articulation to its extremity. The space included between the bones of the two sides as they lie is a nearly regular, oval one, measuring ninety-five millimeters in its greater, forty-five in its lesser diameter. The sternum lies at a little distance from the coraco-scapulae. It is an extremely thin bone, with a stout anterior, styliform projection, at the base of which, on either side, looking upward and outward, is the articular, trochlea-like surface for the sternal end of the coracoid. The width between these articular surfaces measures fifteen millimeters; the length of the process in front of the articulations is twenty-five millimeters. Immediately posterior to the articular surfaces, the bone expands nearly at right angles to the longitudinal axis to a width of about sixty millimeters. The thin lateral margins are nearly parallel with the longitudinal axis, and show three shallow emarginations between the four costal articular projections. The hind angles are nearly rectangular. The bone, as preserved, is only shallowly concave, and shows no true keel, though a more pronounced median convexity towards the front doubtless subserved the function of a carina in part. The left humerus lies in position, and is especially characterized by its enormous deltoid crest (radial crest of Marsh), though otherwise slender. This crest is further removed from the head of the bone than is the case in species of _Pteranodon_. It is directed somewhat downward, and has its distal, gently convex, border about twenty-five millimeters in extent, while the width of the process midway between the extremity and the base measures but sixteen millimeters. The bicipital crest is also prominent. The bone is relatively shorter than in _Pteranodon_. The humerus, as will be seen from the above description, and from the measurements given below, is remarkably like the same bone in _Pteranodon nanus_, as described by Marsh (_l. c. supra_), and but a little larger. In _P. nanus_, however, the coracoid and scapula are said to be firmly co-ossified, and the scapula has of course a different structure.