This interesting species has hitherto been known only by the single type-specimen, a mandibular tooth, contained in the York Museum, originally described by Mr. T. P. Barkas, and recently very correctly redescribed as well as figured by Mr. A. Smith Woodward. It so happens that some years ago a considerable number of these teeth, both mandibular and palatal, occurred in the Borough Lee ironstone: my own collection contains no less than forty specimens, and there are many others in the Museum of Science and Art, so that I may now add considerably to the knowledge of the species