Nos. 20, 21, 29, 31, 32, 33, 34, 35, are examples of the distal ends of humeri of a different type. They are mostly larger than the preceding group, and correspond in characters with the large proximal ends, but appear to be separable into two groups, namely those with a pneumatic foramen on the anterior radial side near to the articular surface, and those where no pneumatic foramen is seen. Unlike the previously considered type, the ulnar side is sometimes more inflated than the radial side. The mesial condyle in this group appears in every case to be an epiphysis, which is wanting. The radial condyle becomes a large flattened slightly convex surface looking downwards, which in some of the species, as Nos. 21 and 32 (in other respects remarkable species), shows an approach to a trochlear character on its anterior side. In Nos. 33, 34 and 35 the mesial anterior concavity becomes flattened and abuts at an angle against the flattened radial condyle. No. 20 shows the rhomboid impression on the ulnar side to be more concave and more ovate. The ulnar condyle remains a smaller but prominent tubercle directed distally. Nos. 21, 22 and 34 show a ridge developed on the ulnar side of the shaft like that on the radial side in the other group, while the radial ridge is not so near to the articular surface. The largest and smallest distal ends of humeri known, both show the characters here enumerated. The great distal end of a left humerus, figured by Prof. Owen, Pl. IV. f. 1, 2, 3 of the 1st Supplement to the Cretaceous Pterosauria, is of this kind, and though imperfect measures more than three inches over what remains of the articular surface. In the small humerus, No. 30, the width over the distal articular surface is 5/8ths of an inch. If it is assumed that the large bone was no more than 5 times the length of the small one, the entire length of the humerus would have been about twelve inches. The smallest humerus, No. 29, measures over the shaft rather more than one eighth of an inch. The Ornithosaurian humerus has but little in common with that of any mammal. Most mammals have the proximal head of the bone hemispherical, and a pit at the distal end for the olecranon process of the ulna, while there is usually little indication of a radial crest, and the proximal and distal ends are in the same plane. In the Bat however the bone is twisted a little so that the slight radial crest looks in the same direction as the distal end, here also there is no pit for the olecranon; but the bone is sigmoid and proportionally much longer than in Pterodactyles. In the horse, hippopotamus, &c., the radial process becomes more developed but never resembles that of a Pterodactyle.