The investigation of the fossil flora of Clacton was first begun by the late Clement Reid in 1916, from material collected by Mr. S. Hazzledine Warren. The work was never completed, and, at the further request of Mr. Warren, it was taken up again in the spring of 1922 by ourselves, when we re-examined the whole material. By far the greater number of Mr. Reid's 111 determinations remain unaltered; but, in the case of a few, we consider that he was mistaken, and further research has revealed a considerable number of unrecognized, or undetermined, species, bringing the total up to 135, a list of which is appended (facing p. 622). Before making any comments of our own, the conclusions to which Mr. Reid's work had led him must be stated. These may be gathered from his letters to Mr. Warren as the work progressed, between February 4th and April 5th, 1916. A few extracts from these follow here. ‘March 2, 1916 … The flora is most interesting, and is well worth further work, as it ought to throw much light on climatic conditions. Have you been able to make out where the stream came from, and what were the deposits that lined its banks? The flora does not agree with that of a stream flowing through London Clay; it points either to a dry climate or to dry gravelly stream-banks: I cannot say which.’ ‘March 16, 1916 … These 58 species point clearly to a small stream (not estuarine), bordered