The extinct genus of Chelydroid Chelonians to which M. Louis Dollo gave the name of Pseudotrionyx, has already been recorded from the London Clay of Sheppey, by Messrs. Lydekker and Boulenger. It is somewhat remarkable, however, that until the recent acquisition by the British Museum of the collection of Mr. J. B. Ogle, no certain evidence had been observed of the occurrence of the genus in the Bracklesham Beds—the English equivalent of the Bruxellian Series which yielded the Belgian Pseudotrionyx Delheidi.