The three species of corals which form the subject of this communication are all from the Lower Lias of the west and centre of England. They were originally described by Duncan3 as species of Montlivaltia, viz. M. rugosa, M. mucronata, and M. victoriae. But in 1890 it was suggested by Freeh4 that many of the so-called Montlivaltia and Thecosmilia from the English Lias should be included in the genus Stylophyllopsis, established by him in that year for certain Triassic corals which possessed in their septal structure, and in other features of lesser importance, characters sufficiently distinctive to justify their separation from Montlivaltia. Owing, however, to the absence from Duncan's monograph of satisfactory representations of transverse and longitudinal sections, the generic determination of the English forms remained in every case uncertain.