OSTEOLOGY OF THE PENGUINS. 401 



Taking the bone in Aptenodytes pennantii, for example, I find 

 it to be considerably longer than the humerus of the same 

 individual, and altogether a bigger and stronger bone. Its 

 sternal end is not conspicuously expanded, while upon the 

 whole a gradual tapering is seen to occur from this end towards 

 the summit, accompanied by an antero-posterior flattening. On 

 the inner side of the shaft an extensive wing-like process is 

 thrown out, extending downwards for some distance from the 

 scapular process. This is highly developed in Eudyptes, in 

 which genus it is perforated by a large elliptical foramen, and 

 which, due to absorption, is in Aptenodytes converted into a 

 great notch. In Eudyptes chrysocome the dorsal end of the 

 coracoid is produced considerably above this part of the bone, 

 and supports at its summit the rather weak head of the bone, 

 having here the form of a mesio-anteriorly produced process or 

 hook. This species has the sternal end of the coracoid thick 

 and strong, being convex transversely in front, and correspond- 

 ingly concave behind, where its surface is roughened for 

 muscular attachment. 



At the inner angle of its sternal end there is an abruptly 

 upturned process, that is quite characteristic of the coracoid in 

 not a few of the Sjiheniscidce. 



Of the Pectoral Extremity. — Wing-modification has been 

 carried to the extreme in Penguins, the limb having more the 

 appearance of a ' flipper ' or paddle of a sea-turtle than the 

 wino; of a bird. With this modification has followed an extra- 

 ordinary compression of all the bones. As a rule, they are 

 flat and oblong, and, apart from size, are characteristically alike 

 in all the species. This flattening of the bones, in the case of 

 the forearm and hand, is in a plane parallel to the plane 

 of the keel of the sternum ; while the humerus has received 

 it in a plane nearly at right angles to this. This last-named 

 bone is, as is the case with the skeleton of the entire limb, 

 entirely non-pneumatic, although there is a wonderfully deep 

 and circumscribed pneumatic fossa. 



Every known species of Penguin has two large sesamoids at 

 the elbow. They occur in life in the insertional tendon of the 

 triceps muscles. 



More or less oblong in outline, the radius and ulna have 



