I. I ntroduction . T he object of the present communication is to show the development and sequence of certain Jurassic strata on the Dorset coast, and to make some comparisons with strata elsewhere. The range of strata dealt with is from the top of the Middle Lias (Pliensbachian) to the lower part of the Fullers' Earth (Bathonian, Vesulian) inclusive. The communication is laid before the Society for several reasons: it was promised many years ago; it forms a sequence to the papers on North Dorset and the Cotteswolds; it aims to give a detailed account of certain fossiliferous strata of South Dorset, to be used as a foundation for the dating of the fossils; and it offers suggestions in the matter of correlation and subdivision as a basis for the work of other investigators. With this stratigraphical paper there is also offered a palæontological paper, to describe some of the new species mentioned, and to figure some other species which are new and illustrative of strata of the same dates. That communication will be alluded to as ‘the palæontological paper.’ The investigations for this paper, which will probably be my last, so far as active field-geology is concerned, were complete in the main several years ago; it was announced in 1893 as nearly ready for publication. Since then changes of residence have involved packing of specimens, and many have not been unpacked again. As a consequence the identification of species must often be given in general terms, as they were set out