My friend Mr. Mackie has handed me an interesting little fragment of jaw, derived from the Gault at Folkestone. The length of the broken fragment of jaw measures 1⅛ inch; its absolute breadth of an inch. It contains three teeth, of which the largest is conical, incurved, exhibiting around its thickened base a series of sculptured linear depressions, parallel with the axis of the tooth, the interior of which has been converted into phosphate of lime; the second and the third also exhibiting similar characters, the third especially being acuminate, and exhibiting the natural apex of the tooth in an uninjured state. The conformation of such a tooth led my friend Mr. Davies to compare it with the homologous structure in the teeth of the Pachyrhizodus basalis of Agassiz, which is described by Sir Philip Egerton, F.R.S., in Mr. F. Dixon's ‘Geology of Sussex.’ The specimen figured in that work was obtained from the Lower Chalk at Steyning. The characters, which are given, are—” apex very brittle, slightly curved inwardly, and solid; the base is hollow, and extends into the substance of the jaw.” It is further stated that in Sir Philip Egerton's cabinet there is a specimen of this fish, exhibiting an unusually thick and strong humerus, as well as large and circular scales, covered with asperities so minute as to be indistinguishable without the aid of a glass.

There are many points of distinction, however, between the Pachyrhizodus basalis of Agassiz, and Mr. Mackie's specimen. Apart from the absolute size of Mr. Dixon's specimen, which is at least double that of the one before me, I am wholly unable to detect in the former any trace of that curious sculptured channelling which is so prominent in the latter specimen. This comparison failing, Mr. Davies showed me some most interesting specimens, also from the Folkestone gault, which exhibited equally perfect evidences of this sculpturing. I would therefore suggest that some temporary or provisional name should be given to this form, which differs from the Pachyrhizodus basalis of Agassiz, both in its stratigraphical habitat and its odontological conformation.