After rock with bone in it, called "matrix", was quarried from Z-line, it had to be screenwashed in Fort Peck Reservoir. This screenwashing was done by putting a few pieces of matrix in a wooden box with a special, fine screen bottom. That way the sediment floats away, but the tiny fossils are left in the box. Unfortunately, many of the boxes we had needed repair and new screening. Barry and I got out of this chore because we were off measuring section, but everyone else teamed up to get the job done.