One of its representatives formed a branch in Picardy in the reign of Louis XIV.
or later.
Lamarck's grandfather, Philippe de Monet, "seigneur de Bazentin et autres lieux," was also "chevalier de l'ordre royal et militaire de Saint-Louis, commandant pour le roi en la ville et chateau de Dinan, pensionnaire de sa majeste." The descendants of Philippe de Lamarck were, adds de Cauna, thus thrown into two branches, or at least two offshoots or stems (_brisures_), near Peronne.

But the actual posterity of the Monet of Picardy was reduced to a single family, claiming back, with good reason, to a southern origin.
One of its scions in the maternal line was a brilliant officer of the military marine and also son-in-law of a very distinguished naval officer.
The family of Monet was represented among the French nobility of 1789 by Messires de Monet de Caixon and de Monet de Saint-Martin.

By marriage their grandson was connected with an honorable family of Montant, near Saint-Sever-Cap.
Another authority, the Abbe J.Dulac, has thrown additional light on the genealogy of the de Lamarck family, which, it may be seen, was for at least three centuries a military one.[6] The family of Monet, Seigneur de Saint-Martin et de Sombran, was maintained as a noble one by order of the Royal Council of State of June 20, 1678.

He descended (I) from Bernard de Monet, esquire, captain of the chateau of Lourdes, who had as a son (II) Etienne de Monet, esquire, who, by contract dated August 15, 1543, married Marguerite de Sacaze.

He was the father of (III) Pierre de Monet, esquire, "Seigneur d'Ast, en Bearn, guidon des gendarmes de la compagnie du roi de Navarre." From him descended (IV) Etienne de Monet, esquire, second of the name, "Seigneur d'Ast et Lamarque, de Julos." He was a captain by rank, and bought the estate of Saint-Martin in 1592.