The distal articular surface is placed entirely toward the narrow end of the bone, leaving at the proximal end a large smooth rhomboid unarticular area, of which every side is a little concave: it connects obliquely the proximal with the distal articular surfaces. The distal articular area is divided by a diagonal ridge into a long oblong area of which the inner and outer sides are sub-parallel and the ends rounded: it is slightly concave in length as well as transversely, and is slightly twisted like the flukes of a screw. Adjacent to this region laterally is the other and sub-triangular part of the articulation. The broad end of the triangle is toward the broad end of the bone; it is concave in length and flattened transversely. The two parts of the articulation are inclined to each other at a large angle, both looking downward and outward, but on opposite sides of the bone. II. Distal Carpal. The tablets of this bone comprise 22 specimens. Nos. 2, 3, 4, 5, 6, 8, 9, 10, 15, 16, 19 and 22 are so mounted as to exhibit the proximal surface. Nos. 7, 11, 12, 13, 14, 15, 16, 20 and 21 show the distal surface of the bone. No. 17 is a cast from the distal sur&ce of a proximal carpal for comparison with the proximal surface of the distal carpal. No. 16 is a cast from the proximal end of the wing-metacarpal for comparison with the distal surface of the distal carpal. No. 20 is a distal carpal of unusual type, 19 is a cast from its proximal surface, and 21 is a cast from the distal surface of the same specimen. The proximal aspect of this bone is rather narrower than the distal aspect; each is sub-triangular in outline, the sides being convexly curved. In the long axis from the apex on the inside to the short outer[Q] side the bone is convex proximally with an oblique transverse depression; in the short axis, that is, between the two longer sides, the middle of the bone is hollow, but the oblique transverse depression makes both sides of the hollow convex,--so that excepting the smooth unarticular triangular area adjacent to the apex, the sub-quadrate articular surface is shaped somewhat like two cones put side by side in such manner that the apex of each touches the base of the other: the apex of that cone which should touch the short side or base of the triangle formed by the bone, is truncated by a depression which exhibits an oval pneumatic foramen. Towards the apex, on the same side as the pneumatic foramen, the margin of the bone is rounded for a small terminal oval articulation which looks outward and upward. [Footnote Q: Outer and inner are here used in accordance with the usual interpretation, and the better to compare with birds.]