In recent discussions arising from the renewed attempts to define more closely the boundary between the Jurassio and Cretaceous systems in Russia, Germany, Belgium, and France, and also in North America, constant reference has been made to the English Wealden deposits as affording a standard of comparison. But, meanwhile, doubt has been thrown, by palæontologists who have studied certain portions of the Wealden flora and fauna, on the hitherto accepted classification of these English deposits with the Lower Cretaceous, on the grounds that the fossils showed strong Jurassic affinities. This opinion has been expressed by the late Professor O. C. Marsh in regard to the reptiles, by Dr. A. Smith Woodward in regard to the fish, and by A. C. Seward in regard to the plants. To prevent further confusion it is therefore desirable that certain facts which have been overlooked in this discussion, though for the most part already published, should be restated, since these facts seem sufficient to prove that, at any rate, the greater portion of the English Wealden series must remain as part of the Lower Cretaceous.