would differ chiefly in the larger obturator foramen, the perforated acetabulum and the unanchylosed condition of the pelvic elements. The pelvis of Apteryx does not make any near approximation. Moreover specimens Nos. 3 and 4 show on the anterior pubic border, about the base of the acetabulum, a slight pit or roughness to which something has been attached, and in the original specimen of Dimorphodon associated with the pelvis are two triangular bones which recall something of the form of the prepubic bones of Echidna. Most German Pterodactyles show on the OS pubis an enormous prepubic bone. In Iguana the pubis forms at its anterior border, a sharp angular process. In Chelydra the process is long and narrower, and arises from the middle of the border. In Echidna this prepubic process has become a distinct prepubic bone and is more elongated. Unlike the marsupial bones it is attached to the pubis by a wide base. The anterior pubic roughness of Cambridge specimens, and the loose bones of the Dimorphodon, &c. indicate the existence of structures in the Ornithosauria homologous with the prepubic bones of the Ornithodelphia. So far as it is comparable with living animals, the ilium is altogether avian, differing in being narrower; and the pubis and ischium are mammalian. The upper anterior corner is the most elevated part of the acetabular border, as in the great Auk and some birds of vertical position of body, and many mammals. FEMUR. Pl. 8. Case. Comp. Tablet. Specimen. =J= _b_ 11 1-16 Twenty-six specimens are mounted to illustrate the Femur. 10 are proximal ends; 16 distal ends. But in the series illustrative of species is an entire specimen of a right Femur 4 inches long. Fragments Nos. 3 and 12 show proximal and distal ends twice as large, but most of the examples are about the size of the entire femur. It is a straight sub-cylindrical bone, flattened in front, a little compressed from front to back distally, and (in one type) compressed proximally from side to side behind. The distal articulation has a broad shallow channel passing down from the front and imperfectly separating two condyloid parts, which extend a little backward and are divided behind. The outer condyle extends a little outward, and so gives the outer side of the bone at the distal end an oblique compressed aspect like that which prevails among birds and many mammals. Proximally the shaft contracts suddenly and is produced upward, forward, and inward as a rounded neck, as long as in the femur of any mammalian carnivore, which expands rapidly at the end to form the hemispherical ball, which articulates with the pelvic acetabulum.