THE ORDER CETACEA. 127 



produced by the ribs during the foetal or infantile state 

 of the animal. The superior semicircular margin has 

 several strongly marked asperities, where several very 

 powerful muscles are inserted. The anterior margin, 

 which is the shortest, is likewise the thickest at the in- 

 ferior part of this, and at the anterior angle ; the cora- 

 coid process [so called from its supposed resemblance 

 to a crow's beak], and the one analogous to the acro- 

 mion just described, both of them projecting 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-hume- 

 ral 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. Besides, 

 the pectoral extremity not being controlled by a cla- 

 vicle, 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 Brachii, or Arm-bone, is short, but thick ; 

 the head is directed obliquely from outwards to inwards, 

 where it articulates itself with the glenoid cavity of the 

 shoulder-blade by means of a smooth and even articular 

 cartilage ; its cubital extremity is almost flat, and is arti- 

 culated by simple ligaments to the radius and ulna. 

 All the external surface of this bone is asperated, for 



