The Dauphin reference article from the English Wikipedia on 24-Jul-2004
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Dauphin

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The Dauphin was the heir apparent to the throne of France under the Valois and Bourbon dynasties.

Guy VIII, Count of Vienne, had a dolphin on his coat of arms and had been nicknamed le Dauphin (French for dolphin). The title of Dauphin du Viennois descended in his family till 1349, when Humbert II sold his seigneurie, called the Dauphiné, to King Philippe VI on condition that the heir of France assumed the title of le Dauphin.

The first French prince called le Dauphin was Jean II, who succeeded Philippe. The last was the Duc d'Angoulême, son of Charles X, who renounced the title in 1830.

List of Dauphins, 1349-1830

Dauphin is also the name of a commune in the Alpes-de-Haute-Provence département, in France