Gypseous Series
in geology, the lower freshwater limestone and marl constituting the Upper beds of the Middle Eocene in the vicinity of Paris, France. They are of white and green marls with subordinate beds of gypsum.
At the Hill of Montmartre is a quarry of gypsum valuable for the manufacture of plaster of Paris. Splendid fossil remains of Eocene mammals have been found in it. Similar gypseous marls are worked for gypsum at St. Romain, on the right bank of the Allier.