REPORT ON THE SPHENISCID^. 



27 



lu Pygosceles the bone narrows more abruptly from its widest part to the angle of 

 union with its fellow than in any other genus. 



In Eudyptes the coracoidal articular surface is more elevated than in other genera. 

 The table shows the dimensions of the clavicle in different species in inches. 



The Coracoid Bone. 



The coracoid bones (PI. Vll. fig. 5) are remarkably strong in every species of Pen- 

 guin. The shaft of the bone tapers gradually from base to apex. The upper or 

 thoracic surface of the shaft is nearly flat, except close to the base, where it is deeply 

 concave. The lower or external surface of the shaft of the bone is convex, and almost 

 cylindrical in form from end to end. The tapering appearance of the shaft of the bone is 

 somewhat obscured by the presence on its inner side of an osseous lamella, which is 

 attached below to about the middle in length of the inner margin of the shaft of the coracoid 

 while above it is connected by means of a transverse bridge of bone to the point of junction 

 of the shaft with the curved extremity of the coracoid. Owing to the mode of attachment 

 of this lamellar process, a foramen is developed in connection with the coracoid, bounded 

 on the outer side by the shaft of the bone, and on the inner side by the lamella in question, 

 while in front it is completed by the osseous bridge which attaches the lamella to the 

 shaft of the coracoid. Through this foramen passes the nerve of supply to the pectoralis 

 medius muscle. The free border of the osseous bridge which attaches the lamellar process 

 to the coracoid bone is provided with a narrow articular surface which articulates with 

 the upper extremity of the clavicle, and with the acromion process of the scapula. 



The base of the coracoid bone is deeply curved to adapt it to the sternal groove, and 

 terminates on the inner side in a well-marked tubercle, which affords attachment to the 



