The happy discovery in the Museum of Marseilles of a new fossil butterfly first drew my special attention to this group of extinct insects, and determined me to make, during my residence in Europe, a careful study of the original types of all that had been previously described. By the great courtesy of Count Saporta, Professor Heer, Dr. ReynÈs, Mr. Oustalet, Mr. Woodward, the Rev. Mr. Brodie, Mr. Charlesworth, and the authorities of the Jermyn street Museum, I was able to study not only all the originals of the Museums of Aix, Marseilles, Zurich, Paris, London, Cambridge and Warwick, but several new types, described here for the first time. As I was unable to visit Vienna, Mr. Brunner de Wattenwyl was good enough to procure for me new drawings, made under his immediate supervision, of the species from Radoboj, described by Heer and preserved in the museums of that city. So that I have either personally inspected all the fossils described within recent times as butterflies, or have procured new and excellent original drawings of them, with the exception of Heer’s Vanessa attavina (Sphinx atava Charp.), which I was unable to find, and two fragments of slight value, viz.: the hind wing referred by Heer to his Vanessa Pluto, and the portion of a hind wing, called Cyllonium Hewitsonianum by Westwood. In the hope of drawing attention to fossil butterflies, which have been hitherto so little studied, I have brought together in this connection all that has been published of this group of fossils, whether of text or illustration; presenting thus, within a small compass, a complete account of our knowledge of these insects, as a basis for future investigations.