Ypresian Stage

(named for the city of Ypres), one of the stages of the middle division of the Paleogene system. It was differentiated by the Belgian geologist Dumont in 1849. In a type locality the stage is composed of a series of so-called Flanders clays (Londinian stage), overlaid by sands containing shells of Protozoa—nummulites (Nummulitesplanulatus). It usually corresponds to the Bakhchisarai strata of the Crimea-Caucasus region.