Ostrich egg

An ostrich egg was the egg produced by an ostrich, a large flightless bird native to Earth.

By the year 5,000,000,000, the last remaining ostrich egg, taken from Earth, was in the possession of the Lady Cassandra O'Brien.Δ17. It contained a feed used to enhance her teleport signal, which was uncovered by the Ninth Doctor, who broke the egg in half. (TV: The End of the World)