North Carolina Museum of Natural Sciences---Lost Horizons
Geologists use the term "horizon" to refer to sedimentry rock of a particular period in the history of the earth. The types of fossils embedded within the rock are frequently used to determine its age. These paintings represent the types of fossils you might encounter if you were digging through the layers of rock deposited since the beginning of the evolution of visible life, with the oldest fossils on the lowest row.