An auction house says it is selling a rare first edition of Charles Darwin's "On the Origin of Species" found in a family's guest lavatory in southern England.

Christie's auction house said the book - one of around 1,250 copies first printed in 1859 - had been on a toilet bookshelf at a family's home in Oxford.

The book will be auctioned on the 150th anniversary of the publication of the famous work. Christie's said the book is likely to sell for 60,000 pounds ($99,000).

Darwin's "The Origin of Species" outlined his theory of natural selection - the foundation for the modern understanding of evolution.

Celebrations around the world have marked the 200th anniversary of Darwin's birth.

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