Knightia is the most common fish from the Eocene lake deposits of the Green River Formation. Adult fish ranged from around 10cm to as much as 25cm long. They lived in large groups and fed on algae and ostracods.
The Green River Formation is one of the richest fossil sites in the world, famous mostly for its fish. Other finds there include bats, giant palm fronds and even a small three-toed horse. The layers of micritic limestone were laid down over a period of around 15 million years.
A grade pictured, the £27 examples will be a little smaller on average, but I always pick good examples to send.