SHOULDER GIRDLE OF HESPERORXIS. 59 



The Coeacoid. 

 (Plate VI, figures 4-6, and Plate VII, figure 4.) 



The coracoid of Hesperornis is quite small, and somewhat resembles 

 the same bone in certain of the Batitce. It is short, thin, and widely 

 expanded at the lower end, the whole bone being somewhat triangular in 

 outline, when viewed from the front. The superior extremity has an 

 articular head, with a facet on the inner side for the scapula, and a 

 larger one, looking backward, downward, and outward, for the head of the 

 humerus. A small compressed process extends above the articulation on 

 the inner side. There is a long decurved process extending forward, in- 

 ward, and downward, to support the upper end of the clavicle (Plate VIII, 

 figure 8). Below the clavicular process, the bone is very thin, and 

 emarginate. There is a sub-clavicular foramen through the shaft of the 

 bone, a short distance below the articular head. The posterior margin 

 sends out a wide, thin process, the extremity of which forms an obtuse 

 angle somewhat above the middle of the bone. 



The lower end of the coracoid has, along its whole border, an 

 articular face for union with the sternum. This extremity is nearly 

 straight, at right angles to the axis of the bone ; but the anterior third is 

 excavated, so that the outline here is concave. This portion of the lower 

 border is much thinner than the posterior two-thirds. 



The following measiu*ements give the size of the coracoid in two 

 individuals of Hesperornis regalis : 



Measurements of Coracoid. (No. 1206.) 



Length, from scapular to sternal articulation, 54.0 mm 



Greatest diameter of scapular and humeral articulation, 13.0 



Least diameter of scapular and humeral articulation, 6.0 



Greatest diameter of sternal end, 49.0 



Transverse diameter of sternal end, 2.5 



Measurements. (No. 1207.) 



Length, from scapular to sternal articulation, 55.0 mm 



Greatest diameter of scapular and humeral articulation, 12.0 



Least diameter of scapular and humeral articulation, 3.4 



Transverse diameter of sternal end, 3.0 



