oftlie SJcelet07i of Bal^jendptera Rorqual. 231 



This must afford attachment to some of the muscles ; the 

 remaining muscles must form connections with the smooth 

 surface, or with the superior margin of the bone. 



The costal or internal surface has several strongly marked 

 prominences and canals, which diverge towards the semicir- 

 cular margin. These canals are evidently produced by the 

 ribs during the foetal or infantile state of the animal. The 

 superior semicircular margin has several strongly marked as- 

 perities, where several very powerful muscles are inserted. 

 The anterior margin, which is the shortest, is likewise the 

 thickest at the inferior part of this, and at the anterior angle ; 

 the coracoid process [resembling a crow's beak], and the one 

 analogous to the acromion just described, both of them pro- 

 jecting anteriorly, are separated by a very deep canal, which, 

 in the recent state, is filled up with a very fat cellular tissue. 

 The glenoid or articular cavity of the shoulder joint is found 

 at the anterior margin of this bone : it is very flat, and there 

 appears to be no attachment of the scapulo-humeral ligament, 

 from which the animal enjoys motion at this part to a greater 

 extent than the other Mammalia ; for the head of the brachium 

 or arm-bone, which is enormous, can ultimately employ all its 

 surfaces; in fact, it can describe full two thirds of a sphere. Be- 

 sides, the pectoral extremity not being controlled by a clavicle, 

 its actions are less likely to be limited. This is the largest flat 

 bone in the skeleton, next to those of the head ; its structure 

 is rather spongy, being only covered with a thin layer of 

 dense substance. The fins contain bones analogous to the 

 superior extremities in man, which I proceed to describe. 



The Os Brackii, or Arm-bone^ is short, but thick; the 

 head is directed obliquely from outwards to inwards, where 

 it articulates itself wdth the glenoid cavity of the shoulder- 

 blade by means of a smooth and even articular cartilage ; 

 its cubital extremity is almost flat, and is articulated by simple 

 ligaments to the radius and ulna. All the external surface of 

 this bone is asperated, for the insertion of the muscles of the 

 shoulder, and also of those which give motion to the fin. 



Of the Bones of the Forearm, — The radius is flat, larger 

 and thicker than the ulna, and offers no striking peculiarity, 

 except the hardness of its compact tissue. Its articulation 

 with the body is the same as with the ulna. The Ulna, or 

 Cubitus^ forms the inferior margin of the forearm ; it is flat 

 but curved through all its length: at the brachial extremity 

 is a flattened tuberose process, which gives origin to strong 

 tendons passing to the extremity of the fingers. The carpal 

 extremity is united to the hand by a powerful tendinous sub- 

 stance : all the body of the bone has externally a dense com- 



Q 4 



