In the year 1837 I examined, microscopically, the structure of certain teeth from the sandstone of Guy’s Cliff, Warwickshire, which had been submitted to me by their discoverer, Dr. Lloyd, F.G.S., of Leamington, the form of these teeth being that of simple canines. The well-marked and peculiar structure, so discovered, and the geological correspondence of the matrix with the Keuper of Germany, induced me to apply to Prof. Jäger of Stuttgart (whose acquaintance, ripening into friendship, I had formed at the Meeting of the German naturalists in 1835, under the presidency of Oken, at Freiburg im Breisgau) for a tooth, or portion of tooth, of a fossil in his collection.