><td colspan="2">Fosses Saint-Ursin</td><td colspan="2">absence</td><td colspan="2">100%</td><td>Le Goffic and Pichon, 1996</td></tr><tr><td rowspan="4">10</td><td rowspan="4">Île de Brunec</td><td rowspan="4"></td><td>Patella sp.</td><td>32%</td><td>422</td><td>34%</td><td>284</td><td rowspan="4">Tessier, 2001</td></tr><tr><td>Mytilius edulis</td><td>11%</td><td>90</td><td></td><td></td></tr><tr><td rowspan="2">Cearstoderma edule</td><td>7%</td><td>16</td><td>N. 82%</td><td>N. 221</td></tr><tr><td>Ostrea edulis</td><td>2%</td><td>6</td><td>O. 6%</td><td>O. 16</td></tr><tr><td>37</td><td colspan="2">Le Parc</td><td colspan="2">presence</td><td colspan="2">N. et O. presence</td><td>Mougne, 2020</td></tr><tr><td rowspan="4">1</td><td rowspan="4">La Plaine</td><td rowspan="2">C44</td><td>Patella sp.</td><td>59%</td><td>3015</td><td>5%</td><td>236</td><td rowspan="4">Dupont, 2013</td></tr><tr><td>Mytilius edulis</td><td>32%</td><td>1606</td><td></td><td></td></tr><tr><td rowspan="2">CO36</td><td>Littorina littorea</td><td>52%</td><td>342</td><td>29%</td><td>191</td></tr><tr><td>Patella sp.</td><td>9%</td><td>61</td><td></td><td></td></tr><tr><td rowspan="2">36</td><td rowspan="2">Clos des Agneaux</td><td rowspan="2"></td><td>Mytilius edulis</td><td>77%</td><td>261</td><td>N. 11%</td><td>N. 36</td><td rowspan="2">Mougne, 2021a</td></tr><tr><td>Ostrea edulis</td><td>4%</td><td>13</td><td>O. 0.9%</td><td>O. 3</td></tr></tbody></table>

Table 2 – Continued.

Tabl. 2 – Suite.
<table><thead><tr><th rowspan="2">Number on the map</th><th rowspan="2">Sites</th><th colspan="3">Main other species</th><th colspan="2">Dog whelks N. et oyster drills O.</th><th rowspan="2">Sources</th></tr><tr><th>Name</th><th>%</th><th>MNI</th><th>%</th><th>MNI</th></tr></thead><tbody><tr><td>29</td><td>Les Plantes</td><td></td><td>presence</td><td></td><td>presence</td><td></td><td>E. Normand in Dupont, 2013</td></tr><tr><td>26</td><td>La Payré 2</td><td></td><td>absence</td><td></td><td>100%</td><td></td><td>Card 85.114.005 AP of the SRA Pays de la Loire inventory; Dupont, 2013</td></tr><tr><td>21</td><td>Comtée</td><td></td><td>absence</td><td></td><td>100%</td><td>105</td><td>Tessier, 2001</td></tr><tr><td rowspan="2">22</td><td rowspan="2">La Cornillais</td><td>Littorina littorea</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Patella sp.</td><td>presence</td><td></td><td>&lt;50%</td><td>44</td><td>Tessier, 2001</td></tr><tr><td rowspan="2">17</td><td rowspan="2">La Cossonière-des-Rives</td><td>Mytilus sp.</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Littorina littorea</td><td>&lt;28%</td><td>80</td><td></td><td></td><td></td></tr><tr><td rowspan="3">19</td><td rowspan="3">La Lucette</td><td>Patella sp.</td><td>&lt;25%</td><td>71</td><td></td><td></td><td></td></tr><tr><td>Littorina littorea</td><td>33%</td><td>80</td><td></td><td></td><td></td></tr><tr><td>Patella sp.</td><td>8%</td><td>20</td><td></td><td>11%</td><td>27</td><td>Tessier, 2001</td></tr><tr><td rowspan="2">24</td><td rowspan="2">Les Missotières</td><td>Mytilus sp.</td><td>41%</td><td>100</td><td></td><td></td><td></td></tr><tr><td>Littorina littorea</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>20</td><td>Moulin Tillac</td><td>Patella sp.</td><td>1%</td><td>4</td><td>97%</td><td>329</td><td>Tessier, 2001</td></tr><tr><td>33</td><td>Petit-Caux "Parc éolien Dieppe"</td><td></td><td>presence</td><td></td><td>presence</td><td></td><td>Barbet, unpublished</td></tr><tr><td>34</td><td>Île Chausey</td><td>Patella sp. presence</td><td></td><td></td><td>N. and O. presence</td><td></td><td>Gandois et al., 2019</td></tr><tr><td>38</td><td>Bas-Verger</td><td>Mytilus edulis presence</td><td></td><td></td><td>N. and O. presence</td><td></td><td>Mougne, 2021b</td></tr></tbody></table>

Table 2 – Continued.

Tabl. 2 – Suite.

Biard (fig. 5). The shells were broken at the suture between the last and the penultimate spire (types 2 and 3). The area opened corresponds to the location of the hypobranchial gland which has the colouring properties. This process indicates individual extraction of each shell (Dupont, 2013). On the other hand, the fragmentation typology has demonstrated the crushing of shells at La Pouplinière and Les Prés Biard (fig. 5). The macrolithic tools used in this process were identified at both sites. At the former, large blocks of stone were used to crush them *en masse*, whilst at the latter the molluscs were crushed one by one with a pebble.

Few dog whelk shells were found intact during the excavations. These complete shells are small: at ZA Pladreau (5 shells less than 17 mm long), on Île aux Moutons (two individuals 15 and 16 mm), at Yaudet (one individual 19 mm) (Campbell, 2007), at ZAC des Terres aux Moines (Hasselin and Joncheray, 1990), at Le Dessous des Cotis (6 of 15 intact individuals measure less than 10 mm), at Clos du Moulin (33 out of 48 type 0 individuals less than 10 mm), at Les Prés Biard (7 intact individuals out of 51: 5 between 17 and 19 mm; 3 below 15 mm), Île Dumet (of 10 type 0 dog whelks, 5 less than 10 mm), Le Grand Essart (of 21 whole purples: half less than 20 mm). On other sites,

as for example Port-Blanc, Mont-Castel and La Pouplinière, the presence of intact shells seems to result from the combination of two uses of the dog whelks, on a large scale for dye extraction (represented by a high proportion of small individuals), and more sporadically for consumption.

### 3.3. Waste disposal

The shell waste from dye extraction were disposed of in pits or ditches. Sometimes, they were dumped on the ground in island environments or reused to stabilise roads (Dupont and Doyen, 2017).

The dyeing properties of the dog whelk flesh are restricted to the hypobranchial gland, which is about 1 mm wide and 5 mm long. It is difficult to tell from the shells alone whether the gland was extracted individually or whether a bath was made in which all the shell debris attached to flesh was submerged. The presence in the same deposit of the different shell wastes (type 2 to 8) tends to suggest that the shell remains were abandoned immediately after the shells were broken. The flesh amputated from the dye gland does not appear to have been consumed.

The differences in composition of the shell middens associated with dog whelks has not gone unnoticed
<figure><img src="image_15.png" /></figure>

Fig. 2 – View of dog whelk concentrations 1 A-C: 1) La Pouplinière, from general view to detail; 2) ZA du Pladreau; 3) Le Grand Essart; 4) « Le Dessous des Cotis » (CAD: C. Dupont).

Fig. 2 – Vues des concentrations de pourpres 1 A-C : 1) La Pouplinière de la vue générale à celle de détail ; 2) ZA du Pladreau ; 3) Le Grand Essart ; 4) « Le Dessous des Cotis » (DAO : C. Dupont).

<figure><img src="image_16.png" /></figure>

Fig. 3 – Number of archaeological sites with dye extraction from shells known, excavated and studied since the 1920s (CAD: C. Dupont).

Fig. 3 – Nombre de sites archéologiques avec extraction de colorant sur coquillages connus, fouillés et étudiés depuis les années 20 (DAO : C. Dupont).

(Cocaign, 1997; Tessier, 2001). Those associated with food waste constituted 32 of the 39 sites considered in this study (table 2). For at least seven of them, the presence of stratified deposits of dog whelks was noted (Staol, Île aux Moutons, Port-Blanc, ZA du Pladreau, Le Grand Essart, La Pouplinière and Le Clos du Moulin). Thus, depending on whether one takes the composition of these deposits as a whole or analyses them as successive events, dyeing can be interpreted as a more or less specialised activity.

## 3.4. Structuring of space and associated structures

As noted above, once the shell is broken, the dye gland is extracted. Different processes are used to prepare and preserve the dye (Cardon, 2007; Macheboeuf, 2020). This diversity and the chronological variability in this activity do not allow standardised structures to be described.

The Dessous des Cotis site has hearths (Allinne et al., 2017) necessary for the indirect heating of the dog whelks (Macheboeuf, 2020). Similarly, a 70 cm wide linear stony
Port-Blanc - Dog whelks

<figure><img src="image_17.png" /></figure>

La Pouplinière - Dog whelks

<figure><img src="image_18.png" /></figure>

Port-Blanc - Dog whelks (N=5798; Moyenne=17mm)

<figure><img src="image_19.png" /></figure>

La Pouplinière - Dog whelks (N=937, Moyenne=22mm)

<figure><img src="image_20.png" /></figure>

Port-Blanc - Oyster drills

<figure><img src="image_21.png" /></figure>

La Pouplinière - Oyster drills (N=102, Moyenne=19mm)

<figure><img src="image_22.png" /></figure>

Fig. 4 – Histograms of dog whelk and oyster drills lengths at Port-Blanc and La Pouplinière (CAD: C. Dupont).

Fig. 4 – Longueurs des pourpres et des murex exploités à Port-Blanc et à La Pouplinière (DAO : C. Dupont).
Le Dessous des Cotis

<figure><img src="image_23.png" /></figure>

0

<figure><img src="image_24.png" /></figure>

<figure><img src="image_25.png" /></figure>

1

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /></figure>

2

<figure><img src="image_28.png" /></figure>

<figure><img src="image_29.png" /></figure>

3

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /></figure>

4

<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

5

<figure><img src="image_34.png" /></figure>

6

<figure><img src="image_35.png" /></figure>

7

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /></figure>

8

<figure><img src="image_38.png" /></figure>

0 1cm

Port-Blanc (N=91314)

Nucella lapillus

<figure><img src="image_39.png" /></figure>

La Pouplinière / Ditch 297- Level 2 (N=25658)

Nucella lapillus

<figure><img src="image_40.png" /></figure>

Port-Blanc (N=1116)

Ocenebra erinaceus

<figure><img src="image_41.png" /></figure>

La Pouplinière / Ditch 297- Level 2 (N=2770)

Ocenebra erinaceus

<figure><img src="image_42.png" /></figure>

Fig. 5 – Typology of broken dog whelk fragments (CAD: C. Dupont).

Fig. 5 – Typologie de fragmentation des pourpres (DAO : C. Dupont).
structure appears to lead to a pit at a building dedicated to this activity (Dupont and Doyen, 2017). Similar heating systems were discovered at Les Prés Biard (personal communication, M. Levan).

At La Pouplinière, dye extraction was developed within a rectangular enclosure with a surface area of 750 m² that had an internal partition probably structuring the different work spaces (a well, a building on stone foundations) (Dupont and Doyen, 2017).

In the known historic recipes, salt was used preserve the qualities of the dye glands for several months (Macheboeuf, 2020). Although there is evidence for salt production at La Pouplinière, Champ du Bois, Le Lomer and Port-Blanc, the peak of this activity was not synchronous with the exploitation of the largest number of dog whelks (Dupont and Doyen, 2017; Daire and Baudry, 2018).

### 3.5. Simple tools for a prestigious product

The evidence for shell processing tools is very sporadic. At Le Lomer, the survey team observed several slabs of schist 20 to 40 cm wide that could have served as anvils. On one of them, an oblong sandstone pebble (12 x 5 x 3.5cm), with obvious traces of abrasion, was found (Jacquet, 2003). On the Île de Brunec, Le Goffic and Pichon (1996) recall the discovery of a “primitive anvil by the 1926 excavators” which “could well have been used to break shells”. At Port-Blanc, a number of macrolithic tools recovered could have been used to break the dog whelk shells: nine pestles on quartz or quartzite pebbles and several anvils or even a mortar (Donnart in Daire and Baudry (eds.), 2018). At La Pouplinèire, a few schist blocks with an average diameter of 60 cm served as anvils. These were associated with 20 cm blocks of quartz which were probably used to crush the shells. Similarly, at the Les Prés Biard site, numerous elongated pebbles have been discovered (unpublished by M. Levan) and may well have been used to crush the dog whelks.

Despite all the efforts of archaeologists in the field, no container with residues of purple dye has been identified. The evidence for the processes and tools that could have been used to break the shells is very limited. This is due to the fact that the dog whelk shells are found in areas of discard that may be slightly separated spatially from the activity areas. On the other hand, at sites with a long chronology and varied activities, the use of the shellfish as dye may have been seasonal or have ceased before the site was abandoned and the associated activity areas dismantled.

A pair of tweezers was found in a concentration of dog whelks at La Pouplinière. This tool could have been used either to extract the gland from the animal or to remove floating waste in mixtures of crushed shell with adjuvants (Dupont and Doyen, 2017). Artefacts associated with fish net production or repair could be evidence for the storage of gastropods in nets prior to their mass processing

(Dupont and Doyen, 2017). A metal shuttle used to darn fisherman's nets was found in the vicinity of a dye gland processing area in Spain (Bernal Casasola et al., 2008).

The evidence for the processes and tools that could have been used to break the shells is very limited. This is due to the fact that the dog whelk shells are found in areas of discard that may be slightly separated spatially from the activity areas. On the other hand, at sites with a long chronology and varied activities, the use of the shellfish as dye may have been seasonal or have ceased before the site was abandoned and the associated activity areas dismantled.

### 3.6. The use of the dye

Several uses for the dye are known: dyeing textile fibres, tattooing, wall painting and illuminated manuscripts (Haubrichs, 2004; Cardon, 2005). Unfortunately, there is no evidence to link a specific activity to any of the listed sites.

### Conclusions

The synthesis offered here shows that the extraction of dye from dog whelks along the Atlantic coast of France is far from being an epiphenomenon. This exploitation extends over the entire natural geographical distribution area of the dog whelk and across a chronology that extends from the Iron Age, or even the Early Bronze Age, to the 14th century, or even the middle of the 18th century. Of the 39 sites recorded, 15 have only been reported in the last 10 years (fig. 2) and have been discovered by means of archaeological excavations with targeted sampling and sieving. This number is probably a significant underestimate since this activity is not always detectable at the time of excavation. In addition to this difficulty of identification, there is also the difficulty of distinguishing a set of tools specific to dye extraction. The latter may be linked to several factors: the rudimentary nature of certain tools; the diachronic nature of the activity, which means that the instruments used may have varied over time; the retrieval of the most precious objects such as cooking vessels, for example; the fact that the structures visible during excavation could have been associated with other activities; the abandonment of dye extraction before that of the site; the seasonal nature of the activity and the accumulation of different activities on a single site.

The composition of the dog whelk dumps is far from homogeneous. The percentage representation of this species varies with respect to the species that were consumed. However, we have noted that the overall composition of a pit or ditch fill says nothing about the specialisation of the activity because these structures correspond to a succession of specialised and domestic activities. The analysis of each site allows us to follow the evolution of dye extraction, such as initial testing, its intensification or even its abandonment. The under-representation of oyster drills compared to dog whelks seems to be linked to the potential to access to
this resource that was less prolonged, limited to the time
of a tide.

At most sites, the sustainable management of the
natural stocks of dog whelks is not identifiable. Shell
measurements show that all specimens from small to large
were collected at low tide. This behaviour shows a strategy
focus on maximising the quantity profit with no desire to
perpetuate the activity.

Dye extraction as a process is far from homogeneous
and hard to identify. Anticipating the use of Mollusca in
dye production at the time of excavation allows a better
description of its chronology and its evolution at a given
site. Placed in the socio-economic context of each period,
dye extraction is perhaps one of the markers of the modes

and influences that may have had an impact on the
presence of human populations on the coast and islands.
Dye is a product of high added value that can be traded
across international commercial networks.

## Acknowledgements

I am grateful to all the persons in charge of excavations,
and to the discoverers of the sites, who allowed me to study
the shells and to Caroline Mougne who gave me access to
her unpublished reports and authorized me to cite it. I also
want to thank Chis Scarre who kindly agreed to correct my
English. I would like to thank Jacqui Mulville who helped
me to improve the quality of the manuscript.

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## Author's contact information / Coordonnées de l'auteur

Catherine DUPONT, CNRS, CReAAH UMR 6566, Campus Beaulieu, bât. 24-25, université de Rennes, CS74205, 35042 Rennes CEDEX, France.

Mail : catherine.dupont@univ-rennes.fr
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