OR OSSEOUS SYSTEM. 99 



more developed than the other, and the nostrils are inclined 

 thus to the left side. The arms of these cetacea are moved 

 in a piece, as fins, and the articulations of the several bones, 

 especially of the hand, are very imperfectly formed. There 

 is no clavicle, but the great expansion of the scapula (Fig. 

 53. n,) presents a large surface for the powerful muscles of 

 the humerus, by which the arm is chiefly moved, the suc- 

 ceeding bones being scarcely moveable on each other in the 

 living state. The humerus (o,) has a large round head, but 

 is compressed at its lower end, like that of a turtle, and 

 the same compressed form is seen in the radius (p,) and the 

 ulna (q,) and in the detached round bones of the carpus (r,) 

 the meta-carpus, and the phalanges of the five fingers 

 (*, t.) 



In the herbivorous cetacea, as in the dugong (Fig. 54,) we 

 find a much nearer approach, in many parts of the skeleton, 



FIG. 54. 



to the ordinary condition of these parts in the land quad- 

 rupeds, than in the piscivorous tribes, especially in the forms 

 of the jaws and teeth, in the cervical vertebra, and in the 

 whole bones of the arms. The cervical vertebrae (a,) are 

 here detached and moveable on each other, and the neck is 

 thus longer and more flexible. The occipital bone (#,) 

 rises to a much less extent upon the cranium and its ele- 

 ments, like those of most of the other bones, remain long 

 disunited. The cranical cavity is smaller considerably than 

 in the former group. All the sutures of the cranium re- 

 main very loose, and the petrous and tympanic portions of 

 the temporal bone are permanently detached from the squa- 

 mous, as in the other cetacea. The frontals are divided by 

 a continuation of the sagittal suture ; the malar or jugal 



H 2 



