advance of these surfaces expands, as it rises upward and a little outward and forward, to the extent of nearly an inch; the hinder and outer side is impressed by a concavity, continued from the costal border; the inner side is smooth and convex: it is not quite entire on either side. The coracoid grooves (Pl. IV. fig. 4, _b_ _b′_) are small in proportion to the sternum, and are divided from each other by an interspace of about an inch; the outer wall of the groove (_b′_), 9 lines in extent, is moderately produced and convex; it appears to be a continuation of one of the initial ridges (_r_) of the keel: the inner wall of the groove (_b_) is deeper, and is formed by the obtuse angle of the anterior border of the sternum, between the medial and lateral emarginations. External to each coracoid groove is a large elliptical pneumatic foramen (_p_) or depression. There is no episternal process. On the convex outer surface of the body of the sternum the “pectoral” ridge (Pl. VI. fig, 1, _k_)[28] is feebly indicated, extending from the outer end of the coracoid groove backward and inward to near the posterior third of the keel. The concave surface of the sternum (ib. fig. 2) shows a number of small pneumatic foramina, chiefly along the middle line to near the posterior third. Behind the costal border the substance of the sternum gradually increases in thickness from the sharp lateral margins to the middle, above the base of the keel, and shows there a fine pneumocancellous texture (Pl. XI. fig. 4). _Scapular Arch._ (Plates III. & VIII.)