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to be Fox Hills laminated sandstone appear and the beds become buff-colored in places. Over most of the area between the mouth of the Big Dry and the Musselshell the Fox Hills is about 60 ft thick. Opposite to Mr. John Willis ranch on the east side of the Big Dry 38 miles S. of Glasgow a 4 in. stratum of shells was found near the top of the marine beds. They are Corbulas and are overlaid by a compact six in stratum of limestone. This stratum was estimated to be 12 feet below the limonite-covered sandstone which marks the top of the marine beds. Below the corbula stratum there are frequently larger laminated sandstones that split into very thin flat layers and are marked by worm tracks. A different species of Lamellibranch east and one species of gastropod were also found in these rocks about 20 feet below yellow sand. In many places there are layers of fine grained sandstone covered with limonite, rusty red colored, below the rounded typical basal sandstone concretions. These sandstones are frequently formed in irregular squares and would seem to indicate a drying up of ponds where the cracks had filled with sand later.