Notwithstanding the large number of Mammalian remains which have been found in the Brick-Earth of the Thames Valley, they have for the most part been portions of the larger forms, and very few examples of the smaller Mammals have hitherto been discovered. Professor W. Boyd Dawkins and Mr. W. A. Sanford (Brit. Pleist. Mam. Pal. Soc. vol. for 1864, p. xxxvi, 1866) have noticed the occurrence of Arvicola amphibia in the Pleistocene of Ilford, Crayford, and Erith; while from the last-named locality Mr. R. W. Cheadle (Proc. W. London Sci. Assoc. vol. i. p. 71, 1876) recorded the remains of Spermophilus, which Mr. Lydekker has more recently (Cat. Foss. Mam. Brit. Mus. part i. 1885, p. 212) referred to Falconer's species S. erythrogenoides.