The Choptank Formation is part of the Chesapeake Group. The formation receives it's name from the Choptank River, Maryland. The Choptank Formation is confined to the Southeastern portion of Prince George's County. The Choptank Formation lies uncon- formably upon the Calvert formation. The unconformity is in the nature of an overlap, but is not easily discernible even where the contact is visible. The best place to observe the unconformity is in the portion of the Calvert Cliffs just below the mouth of Parker Creek. Even here it can not be seen from the beach, but is visible from a boat a short distance from the shore. This unconformity is also proved by the fact that at the above-mentioned locality the fossil- iferous bed which lies lowest in the Choptank formation rests upon the Calvert,