Macrurous decapod crustaceans are generally uncommon and are often incompletely preserved. However, at certain horizons in the Speeton Clay (Ryazanian–Albian) and Atherfield Clay (Lower Aptian) of Yorkshire and the Isle of Wight respectively, macrurans form the dominant element of the fauna. Two species in particular, Meyeria ornata (Phillips) and Meyerella magna (M'Coy), are not only very common in these formations, but are also very well preserved. Recent collections have yielded a large number of specimens of both species. This material is examined with the aid of SEM techniques, gross morphology is discussed, and the details of the exoskeletons are compared. In the case of M. magna, examples are figured which show traces of a colour pattern and the effects of regeneration on the first pereiopods. A discussion is included of the possible function of the appendages in M. magna and M. ornata, and of their other, unique features. Finally, the mode of life of both species is inferred from a consideration of their morphology, and of the evidence from their preservation, distribution and relationships with associated faunas.