142 ODOKTORNITHES. 



hemispherical, and adapted to the subcircular pit in that bone. The 

 acromial process of the scapula is conical, short and pointed, and does not 

 project beyond the articular portion of the bone. The shaft is hollow at 

 the lower end. 



In the genus Apatomis, the scapula (Plate XXIX, figures 1, la, 2-4) is 

 elongate, and distally flattened. In a side view, the lower half is curved, 

 while the upper or distal half is nearly straight. In a front view, the bone 

 appears regularly curved throughout. The proximal end is moderately and 

 gradually expanded transversely, and bears the two customary articular 

 surfaces. The upper and larger of these, forming the scapular portion of 

 the glenoid fossa, is very oblique to the plane of the bone, and is 

 distinctly convex in both directions. It increases in transverse diameter 

 toward the base, instead of becoming narrower in that region, as in 

 Ichthyornis. The articular surface for the coracoid is much as in that 

 genus, being sub-hemispherical, and adapted to the pit on the face of the 

 coracoid. This articular face is bounded internally by a distinct ridge, as 

 shown in figure 3. 



The principal difference, however, between this scapula and that of 

 Ichthyornis is shown in the development of the acromial process, which in 

 Apatornis is highly developed, and projects far beyond the articular 

 surfaces of the bone, as in Graculus. Anteriorly, this process is obliquely 

 truncated, so that at the end it is blunt, and somewhat wedge-shaped. Its 

 general direction is inclined at an angle of forty-five degrees with the 

 direction of the shaft of the bone at its origin. 



The shaft of the scapula is perfectly preserved in specimen number 

 1734. It is here broadest just below the middle, where the upper 

 edge becomes thin, and somewhat expanded. Beyond the middle, the 

 bone tapers to near the distal end, and the extremity is rounded. The 

 scapula decreases pretty regularly in thickness from near the proximal to 

 the distal extremity, where it becomes thin and blade-like. 



The following nieasureinents indicate the size of the scapula in 

 Ichthyornis and Apatornis. 



