Mr. alfred craven, who for some months past has been occupied in making a collection of the organic remains found in the Gault at Folkestone, has submitted to me for examination and description (if requisite) a specimen of a Pycnodont jaw which, both for the perfect condition in which it is preserved and for the peculiarity of its characters, is worthy both of description and representation. The specimen is the right mandible with most of the tritoral teeth preserved in their natural position. It betokens a fish of the largest size of the family to which it belongs, rivalling in this respect even the Pycnodus gigas of the Jura beds. The symphyseal border (PI. III. Fig. 1 s) measures two inches and eight-tenths of an inch in length, and half an inch in thickness. As the anterior extremity is wanting, the natural size was probably half an inch longer. The outer margin of the jaw measures four inches, and the basal line—connecting the outer and symphyseal elements of the triangle—three inches and two-tenths. The dental armature is composed of four ranks on the anterior and three on the posterior area of the mandible. The inner row (Pl III. Fig. 1 a) consists of teeth very considerably larger than those of the succeeding rows. Six of these are retained; but as the anterior extremity of the bone is broken, there were probably one or two more. The individual teeth measure nine-tenths of an inch by four-tenths. They are elliptic in outline, but slightly crescentic on the anterior margin.