26 



THE VOYAGE OF H.M.S. CHALLENGER. 



inasmuch as it rounds insensibly into tlie posterior border without the intervention of 

 the well-defined angle which obtains both in Eudyptes and in Aptenodytes. 



In short, with regard to the scapula as to the sternum, there are two extremes, repre- 

 sented by the genera Aptenodytes and Pygosceles, and two means, represented by the 

 genera Eudyptes and Spheniscus. 



The following table shows the principal dimensions of the scapula of different species 

 in inches. 



The Clavicle. 



The clavicles of opposite sides are united together at an acute angle to form the 

 furculum. The furcular angle is devoid of any hypocleidium, and is attached to the 

 sternal keel only by ligament. The curvature of the clavicle is strongly pronounced 

 and forms about one-third of a circle. Flattened from side to side, the broadest 

 part of each clavicle corresponds to the point of articulation with the coracoid bone. 

 From this point the bone diminishes in breadth upwards and downwards. The upper or 

 scapular extremity of the bone is bevelled at the expense of its lower border to articulate 

 with the acromion process of the scapula, while the lower extremity is fused with its 

 fellow of the opposite side. The internal surface of the bone is smooth, and lies in 

 contact with the interclavicular air-sac, while the outer surface presents a broad shallow 

 depression, from which fibres of the pectoralis major muscle take their rise. The 

 coracoidal facet is situated on the outer side of the anterior border of the broadest part 

 of the bone, and articulates directly with the apex of the coracoid bone. 



The clavicle presents no distinctive points of importance in the various genera. 



