Until very lately, the only fossil mammifer known to science from the Upper Oolite beds (Purbeck series) was the Spalacotherium tricuspidens of Professor Owen, a small insectivorous form referred by him, with some reserve, to the placental series. It was discovered by Mr. W.R. Brodie in one of the so-called “Dirt-beds” of Durdlestone Bay, Purbeck. That meritorious collector continued his researches during the years 1855–56, and had the good fortune to discover some other mammalian remains, which were transmitted to London about the end of last December for description by Professor Owen, They were all found in what is called the “Dirt-bed” No. 93, of Austen's “Guide.” Before these remains had reached London, Mr. Samuel H. Beckles, so favourably known from his researches in Sussex and the Isle of Wight, after free communication with Sir Charles Lyell about the importance of a close and sustained search for mammalian remains at Purbeck, proceeded to Swanage for the express purpose of carrying it out. Before a fortnight had elapsed, Mr. Beckles, by a series of well-directed excavations, had discovered several mammalian jaws besides numerous reptilian remains, in the “Dirt-bed” No. 93. When the first line of section ceased to be productive, or could no longer be worked, he opened new ground, under difficulties which would have damped the ardour of a less earnest inquirer. The labours of Mr. Beckles have been crowned with the success which they deserved.