Dentary bone. Broken at both ends, and wanting all its teeth, this interesting fossil shows the suture where its whole length rests on the angular bone which almost reached to the termination of the beak, quite unlike what is seen in any German Pterodactyle. It is a narrow mandible, less than three quarters of an inch wide, with the alveolar margins parallel. The palatal surface 1-1/2 inch long, is divided into 3 equal strips; the middle one being a deep glossal groove, slightly narrowing in front, and deepening behind, made by two inclined flat surfaces. The lateral strips are horizontal behind, and in front slope a little outward. The tooth-sockets are oval, directed outward, and as long as the interspaces, though these seem to get longer behind. In an inch and a quarter there are four teeth. Below the teeth, the sides of the jaw are compressed: though nearly parallel at the hinder fracture, the flattened surfaces approximate in front till they meet in a sharp keel, which appears to make an acute angle of about 45° with the palate; and below, where the jaw is an inch deep extends for half an inch in front of the suture with the angular bone: this suture is straight and irregularly concave, and in an inch and a quarter approximates to within 5/8ths of an inch of the palate. IV. Ornithocheirus tenuirostris (Seeley). Case. Comp. Tablet. Specimen. =J= _c2_ 12 1 Middle part of a premaxillary bone fractured behind and in front, slightly distorted by compression; it is 2-1/8th inches long, and nearly resembles _O. compressirostris_ (Owen). The palate is about 1/2 an inch wide in front, and 5/8ths of an inch wide behind; it is compressed mesially into a strong angular keel, between which and the teeth there is a shallow groove on each side. The groove dies away behind, and the converging parts of the keel occupy the whole space between the teeth. The teeth-sockets are small, elliptical, not opposite to each other, and placed along a distinct flattened tooth area, which looks downward and outward and separates the palate from the side of the jaw. The first pair of sockets preserved are almost 3/16ths of an inch long and 1/16th of an inch wide. The interspace between that tooth and the next tooth behind is 7/16 of an inch. Separated by similar interspaces, behind these on one side are two sockets, and on the other side one socket. The sides are flattened in front, and convex behind, (making the section of the jaw lanceolate); they are compressed and round into a narrow rostral keel. The height from the palatal ridge to the rostral keel in front is 11/16ths of an inch; behind it is fractured, but the height was probably 14/16ths of an inch. The palatal keel, distance of the teeth, and proportions of the jaw, distinguish it from O. compressirostris (Owen). V. Ornithocheirus Oweni (Seeley). Case. Comp. Tablet. =J= _c_ 20