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the third stage from the bottom of the middle section of the Jurassic System (Period). It was differentiated by the Belgian geologist Omalius d’Halloy in 1843. A typical cross section is composed of oolithic limestones that are clayey on the top. A complex of ammonites, such as Parkinsonia parkinsoni, Oppelia aspidoides, and others, is the predominant fauna. Deposits of the Bathonian Stage are known in many countries of Western Europe. In the USSR, Bathonian marine deposits are found in the Crimea, the Caucasus, the Volga Region, the Soviet Far East, and the lower course of the Lena River.